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Idle passage plugged, among other things, 81 CM400T

kbongos

Veteran Member
Joined
May 30, 2022
Total Posts
459
Total likes
164
Location
Minneapolis, MN, USA
So I have been learning how to clean these carbs a little more each time I tear them apart. I really appreciate the helpful info and advice all of you experienced people share. After reading a few helpful posts, I start blowing air and carb cleaner and sticking pointy wires down these orifices where the sun don't normally shine. Some people point out the Idle circuit as being a common plugged up circuit. I figured out mine is plugged up. It's down that middle tube with the black plug. It has a pressed in brass orifice about half way down, before that is a hole leading to under primary jet next to it. So I can run a wire down this idle hole and it bottoms out near base you can see(about 1 inch down). I can stuff a tight fitting tube in there beyond the hole joining it to the primary, and then apply air pressure, or shoot carb cleaner. I have tried wedging the carb cleaner tube as tight as possible and blasting. Nothing seems to work, carb cleaner just sits there, no air flow detected. The cut-away of these carbs Tom posted were helpful in trying to understand it. Very tiny passages, leading over to those 3 tiny holes in the body near engine, last little hole above the idle adjustment screw with the spring and rubber washer. I have tried blowing air or carb cleaner in this idle air adjustment hole - I try to plug the 3 tiny holes and also a hole on the inner side of the air cutoff valve assembly that it seems connected to.

I have never done the full carb clean thing in ultrasonic or hot lemon juice, pine sol, or can of carb cleaner thing. Maybe that would help. Sticking a wire down this hole it bottoms out, I am guessing it hits a right angle junction and that's normal. Any thoughts or suggestions welcome! Thanks. Karl in MN
 

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Post a picture of your old idle mixture screws please.
If you spray in the mixture adjust hole do you get spray coming out of the 3 transition ports? I'm thinking there's a possibility that the tip of the mixture screw is broken off and lodged in it's seat.
I would go ahead and pickup a couple liters of Pine Sol to soak each carb in individually overnight, 8-10 hours. wash, rinse dry and recheck. Repeat as needed.
 
It's been a while but you are on the right track. I remember feeling successful when I finally found the deep jet that is almost an inch or moredown and cleared it eventually with a high E acoustic guitar string that must have had a very tiny chisel type end from being cut with a side cutters. When it went through after being spun with my fingers like a drill, I got spray to go through into the throat area.

Why they put an orifice so deep in there that can't even be seen, plus having to block all the other passages to leave only the path to the throat open, is a confounded mystery to me.

You are very close, don't stop till that tiny hole in the throat blows spray.

To date my CB400T2 stumbles in midrange until really fully warmed up, but then it's all go go.
 
Longdistancerider posted the original several page "How to.." thread at the old forum a couple years ago, I think. Anyways, I read every word several times. I don't think I'd have saved those very gummed carbs without his work. Read and heed his words.
 
Good news, I got one side of this idle passage to breath - pass air! Air goes to the three tiny idle holes, and the idle adjust spring loaded needle passage, and the side hole in the air cut off. I just got a little more aggressive shoving that guitar string down, at some point I put a little curve at end of guitar string, and poke at it. At some point it would go slightly further. Also shoved it down this air cut off hole.


The other side is still plugged up, but at least I know it can be done. So this passage leads to these three tiny idle holes near exit of body, the tiny idle hole closest to exit is directly in line with this idle adjust pin that screws right up into it. And the passage goes to a hole in the air-cut off assembly. I put air pressure into this gas inlet idle passage and it passes air to all these areas, covering them with fingers and you can hear or feel that it goes to these places. The cut-away pictures posted in the sticky by the guy with the book was helpful in figuring out the passage ways.

I believe I have been just living with this idle circuit plugged on both carbs for a long time. I recall adjusting this idle screw and getting no change at all, which would make sense if they are plugged up.

20220608_163645_air_cutoff_edit.jpg 20220609_001715.jpg 20220608_164820.jpg 20220608_163816_jet_holes.jpg 20220609_001612_idle_screws_air_cut_valve_edit.jpg

If I got any thing wrong here, let me know and I will try and correct it ;)
 
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Post a picture of your old idle mixture screws please.
If you spray in the mixture adjust hole do you get spray coming out of the 3 transition ports? I'm thinking there's a possibility that the tip of the mixture screw is broken off and lodged in it's seat.
I would go ahead and pickup a couple liters of Pine Sol to soak each carb in individually overnight, 8-10 hours. wash, rinse dry and recheck. Repeat as needed.

Thank you LongDistanceRider for your expertise. Those mixture screws can be trouble, I recall squashed washers and rubbers and stuck springs in the past. But those seem OK. Got 1 of the 2 carbs clear to blow air from bottom of idle pressed in jet. But other one is plugged up good. So I took the two carbs apart more fully and have them brewing in the crock pot, to start with in some hot water, dish soap and a little cleaning vinegar. I will be looking for some Pine Sol next shopping trip. On the plugged carb I do get air passage from idle mix screws and 3 little idle holes, and hole in air-cutoff. So the blockage I believe is up near base of this idle jet that is pressed in. After pushing piano wire thru and studying the passages I am getting a better understanding of this complicated little beast. Under the air cutoff are two passage ways in this idle circuit(one at a 45 degree angle) with the bee-bee plugs showing the manufacturers drill passage ways. I'm sure you don't want tot take those out, that would be last resort. The primary jet down in the hole did have a screw driver slot, I made a flat head screw driver out of blunt end of drill bit and grinding wheel and gave it some try to remove, but after 40 years they don't want to budge and I didn't want to push my luck. Got one plastic end cap off those vacuum ends, and got in there with flathead and got the big needle out. Other carb that plastic cap is stuck good so I have to make special tool, review notes, or something, as I don't want to wreck any of this delicate stuff. Think I need something I can stick on inside to grab the inner lip and pull. I'll admit I didn't have the motivation to pull all the springs and flaps and stuff off the two carbs, for now they are bathing in the crockpot. It's like a voyage into the jungle this stuff. If I ever get this thing all working again I promise to never use ethanol gas again, drain it properly for the season, and do my oil changes regularly.. ;)
 
Yeah, the cleaning takes lots of patience and time. The screw in idle jets will usually unstick after prolonged soaking with PB Blaster, like spraying it full every few hours for 2-3 days. The press in type can be pulled.
What carbs do you have? VB22??
 
Yeah, the cleaning takes lots of patience and time. The screw in idle jets will usually unstick after prolonged soaking with PB Blaster, like spraying it full every few hours for 2-3 days. The press in type can be pulled.
What carbs do you have? VB22??

Yes the VB22's. I'm learning that these other two that do not remove so easily are more than just a simple orifice, but an emulsion tube with the holes in the side, like the main secondary that comes out easily. I will try the more aggressive cleaning agent(pine sol or other specific carb soak cleaner), as the best next step. The poking piano wire down there obviously has it's limitations and I could just be scratching the inside all up. And I need to make a better screw driver for the one with the slot(the primary) and PB blast it as you say, heat it up, be careful and slow. It would be nice to get them out if they are a more complex emulsion tube.

Here is interesting link http://globalcxglvtwins.forumlaunch.net/viewtopic.php?f=7&t=32 where they talk about pulling these pressed in idle ones out with an easy out, another person mentions doing it with a self tapping bolt, I suppose maybe you could try to put threads in it with a threading tool. But, a good soaking can only help and hopefully might clear them.
 
LRCXex who wrote the thread is actually Larry Cargill and he has a business now rebuilding the CX and GL carbs plus a book on it http://donlhamon.com/carbbook.html
The picture we have of the carb circuits are courtesy of Larry.
Yes, the idle jets are far more complicated than just cleaning the 1 fuel orifice, it is an emulsion tube and the air side of the tube will collect debris clogging it up.
The latest removal for the press in jets is to tap the jet with a #4-40 tap, screw in a long 4-40 machine screw with a nut and washer installed. Once the screw is firmly in place you turn the nut to pull the jet. The washer serves as a thrust plate to minimize any carb body damage.
The screw extractor method works IF the tool is a machine shop grade version. The common ones people find and try to use almost always snap off ruining the carb.
 
LRCXex who wrote the thread is actually Larry Cargill and he has a business now rebuilding the CX and GL carbs plus a book on it http://donlhamon.com/carbbook.html
The picture we have of the carb circuits are courtesy of Larry.
Yes, the idle jets are far more complicated than just cleaning the 1 fuel orifice, it is an emulsion tube and the air side of the tube will collect debris clogging it up.
The latest removal for the press in jets is to tap the jet with a #4-40 tap, screw in a long 4-40 machine screw with a nut and washer installed. Once the screw is firmly in place you turn the nut to pull the jet. The washer serves as a thrust plate to minimize any carb body damage.
The screw extractor method works IF the tool is a machine shop grade version. The common ones people find and try to use almost always snap off ruining the carb.

In thanks to Larry, a diner for two
20220609_210836_crock_pot.jpg
More scratching with various piano wire, no results


We tap into the pressed in idle brass jet emulsion tube
20220610_210438_tap40.jpg
And pull
20220610_211403_pull_1.jpg
The cork
20220610_211417_pullout.jpg
So tasty
20220610_211515_dirty1.jpg
After getting cleaned up a little
20220610_211927_clean38a.jpg
Notice the scratching from the air cutoff orifice
It was actually plugged mid way thru thru the straight and narrow
Scratching down with a G string straight down might have worked if I had known
20220610_211941_clean_tophole.jpg
But now I'm a happy biker dude, Happy that maybe this will make my
cylinders roar, and not run lean on one
20220610_212046_happy_karl.jpg
Put away the tools of torment and call it a night


20220610_213152_tools.jpg


Wow, software sucks, I don't want a pickle, just want to ride my motorcycle
 
I hear you. Picture orientation in this forum software is all about how the phone is held when you take the pic. Our software is older and doesn't have all the latest features, but if you go by these tips your pics will be properly oriented
It's all good! I should refrain from whining. The forum software is a little quirky, The 'insert image' was taking a long time, and freaking me out a little. So I switched to 'advanced' mode and used the Attachment feature. That freaked me out a little too, but I muddled through it. Maybe the forum get's a little busy and perplexed at times. I know I do :lol:.

Don't forget to do the dance.
balibearian - I promise I will do the dance when it's appropriate. The forum dance with double quotes.
Gonna slap this fine twin back together and see how it rumbles today. Gonna get hot out and I love :heart: my 395cc cool down machine. Stay cool, thanks for the great forum and all the wizardly tips shared.
 
So I got it back together the other day. I will share a major stupid mistake I did. Fortunately my bike lived and is now running reasonably well.


So the mistake was with putting back in some carb parts I've never had out before. They are like brass nipples that go under the secondary jet and protrude and protect that large needle. I put them back in not from inside 2ndary jet hole, but just stuck them in from the inside of the carb. Now the problem is that they are not screwed in but just set in place lightly. I should have used my brain a little more at that time.


Get it put back on bike, took it for a test ride around the neighborhood. It runs really bad, I cannot accelerate past about 30 miles an hour. Get it home and started using my brain and at some point I think of those two parts and just realized the stupid thing I did. And I tore it apart just hoping that those 2 pieces did not dislodge and disappear. If they did they would probably get sucked into the engine.


Fortunately, they were still there. I put them where they belong safely pressed in under the secondary jet and emulsion tube. And now it's running reasonably well - as far as these things go - some issues with initial gas leakage, not a really great idle. But, I was able to take a nice cruise, got it up to 70 MPH. I really need to get some tools to be able to adjust that carb sync setting that they made very difficult to get to.


Having the two carbs apart for some cleaning I had to revisit the effort to putting them back together. This itself is a tricky operation, getting that sync set screw with the spring in the notch while also getting the two gas tubes set back in. You can see I have a cheat piece of tubing on the accellerator pump tube. This was from long ago when I first took them apart and that tube was terribly stuck. I broke the end getting it out. As a fix I just shortened it arranged a new slot for the o-ring, and then the tubing to make it long enough. Not the greatest fix.


Here are pics of some jig wire I used to pull aprt this sync spring so I had two hands to work with. And using another piece of wire to wind that light spring that works the choke a couple times around to get the needed tension.


20220611_142549.jpg20220611_140330.jpg

Thanks everyone for your moral support!
 
So just an update. I had to wait for some parts from ebay, my gaskets were ratty. I got creative and just ordered some 'kits' for other bikes. Like this one for a CB650.
4xcarb_kit_cb650_81_82.PNGThis way I got 4 sets of gaskets and a bunch of other parts that might fit my CM400T. Got lucky and they turned out to match. The price can be lower to buy these 'kits' instead of just the particular pieces you really need. I spent some quality time cleaning those seats the gas float valves go to, with some sandpaper and steel-wool on the end of a stick. And I got the other idle pressed in emulsion tube out with the 4-40 tap and screw method. It was also ratty looking.

20220617_223034_nasty_idle_emulsion_tube1.jpg

Cleaned it up and easy enough to press back down there. As Jim pointed out it is marked as a 38, which is quite a small hole in the center, something slightly larger than the high E guitar string.
20220617_224235_clean_idle_with_wire.jpg 20220617_223157_nasty2_idle_next_to_new.jpg 20220617_223249_new_idle_screw.jpg

Here it is next to some extra parts from this CB650 carb kit. Looks pretty similar to the screw in one from the CB650 kit. And I used the new idle screws that seemed like a match as one of mine was cut into by someone before me, and the other one had that cap stuck on.

I tried my hand at getting the slotted primary emulsion tubes out, with no luck. I left this note on the sticky thread titled 'Extract Primary Emulsion Tube':
"I just tried a second time getting my VB22 ones out, no success. I made a screw driver out of a drill bit, put a flat on the blunt end with a grinder. First time the flat was not very good. Second time it was better. But, I should have let it sit in the PB blaster. Another problem was the screw driver I made out of the drill bit was not so great because I just used a vice grip on the other end to serve as a handle. That didn't work so good. Next time I will find an old screw driver with proper diameter shaft with proper handle that you can hold and put proper pressure on it. So I have only succeeded in rounding off my brass slot down in the tube to some degree. Fortunately it seems to run OK and so I am happy with the Jim #1 option of just leave it as is for now."

It is running well now, so I'm pretty happy with my effort here. It starts first time without messing with choke. I do probably have some fine tuning with that carb sync screw and the idle screws, but I'm happy enough with it for the time being until I craft the tools and methods to get at that silly sync screw.

I experimented with the float level 'tube' method. Here is a pic that shows it.
20220618_100013_tube_trick1.jpg20220617_223320_oldfloats.jpg

So it allows you to see the level thru the tube. This does require a nicely sealed empty bowl screw, as you need to loosen that a little to allow flow, and it will leak at the screw if it doesn't have a nice new o-ring at the end. I wrapped some teflon tape around it's threads and o-ring. Not sure if that's a good idea but it did work. I have the new style floats that use the non-adjustable float pins. As you can see mine are yellow and old and I may replace them, maybe I will try switching to the old round style with adjustable pins. Oh, and if you do this tube measure thing, be careful as it has the drawback that it defeats the overflow tube so poses some risk. And if you drive with it on that is probably a little sketchier to. You can see I wrapped my idle rubber plugs with some teflon tape as well. They were loose and this seemed to tighten them up. And I did do that a few years back and the teflon tape did seem to hold up and not disintegrate or go nasty. Of course the proper thing would be to just get new ones. I do have those on order. I ordered another 'kit' for yet another different bike, a CX500, but it looks like it's got probably the same plugs and what I wanted most is the diaphragms(air-cut and accelerator spurter). Hopefully they are a match. We will find out. And I found this deal on motor oil. I was hesitant to buy it, but it seems like it is appropriate from what I read. And a bargain at Wally World at $12. That along with new oil filter from Ebay and my bike is a happy camper. And I have promised my bike I will change oil regularly to make up for the past abuse. The oil light when warmed up blinks a little in disagreement.
carb_repair_kit_cx500_80to82.PNG20220618_125706_cheap_15w40_oil.jpg20220618_110236_oil_filt1.jpg

I'm pretty sure I did not wreck the end of that oil bolt and the surrounding fins. I'll blame that on the previous owner. It still works OK.
 
Good trick with the teflon tape and the rubber plugs. I just used a dab of gasket sealer. No new plugs in the kits I bought a couple years ago but plenty other stuff that I didn't need.
 
And I found this deal on motor oil. I was hesitant to buy it, but it seems like it is appropriate from what I read. And a bargain at Wally World at $12.

While I see that it's diesel oil, as long as that oil is rated JASO-MA then you'll be fine but if not it might give you trouble with the wet clutch. Most of us are using Rotella T4 15w40 diesel oil.
 
I've been getting the GN4 10w40 from the Honda Dealer and it's actually about the same price (or a bit cheaper) than getting the Rotella T4. But only from a dealer, it's ridiculously expensive if you get it from Amazon or other online vendors. My guess is because of shipping hazardous materials drives up the cost. If you have a local Honda dealer nearby (and not a franchised small shop like Don's Cycle World) it might be worth giving them a call to check on the price.
 
Good point, but as with most things about rural living I don't have a Honda dealer near me (unless, in the rural scale of distance, one considers 35 miles or so nearby and at the cost of gas right now it's counterproductive). Problem is, most Honda dealers are pretty arrogant these days, especially when you walk in looking for parts for one of their vintage models. I've been turned off by most of the few dealers in a 75 mile radius around me.
 
That sucks. The Honda dealer near me won't personally work on my bike, except to do a tire change, but I wouldn't trust young guys unfamiliar with these bikes to work on them anyways beyond a tire change and/or fork seals anyways.

I've actually ordered quite a number of parts from that dealer for both bikes. He's pretty good at looking it up, giving me availability and when to expect it. He's always been good at calling me if the expected time changes and when it arrives. When I get there, it's in a clearly labelled box ready to go. I've worked at the parts counter before when I was younger and you really come to appreciate small stuff like that. Their prices are pretty competitive with online dealers like partzilla, especially if you factor in the shipping it ends up being about the same or maybe a dollar or two difference.

My Yamaha dealer on the other hand, those guys are all over the place and lose parts when I come to pick it up and never call me if there's a delay. I have to chase them down to find out what's going on. I gave up on them and just get OEM from the usual online vendors if it's anything Yamaha.

Do your local dealers just refuse to even look up your models on the computers? The Honda parts guy over here looks it up no problem. He knows that there's still a fair amount of stuff you can get, especially seals and the like. Obviously they won't be finding pistons and more specific parts.
 
They'll look up stuff but they're never that happy about it and often seem annoyed that it's so old and requires more digging. Not that I have many near me (maybe 3 or 4 in a 60 to 80 mile radius) some dealers will just flatly say it isn't available anymore. And for me, the distance is a bigger factor now with fuel prices where they are.
 
Distance is just an excuse to run out there on your bike! :biggrin:

But I hear ya. That sucks you got people who aren't very helpful. Once you've had a good parts guy who is helpful it's such a huge disappointment when you've had to deal with anyone else. Shout out to anyone here who works the parts counter or even just inventories the parts in the back room.
 
Agreed - last comment before we get back to the OP's topic, but I was spoiled long ago by having 3 thriving Honda dealers in the greater Tampa area, one of which had the best parts guy who also did all their machine work, the best guy for boring cylinders the area ever had. He's long since gone now along with the dealerships, replaced by the conglomerate-owned Powersports d-heads.

Now, back to idle passages, carbs kits, and diesel oil :)
 
Agreed - last comment before we get back to the OP's topic, but I was spoiled long ago by having 3 thriving Honda dealers in the greater Tampa area, one of which had the best parts guy who also did all their machine work, the best guy for boring cylinders the area ever had. He's long since gone now along with the dealerships, replaced by the conglomerate-owned Powersports d-heads.

Now, back to idle passages, carbs kits, and diesel oil :)

Small OT update to this: visited my local Honda dealer yesterday to get some oil and haven't been there in over a year. Same guy who knows his stuff is still there and was surprised he remembered me, hah. In any case, just for kicks, I asked about D7EA plugs, he looked up the plug the CM400A in less than 15 seconds because I was unsure if it was D7 or D8 (it's D8) and grabbed the last two XD05F caps on the shelf. Prices were all the same as getting it online, maybe give or take a dollar here and there.

If you guys have a local Honda dealer that is a reasonable driving distance (I know it's not for Tom) it may be worth it for you to at least call, or check it out in person. I've noticed with older stuff, if you just rattle off part numbers that you know are still made (i.e. by cross-referencing availability on partzilla) they just type it into a keyboard and order it for you. After you've done that for a few orders, tell them what it's for and if they're decent folk they won't get that attitude about looking it up.
 
I feel pretty spoiled and lucky to have all the help from people of this forum. It's really priceless. The amount of experience and knowledge is remarkable. You all can OT post all you want on my posts ;) Maybe the more useful info found in posts can be cultivated into 'sticky' posts if that makes sense.
 
I feel pretty spoiled and lucky to have all the help from people of this forum. It's really priceless. The amount of experience and knowledge is remarkable. You all can OT post all you want on my posts ;) Maybe the more useful info found in posts can be cultivated into 'sticky' posts if that makes sense.


I just re-viewed this post as a way to spin up the gray matter before I fix my leaky carb on my CB400Tii. You did such a great job with this, pics and all. Thanks.
 
I feel pretty spoiled and lucky to have all the help from people of this forum. It's really priceless. The amount of experience and knowledge is remarkable. You all can OT post all you want on my posts ;) Maybe the more useful info found in posts can be cultivated into 'sticky' posts if that makes sense.

I was trying to steer it back but just to be polite. I'm as bad as anyone about interjecting thoughts OT, but truthfully it often creates situations that others learn from too so it isn't always a bad thing. We're happy that you're getting a lot out the forum, that was our intent when we left HT and started over here with VHT - to get back to the reason HT was founded to begin with, offering advice and sharing information between vintage Honda twin enthusiasts.
 
I just re-viewed this post as a way to spin up the gray matter before I fix my leaky carb on my CB400Tii. You did such a great job with this, pics and all. Thanks.

Thanks, good luck with the carbs.

Good trick with the teflon tape and the rubber plugs. I just used a dab of gasket sealer. No new plugs in the kits I bought a couple years ago but plenty other stuff that I didn't need.

I did that many years ago because the plug was rather loose, and the added teflon tape tighted it up. And it really did hold up well from what I could tell, considering it is sitting in gas the whole time. The rubber plug was starting to decompose so I think the teflon tape helped contain it. I did finally get some new rubber plugs that will go in next time I have them apart. I made the mistake of using some silicone sealant around that big square gasket. While it did seem to work as a quick fix it was ugly to try and clean off and it looked like nothing but trouble as getting tiny piece of that silicone crap gumming things up. I have started to hate that silicone stuff. They should put a warning on the tubes, 'this may harm your mechanics, use at your own risk'.

And kids, always wear eye protection whilst spraying carb clean in tight spots! I finally got a good enough blast in one eye to take this serious. It kinda stung for a good while, and luckily eyes still work(as good as can be expected for my age).
 
I think I used a tiny dab of Gasketcinch. I need 2.00 readers for almost everything now so forgetting about carb spray ricochet isn't as bad as it was.
 
Thanks, good luck with the carbs.

I made the mistake of using some silicone sealant around that big square gasket. While it did seem to work as a quick fix it was ugly to try and clean off and it looked like nothing but trouble as getting tiny piece of that silicone crap gumming things up. I have started to hate that silicone stuff. They should put a warning on the tubes, 'this may harm your mechanics, use at your own risk'.

And kids, always wear eye protection whilst spraying carb clean in tight spots! I finally got a good enough blast in one eye to take this serious. It kinda stung for a good while, and luckily eyes still work(as good as can be expected for my age).

YIKES !
I will add that I bought COMPLETE carb rebuild kits made in china from eBay vendors to save mucho money on my '82 cm450customs and praying that only the rubber within the kits was usable and to throw out the "gold" bits.
I used a hair dryer to heat up and add stretchability to the too-small chinese "square" float-bowl gaskets but they've done their job since.
I also had to source slightly larger fuelgas crosspipe O-rings so the fuelgas crossover pipes between the carbs would not leak.
 
Hey Everyone!

Some updates on me, as I have just been lurking lately ;)
My 81 CM400T has been running good! When I got it going this spring the carbs leaked
and the battery was weak(stored it inside, kept it charged). But it just fixed itself.
It took a few days for the carbs to stop leaking, and the battery seems to have somehow
gone from weak to good. And since it starts now easily it's not stressed. Getting those carbs
cleaned out last year was the ticket, and I have VHT to thank for help with that.
It is so nice when it just fires up on a first crank. Before carb fix I was worried I'd burn out
the starter due to how long I'd have to crank it and play with choke.

The carbs were leaking but I just drove it around some short drives, toggling the gas line
on briefly, and thankfully carbs settled in and stopped the stupid leak. This might be a useful
tip for you all to try if you get the dreaded leaky carbs in spring startup or putting them back on.
I'm sure it's those flaky float valves just being somewhat finicky to settle in.

My LED light upgrade from last year is working ok, I had a problem with one side not turning on unless
I nudged the turn switch , but that has fixed itself as well - I think it was just oxidized switch
and the lower current of LED. I would like to find a higher power brake light, the LED seems
less than bright, and I would feel safer with a very bright brake light. And I have to fix
the switch arrangement on the front brake lever, it has some free play in it and the brake
light will stay on unless I bump it forward. I had jammed a piece of rubber in there as a
solution last year but that fell out and I need to fix that better.

There are a ton of other maintenance things I should do on this bike, but it's going to have to
wait until someday(hopefully soon) when I can retire from the dreaded 9to5.

Best regards to all my the Twin fans out there!
 
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Glad everything is coming around for you. The float needles will accumulate fuel deposits causing them to stick or leak. Usually knocking on the float bowls with a screwdriver handle when first filling them fixes the sticking. Adding Sta-Bil or Sea Foam to the fuel will help clean them.
 
I got so fed-up with things like that I just run sta-bil marine grade year round, every fill up. It helps to drop the bowls at the end of the season and get rid of any crud that accumulates at the bottom.
 
Glad everything is coming around for you. The float needles will accumulate fuel deposits causing them to stick or leak. Usually knocking on the float bowls with a screwdriver handle when first filling them fixes the sticking. Adding Sta-Bil or Sea Foam to the fuel will help clean them.

I got so fed-up with things like that I just run sta-bil marine grade year round, every fill up. It helps to drop the bowls at the end of the season and get rid of any crud that accumulates at the bottom.

Thanks for the suggestions guys, I will try some of that sta-bil or sea foam, as gummed up carbs I have learned is a major problem. I felt like I was doing open heart surgery on the things to get the gunk out.
 
Thanks for the suggestions guys, I will try some of that sta-bil or sea foam, as gummed up carbs I have learned is a major problem. I felt like I was doing open heart surgery on the things to get the gunk out.

Marine grade is cheaper per oz and requires less. It has a fill line spout thing on it. Just hold until it reads 1/4 oz then dump it in per 2-5 gallons of gas. If you go a bit over it won't hurt anything. Been doing this for a couple of years now and no problems. Best thing to do is drain the bowls, remove the petcock and drain the tank. Put that gas in your car. Then fill it up fresh at start of the season. But the sta-bil helps if you're lazy and forget.

I've tried Seafoam in the past, doesn't seem to help. The Lucas ethanol treatment and others also seemed to do nothing.
 
Some updates on me ... And I have to fix
the switch arrangement on the front brake lever, it has some free play in it and the brake
light will stay on unless I bump it forward. I had jammed a piece of rubber in there as a
solution last year but that fell out and I need to fix that better.
So I believe my problem here is the spring in the master cylinder, it needs to push that lever
so it closes the brake light switch off, with no adjustment possible to take up slack. I took
the lever off and looked it over, looks like the dust boot has got a crack.
I then found some useful master cylinder info here on VHT, Wheels, Tires and Brakes, and a few other
sources. I will start with disassembly of this master cylinder, check the condition of it and spring.
Maybe I can just stretch that spring out back to size. And this might be a good chance to try and
flush the line down to the caliper and get some fresh fluid in it.
 
So I believe my problem here is the spring in the master cylinder, it needs to push that lever
so it closes the brake light switch off, with no adjustment possible to take up slack. I took
the lever off and looked it over, looks like the dust boot has got a crack.
I then found some useful master cylinder info here on VHT, Wheels, Tires and Brakes, and a few other
sources. I will start with disassembly of this master cylinder, check the condition of it and spring.
Maybe I can just stretch that spring out back to size. And this might be a good chance to try and
flush the line down to the caliper and get some fresh fluid in it.

Is it possible the brake light switch is pushed too far into the hole in the perch? (if it uses that style) I bought the aftermarket version switch for my 450 and found it slid too far into the perch and the light was on all the time as well, had to super glue it in position.
 
Is it possible the brake light switch is pushed too far into the hole in the perch? (if it uses that style) I bought the aftermarket version switch for my 450 and found it slid too far into the perch and the light was on all the time as well, had to super glue it in position.

I don't think it has any adjustment, there is a plastic pin that fixes it in one place, only a single screw holds it on. I took a few pics. I probably should have made a new post under brakes, if you want I will try to tackle that, I'm guessing moving posts around to appropriate places is a bit of work for you. Or if you have any suggestions on posting etiquette, feel free to holler.

So you can see the switch is small plastic momentary, with built in spring pushing it out, very small travel. The lever has a knob on end that pushes the master cylinder in, and when you let go it needs to spring out and push in that momentary switch in.

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ADD: I suppose it could be calipers pads are getting too small, worn, and if replaced with new ones of right size this might be the solution.
 
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I wasn't sure if it had the same style switch and now that I see the design, I realize and remember the difference. In your case, I think it's the master cylinder itself, gummed up inside a bit and the piston not full returning to the released position giving you lever slack that allows the switch to stay on. I've owned older Hondas with that style master cylinder and the internals can get sludged up enough that the piston doesn't move as freely as it should while still functional despite really needing to be rebuilt.
 
Probably need a new switch but you could glue a spacer pad on to the lever in the meantime.
Looks like a spacer will work fine the lever has a flat spot that presses the switch in, so I can just attach spacer and can always removed if a better fix found.
Probably a good to disassemble and look over the master cylinder for other reasons. Appears that I could replace the whole thing for under $50 if things
go wrong. I'm going to detach the calipers and try pressing in the pad, see if that takes up the slack.
 
So I took the caliper apart and cleaned it. When I squeezed it open it did push the hand lever back and take up the slack, pushing in the brake contact switch. Clean it up, put back together and it still has too much free slop in play before braking action, and this slop prevents the brake switch from dis-engaging. The pads look like they have enough thickness left to them. These systems have to allow for brake pad thickness change. I would think by some one way valve that allows it to pump up, but not to much down, something like that. I would think this valve would be part of the master cylinder. So next plan of action is to disassemble, clean, inspect that, and open bleed valve and flush it out.

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There are two holes in the reservoir floor, one lets more fluid in to be pumped, the other is very tiny and is the pressure release, so that it does not just continuously pump tighter.

When you take apart the master keep track of the order and direction of each little piece. If you even reverse something, it may not work right. My 78 Hawk 400 had the same master, it looks like. It was a total loss, pitting in the bore. I bought an aftermarket Rebel 9/16 (14mm) bore unit but had to grind the tip that pushes the master piston because the lever reach was just ridiculous, and then shim to limit the resting position of the lever. Finally had to fiddle with positioning of the switch to work at the right spot.

The pressure release gets clogged easy. I hope yours cleans up good. The caliper piston rides out further as the pads wear.
 
Looks like a spacer will work fine the lever has a flat spot that presses the switch in, so I can just attach spacer and can always removed if a better fix found.
Probably a good to disassemble and look over the master cylinder for other reasons. Appears that I could replace the whole thing for under $50 if things
go wrong. I'm going to detach the calipers and try pressing in the pad, see if that takes up the slack.

Before you take down your master use the lever to pump out the caliper piston or you'll be using compressed air to get it out. It needs to come out to clean all the junk in the caliper body, and the seal groove. You may consider getting a new hose too they get soft and spongy inside from age, even can swell shut over time. New hose gives a good solid feel.
 
If you're going to take plunger out you might as well replace the plunger itself as the seal may get boogered up in the process:

https://www.davidsilverspares.com/CM400A-AUTOMATIC-1981-USA/part_166040/ -- Aftermarket plunger kit
https://www.davidsilverspares.com/CM400A-AUTOMATIC-1981-USA/part_116876/ -- Reservoir o-ring. These do go bad and then it can slowly leak into the threads and elsewhere.
https://www.davidsilverspares.com/CM400A-AUTOMATIC-1981-USA/part_116866/ -- Caliper piston. If your piston has pits on it you should replace it, however I will say if it's just a tiny pit then you can get away with it. Someone here may not like that statement and say you should replace it no matter what, but if funds are tight and it's a lone pit by itself and the brake action is OK I say you can get away with it for now.

I just switched the brakes on mine to DOT5/Silicone recently. It's easy to do if you have a vacuum bleeder tool. One way of doing it is removing the entire brake system and cleaning it out with acetone or denatured alcohol then use a heatgun to force dry residual and let the hose dry out naturally over night. The other method is using the vacuum bleeder to vacuum out any remaining glycol in the system at the bleeder, vacuuming out the residual glycol at the reservoir then do a flush with the DOT5. If you do the flush method you will be fine. It's OK to have a very minute amount of glycol remaining in the system and doing 2 or 3 reservoir flushes will be OK. Tom was saying when he used to do it for police fleet vehicles they more or less did the same thing... just flushed it and it worked fine.

If you flush it out, then use the vacuum bleeder and do about 2 or 3 reservoir top offs you will have a firm lever feel like before. Put some DOT5 in it and never look back with having to deal with brake bologna ever again. The spongy lever, etc. is all myth.

Regards to the switch, I had mine go bad years ago because the master cylinder plunger developed a small leak and was leaking into the switch and actually was slowly melting the tip on the switch.
 
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