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I need a mechanic Southern Indiana---CM400A

khatton

Member
Joined
Jun 30, 2022
Total Posts
15
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0
Location
Evansville
1981 CM400A with 17k miles. I had all new gaskets, tires, chain, fork seals, petcock, oil and filter in 2014 when I bought it with 3500 miles. I rode it like crazy for a few years, new ceramic brake pads and switched to dual cylinder, had a tune up done and oil change while I was in Florida in 2019 but now it's been sitting. I haven't put 500 miles on it since then. The retired Honda mechanic that did the previous work is no longer available and not one of the shops in town will touch it due to age/liability. What's a person to do?

It still leaks oil as most old Honda's do, I'm not worried about that as I check it all the time. It needs an oil change and new plugs, it won't idle while I'm stopped so I had to use throttle and brake both to get it home last time out a couple weeks ago. I'm assuming that's carb related??
I also noticed my rear lights come on solid but won't blink, my brake light is fine, I have no headlight or front lights/turn signals.

I have the tools, the space, the service manual and owner's manual but I'm chicken. I'd rather pay someone that knows what they are doing instead of screwing it up and making it a large garage decoration. I'm now physically able to ride it more (thanks to a new doc and new physical therapy); even a couple hundred miles trip but not until it gets some TLC.

Can anyone advise me on the best plan of action locating a mechanic?
Thanks,
khatton
 
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I've been to Evansville a few times for a music fest - nice town :) I'd maybe check with shops in town to see if they know of any guys around who are into older Hondas. It does pay to have someone with the proper knowledge. You will get offers of help here, but if carbs need going through you'd best send them to an expert or haul the bike up to Bloomington or Indy. I picked up a 400A myself a while ago and sent out the carbs for rebuilding with good results. Still sorting the rest of it out after a 30 year nap! (the bike, not me, ha ha) Good luck and welcome aboard, Ron
 
If you can't find someone we can totally guide you through the maintenance on here. The oil change and plugs are pretty simple to do. Any basic, cheap metric 1/4" socket set will do... even the harbor freight ones. If lights stay solid and are not blinking it could be a bad turn signal relay. They are cheap and you can get them from any auto parts store. Only two wires, it's in the left side cover. If head light and front lights aren't working check the head light fuse on the left side cover. It could also be a bad ground in the headlight assembly.

Bad idle could be caused by many things. Could be carb related, but could also be the stator or CDI causing funny running. On the CM400A's there are two drain plugs at the bottom of the bike for draining out the oil blow-by. If you don't pull these plugs out at least once a year (or just ride without them) sludge builds up in the airbox and makes it run poorly. Check for two larger black hoses at the bottom of the bike, near the center stand. If they have plugs, pull them out (do it outside or with a drain pan) and very likely a bunch of sludge will come out. Take the seat off, and you will see an air duct with 3 screws. Remove the 3 screws and look inside make sure there isn't a bunch of that sludge in there and inspect your air filter. Make sure there isn't a mouse nest in there (happened to me and others multiple times before, especially if the bike has been parked a long time).

If you need pictures of any of this let me know. I have a 79 CM400A so the bikes are basically the same, the main difference is your carb has some newer EPA features that mine did not.

What service manual? If you're using the Clymer it's OK for the tune up procedures, but likely has some incorrect info on engine rebuilding which sounds like you don't want to do so it shouldn't be a total loss. We have PDF copies of the official factory service manuals here.

The gas you've been running... have you been using fuel stabilizer in the tank? If not, and it's sat for more than like 3 months (some say as little as a month or even a couple of weeks, but I've noticed you can get away with a few months just might not run well) then the gas probably broke down and gummed up the idle jet passages in the carbs.

Oil leaks, particularly from the head are unfortunately kind of normal. Especially if aftermarket gasket kit were used. Mine weeps as well, and I just keep an eye on oil level. So as long as it's not getting into things causing a fire hazard and you're not losing tons of oil you can get away with it for quite some time.
 
Finding a shop for anything more than 15 years old or so can be difficult. Fortunately the maintenance needed for these models is pretty simple stuff.
I'm curious about the oil leaks, the most common are the oil filter cover and the valve cover. The oil filter is easy, just needs a new O-ring when the filter gets changed. The valve cover is usually caused by the two bolt grommets in the cover having dried out and shrunk so the clamping pressure on the gasket isn't enough. Do not try to tighten those 2 bolts, you can check that they are tight but that's it. They are a shouldered bolt that stops when the shoulder hits the rocker arm stand, tightening more will shear them off.
 
Finding a shop for anything more than 15 years old or so can be difficult. Fortunately the maintenance needed for these models is pretty simple stuff.
I'm curious about the oil leaks, the most common are the oil filter cover and the valve cover. The oil filter is easy, just needs a new O-ring when the filter gets changed. The valve cover is usually caused by the two bolt grommets in the cover having dried out and shrunk so the clamping pressure on the gasket isn't enough. Do not try to tighten those 2 bolts, you can check that they are tight but that's it. They are a shouldered bolt that stops when the shoulder hits the rocker arm stand, tightening more will shear them off.

Ah yeah, totally forgot to mention the valve cover grommets. Pretty sure none of the aftermarket gasket kits include this either so it's probably very common to miss replacing them. The part number is 90441-413-830 you'll need two. You can get them from a variety of places. One is Partzilla, https://www.partzilla.com/product/honda/90441-413-830. The other is David Silver Spares, https://www.davidsilverspares.com/parts/by-part-number/partnumber_39920. If you have a local Honda Dealer you can call them and have them order this part. That's probably the cheapest way to go as ordering it online from either of those two vendors will likely incur an $8-$10 shipping fee just for a couple of small parts.
 
I have the Honda service manual, I ordered it from Honda a few years back and they printed it for me, was a little over $60.
It covers '78 CB400T, CB400A; '79 CB400T, CM400T, CM400A; '80 CB400T, CM400T, CM400A, CM400E; '81 CB400T, CM400T, CM400A, CM400E AND CM400C.
I have a '81 CM400C parts bike incl 2 seats and everything but a title, half a frame, gas tank, CDI. If there is anything I need, I probably have it and just don't know it.
I understand some things have to be replaced, others can be refurbished/rebuiltwith time and knowledge. I work again tomorrow but off 5 days after that and will have time to do one thing at a time coming back here for help as needed. I've worked on old cars but never an old bike .
thanks,
khatton
Honda service manual pic.jpg
 
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I have the Honda service manual, I ordered it from Honda a few years back and they printed it for me, was a little over $60.
It covers '78 CB400T, CB400A; '79 CB400T, CM400T, CM400A; '80 CB400T, CM400T, CM400A, CM400E; '81 CB400T, CM400T, CM400A, CM400E AND CM400C.
I have a '81 CM400C parts bike incl 2 seats and everything but a title, half a frame, gas tank, CDI. If there is anything I need, I probably have it and just don't know it.
I understand some things have to be replaced, others can be refurbished/rebuiltwith time and knowledge. I work again tomorrow but off 5 days after that and will have time to do one thing at a time coming back here for help as needed. I've worked on old cars but never an old bike .
thanks,
khattonView attachment 16558

CDI from the CM400T/E/C won't work on the CM400A. Seat, tank and outer frame parts such as wheels and brakes will work and the ignition coil. The cylinder and carbs will be useless to you. If your CDI goes bad I make repros for the Hondamatic.
 
The cylinder and carbs will be useless to you.

Thank you very much. I was actually thinking I'd have the extra set rebuilt and then swap them out. I bought a set of 2 re-build kits already thinking a family member might do it but they don't really have the time.

khatton
 
The Carbs for the CM400 A were only made by Honda one year for that model . I dont believe the carbs on your parts bike will work on the A model. You can buy the correct carb kits from Sirius Consolidated.

Bill H
 
The Carbs for the CM400 A were only made by Honda one year for that model . I dont believe the carbs on your parts bike will work on the A model. You can buy the correct carb kits from Sirius Consolidated.

Bill H

Carb kits are universally bad. Just buy the OEM float needles if needed. The brass rarely wears out that extreme where it would warrant replacement.

You can still get the OEM gasket kit for the carbs from DSS.
 
The VB24 carbs come in A, B and C variants. They are interchangeable between the A models including the 450A. The VB24A carbs found on 1978/79 models do not have an accelerator pump so the B or C versions are a better choice. 1980 saw the advent of non-adjustable floats which require the Honda float needle to get the correct height, aftermarket ones are either too long or too short.
I recommend that anyone with the non-adjustable floats convert back to the early Black floats from 1978/79 which allows for adjusting and can make use of the cheaper aftermarket float needles, only buy the Viton tipped ones.
The VB24 carbs are a smaller external diameter so swapping in the larger manual transmission carbs, VB21/22, cannot be done. People have tried using the manual trans carb insulators with the larger carbs on the A models w/o any success. The engine is over carbed and doesn't respond well.
 
As LDR said the 81 CM400A has the VB 24 C carb. The carb kit for those from Sirius is OEM and are made in Japan. The kit includes the needle jet set, idle screw with the spring ,o-ring, and small metal washer, pump diaph with spring and pump set rubber ,air cut valves with spring and o-ring, float valves for fixed and adjustable floats ,needle set holder , 68,112 , and 35 jets, complete gasket set and o-rings. The only thing missing is the rubber plug which as LDR said are common and on the net. The cost of the kit from Sirius is $70.00.

If you use the sticky from LDR as a guide you should be able to rebuild your carbs.


Bill H
 
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Take the seat off, and you will see an air duct with 3 screws. Remove the 3 screws and look inside make sure there isn't a bunch of that sludge in there and inspect your air filter. Make sure there isn't a mouse nest in there (happened to me and others multiple times before, especially if the bike has been parked a long time).

Air filter looks great, it was changed in 2018 and I know that's 4 years ago but it hasn't been ridden much at all. No sludge, no mice; there is a very thin plastic piece that is wavy doesn't look like it has a job but must do something? There was oily gas in the bottom, is that bc I left the petcock open or ??

The VB24 carbs come in A, B and C variants. They are interchangeable between the A models including the 450A. The VB24A carbs found on 1978/79 models do not have an accelerator pump so the B or C versions are a better choice. 1980 saw the advent of non-adjustable floats which require the Honda float needle to get the correct height, aftermarket ones are either too long or too short.
I recommend that anyone with the non-adjustable floats convert back to the early Black floats from 1978/79 which allows for adjusting and can make use of the cheaper aftermarket float needles, only buy the Viton tipped ones.
The VB24 carbs are a smaller external diameter so swapping in the larger manual transmission carbs, VB21/22, cannot be done. People have tried using the manual trans carb insulators with the larger carbs on the A models w/o any success. The engine is over carbed and doesn't respond well.

Appreciate that info but it is so far over my head it might as well be in Japanese.

The headlight fuse was blown, there were 2 extras in the cover so that was an easy fix. The other lights did not come at all but I have removed the rear fender, disconnecting the rear wiring so I'm assuming since there isn't a complete circuit that they will all work when I put it back together.

Oil has drained, can't find the filter I bought 2 years ago so ordered a 2 pk from amazon. I'm going to go ahead and put the cover back on/bolt back in so I can give her a bath.
I didn't realize how much she needed a clean-up. Since there's no dumb questions if I cover/keep the wiring dry, can I just spray foam cleaner everywhere else, wash her up and rinse her off with mist from the hose? There's a little rust here and there so I'd like to see how much might be hiding under the dust and dirt. I cleaned the chain with spray parts cleaner to remove all the gummy gunk, gonna scrub with brush tomorrow to remove the surface rust then check how much play there should be before I lube it back up.

Thanks for the help.
khatton
 
The oily gas in the air filter is because no one pulled the drain plugs on the air box, should be done every oil change.
GEDC2511.jpg GEDC2510.jpg
You'll want the drain pan under them before pulling them, remember to put them back in.
 
The oily gas in the air filter is because no one pulled the drain plugs on the air box, should be done every oil change.
View attachment 16662 View attachment 16663
You'll want the drain pan under them before pulling them, remember to put them back in.

Yes, that oily gas is what I call sludge. Mostly because by the time you notice the really poor running and pull those plugs it can be gross blowby sludge that comes out. Especially if its never been done.
 
I'll pull those in the morning. I forgot to ask about my gas tank. It actually looks pretty clean but the last few dregs of gas that I drained were dark and when I shook the tank I heard a little rattle. I did run seafoam thru it in the last 2 gallons before emptying it. Should I leave it or treat it and if treating, what do I use?
 
Drain plugs on the air box were pretty nasty. I left them open all day, poured some Seafoam thru them and put plugs back in this morning, oil filters are here so that job is done. Found a couple cotter pins needing replaced, did that. Still no front marker lights and the rear ones are on solid so I'll be lookinga at the relay next. She's had a decent bath and some minor rust removed, there's alot of white oxidation but I can live with it for now unless someone has a really good product they recommend besides elbow grease.

I'll be making a new seat cover tomorrow/this week as I already drafted the pattern several years ago and the duct tape repair isn't holding up.

I feel pretty accomplished with all the help. Thanks!!
 
...

I have the tools, the space, the service manual and owner's manual but I'm chicken. ...

Oh yeah? I can't repair a seat, let alone draft a new pattern. But you can! And you can turn wrenches also. Here's where I draw the line: Did today result in ANY positive improvement, even if I identified a new setback? If the answer is yes, i keep moving, which means moving the peg forward. What are my options? A man is wealthy not from cash but from options.

I'm tackling a new steering rack in our 2006 Honda Pilot. Never done it before on any car, but the concepts of turning wrenches is universal. So far it's been pretty miserable, with each session wondering how much it's going to cost to get it towed out of my garage on 4-wheel dollies because there's now no way to drive or push it anywhere. Each insurmountable obstacle has been so far overcome with patience, trying to new things, waiting and reevaluating. Sometimes with new tools purchased, etc.

Each YouTube video shows a different technique, and following the Honda service manual isn't an option. But by chipping away at the impossible we're getting it done. Now I have new lines ordered ... in for a penny in for an extra $240 in parts ... because I do not want to have to do any of this again on this vehicle. And as of yesterday, I can the light at the end of the tunnel.

Reduce projects to bite-size tasks, and tasks to whatever method or technique works, stay focused and methodical. You can do all of this but it's overwhelming when considering everything all at once. Don't do that to yourself. Pick a priority, even if it's just working from a checklist of stuff you want done. And then on to the next.
 
Fixing up an older bike is like eating an elephant, one bite at a time.
Might check those front light units to see if someone used rears instead. Look in the socket for 2 little slugs. If there's only 1 in the center than it's a rear light unit. 2 means it's right.
 
Did today result in ANY positive improvement, even if I identified a new setback? If the answer is yes, i keep moving, which means moving the peg forward. What are my options? A man is wealthy not from cash but from options.

Thanks for the vote of confidence, positive thinking trumps being a chicken.

And here I am again...didn't get any seat work done due to kids coming to visit but I did change the relay and I have rear turn signals but the front ones don't even come on. I already checked and replaced the headlight fuse and the other two were good. Checked the bulbs, both were shot; back to the store for new bulbs.
Now, headlight good, front lights good and front turn signals good; rear turn signals and brake light good but no tail lights.

Started her up, heard very minor noise/backfiring then the longer she stayed running it backfired out the left side by the carb and I saw smoke. Turned it off and quit for the day.

khatton
 
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Finally found some tinkering time, carbs almost off. Having trouble with the 3 cables but help on the way. The intake boots (are these the above mentioned insulators?) disintegrated when I finally got the carbs loose but the air box boots are still in useable condition, they were more flexible so didn't crack or chip off.

So, gonna have to order the intake boots plus I'd like to get an assortment of the JIS screws to replace the rusty ones as I go. Not all of them need replaced so an assortment would be good to have on hand.
 
Remove the carbs out the left side with the cables attached. Then remove the cables. Sounds awkward and it is but still easier than doing them in situ.
Yeah, carb insulators are the head to carb boots. Not surprised they came apart on you.
 
I had them out the left side but wasn't sure how to unhook them, just kept tinkering til one came loose so finally got cables off. I don't think they look that bad as I was expecting them to be covered in residue/grime/soot but son-in-law said it's probably clogged down into the holes/ports/openings. They are going to the ultrasonic cleaner/soaker then will be taken apart for further cleaning.

hc1.jpg hc2.jpg hc3.jpg hc4.jpg hc5.jpg hc6.jpg hc7.jpg
 
What is this set? VB24 CARE3 ?

They came with the parts bike I bought that was supposedly an 81 CM400A, same as mine. But the remaining frame is marked 81 CM400 C or T I can't recall atm, but not A. I have so many boxes of parts that I don't know if they'll fit or not. I'm really not a dumba**, I spent either $100 or $125 and I know I have some htf extras like the side covers. One of these days I'll get my grandkids over to help sort, organize and look for part numbers.what carbs are these.jpg
 
I don't like that float system Honda/Keihin came up with starting in 1980. It's non-adjustable which means you have to buy the expensive Honda float needle to get the correct float level. Aftermarkets are either too long or short.
I convert all of those over to the VB21 floats and needles which allow me to find aftermarket Viton tipped float needles and be able to adjust the float level. The early float and needle cost about the same as 1 late style float needle.
 
The floats themselves are probably fine, you need the float NEEDLE. If there's no cracks in the plastic and they actually float in gas then they're OK to re-use.

When you take the float off use a punch or a really tiny nail, etc. and a small hammer to push the pin out. DO NOT USE VICE GRIPS/PLIERS TO REMOVE THE PIN OR YOU WILL GOOF UP THE PIN AND IT MAY CRACK PART OF THE CARB BODY ON REASSEMBLY.
 
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