1979 Honda CM400A tune up

Like Jim said. I just went through this on ToniAnn's bike and Jim's advice was able to give it enough space to center the wheel and not have it rub.

In regards to the USB charger, does it have an in-line fuse? If not, add one.

Sorry to hear about burning your leg and almost dropping it. Been there plenty of times, but never with a dog coming out to bite me!
 
And if you're looking for a phone mount this one is pricey, but very nice: https://www.amazon.com/RAM-MOUNTS-RAM-B-149Z-UN10U-Handlebar-Coated/dp/B00JUWB6SO

They also have specific sized ones for phones on their site: https://rammount.com/

Doing it that way, you can buy the components separately. If you get one and stay with the "X" design mount, just make sure you get an extra "web" piece and glue the side rubbers. Otherwise, works well. I even have one that is specifically for my GPS for long trips. I got an old Nuvi 2597 for peanuts on eBay, and it's specific ram mount, then I program the long trip into their software on a laptop. You can then customize it for motorcycle trips or map it out yourself. Works great.
 
AmiraliM said:
4. How do I lube the cables? I tried one and the lube doesn't seem to want to go in where it needs to go. How many cables are there? Do I lube both ends?
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Did the mechanic do this for you?

You can lube cables with any spray can lube and some duct tape. Tape up one end of the cable around the spray tube so you can pressurize one side. Spray until the lube drips out of the other side.

You can buy a tool to take the place of the duct tape. I have both of these because of the Valkyrie, the cheaper one should be good enough. They are not needed for speedometer cables, at least not for my Motion Pro cable, because the cable snake is removable.

https://www.amazon.com/Motion-Pro-08-0182-Cable-Luber/dp/B0012TYX9W
https://www.amazon.com/MOTION-PRO-Cable-Luber-V3/dp/B072WFYF6X
 
The throttle cables just loosen the two screws under the throttle assembly and the top cab pivot out of the way. You can simply spray the lube and work it back and forth until it drips out the other end of the carbs.

Choke there's not much you can do. You can remove the choke lever by loosening the nut on its holder at the handle bars and let it fall down. Lift the choke know up and pull it out of the bracket. From here you can pull the lever out and spray down it.

The parking brake, loosen the adjuster entirely and spray lube. If you can't get it out enough to get a tool in there don't worry about it. Its a real pain to get it removed from the other end. Just keep spraying it with the nozzle and working it until it gets a good feel. Not a critical control cable imo.

Fwiw, I use pj1 cable lube. Can get it online, but most powersports dealers sell it locally for the same price.

If funds are tight just get a cheap bottle of motor oil. You can just pour it in the throttle assembly and keep working it.
 
Nobody replied about your fuel line (whoops!). Get 5.5mm fuel line from the dealer and ask for the clips. Don't bother with the 1/4 inch stuff for lawn mowers. It might fit, but requires the worm gear clamps and they need to be on very tight or they will leak.
 
Hey Amirali,

Just checking in. Is the bike still running well? Have you been able to get any of the other tune up procedures done on your list?
 
Hi guys, hope everyone is well.

Update:

I changed the brake fluid and the reservoir diaphragm. The tires were changed by the mechanic and are working fine for the most part.

The only issue is that when I have a passenger, and we go over a bump, the rear tire scrapes against the rear plastic fender. I have put the shock absorber on the highest setting but this is still an issue with potholes and such. Any ideas? Should I cut the bottom part of the fender off?

Another issue I have is the speedometer. Unfortunately, the needle is jumping ALL over the place. I lubed the cable throughly with pj1 cable lube but the needle is still jumping. Any ideas how to fix this?
 
You're talking about the rear suspension bottoming out with a passenger. You need new shocks. The max load out for the CM series is 400 lbs. GVW=800 - Bike weight = @400 equals the 400 lbs. load.
I like Progressive Suspension shocks. https://www.progressivesuspension.com/products/2697/1981/honda/cm400acet Note there's standard and Heavy Duty springs available so I'd suggest a phone call to them to discuss which would be more suitable.
 
LongDistanceRider said:
You're talking about the rear suspension bottoming out with a passenger. You need new shocks. The max load out for the CM series is 400 lbs. GVW=800 - Bike weight = @400 equals the 400 lbs. load.
I like Progressive Suspension shocks. https://www.progressivesuspension.com/products/2697/1981/honda/cm400acet Note there's standard and Heavy Duty springs available so I'd suggest a phone call to them to discuss which would be more suitable.
Click to expand...

Thank you very much for this. The issue is that my passenger and I don’t even weigh 300lbs combined. This was not an issue with the old tires but I think the new ones are too big

Shall I still change the shocks?


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I bought a pair of TEC shocks for my bike. You can get them for $80 and it is a direct replacement. Unless you have experience taking apart shocks, just get a new pair and be done with it.
 
2 up at 300 lbs means you can use the standard spring.
For the tight budget I'll point you at these shocks https://www.tecbikepartsusa.com/HONDA_CB400T_CB400TI_CB400TII_Shocks_Hawk_Super_p/j-sh20-hcb400t.htm Same shocks DennyK mentions and I have them on my CB400T1.
By too big a rear tire I'm guessing you have the 130/90/16 size. The original size 4.60-16 equates to a 120/80/16, narrower with a lower profile. Not much you can do there since finding the original size or even a 120/90 is tough.
 
Maraakate said:
If you're careful, yes.

I have instructions on how to get it apart here: https://www.vintagehondatwins.com/forums/showthread.php?8561-Replacing-odometer-glass-or
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Hey Amirali,

My speedo still works fine, but I ordered 30,000cc differential oil and will take mine apart in a week or two to show you how to do it and make a guide. I need to do it to my CB550K anyways (likes to bounce about a 5mph range at highway speeds), so will be a good way to test it on multiple speedometers.
 
Maraakate said:
Hey Amirali,

My speedo still works fine, but I ordered 30,000cc differential oil and will take mine apart in a week or two to show you how to do it and make a guide. I need to do it to my CB550K anyways (likes to bounce about a 5mph range at highway speeds), so will be a good way to test it on multiple speedometers.
Click to expand...

30 liters sounds like an awful lot, is that a typo?
 
stl360+450 said:
I think it's cst rather than cc. It looks like cst is centistokes, a unit for viscosity.
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Probably, but for some reason everywhere I see these oils for sale and in conversation (it's also used for tonearm dapening in turntables) they list the weight as ccs.
 
I gave it a try on the 550 speedometer which likes to bounce around a bit between 50-60mph and also bounces when you get near 8-9K RPM during a shift.

It's kind of difficult to get the top part off. It's sort of crimped in there and you have to mount that part in a vice and lightly hammer to get it off in order to get access to the dampener.

The plastic stoppers for the numbers are also delicate. Sometimes you get away with it, other times you don't. This time I did not for the trip meter.

Either way, I got the cap off for the dampener and put the oil in it. Made a little bit of a difference, but not much. Wasn't worth making the speedometer worse. Face also cracked on reassembly. Not a huge deal to get another face for the 550s but it IS a big deal for the 400s as I don't know anyone who makes repros.

I'll just source another speedo at somepoint for myself and rely on a GPS mount for now. But for Amarali, I suggest not taking it apart and sending it to an expert or finding another one. Unless you don't care that it's broken and want to give it a try. I was careful and still broke some of it. You also have to be careful for that clock spring and there's a mark on the bell housing for the needle alignment. You have to hold that at the alignment mark and put the needle back at the stopper position or it will be off. Best to test going up and down the street with a GPS. It will be a compromise no matter what as these speedos have ranges where they are more accurate than others (typically highway cruising speed).
 
even after my speedo rebuild, my needle jumps a little and is around 3-6 mph off gps speed.
 
Maraakate said:
I gave it a try on the 550 speedometer which likes to bounce around a bit between 50-60mph and also bounces when you get near 8-9K RPM during a shift.

It's kind of difficult to get the top part off. It's sort of crimped in there and you have to mount that part in a vice and lightly hammer to get it off in order to get access to the dampener.

The plastic stoppers for the numbers are also delicate. Sometimes you get away with it, other times you don't. This time I did not for the trip meter.

Either way, I got the cap off for the dampener and put the oil in it. Made a little bit of a difference, but not much. Wasn't worth making the speedometer worse. Face also cracked on reassembly. Not a huge deal to get another face for the 550s but it IS a big deal for the 400s as I don't know anyone who makes repros.

I'll just source another speedo at somepoint for myself and rely on a GPS mount for now. But for Amarali, I suggest not taking it apart and sending it to an expert or finding another one. Unless you don't care that it's broken and want to give it a try. I was careful and still broke some of it. You also have to be careful for that clock spring and there's a mark on the bell housing for the needle alignment. You have to hold that at the alignment mark and put the needle back at the stopper position or it will be off. Best to test going up and down the street with a GPS. It will be a compromise no matter what as these speedos have ranges where they are more accurate than others (typically highway cruising speed).
Click to expand...

You maybe aware of this place who has a variety of glass lenses new for various models, just not the CB400 ones specifically. There maybe a set of lenses that are from another gauge that will substitute???

I used his services for the restoration of the CB350F gauge set a while back. He refilled the dampers as part of the process.

I have been into many gauges for various Honda's over the years for refacing the faded faceplates for full bike rebuilds. I will be interested in seeing the damper rebuild/refill especially.

https://www.cb750faces.com/en/28-honda-cb550-four
 
Flyin900 said:
You maybe aware of this place who has a variety of glass lenses new for various models, just not the CB400 ones specifically. There maybe a set of lenses that are from another gauge that will substitute???

I used his services for the restoration of the CB350F gauge set a while back. He refilled the dampers as part of the process.

I have been into many gauges for various Honda's over the years for refacing the faded faceplates for full bike rebuilds. I will be interested in seeing the damper rebuild/refill especially.

https://www.cb750faces.com/en/28-honda-cb550-four
Click to expand...

Yes, I was planning to get a set faces from this vendor. He apparently does good work.

However, with the CB400 he does not make them but it's possible one of the other faces he sells does work. The 400A is unique, it has green curves to indicate what gear to be in for 1 and 2.

I already put the speedo back together, but I can pop it apart again to show you. There's not much to see. Basically I took the face and needle off, then put the assembly in a vice. Take a 7mm socket to remove the nut for the dampener/needle assembly of the top plate. With a flathead and hammer I tapped on the edges to pop the top plate off. This is harder than it sounds because of the crimp/stake-like configuration it uses.

Once you get this far, you must very carefully lift up and be mindful of the coil spring orientation. It may unwind a couple of times. There is a small clear rubber cover over the dampener. Take it off, and I just pumped new oil in there. Put it back together. This is the part that easy to mess up and I knew this from before but forgot since it's been a long time. There are plastic pieces on the numbers for where it "stops". These MUST align with that top plate. The "bottom" of it for the total mileage "plugs in" to the plate. The "top" of the odometer "plugs in" to the plate. After you do this then flip it upside down. I put the same oil in the bell housing.

Calibrating the speedo is slightly annoying, but I noticed on mine there was an alignment mark. It appeared they put a red check-mark where the alignment is. When I held the bell housing where the check mark was to hold it at that starting point I then rotated the needle to set it back to 0. Let go and then flip the needle up with your finger to see if it returns. Go for a ride with the top cover off and adjust accordingly.

There's probably a more complete way to get that dampener apart. I was unwilling to go that far. I do have a junk CB500 speedo, which is smaller and not usable for me, maybe I can try and get that one further apart to see if it makes a difference.
 
dougrun said:
even after my speedo rebuild, my needle jumps a little and is around 3-6 mph off gps speed.
Click to expand...

I have heard anecdotes that getting new rubber grommets for the 10mm mounts and a new cushion helps. Apparently these get hard/shrink and they serve to dampen the vibration which makes the needle jump. This sounds like it could be true, because at least on my 550 it works pretty well until you get to about 45-50mph or if you rev it high then shift. However, how much it really makes a difference I cannot say. The problem I had with testing it on the bench is that the drill could only spin it up to about 25mph.

I see no reason that you couldn't try to make your own cushion by using that self-sealing silicone tape, i.e. "rescue tape" to wrap the speedo and then put the used cushion around it to make it tighter and see if it helps. It would be hidden and still look original. However, the cushions are still available from Honda.
 
Cross referencing the fiche to see what the cushion fits it appears it does fit a 77 CB400F Super Sport, CB350, CB360/CL360. So the CB400F face plates may fit the CB400 twins. You'd have to measure and contact the vendor to see if the size is the same. No idea as I don't have the bike.
 
Maraakate said:
Yes, I was planning to get a set faces from this vendor. He apparently does good work.

However, with the CB400 he does not make them but it's possible one of the other faces he sells does work. The 400A is unique, it has green curves to indicate what gear to be in for 1 and 2.

I already put the speedo back together, but I can pop it apart again to show you. There's not much to see. Basically I took the face and needle off, then put the assembly in a vice. Take a 7mm socket to remove the nut for the dampener/needle assembly of the top plate. With a flathead and hammer I tapped on the edges to pop the top plate off. This is harder than it sounds because of the crimp/stake-like configuration it uses.

Once you get this far, you must very carefully lift up and be mindful of the coil spring orientation. It may unwind a couple of times. There is a small clear rubber cover over the dampener. Take it off, and I just pumped new oil in there. Put it back together. This is the part that easy to mess up and I knew this from before but forgot since it's been a long time. There are plastic pieces on the numbers for where it "stops". These MUST align with that top plate. The "bottom" of it for the total mileage "plugs in" to the plate. The "top" of the odometer "plugs in" to the plate. After you do this then flip it upside down. I put the same oil in the bell housing.

Calibrating the speedo is slightly annoying, but I noticed on mine there was an alignment mark. It appeared they put a red check-mark where the alignment is. When I held the bell housing where the check mark was to hold it at that starting point I then rotated the needle to set it back to 0. Let go and then flip the needle up with your finger to see if it returns. Go for a ride with the top cover off and adjust accordingly.

There's probably a more complete way to get that dampener apart. I was unwilling to go that far. I do have a junk CB500 speedo, which is smaller and not usable for me, maybe I can try and get that one further apart to see if it makes a difference.
Click to expand...


Frank, That sounds pretty complex, so please don't take it apart again for me. Next time your in one doing that work just post a step by step of the procedure. My nemesis has been the smaller CB350F and CB400F units. I have never done any damper fluid work on anyone previously. The smaller ones are a 50/50 crap shoot that they still work again after just doing a reface has been my experience with that style. The larger faced ones never an issue with them not working after a reface.

Regarding the grommets and cushions, as you noted both are still available presently from Honda. I always replace both items when doing a rebuild of the units. After a repaint of the outer cans and new faces, they deserve a new set of damping rubber mounts and cushions.
 
Flyin900 said:
Frank, That sounds pretty complex, so please don't take it apart again for me. Next time your in one doing that work just post a step by step of the procedure. My nemesis has been the smaller CB350F and CB400F units. I have never done any damper fluid work on anyone previously. The smaller ones are a 50/50 crap shoot that they still work again after just doing a reface has been my experience with that style. The larger faced ones never an issue with them not working after a reface.

Regarding the grommets and cushions, as you noted both are still available presently from Honda. I always replace both items when doing a rebuild of the units. After a repaint of the outer cans and new faces, they deserve a new set of damping rubber mounts and cushions.
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It's slightly complex, but if you have some basic mechanical aptitude it's not hard. It's more about following directions. I forgot about the tabs on the numbers. I'm a bit disappointed in myself that I forgot, having done this a couple of times before.

I suspect, but have no idea, that the clock spring may play a role and that it's possible they get a bit stretched and it causes this failure.

I also suspect the cushion and grommets are a hack solution. My DT250 vibrates way more and that speedo works fine and I have not done any cosmetic replacements to it.

I'll rip apart that CB500 speedo for you. That thing was junk anyways and I'll probably need it now to steal the trip meter numbers out of it. It's already apart in a box of misc parts.

When I first got the CB550 running the tach was all over the place. I took this one apart, it's obviously less complex. All I did was clean the hardened grease off the gearing and use dow molykote on the gears. The inside of the bell housing I just wiped the old grease off and used some wheel bearing grease in there. That fixed it up. Never even took apart the dampener.
 
Back to Amirali's issue... getting it apart is not for the faint of heart. If it kinda/sorta works I would leave it be. In the meantime, get a cheap phone mount and just use GPS on it. You can get a USB "Power Bank" and run a long cable along the frame under the tank to easily get USB charging while not having to run a cable off the battery and it's easily reversible if you ever decide to get rid of the bike. The power bank fits under the seat in a stock configuration.
 
Amirali,

I have found an app for android that works very well as I need it anyways since my CB550 speedometer needs replaced. An ad or two sometimes upon opening or closing, but otherwise works very well. It's simply called "Speedometer GPS". https://speedometergps.page.link/Share. There are cheap phone mounts, but the most popular one and one that works well is the Ram mounts. A cheap one will probably work fine, just keep an eye on it.
 
Hi guys,

Sorry I have been absent for a bit.

The bike is running fantastic and everything works as it should.


The speedometer works fine for the first 3-4 miles of the ride. Honestly, I don’t go that fast and I have an ok understanding of my speed so I am not too bothered by it.

I used a carb cleaning fuel additive and it has been a GAME CHANGER. The bike runs so well even 4 tanks later that I had to decrease the idle.

Hope everyone is enjoying last bits of the summer
 
AmiraliM said:
Hi guys,

Sorry I have been absent for a bit.

The bike is running fantastic and everything works as it should.


The speedometer works fine for the first 3-4 miles of the ride. Honestly, I don’t go that fast and I have an ok understanding of my speed so I am not too bothered by it.

I used a carb cleaning fuel additive and it has been a GAME CHANGER. The bike runs so well even 4 tanks later that I had to decrease the idle.

Hope everyone is enjoying last bits of the summer
Click to expand...

That's good. Out of curiosity what in-tank fuel additive did you use and how many ounces per gallon?
 
AmiraliM said:
This one

https://www.amazon.com/dp/B007PCQJFQ?psc=1&ref=ppx_yo2ov_dt_b_product_details
I put just a couple drops in 3/4 tank


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A couple of drop is inconsequental. It's 4oz and the back says it treats 12 gallons. So, ideally about 0.5 to 1oz (or about 1/4 of the bottle) per complete tank fill up (which is about 2.5-3.0 gallons depending on what size tank you have).

What probably happened is the bike being in constant use and with fresh gas flowing it likely broke loose some crud. Which is still good.

PS: Only use 87 in these. They don't need 91 or 93 octane.
 
Maraakate said:
A couple of drop is inconsequental. It's 4oz and the back says it treats 12 gallons. So, ideally about 0.5 to 1oz (or about 1/4 of the bottle) per complete tank fill up (which is about 2.5-3.0 gallons depending on what size tank you have).

What probably happened is the bike being in constant use and with fresh gas flowing it likely broke loose some crud. Which is still good.

PS: Only use 87 in these. They don't need 91 or 93 octane.
Click to expand...

Hmm interesting!
It was night time and it’s possible I put in more but not sure.

I have been putting 93 this whole time, thinking it has some benefit? Is it worse?


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It's a waste of money as the bikes don't need it. Also, it may ironically promote more carbon build up. Never verified that to be true. But either way, it's wasting money.
 
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