Topic: CM400T newbie

[Seattleit]

Hello
I am new to motorcycles, so I bought two. A 79 KZ400 and a 80 CM400T. My question is about the CM400. The PO claims to have rebuilt and sync carbs. It starts up nice, idles smooth and sounds smooth all the way through the range, but while cruising at around 4500 or so with a steady throttle it sometime surges/jerks like the chain is jerking. It still sounds normal no sputter or anything audible. So I looked at the drive chain and it has a lot of play. It doesn't appear that you can adjust the chain like on the KZ from the rear wheel. How do you adjust the drive chain? how much play should it have. It looks like 4" or so. I have a Clymers on order but wanted to see if anyone had any knowledge first hand. My buddy says forget the chain, the carbs are likely out of sync.

 Second issue the handle bar wiggles up and down like the risers are loose on the tree but they are tight. If I replace the riser cones (or whatever they are called) will that tighten up. when I pull down its tight but I can push the whole bar up which is kinda scary for a newbie. Thanks for your time and any info you can give me. great site.

[Johnie]

Welcome to the board...I have done restoration on the CM400's. If I understand correctly, it sounds like you may have some missing bearings in the steering head there. Should not be that loose at all. There are bearings and races in the top and bottom of that triple tree as it is called. The tree is what the bars mount too.
I wonder if the surge situation could be clutch slippage?
Yes, you can adjust the chain by the rear tension bolts unless the previous owner put something else on there. Adjust the chain to 3/4 inches play at the center. I have attached a pic of the chain tension bolt on my 80CM400E. To do the chain you have to loosen the rear axle nut on the right side first. Then turn the 2 rear tensioner bolts slowly and evenly to keep the rear wheel straight. Once you have the 3/4 in play at the center of the chain tighten the lock nuts and tighten the axle nut. If those sprockets are worn you may have the chain go slack, tight, slack, tight, etc. as you spin the wheel. If that happens you may have rusted chain connections and will need to replace the chain and both sprockets.  This should give you some direction. You can click the pic to enlarge it.

[Seattleit]

Thanks
The pics were perfect, I found the axle nut and the chain adjusters on the end of the wheel. It's raining so I will have to wait to ride to see if the chain fixed the jerking. The chain felt really loose but when I measured it was really only about 2 1/2" so it didn't need that much. It could be the clutch not sure how to tell. Is there any way to tell if its the carb sync or clutch or chain?

Another possiblity is the throttle cable is adjusted all the way out and still tight, so I ordered two new cables.

I don't think I am calling the risers by the right name. The tree has good bearings, its the things that hold the handle bars. I circled them in the attached pic. Not sure what the name of this is but it has a rubber cone on top and bottom both are worn and causing the handle bar to wiggle up and down. I could not find new bottom rubber pieces but I did find new top rubber cones. I was wondering if I replaced them would it help the handlebar wiggle.

Last question I noticed compared to the KZ400 the Honda seems not to have much power at lower rpm, but when it gets to 3K or 4K it seems to blast off. I feels like a turbo charged car if that makes sense. The KZ feels a little more even all the way up.

Agian I am new to motorcycles so its really hard for me to tell what is fine and what needs adjsuting. Both bikes seem fun and they seem like good first bikes. Again thanks for the help.

[Johnie]

After looking at your pics it appears the PO installed handlebar risers on there. Those must be what are loose. I do not believe those are OEM but aftermarket, unless those were standard on the T model?  Take a look at my pics and you can see the bar mounts are cast into the top tree. Never any movement at all. You will need to tighten those up from the bottom bolt you see there. If that is as tight as it goes they you must have worn rubbers.

The CM400 does not have a ton of power at the low end.  That is normal so don't worry about it. If you want low end power you will need a 750 .

I think you may find tightening that chain up will make a big difference. 

Is the tank clean and no rust? You could have bits of junk getting into the carbs. These carbs are so easy to work on. You just take off the bottom screws and the bowl comes right off. Be careful not to strip those screws and be sure you have the right tools. If you strip those you are in trouble. Once you get the carb bowl off the bottom you can check for crap in the float bowl. It is also easy to clean the jets. But if they guys already did that then you should not have to worry about it.  Sync is the last thing you would do to a bike, after you make sure the valves are properly adjusted. That will be listed in your manual.

[Johnie]

After looking at a Honda parts list those risers are standard on the T model. Take a look at the parts picture I downloaded below. As you can see there are rubbers on the top and bottom of the long bolt. Try tightening that bottom bolt in your pic and go from there. Don't assume that because it is a 1980 you can not get parts from your Honda dealer. I was able to get parts from them. If they do not have the rubbers and what you need, check Western Hills Honda in Ohio. They have a lot of old Honda parts and I was even able to get new OEM mufflers from them for my CM400.

[Alan F.]

I've got a CM400C patiently waiting it's turn, it has the rubber mounted risers and seems to use exactly the same rubber cones as my 92 750 nighthawk, I'd almost bet that the rubbers from any honda with rubber mounted risers will fit.
-Alan