Engine and Clutch seem good bike won't move?

[dstewart1476]

Hello, I've been searching the forum looking for a thread about this issue but can't find one. Hoping someone might be able to offer some ideas.

I have a 1979 xs400 engine starts, idles and runs great. Clutch works and you can shift to all gears. Ran great on the bench and around the neighbourhood. I took it for a longer 30 km ride and noticed it starting to have problems when the RPMS hit 5-6k. Again engine running fine but as I applied more throttle the RMPS increased but road speed does not. After a bit at 5-6k rpm it would slightly lurch and take off. This was happening in all gears. By the time I got home things had got worse. Came to a stop and was barely able to roll off again. I'm not sure what is going on?

I thought maybe one cylinder was not firing all the time but I checked and both pipes are HOT, spark on both sides, sounds and feels smooth on both sides.

Any ideas or advice are appreciated. thank you

 

[CaptChrome]

Welcome to the forum.

Engine revs increasing without an increase in road speed is a classic sign that either your clutch is not adjusted properly or that the clutch is worn out and you need to replace the plates. I would measure the clutch plates and compare them to the service limits in the manual and also adjust the clutch release mechanism per the book.

 

[tstidham]

When I first got mine, it had some slipping at higher rpms as well, but so long as I drove easy it was fine. Eventually I decided it was time to replace the clutch and upon disassemble, I could see the friction disc's were in bad shape. Chunks of material had exited the chat off them. I used a mad hornets brand kit off Amazon and have about 1000 miles on it so far and all is well. That includes tons of low speed clutch feathering abuse while practicing for my official MC endorsement.

 

[dstewart1476]

Thank you both for your quick replies. I do appreciate it. I wasn't certain what to do next but it looks like I am headed to a clutch rebuild. Before I do go all the way with that I wanted be sure I consider ALL the simple things first. I see many mentions of one or two BBs that are part of the clutch. Sounds like they are part of the actuator maybe and tend to go missing? I'm looking at a take apart diagram in a Clymer manual and I only see one BB listed after the push rod. Are there others I should look for? Thank you

 

[salsasaul]

Thank you both for your quick replies. I do appreciate it. I wasn't certain what to do next but it looks like I am headed to a clutch rebuild. Before I do go all the way with that I wanted be sure I consider ALL the simple things first. I see many mentions of one or two BBs that are part of the clutch. Sounds like they are part of the actuator maybe and tend to go missing? I'm looking at a take apart diagram in a Clymer manual and I only see one BB listed after the push rod. Are there others I should look for? Thank you

If I remember correctly, my ‘82 xs400 had only one bb for the clutch pushrod, but it is a whole different motor

 

[dstewart1476]

Thank you for your reply. I've purchased a set of plates and a "new" actuator. I damaged mine trying to undo the lock not to adjust the clutch. I'll let you know how it goes.

 

[gpounce32768]

only one "bb" on my '82 Seca. Not similar to this case but on one occasion after sitting for a while the clutch pads got stuck to the disk, took a bit of back and forth shoving of the bike to get them loose. The symptom made me think that the clutch actuator wasn't working. In the course of debugging I had the clutch actuating mechanism apart and it sure needed cleaning and regreasing, so well worth going in IMHO.

 

[dstewart1476]

Thanks for the tip. I'm waiting on parts and will update everyone on my progress. Until then I'll try rocking the bike.

 

[dstewart1476]

OK update for you. The kit arrived today but before I put it in I thought I should revisit the simple things. I removed the clutch cable, lubed it and re ran it with a straighter path (no 90's). I got brave and really leaned into the lock nut on the clutch actuator / adjuster. I was afraid I was going to snap it off it took a lot of force. Loud CRACK and it came loose. Made the adjustment and buttoned everything back up. Fired it up and it appears to be working. I applied throttle and eased out the clutch, felt the friction point and it rolls off strong. I need to go for a ride and see if the problem returns but so far so good. Bonus, clutch lever is waaaaaaay smoother and does not hurt my arm to use anymore. Fingers crossed. More updates to follow. - thanks

 

[dstewart1476]

Ok went for a ride to take it through all the gears. Everything seemed fine, shifting power, revs etc. and the clutch is very smooth now. Then I got into top gear. Same problem sometimes around 5k rpm. Revs high with no additional power then surges forward after a bit. Does everyone still recommend rebuilding the clutch? Replacing the spacers and plates?

Does the oil need to be specific for wet clutches? I used 20w-40 like it says in the manual but it did not say for wet clutches. I noticed this as an option when I went to buy oil in preparation for the clutch rebuild. Thanks everyone.

 

[tstidham]

It is recommended to use a wet clutch friendly oil. I switched to using the Shell Rotella T4 15w40. Even though it's a diesel engine oil, it is wet clutch friendly and easier to get (and cheaper) than many motorcycle specific brands. If you google it, you'll find many such posts stating how well it works and many of the posts started when Yamaha discontinued their yamalube 20w40 oil.

 

[JPaganel]

It is recommended to use a wet clutch friendly oil. I switched to using the Shell Rotella T4 15w40. Even though it's a diesel engine oil, it is wet clutch friendly and easier to get (and cheaper) than many motorcycle specific brands.

What you are looking for is a JASO-MA or JASO-MA2 certification. Many diesel oils have it.

It is usually on the back of the bottle in small print.

 

[dstewart1476]

Cool thanks. Just waiting on a gasket to arrive then I can rebuild the clutch.

 

[tstidham]

One tip I learned from an old MC mechanic, coat both sides of the new paper gasket with white lithium grease and it becomes reusable if you ever need to go back in to that cover. Plus the grease helps the gasket stay in place while assembling.

 

[dstewart1476]

Ok so, I adjusted the clutch at the engine a bit more and BOOM. It's working. Bike goes fast and shifts well. I think I'm good now. I have all the parts for a clutch rebuild and I'll hold onto them just incase. Now I just need to get the battery charging.... old bikes right. They keep you busy. Thanks everyone.

 

[chandlxr]

Hey What handle bars are on your bike?

 

[dstewart1476]

Ya know what, not sure. I went to a swap meet and bought a few for $10. They are kinda like straight drag bars. Here is another angle.