My 1977 has a vibration/over-reving problem

[Exitaph]

I'm getting a high vibration and what I think is over-reving when my bike gets to around 2k-3k rpm. It started doing this last year as I was putting it away for the winter. It ran fine before that. I'm still kind of a noob at all this and I'm not sure where to start. Here's a video that shows what's happening.

I hadn't changed any carb settings or modified anything when it started happeing.

I think it really only does it while idle and in first gear. But It's hard to tell in other gears going down the road. I've searched quite a bit but couldn't reallly find someone with the same problem.

 

[5twins]

If you mean the way it shakes around when you rev it, that's kinda normal. These things just vibrate a lot. If you think it's gotten worse than it used to be, maybe a carb sync will help. Ever checked that?

 

[Exitaph]

I'll try re-syncing the carbs. Thanks for the suggestion, I hadn't thought of that. I've kind of accepted the fact that these bikes vibrate a lot.

I'm mostly worried about the over revving at about 2.5k rpm. It always use to get louder at a smooth rate. In the video you can hear it jump up in loudness around 2.5k. I'm increasing the throttle at the same rate the whole time.

 

[retiredgentleman]

Vibration is part of owning these bikes. If my bike would stop vibrating, I'd think something is wrong.
You should have a good look at your ATU, to be sure its not hanging up or sticking closed. These engine will go up to 2500 rpm with the timing only at the retarded position. The timing needs to advance in order to go above 2500 rpm. If your ATU is sticking up to 2500 and then snapping quickly to some degrees advanced, you might see a burst of rpm at the 2500 area.

 

[Bob Kelly III]

that sounds like the best possable answer RG ! good man !
but what are you calling the ATU ????
I am assuming you mean the timing and advance unit up top in the head.... a sticky centrifical advance is probably causing his odd running for sure
it would be wise to read the technical section under forums/garadge and you'll find it above the garadge there.... it's full of good stuff
so check out the ignition timing and centrifugal advance section.... you'll see that a sticky advance on the older modles is a common problem
and how to fix it....
and Yes Carb syncronization will really cut down on allot of the vibrations !
.....
Bob.........

 

[Bob Kelly III]

Exitaph : Umm...over reving at 2.5k rpm is an impossability...... over reving occurs when the tach is red lined... way up there in RPM
so that term does not fit here.... so we're trying to figure out what you mean by OVER reving at such a low RPM.... and it doesn't make sense !
if you mean a quick change in RPM when slowly advancing the throttle then Retiredgentalman probably already answered the question for you.
I would pull the advance unit pull the rod out lube and clean it and put it all back together and then re time the bike.
be carefull of those springs don't streach them !
hope that helps.....
Bob.........

 

[Exitaph]

After looking at the ATU/centrifugal advance it indeed hangs up. Takes a bit of force to open it and it doesn't close all the way on it's own. My manual says to add a lightweight grease to the pivot pins but it doesn't say anything else. Do I have to disassemble it? And will that throw off my timing? I don't have one of those timing light things yet.

Bob, you're right about the over revving thing. I wasn't quite sure how to explain it. I guess it's not really over revving it just sounds odd.

 

[DaveO]

Exitaph's description is a little confusing but is the clutch slipping when it gets to 3000 revs?

 

[5twins]

Yes, there is more to lube. You have to lube the advance rod that runs through the cam. Here's a thread with details .....

http://xs650temp.proboards.com/thread/1372

 

[Bob Kelly III]

there ya go ! thanks 5T !
good luck Exitaph ! take your time and do it right .
....if you run into trouble check out the technical section above the Garadge forum.
Bob........

 

[Exitaph]

Thank you all for your help and suggestions. Today I carefully removed the advancing rod, cleaned it (it wasn't really dirty), put new grease on it, and carefully put it back in with the pins in the right orientation. Started it up but now it does the unusual revving at about 1500 rpm. So I guess I made it worse. The advancing rod is still sticking.

Here's another video showing how my weights behave.

Does the grease have to be extremely light? Are my springs not strong enough? I looked at some other peoples videos of their advancer weights and they spring right back in to position. Mine certainly do not.

 

[5twins]

I guess I should have explained things a bit more and better. You can't get much grease on the advance rod, not any really that will stay where it's needed once you stick the rod back in. But, Yamaha obviously figured on this happening so provided a spot for grease. The bushing on each end of the cam has grooves around it's I.D. ......

Clean them out and pack them full of fresh grease .....

This will provide a reservoir of lube for many years to come. This is a maintenance item but you're right, it isn't mentioned in any of the manuals. You'll need to re-do it maybe every 5 or 6 years.

The cleaning and little bit of greasing you've done did help some. The advance is now "unsticking" and working at a lower RPM than it was before. It's just not quite enough yet.

 

[retiredgentleman]

As 5twins says, your advancer is still sticking. If you've seen other videos, you know it has to snap back smartly when released from full open.
When I had the mechanical ATU, I spent a lot of time trying to make it work correctly. I finally came to the conclusion, that it was just plain worn out. It requires that all the mechanical pieces fit together with close tolerances and that the spring tension is just exactly as it was when it left the factory. After 30 or 40 years the tolerances are are loose and the springs have the wrong tension.
I had a Pamco, and so I added the E-advancer. The E-advancer eliminates the mechanical ATU. It makes a world of difference, as the engine rpms ramp up nice and smooth. Electronics always beat out worn out mechanical parts.

 

[Exitaph]

It's making more sense now. I'll clean it out again and only grease that groove on each side and see how that helps. And I'll probably get some new springs anyway to eliminate that possibility.

 

[Michaelo]

Go for the springs Exitaph, light oil on the posts that hold the weights....clean the posts and the corresponding holes in the centrifugal weights so that they move freely without the springs.....replace springs

Edit: replace springs with new ones

 

[weekendrider]

A heads up. Mikes replacement springs didn't have a very good reputation. It has been awhile since anyone has posted about them but the "fix" used to be cut the hook off and bend half a coil up for a new hook.

 

[gggGary]

A heads up. Mikes replacement springs didn't have a very reputation. It has been awhile since anyone has posted about them but the "fix" used to be cut the hook off and bend half a coil up for a new hook.

Yup done that. Think that's how the resto is running (awesome) And no I've never lost one of those microscopic e-clips.
You also have to get out the timing light and check timing at idle and full advance. Full advance is the important setting. But there's ways to adjust the range.

 

[Exitaph]

Well I got new springs and the weights snap back freely now but the bike was still advancing too early. So I did the trick of cutting off a hook and making a new hook on each spring to make them tighter. But the bike is still advancing too early. About 1500-2000rpm.

And all at once too. I ran the bike with the advance cover off and watched the wights. They snap into full advance within a 200-300 rpm change. I guess I'm not really sure how it's supposed to work but I know it doesn't sound right. Is it safe to just keep shortening the springs until the engine sounds right?

 

[Exitaph]

Ok so I took off another coil on the springs from mikesXS and it seemed to have helped a lot. The weights snap back into position now. It still quickly goes to full advance around 2500rpm but only while idling. I don't hear it going down the road anymore. So problem solved, I think?

 

[TwoManyXS1Bs]

Maybe you'd like to explore ignition retardation?

http://www.xs650.com/threads/xs650-ignition-timing-revisited-are-we-too-advanced.45197/