Tight cam chain makes shifting hard

[CanadianSteve]

Hey Gentlemen, posting this issue just out of curiosity and to see if it makes sense to the more knowledgeable members of the forum.

My '78 has been running great. I have VM34s on them, Boyer Bransden ignition, and I think it's pretty dialed in. Nice and peppy, fun to ride, except pretty noisey fron the engine. I'm running 20W50 as recommended to quiet things down, but still a lot of chatter. Intake is gapped at 0.004" and exhaust at 0.006". I might tighten the intake to 0.003" soon, but that's where I am at now.

The interesting part is that my buddy Bosco659 took my bike out for a little ride and said something like "it runs good but man it's a lot noisier than mine".

So I took the bike home and adjusted the cam chain tensioner while the bike was hot. When I tightened it up the plunger in the middle of the tensioner was still moving a little bit but less than before, all in all I think the tensioner bolt was turned .5 to .75 of a turn.

When I took the bike out after, it was way quieter but shifting was exceptionally hard. When the chain was looser, gears just gracefully slipped into place when asked. It was really satisfying and smooth. Neutral was easy, first through fifth was easy, just really nice to shift. After tightening the cam chain, shifting was hard, needed more pressure, and seemed to clunk into place ... but not in a good way or like before. It was so frustrating I've loosed the cam tensioner just to get shifting back where it was.

I told Bosco I would post this, we are both interested in your thoughts.

 

[gggGary]

My first reaction is
correlation does not imply causation.
don't see one making the other happen.
Look elsewhere for hard shifting.
If shifter moves without binding, clutch cable, adjustments would be my first investigation.

 

[bosco659]

Steve’s bike runs great - I wish my XS had that much get up and go . I too am puzzled his shifting issue, as the chain adjuster should have zero effect on the tranny. I’ll be watching this thread with interest.

 

[Raymond]

Don't make any sense to me. Point to clarify - after you loosened the cam-chain tensioner, did you find the shift went back to how it felt before?

I'll be interested to see what the experts say. @5twins . . .

 

[bosco659]

Hey Gentlemen, posting this issue just out of curiosity and to see if it makes sense to the more knowledgeable members of the forum.

My '78 has been running great. I have VM34s on them, Boyer Bransden ignition, and I think it's pretty dialed in. Nice and peppy, fun to ride, except pretty noisey fron the engine. I'm running 20W50 as recommended to quiet things down, but still a lot of chatter. Intake is gapped at 0.004" and exhaust at 0.006". I might tighten the intake to 0.003" soon, but that's where I am at now.

The interesting part is that my buddy Bosco659 took my bike out for a little ride and said something like "it runs good but man it's a lot noisier than mine".

So I took the bike home and adjusted the cam chain tensioner while the bike was hot. When I tightened it up the plunger in the middle of the tensioner was still moving a little bit but less than before, all in all I think the tensioner bolt was turned .5 to .75 of a turn.

When I took the bike out after, it was way quieter but shifting was exceptionally hard. When the chain was looser, gears just gracefully slipped into place when asked. It was really satisfying and smooth. Neutral was easy, first through fifth was easy, just really nice to shift. After tightening the cam chain, shifting was hard, needed more pressure, and seemed to clunk into place ... but not in a good way or like before. It was so frustrating I've loosed the cam tensioner just to get shifting back where it was.

I told Bosco I would post this, we are both interested in your thoughts.

Not the root cause of shifting issues, but maybe your cam chain tensioner is missing the rubber or copper damping washer? That will make things noisier.

 

[CanadianSteve]

When I backed the tensioner off half a turn, shifting returned to the previous experience (smooth and light). My only thought is that it's advancing the timing and making it run too hot, but I can't imagine half a turn would have that much impact.

 

[Jim]

It's an interesting one alright.
Like Gary sez though..."correlation does not imply causation."
I can't think of a single thing the tranny and cam chain have in common. They don't even ride inside the same compartments.

Grasping at straws here.... did you have the left cover off at the same time? Threw the clutch out of adjustment in the process?
Other than that....

 

[nj1639]

Chasing a startup tick some time ago.......
Using the long handled screwdriver couldn't pin it down. Each valve cover checked.
I pulled the cam tensioner to see if it had the copper dampening washer. It was there.
I tightened the tensioner down a bit to where there was still movement. Checked the valves, 3 and 6. On startup the tick was gone.
On road testing I now had a strange decell flutter in the engine.
Backed the tensioner a wee bit. Checked valve lash.....no change. Slight tick on startup but decell flutter was gone.
Go figure.
Shifting was fine all along until on a whim I thought I'd adjust the clutch to where there was no rear wheel movement in neutral. Third gear was then a bear to get in. Readjusted the clutch from scratch, loosen the tension under the side cap, loosen the cable at the perch etc.etc. Back to "normal".
Observations?
Small adjustments to the tensioner didn't change the valve lash according to the feeler gauges - though what was that decel flutter? It's gone now.
Conclusion?
Seems there are very fine lines to deal with, but I'll live with the slight (now) startup tick and the clunk going into first gear on a cold engine. Nature of the beast?