Chain comes off with high torque

#1
My sprockets are aligned properly. I checked the wheel sprocket for bowing. I've tensioned the chain as much as I can comfortably. When I throttle up, the chain starts to get slack on the underside of the sprockets. I would expect this from flex in the jackshaft. Any time I really dig into the gas, the chain will come off. It's not breaking, just coming off the sprockets.

If you're not familiar with my bike, Honda GX270, Comet 40 series driver, Comet 44 series driven, modified mini baja 165 frame.
 

trinik7597

Active Member
#3
could be your rear sprocket is bent even though aligned properly . try spining your wheel and see if your chain goes from tight to looser and if not bent maybe out of round there should not be enough flex to make the chain go slack
 
#6
could be your rear sprocket is bent even though aligned properly . try spining your wheel and see if your chain goes from tight to looser and if not bent maybe out of round there should not be enough flex to make the chain go slack
It doesn't do this. This was my first thought. I even used a run-out gauge to see if it was bent. No dice.
 
#7
sounds like your engine plate is flexing. squeeze the top and bottom of the chain together and see if you get any movement there
It flexes. Probably more than it should too. I'm going to weld some gussets this evening and see if I can't stiffen it up. Thanks for the suggestion.
 
#11
He said in his first post he has a TAV.

I am sure his question was more in reference to "Why is this person asking/talking about stall when I have a TAV?".
I wish I could give myself more credit, but I actually didn't know what clutch stall was. I only knew of engine stall caused by a clutch. However, I do now. Thanks, Tempest!
 
#12
might have to put a tensioner on the chain. if you do, put it on the lower side. i got stretch at first, had it come off 2 times. i have a GX390 but my motor plate is 1/4". the oem plate is TOO thin.
 
#13
might have to put a tensioner on the chain. if you do, put it on the lower side. i got stretch at first, had it come off 2 times. i have a GX390 but my motor plate is 1/4". the oem plate is TOO thin.
I think mine is a 1/8th. It's been so long since I made it. I bought a freewheel sprocket not too long ago, but I've been dreading mounting it.
 
#15
might have to put a tensioner on the chain. if you do, put it on the lower side. i got stretch at first, had it come off 2 times. i have a GX390 but my motor plate is 1/4". the oem plate is TOO thin.
I think I'm going to add a motor plate as well. I'm already putting a tensioner on. Stock pred 212 and the torque makes motor plate flex on my ARCO.

Might be an SOP (standard operating procedure) on any plate that is thin.
 

george3

Active Member
#16
My sprockets are aligned properly. I checked the wheel sprocket for bowing. I've tensioned the chain as much as I can comfortably. When I throttle up, the chain starts to get slack on the underside of the sprockets. I would expect this from flex in the jackshaft. Any time I really dig into the gas, the chain will come off. It's not breaking, just coming off the sprockets.

If you're not familiar with my bike, Honda GX270, Comet 40 series driver, Comet 44 series driven, modified mini baja 165 frame.
Post pics.
 
#17
I had lots of issues until I beefed up my driveline because of flex. Its difficult to troubleshoot too, because it really doesn't show you the flex until it's under load (like when you are riding it). Just a suggestion: throw it on a stand- lock up the rear brake and give it some gas to observe possible flexing areas.
 
#19
I had lots of issues until I beefed up my driveline because of flex. Its difficult to troubleshoot too, because it really doesn't show you the flex until it's under load (like when you are riding it). Just a suggestion: throw it on a stand- lock up the rear brake and give it some gas to observe possible flexing areas.
It's definitely flex. I made a crappy diagram to show what I think is happening.



With the belt pulling one way, and the chain pulling the other on a lever, its twisting my jackshaft mounts which is causing flex in the motor plate. I'm going to weld gussets this evening and see if that helps.
 
Top