Strange question

Hello all, I know this is an absolute nightmare to try and figure out over the screen, but we’re pretty stumped and I wanted to see if any else had experienced something similar. On my 94 750, I’m getting a strange pulse/“whomp”/vibration in the left peg and from near the back of the case. The kicker: it only occurs at low speed, and 4th-6th gear. Low revs and between 40-60mph. Doesn’t occur during a pull or in 1-3, and stops when you pull the clutch in. Not that I think it’s related, but it didn’t start until right after I had a new rear tire installed this past Saturday. Noticed this when I was out scrubbing the coating off and took it straight home. Just had a friend/long time VFR owner take it out and he confirmed the same symptoms. I don’t know the age or mileage of the chain, but the rings look okay and I just serviced it with the 2 stage Honda pro clean/lube not 100 miles ago. Anything up to and including a wild guess is welcome. TIA

 

I'd start with what has changed between now, and before it started....the tire.

 

No strange marks or signs of rubbing, weights are still on and if you run through the gears on the stand nothing is out of the usual. Issue ceases when clutch is pulled in, so thinking it is elsewhere


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It has to be the rear tyre. Is it seated on the rim correctly? Balanced? Can you try another wheel? Take it back to the shop and get them to have a look

 

sure could be a bad cHaiN, innit M8 ? since u dunno mileage ? get it up and spin the rear wheel and check that chain tension isn't too different tight/loose.

 

oooh, oooh, oooh, me, me, me, pick me, my hand is up, I have an idea, call on me...

It's the chain. You just don't have it adjusted properly, you're close but it's not quite right.

The weird "whomp" you're getting (during your long, low-RPM, low-speed pull in a high gear) is due to the V4 engine's firing order, 1-0-1-0-0-1-0-1-. The really close double-pulse of power (separated by only 90 degrees) between the firing of cylinder #4 and #1 always puts a jolt of power through the transmission and final drive. In this case, under the parameters you described in your original post (with a slightly out-of-proper-adjustment chain) is causing the chain to yank/whip/snap.

If you were to mount a GoPro camera (in a way that it can record the chain's behavior) and ride the bike through the speed and gear parameters where you're getting the "whomp" I'm betting you'll see some pretty odd-looking chain behavior.

 

thanks, gonna start there this weekend


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