Sudden excessive vibrations

[LeBouc]

Hi all. I had balanced my carbs, went for a ride and it was unbelievely smooth. Until I reached a stop. From there, the vibrations became quite strong, enough to put my right hand asleep after 15 min of riding. I have re-checked the carb balance, changed the chain and sprockets which where at the end of their life, reajusted the clutch at both ends of the cable and verify the wheels for any play. I did those last ones in case but the engine vibrate even on idle. I have checked the compression and it hasn't change - not perfectly equal when comparing the two sides but not enough to induce a sudden change in vibration. I suspect the clutch barrel bearing but I want to know if any of you have experienced this type of sudden change in vibration and what was the reason for it. Thanks!

 

[DennisW]

Hi, I have actually had the same problem the last few weeks after balancing my carbs. It turned out that the fuel cock was not clean, resulting in the engine not getting enough fuel. This made the engine run lean, which generated a lot of vibrations. Maybe this is also your case.

 

[LeBouc]

Hi, I have actually had the same problem the last few weeks after balancing my carbs. It turned out that the fuel cock was not clean, resulting in the engine not getting enough fuel. This made the engine run lean, which generated a lot of vibrations. Maybe this is also your case.

Thank you. I will check that. The spark plugs should be able to tell me if that's the case!

 

[DennisW]

You could also remove the hose from the carbs, and set it to PRI, to see if the gasoline flows nicely. My spark plugs were quite dark, indicating a rich mixture, so the spark plugs may not be the best method to check this. Kind regards

 

[GuyS]

I did “run smoothly”. But then all of a sudden when you came to a stop, there were vibrations. It’s possible one of the floats got stuck. But even that doesn’t explain. The sync or idle mixture going out of whack just like that too,.. doesn’t make sense. Did you check the valve clearances? It might be something mechanical as well, but that could be a whole lot of things ….bearings…etc. etc