Vibration on left side of bike

[mijohnso]

So I went on a short ride with my wife yesterday, and at about 80mph, the bike vibrated like crazy, but only on the left side! I recently (ghetto)synch'd the carbs, and it usually runs pretty smooth with just me on it. I haven't been able to troublshoot much (like check if it does the same thing with just me on it, or listen closely for any abnormal noises), and I know it is the engine because when I pulled the clutch in and let off the throttle, the vibration stopped. My wife said her left foot fell asleep because of vibration, and my hand nearly vibrated off!

Have any of you experienced anything like this? I am going to try to isolate the problem tonight, but any suggestions would be helpful.

Thanks!

[Yamifj1200]

I think you need to sync those carbs properly. If all the cylinders aren't working together they are working against each other.

Eric M

[andyb]

I agree with Eric and would assume that something is loose on that side, motor mount or whatever.

[racerman_27410]

+1 on a real carb synch.

the left side is where the FJ likes to vibrate when the carbs are out.


Kookaloo!

[Arnie]

Yeah, I agree with all the other replies you've received...sync the carbs properly

HOWEVER, what you're describing sounds more substantial than that.  Check that the lower frame rail has all the bolts in place, not snapped, and tight.  You may have to remove the footplates to check the bolts at the rear of the rail.

Cheers,
Arnie

[Mark Olson]

check the chain tension , if it is too tight it will cause vibration with two up riding.

[Scooterbob]

check the chain tension , if it is too tight it will cause vibration with two up riding.

+1 on chain tension.  Had that issue myself a while back.

[mijohnso]

Checked everything suggested on this thread, and nothing worked. I even drove my bike to doug's house to use a "real" carb tuner, only to find out that the carbs were tuned perfectly with my ghetto method (maybe better...) (thanks for the help Doug). Anyways, after a fresh sync, some of the vibration went away, but it is still not great, and from my best recollection, it is worse than when I first tuned the carbs a month ago. Chain is not too tight (might be a tad loose), all bolts seem to be as tight as they need to be..

I have ridden it in the rain a little (maybe 5 miles) recently, and my left fork tube did spew fork oil all over the front left side of the bike. I also recently replaced the anti-dive unit on the left and added some 10w Fork oil. The main problem is, I know it is engine vibration because when I pull the clutch in, everything is as smooth as glass (or as doug's bike).

I am going to try to take apart and service the motor mounts. Does anyone have any tips on doing this for an '86 or similar? Thanks for all of the suggestions guys...

[carsick]

http://www.fjowners.com/index.php?topic=594.0

Not sure if it's applicable to earlier models, looks like a '91 up in the pics.