gl 1800

imported post

I doubt an engine mount would cause this, the engine is hard mounted to the frame. If you know for sure the front end (tire, wheel bearings) are not to blame then at those miles I think the alternator could be one cause. They do fail at even lower miles...

imported post

A misfire could also cause engine vibration. When was the last time you replaced the spark plugs?

imported post

Hey gang,

My neighbors 04 has a similar vibration at freeway speeds that almost pulsates up through handle bars. It's not the wheels as when the clutch is pulled in, it stops, as soon as the clutch goes out, the vibration comes back.

Plugs and alternator, great place to start, any other ideas?

Toy4Rick

imported post

Alternators are a known cause of vibrations so that's a good starting place. DaveO is probably the man who will know all the other places to look.

imported post

If it only vibrates at 70 it has to be in the wheels or other rotating components such as the drive shaft otherwise it would do it at the same RPM in any gear.

imported post

How should the alternator be checked/tested for a possible issue that might cause this?

Drive shaft, how could we isolate it?

Thanks in advance
Toy4Rick

imported post

If it were the alternator, which I doubt, it would do it at 3000 RPM stopped or in any gear at 3000 RPM, which is the RPM at 70 MPH in 5th. The driveshaft would probably vibrate when accelerating through that speed or decelerating from a higher speed. That could probably be confirmed by putting the bike on the center stand, tying the front wheel to the stand,start the engine, put it in 5th and accelerate to 70 MPH. I should put a disclaimer in here"don't try this at home". If the rear wheel is out of balance it will vibrate but at a different rate than the shaft.

imported post

A simple test to separate engine and transmission vibration from wheel, road serface and driveshaft vibration..... take the bike out on a open road until the vibration starts, say 70 mph if that is your case. Release the clutch anc back off the throttle, coasting at the speed vibration was felt. If vibration continues... it has nothing to do with the engine, alternator or transmission.

imported post

When the clutch is pulled in, the vibration stops, once the clutch is let out, the vibration returns.

Toy4Rick