I have an 81 FXWG, punched .040, mild cam, S&S carb, 4 speed kick/electric. This girl is vibrating my teeth loose. Seems to have recently become worse. I was suspect of the final drive due to the compensator not being in the best of shape. I was having issues as well with the primary chain constantly stretching. I purchased a primary belt drive and installed. Some of the vibration seemed to ease up, yet under throttle, it goes ape. I have ruled out wheels and tires. The vibration is ONLY under throttle. I have decided to pull the bike down and completely go through it from the ground up. With it being 27 yrs old, it has it's share of problems.The heads have a little build up on them and the pistons do as well. I noticed recently the front cylinder would smoke on occasion at traffic lights. Should I look into the bottom for the vibration? I plan on turning this project around soon and want to avoid pulling this engine again. Also....any ideas on making this four speed a little more highway friendly? Off the line it has tons of torque, just runs out too soon and tachs too hard at 60+.

JD

 

Was your top motor mount tight? Check the bolt for that to ensure it has sufficient threads to pull the mount up tight to the frame, not just "bottoming-out" the nut on the bolt threads.
Did you do a compression check to see if the two cylinders were within 10% of each other?
Check your bottom end with a dial indicator (or even feeler gauges will work) for runout. Check your manual for acceptable specs.
Original gearing on FX models (I think most of 'em anyway) was 23 transmission / 51 rear wheel. You could try a 24 tooth sprocket on the transmission with the stock 51 tooth wheel sprocket. Another combination that might work for you is a 23 tooth transmission sprocket and a 49 tooth wheel sprocket. Either of those should drop your freeway RPM's some without taking too much away from low speed performance.
I hope your project comes together well for you.

 

i have a 75 shovel and a recent vibration at the high end of throttling and it turned out i blew a gasket between the heads (exhaust manifold i guess you'd say) so yeah they always need checking

 

Bump the counder shaft sprocket up to the 24 if your now running a 23 and install a new chain and check the rear sprocket for wear.
Has he vibration changed or gotten worse?
Is the bike new to you, how long have you been riding this bike?

 

vibration at top end is common
beside being hard on the back........lol
better get used to it
there hard ridin bikes
then again thats the charm of them