View Full Version : too much vibration.

09-01-2004, 07:42 PM
Howdy to all. Since this is my 1st post I apologize for the length. I had an S&S 100" retro put into my 1982 FXR 2 yr. ago. Since then I can't ride the bike more than about 75 miles without something rattling loose. A brief list: Stator, outer primary bolts (constantly), selenoid, exhuast nuts, rear axel nut. The following bolts have broken: rear motor to tranny, inner primary (two), and starter. My inner primary is now cracked at the top left motor hole. I have inspected the frame and motor mounts and find no cracks. The rubber mount looks good as well. The vibration gets worse as the rpm's get higher.

My questions are: how do I make sure that the motor and tranny are aligned?, How can I tell if the primary chain is aligned?, What else should I check before splitting the case to check flywheel.

Thanks in advance.

09-01-2004, 08:09 PM
Hi Rotten, welcome to the forums.

Sorry to here about your vibrations,

Sounds like you motor & trans is may be misalinged abit, I'm enclosing a tutorial how to get it set correctly.

Also follow the Service manuel to make sure your motor is set in the correct position.

On a second note the most likeliy culpret is your motor & or primay is not balanced correctly. I run fluid damphners on place of the stock flywheel with great success, it will centrifically balance your motor as it runs.

I have done this on many dyna frames over the years & it just takes a little playing with to get right.

09-01-2004, 09:34 PM
hey rottin- welcome to the madhouse....

i'm with wide on this one. start with the simple stuff and check alignments and loose mounts/stabilizer rods.

howver, you got me a bit confused since the most common large displacement s&s shovel is a 93 cu in. is this something you had custom made? if so, then the dynamic balance might be off due to mismatched components. a "standard" balance factor or 60% is used, although some engines require a different measure. the balance factor is the ratio between the crankshaft weight and the reciprocating weight (pistons, pins, rods). the reciprocating weight is usually matched to 60% of the crank weight.

check the easy stuff first. buy a proper (read- moco, not haynes) manual and go to town. if you need more help- we're all here...


09-02-2004, 08:47 PM
All good advice from the guys. My .02. Motor mounts that look good but are soft from age and use will rise hell with the engine and primary.To soft mounts allow the engine to be a "paint shaker" instead of stablizing the engine.

Also like wide was saying front and top stabilizer adjustments are critical.

Let us know how she goes.