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View Full Version : 39 MM front end assembly - am i missing something?



racewiththedevil
05-05-2016, 5:36 PM
locks up when i bolt it down.
it's a 39mm sporty front end from a 2003 (i think) that i am putting on an '87 sporty frame.
races are pressed into the frame. got the shield then bearing on the bottom, put it in the head tube, then bearing and shield on top, then top triple and bolt with washer.
when i crank down the top bolt it locks up the whole assembly.
am i missing a spacer or washer or something?
any help is appreciated, thanks.

BadMonkeyMW
05-05-2016, 5:59 PM
locks up when i bolt it down.
it's a 39mm sporty front end from a 2003 (i think) that i am putting on an '87 sporty frame.
races are pressed into the frame. got the shield then bearing on the bottom, put it in the head tube, then bearing and shield on top, then top triple and bolt with washer.
when i crank down the top bolt it locks up the whole assembly.
am i missing a spacer or washer or something?
any help is appreciated, thanks.

I would advise you to get a factory manual to help you with this. The issue is that you don't just 'crank down' the top bolt. Front ends on motorcycles has a pre-load that is specified for the neck bearings. You generally measure that pre-load by measuring what's called fall away. Basically, fall away is the distance you have to move the front wheel off it's centerline before it falls to the fork stop on it's own. As you found out, if you just tighten the top bolt down, it will lock up the bearings. I believe on a narrow glide, the spec fall away is about 2 inches, but keep in mind the front wheel has to be off the ground to check it. Good Luck.

bobscogin
05-05-2016, 7:38 PM
Check to see if the bottom tree is contacting the bottom of the neck anywhere around the circumference of the bearing seat. Install, tighten until it drags, rotate back and forth, and look for marks. The cup could be a little deep. You may need to put a thin shim under the bottom cone even though the parts book didn't show it. If that's not the problem, at least you've eliminated a possibility.

Bob

hillcat
05-06-2016, 5:23 AM
I would advise you to get a factory manual to help you with this. The issue is that you don't just 'crank down' the top bolt. Front ends on motorcycles has a pre-load that is specified for the neck bearings. You generally measure that pre-load by measuring what's called fall away. Basically, fall away is the distance you have to move the front wheel off it's centerline before it falls to the fork stop on it's own. As you found out, if you just tighten the top bolt down, it will lock up the bearings. I believe on a narrow glide, the spec fall away is about 2 inches, but keep in mind the front wheel has to be off the ground to check it. Good Luck.

Once you are close,the difference between too tight and too loose is pretty close.
Not much of a turn of the wrench.