[soconnoriv]

Hi, I'm sort of getting to the end of my CB900C restore. Finally got the bike back to stock and away from that "retired cop" cruiser fairing kit. All lights and buttons work now!!!!!!!!!!

Anyways, I'm putting the brakes back onto a rebuilt front fork that I got off ebay, but the right brake caliper mount seems to be touching the disc when fastened down. Here's a a couple of pictures of the right and left sides:

Here's the right side (the problem):

Here's the left side:

It's not crushing down on the disc, as I can still spin the wheel, but you can hear the disc sliding on the mount VERY slightly. I took off the wheel to check if I mistakenly put a washer on the axle bolt for whatever reason, but the only thing that was there was the bearing spacer.

So here's my question: Is there a way to adjust this? Do people just add washers beneath the mount brackets to correct for the spacing?? Everything else with these forks seems fine. They're even off of the exact same year of my model (1981).

 

[hillsy]

So this is a "different" fork? Do you still have the original one? Did it line up properly?

Time to do some measuring - like is the wheel centred in the forks, space between rotor and fork leg, etc.

You may have a spacer on the RHS axle that's too big.

 

[soconnoriv]

So this is a "different" fork? Do you still have the original one? Did it line up properly?

Time to do some measuring - like is the wheel centred in the forks, space between rotor and fork leg, etc.

You may have a spacer on the RHS axle that's too big.

I'll have to dig them back up to measure them. Hopefully tomorrow I can.

As far as the previous install, i never had any issues with the brakes and I was always able to move the bike around without hearing any noises coming from the front disc. Think there are any places to find a correct/nominal measurement for fork spacing?

Is there actually such thing as different sized spacers?

 

[hillsy]

The easiest thing to do if you still have the old forks is to slot the old RHS fork back in and see if the caliper is in the correct spot. If so, then your new fork is therefore different.

 

[Geeto67]

Did you put a straight edge against the fork to make sure it was not bent?

I have never ever heard of someone buying just one fork leg unless they were going to replace the upper chrome tube. Usually you buy forks in pairs because if they are tweaked slightly, they are tweaked in a complimentary way.

Try rotating the chrome tube portion around in the tree and see if it makes a difference as to spacing.

 

[44dwarf]

Try swapping the wheel spacers.

 

[TrialsRider]

... putting the brakes back onto a rebuilt front fork that I got off ebay ....

That just raised warning flags with a bunch of readers. I'm guessing most here would not trust an flea bay seller to rebuild their front forks. What was wrong with your original forks that prevented you from replacing the slide bushings, seals and oil yourself?

… maybe try rotating the stanchion tube in the triple trees and see if the problem goes in the other direction. Or inspect the axle and make sure it isn't splaying the fork legs out at the bottom. When things don't line up nice at the brake callipers there is usually a reason for it.
oops, Geeto touched on at least one of those recommendations.

 

[hillsy]

Did you put a straight edge against the fork to make sure it was not bent?

When you tighten up the axle it should pull the fork lowers in anyway, so a bit of fork bend shouldn't affect the caliper spacing.

Ummm....please tell me you've tightened up the axle during all of this?

 

[TrialsRider]

If it's anything like the CB650SC in my garage right now, the axle screws into the left leg, the pinch bolt in the right leg goes through a grove in the axle. The pinch bolt needs to be completely removed before you can back-out or insert or tighten the axle. It's kind of a funky setup. Point being there is not a lot of room to mess around with adding spacers etc.

 

[Teazer]

Hang on a minute. Both calipers are too close to teh wheel on both sides and appear to need to be spaced out a bit, but are they not twin piston sliding calipers that are designed to move side to side and should always lightly rub on the "fixed" side.

Do those calipers move freely from side to side by at least a few mm or are they all seized up?

 

[hillsy]

Hang on a minute. Both calipers are too close to teh wheel on both sides and appear to need to be spaced out a bit, but are they not twin piston sliding calipers that are designed to move side to side and should always lightly rub on the "fixed" side.

Do those calipers move freely from side to side by at least a few mm or are they all seized up?

Yeah - it's probably this.

 

[soconnoriv]

Did you put a straight edge against the fork to make sure it was not bent?

I have never ever heard of someone buying just one fork leg unless they were going to replace the upper chrome tube. Usually you buy forks in pairs because if they are tweaked slightly, they are tweaked in a complimentary way.

Try rotating the chrome tube portion around in the tree and see if it makes a difference as to spacing.

I used a straight edge and checked it no problems.

Sorry for the mis-understanding, but when I said "fork" I meant both of them as a whole. Both are new and hold air pressure no problem.

I ended up finding the issue though! (Really dumb too)

Somehow a wad of grease and kitty litter got stuck in the groove of the axle where the pinch bolt passes through. I guess the groove is big enough that when the pinch bolt is through it but not tightened, the fork can have a small amount of left/right play... So i guess the kitty litter got crushed and kept pushing the axle over just enough to offset the fork and caliper mount!

Cleaning it out, then holding the fork firmly against the axle spacer while tightening the pinch bolt fixed this problem pretty quick.

Thanks for the help though

 

[soconnoriv]

Try swapping the wheel spacers.

I tried that too, It ended up being a piece of gunk inside the axle groove that offset the fork enough to change the caliper positioning. Really dumb problem but at least I found it!

 

[soconnoriv]

That just raised warning flags with a bunch of readers. I'm guessing most here would not trust an flea bay seller to rebuild their front forks. What was wrong with your original forks that prevented you from replacing the slide bushings, seals and oil yourself?

… maybe try rotating the stanchion tube in the triple trees and see if the problem goes in the other direction. Or inspect the axle and make sure it isn't splaying the fork legs out at the bottom. When things don't line up nice at the brake callipers there is usually a reason for it.
oops, Geeto touched on at least one of those recommendations.

The original forks that I replaced were corroded beyond repair. The tubes were totally shot, and the aluminum ends were pretty bad around the wipers too.

Yeah, before I rotated the tubes. I checked them with a straight edge. The problem ended up being a stupid piece of solidified crap that got into the axle groove and was able to offset the fork when I tightened the pinch bolt. After getting rid of the gunk, I pushed the fork against the axle spacer while tightening the pinch bolt, and it fixed the problem instantly. Dumb, but at least it was an easy fix.

Thanks for the help

 

[soconnoriv]

When you tighten up the axle it should pull the fork lowers in anyway, so a bit of fork bend shouldn't affect the caliper spacing.

Ummm....please tell me you've tightened up the axle during all of this?

This particular bike has a pretty unique axle. The axle itself screws into the left fork (the fork itself is threaded), and the right fork fastens to the axle with a pinch bolt that also passes through a groove in the axle.

The problem ended up being a lump of crap that got into the groove (the groove is slightly larger than the bolt to allow some play) and offset the fork over to one side enough to create this issue. Took me a little too long to figure it out but it's all good now.

 

[soconnoriv]

Hang on a minute. Both calipers are too close to teh wheel on both sides and appear to need to be spaced out a bit, but are they not twin piston sliding calipers that are designed to move side to side and should always lightly rub on the "fixed" side.

Do those calipers move freely from side to side by at least a few mm or are they all seized up?

The calipers I have slide left and right no problem. What you were looking at in the picture was the caliper mount, without the calipers installed.

The issue ended up being a wad of crap that got stuck in the axle groove. It managed to push the pinch bolt over enough to make this issue. All is good though now. Thanks for the pointers though

 

[hillsy]

Axles screwing into the fork leg is not really "unique" but anyway you figured it out.

Lesson learned is make sure you have everything properly bolted up before you measure stuff.

 

[kerosene]

and clean

 

[Geeto67]

You don't have to individually reply to everyone's post telling us it was a wad of grease and kittly litter. Once at the end would suffice.

Glad you figured it out. Always make sure you clean everything prior to reassembly.