[97dirtybird]

I bought a bike from off of here from az_bb. Great bike and has many aftermarket parts. I have a major problem with the front brakes. It has a violent shake down when anymore than one finger is used on the front brake. It still pulsates with one finger.. basically have to apply 5-10% pressure. Delinked with stock master, pretech calipers, technical sport racing brackets. I think the problem is that the calipers are mounted way too low and far away from the forks leading them shake almost like at the end of a stick. I think they need a bracket at the bottoms of calipers to connect to bottom of forks or bottom of caliper mounting brackets. Any thoughts? Az_bb said his honda shop could not locate problem and rode it like this for years.

 

[-Tom-]

Rotors good? Could be that they're warped for some reason?

 

[beestoys]

Considering the loads the caliper see's I'm betting your on the right track with the brackets. One way to confirm would be to mount a camera to the fork or body work aimed at the calipers and see how they act.
Where is the bike located now?

 

[ptxyz]

if you suspend the front wheel, does it spin freely? in other words, the disc brakes will drag slightly but, it should be even without "hanging up" in spots.

 

[97dirtybird]

Yeah everything was said to be fine after being looked over many times. Rotors and calipers. I thought about the cameras but don't have access to any. I can look down and see the bottom of the forks and they vibrate back and forth. I'm in ohio. I'd have to dig out my cherry picker to get the front end suspended, would be quite the process lol

 

[97dirtybird]

Just looks poorly designed to me only having two mounting bolts way up high, and none down low. Lots of torque on the calipers.

 

[fizzy]

When you say pulsation/ shaking, can you be more specific? Does the lever pulse. Do the bars shake from side to side. Does the whole bike shake ? etc.
Also, if you do emergency stop from 50 mph, what happens?
Have you considered hydraulically eliminating one calliper at a time to pinpoint the trouble?

Edit: worn fork bushings?

 

[ptxyz]

if you have a low enough jack, you can gently (use a block of wood) jack up under the front of the oil sump with the bike on it's center stand to raise the front.

while you're "up there" (front wheel suspended), give things a wiggle to ensure there's no play in the steering head bearings, wheel bearings or fork bushings (again, gently... bike's a tad precarious when supported thusly...).

those brakes look great, i'd like to think whomever made those adapters didn't leave you with a non-functional mess. i have an adapter on my klr650 with an sv650 caliper and oversize rotor but, it's positioned much closer to where the stock one sat.

 

[97dirtybird]

Yeah the whole front end shakes. The bars go back and forth pretty hard possibility up and down as well, not side to side. It does this at all speeds when I use the front brake. A alot rougher the faster your going. I originally thought the rotors, but was told they checked out fine. I wonder how much it would cost to just have it looked at. I have thought about eliminating calipers to determine which side but I bet its both.

 

[iXXion]

Easy enough to throw a set of stock calipers on there and check it out.

And yes, I cannot see why those mounts would NOT be a problem. I agree there is way too much unsupported stress.

 

[fizzy]

Instead of a camera mounted to the bike, have someone next to you in a car take video with a phone camera if that's all you have.

Fork bushes? I am thinking of a stiction feedback loop. Perhaps the forks or triple tree were damaged in a prior accident.?

Additionally, that front wheel looks non stock, perhaps the wheel spacers are wrong, tweaking the forks or misaligning the brakes.

 

[97dirtybird]

Ok, perhaps I will throw the stock calipers on there this wke. Hopefully all stuff needed was given. Indeed they are different wheels, supposedly was never in a accident.. From my understanding with bad fork bushings you have constant play and clunking in the steering. I only have this issue when brakes are applied. Thanks for all the replies.

 

[beestoys]

You say you don't have any headstock movement right. What your describing also sounds like loose bearings. If they are tight and you have the 5# drag Honda recommends for stock forks. Then I agree caliper swap to see if it goes away. I'd not ride it either till it's figured out. If either one of the brackets fail it's going to get very ugly fast.
Hopefully that wheel will allow the stock calipers to be bolted back on.

 

[fizzy]

What about the wheel spacers? This non standard setup maybe forcing fork legs together or apart slightly.

Also, are the centreline of callipers = centreline of discs?

 

[beestoys]

Hmmm
Looking at those wheels now if that isn't a dip coating I'm thinking those are DIA MAG carbon fiber.

 

[fizzy]

Hmmm
Looking at those wheels now if that isn't a dip coating I'm thinking those are DIA MAG carbon fiber.

I thought it was a wrap. If this is a carbon fibre wheel it may have hidden damage that only shows up under braking forces.

 

[beestoys]

I thought it was a wrap. If this is a carbon fibre wheel it may have hidden damage that only shows up under braking forces.

Suspecting they may be carbon the spoke design looks very similar to bears old 3 spoke DiaMag.
Second the hidden fracture damage of carbon fiber. It's great for weight saving but you have to keep on top of it.

 

[97dirtybird]

You can see this bike about 24 spot in our bikes for sale section. Yes they are diamag carbon fiber wheels. Seller mentioned that he never sent the wheel back to them to have checked. Had about everything else looked at.. This was almost a deal breaker when looking at bike its that bad. Prob big money to send back to UK to have checked. I'm hoping just caliper setup now at this point. Anyone in the states that can check this?

 

[beestoys]

Let me check with Bear he ran the Diamags until he parted it out. He may know a stateside location. You might also want to contact DiaMag as well and see if they have a source.
I also know a MotoGP and Superbike contact I'll ask as well.

 

[fizzy]

Can you fit a standard blackbird wheel back on without messing with the brake setup?