06 ABS question?

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tstaff

tstaff

tstaff
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06 A, From day one has had an odd feel when the bike was stopped but running. Example; when stopped at a traffic light holding the bike still with the front lever pulled, you could feel the pressure release then grab & the lever would pull closer to the bar, if you release the lever & pull, it would be back at full strength. Didn't think it was a big deal, never happened when moving just figured is was something with the ABS system until this weekend. Somethings up; stopped at a friends shop, bike is facing up hill, i set on the bike & pick it off the side stand while holding the front lever i feel the front lever release/grab, release/grab, release/grab until the lever is back aginst the handle bar. It has never done this before, no ABS warning light, nothing to indicate there maybe a problem with the system, i'm a little worried that i have a problem, maybe just air in the system or something but it's got my attention. Anyone else having similar issues?

At no time have the brakes acted strange while approching a stop, only when stopped, the brake pedal has never done this, front lever only.

 
tstaff - I was hoping the more technically astute would reply sooner, but I'll tell you I've never had any of the symptoms you describe. Never had a pulsing at stop with the lever coming back to the bars, etc. Only time my brakes/lever pulsates is when practicing panic stops or the two real panic stops I've done. Bleeding the brakes might be a fairly easy and good first step in solving your problem. Good luck and let us know what you finally figure out!

 
Made the appointment with my dealer for this friday to get it checked out.

Started doing a bit of digging myself to see if i could find a problem, leaking brake fluid, etc. No leaks that i can see. I jack up the front wheel to try & reproduce the lever fade, here is the strange part; with the front wheel off the ground i slowly rotate the front wheel while applying light pressure to the lever, brake pressure slowly fades until the lever is all the way into the bar & i can still turn the front wheel by hand, no front brakes whats so ever :eek: when i release the lever & repull it is back at full strength? Even more strange; If i don't rotate the front wheel the lever will not fade? All this is being done while the key is in the off position. Going thru the service manual it seems with the key off the brakes should operate like a standard non ABS bike, the ABS light comes on & go's out as normal upon start up & shows no error codes on the dash, any ideas how this is possible?

Thanks

Tom

 
Last edited by a moderator:
tstaff said:
Made the appointment with my dealer for this friday to get it checked out.Started doing a bit of digging myself to see if i could find a problem, leaking brake fluid, etc. No leaks that i can see. I jack up the front wheel to try & reproduce the lever fade, here is the strange part; with the front wheel off the ground i slowly rotate the front wheel while applying light pressure to the lever, brake pressure slowly fades until the lever is all the way into the bar & i can still turn the front wheel by hand, no front brakes whats so ever :eek: when i release the lever & repull it is back at full strength? Even more strange; If i don't rotate the front wheel the lever will not fade? All this is being done while the key is in the off position. Going thru the service manual it seems with the key off the brakes should operate like a standard non ABS bike, the ABS light comes on & go's out as normal upon start up & shows no error codes on the dash, any ideas how this is possible?

Thanks

Tom
Click to expand...
This could be a simple as air in the line, depends on the sequencing of the application. If, when turning the wheel, the initial application produces no braking, but a subsequent application does, this a classic air in system pump up. The ABS is not on if the key isn't, so it's not a part of the problem, unless you have a sticking valve in the ABS module, dumping pressure and producing the symptom. This seems to me, though, the more I read, to be air in the system, no doubt complicated by the linked arrangement, which would make for an interesting bleed procedure. IMHO of course... ;)

 
This could be a simple as air in the line, depends on the sequencing of the application. If, when turning the wheel, the initial application produces no braking, but a subsequent application does, this a classic air in system pump up.

That's what is strange; initial light application of the lever feels fine but then slowly bleeds off to nothing when lightly holding pressure on the lever (no pumping) with the front wheel turning. If you pull the lever firmly or don't have the wheel turning the lever feels solid & will not fade.

 
If the lever bleeds down while the bike is not moving/wheel is not turning I would suspect either the ABS or the master cylinder. A smooth, gradual loss of pressure would convict the MC. I've had this problem on old cars. The bumpy, intermittent loss sounds like an ABS problem to me.

The loss of brake pressure while turning the front wheel could be excess runout on one or both of the rotors. Too much runout - side to side wobble - pushes the brake pistons too far back into the caliper. The result is a single squeeze of the brake lever doesn't move enough fluid to move the pistons far enough to generate any braking.

Lots of possibilities here...

- JimY

 

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