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On or off throttle clank/clunk

4K views 20 replies 5 participants last post by  nigelrb 
#1 · (Edited)
Okay.... I have not torn the bike down to figure this out (Yet...). SO- as descriptive as possible.. maybe?

If I let off the throttle abruptly, pull in the clutch fast, or go from 100% off-throttle to on (not 100% on.. we know how that'd go in 1st gear) I get a strange hesitation, then clunk/clank, and she goes normal. Does the same thing letting off slightly when clutch-less shifting but also using the clutch (rarely do this...). Easiest way I can think to "equate" the sensation is if you have something rolling around in your trunk/truck bed. So from off-throttle to on you have a moment of hesitation, then the "weight"/"load" hits the back with a clunk, then you accelerate fine/normal. Letting off gets a near-immediate thunk like you hit the brakes and your cargo hit the front of the bed. Make any sense for this analogy? Anyway. My initial assumption was to adjust my chain (as it feels almost like excessive.. severely excessive) chain slack being taken up.. but that doesn't even make sense coming off throttle.

2002 CBR 954, about 47,000miles.. original clutch =) SO thoughts? I was thinking maybe the clutch... but I really only use it to start moving from dead-stopped and don't feel any slipping under hard throttle. Ideas would be great! Also going to start tearing through the manual.

Edit: Might be worth mentioning... this problems seems less noticeable at higher rpms. The "smoother" the shift (usually at high-rpm) the less it does it... I'm still thinking clutch-related... but I'm no trans guy by any means.
 
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#4 ·
Difficult to say from a distance, but could it be (?) a strange thump in torque common with those new fangled Fuel Injected bikes, made worse by a worn/failed component?

My XX is lovely when I am rolling off and rolling on the throttle - as in riding it on the road, smoothly and responsibly.

If, however, at lower rpm, I wack open the throttle, it feels like it has bogged down for a second and them gets going with a bit of a lurch.

On a dyno, it has very clearly lost AFR control. Do I need to say at this point that I have a full aftermarket exhaust. :wink

So, is there any chance that it is an engine torque transient due to a failing electrickery component? ECM fault codes?

The solution is of course a Carburettor'd CBR-RR bike, that only has lashings of silky smooth torque.

[With the added benefit of regular Carb re-fresh work, which is a pleasure to do :devil].
 
#9 ·
If, however, at lower rpm, I wack open the throttle, it feels like it has bogged down for a second and them gets going with a bit of a lurch.

So, is there any chance that it is an engine torque transient due to a failing electrickery component? ECM fault codes?

Not even opening it fast. Just going from off-throttle to open a bit coaxes the sound out. Most noticeable shifting 1st to 2nd (with or without clutch.. with clutch seems worse?) but with the neutral passthrough that doesn't shock me. On let-off it doesn't always seem to do it, unless I pull the clutch in a bit above idle (lets say 2500rpm or so) or slam the throttle shut (not normal but I tested it out and it provokes the stated noise of doom)

Electrickeery component is also a possibility =) But this "feels" mechanical... still would not dare rule out a failed something with zappy power.
 
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#6 ·
Thanks for the replies fellas! I can verify chain slack is not an issue (first thing I did was clean/lube/adjust) just to rule it out. It kind of feels like excessive chain slack.. but I do 400 mile chain cleaning and lube and adjust when needed. But it gets checked frequently.

I have to pull the wheels off to get the new hoops mounted anyway so I'll look at wheel bearings and cush drive (honestly hadn't even thought of the cush drive getting beat up for 47k miles...). Might take some time to get to it.. but updates to follow.
 
#13 ·
Still haven't got to this to be honest.. sadly riding has taken second stage to life. FML? Really wish I could get out more! Need to look into this problem but at the rate I'm riding it isn't that much of a problem. Is it sad to say I've spent more time at the gym than I have riding??!?!?! Pretty sure that's a yes!
 
#16 ·
If I don't end up selling my sweetest Serenity I have to locate this issue.. the cush drive seems possible... but honestly (as a person that does almost all of their own maintenance) seems like something in the clutch. Always subject to be wrong. I just need to time to ride let alone fix an issue....
 
#18 ·
The feeling of riding in general. The first ride on her was simply serene. I had not rode in a few years, and aside from being on a litrebike as my first ride in about 6 years it was just beautiful. SO... she ended up being Serenity... the feeling I get when I ride her.

Pretty sure at this point it is the cush drive.. still have not had the weather cooperate to go check it out though.. soon~!
 
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