Shudder/Clunk When Downshifting

stormypetrel

Registered
Hello everyone,

Just picked up a busa with 19k on it and when I test drove it, everything seemed to run like a dream. Fast forward to the other day when I made a crappy downshift without blipping the throttle and there was this terrible studder. The bike shook and made a loud knocking sound till it caught in gear (with the throttle). I've been able to recreate this, but only while downshifting by releasing the clutch with no throttle. I know this isn't proper, but I don't think it should be doing this either. It is worse in the lower gears than in the higher gears, but still there.

I have increased the idle to 1250 and that helped quite a bit, it was at 1000 before. I replaced all the cush rubbers and just replaced the chain. Sprockets look fine and I'll replace them both when they come in the mail.

Anyone have any ideas? Thanks!
 
Yes that is what it feels like, is that normal for these bikes? I've been riding a gsxr 750 my whole life and each ****ty downshift never caused anything of the sort.
 
Broken clutch spring, Broken clutch fiber plate.

Pull the clutch I am sure you will find a bad broken fiber.

Thats my guess broken clutch fiber.

personally I wouldnt ride it. something broke and its floating around in your oil.

As I say though Aint my ride.....
 
I'm not doubting you, I just have a lack of knowledge on the subject. Why does it only affect the downshift? Why does a burst of RPM make this issue disappear?
 
I am not a physics engineer nor have I crawled up in behind the clutch cover to watch the clutch plates reactions to different scenarios, I am speaking from past expierence on the symptom you described. Could be something with the energy motion being reversed on the plates / basket causing this.
Have you pulled the clutch cover to inspect the clutch yet?
Pull & inspect the clutch and give us your evaluation.
 
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