Cycle Forums: Motorcycle and Sportbikes Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Whadaya think. After getting my bike, 94' zx9r, dyno'd. I noticed that under hard acceleration in 2nd I appear to have either a bad gear or worn shifter forks. Reason being is that the bike seems to skip as if there is a tooth missing on the sprocket.

Any insight on this kind of problem.

Am i causing the bike/tranny any more problems by riding in this condition.
 

·
Registered
Joined
·
17 Posts
Does it only do this in second? Not in first or third at all?

It soulds like you may have broken a tooth off of one of the gears for second, which would be bad to leave that way. It'll further damage the transmission just having the tooth missing, andwhere did the tooth go? What if it gets caught between other gears? It could be a mess, especially at high speeds...

Now, I've seen a tight worn-out chain with a tight and loose spot do basically the same thing, but you should see it to at least some degree in other gears as well. So check very closely and carefully to see if it's appearing anywhere else.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
espresso said:
Does it only do this in second? Not in first or third at all?

It soulds like you may have broken a tooth off of one of the gears for second, which would be bad to leave that way. It'll further damage the transmission just having the tooth missing, andwhere did the tooth go? What if it gets caught between other gears? It could be a mess, especially at high speeds...

Now, I've seen a tight worn-out chain with a tight and loose spot do basically the same thing, but you should see it to at least some degree in other gears as well. So check very closely and carefully to see if it's appearing anywhere else...
It only does it in second and under very hard acceleration. One other thing to note it just start doing this after a run on the dyno. ;(
 

·
Registered
Joined
·
17 Posts
Yeah, sounds a lot like a missing gear tooth to me.

Can't imagine who would have dyno'd a bike in second gear. Pretty useless for doing any tuning.

Also, unless someone threw it into second gear from neutral without using the clutch and with a stopped roller on an inertial dyno, it should not have broken from anything regarding the run itself. If the bike was run in second gear, it may have simply been the one stress event when the tooth finally failed; however, if the bike was well-maintained and relatively low-mileage, I would be very troubled by this. Were you present for the dyno run?
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5
espresso said:
Yeah, sounds a lot like a missing gear tooth to me.

Can't imagine who would have dyno'd a bike in second gear. Pretty useless for doing any tuning.

Also, unless someone threw it into second gear from neutral without using the clutch and with a stopped roller on an inertial dyno, it should not have broken from anything regarding the run itself. If the bike was run in second gear, it may have simply been the one stress event when the tooth finally failed; however, if the bike was well-maintained and relatively low-mileage, I would be very troubled by this. Were you present for the dyno run?
Yeah, I was present, I don't think that the dyno did it. We, mechanic and myself just noticed it when he ran through the gears getting to 4th gear for his roll-on tests. It seems to slip under hard acceleration.
So you suspect a missing tooth?
Damn!
I have talked to 2 mechanics since my last posting and both suspect either worn dogs or gear shifter fork, I'm just not sure.
With this kind of work I do not want to get screwed when I do take it in to get repaired.
Woest me
:(
 

·
Registered
Joined
·
17 Posts
robski said:
Yeah, I was present, I don't think that the dyno did it. We, mechanic and myself just noticed it when he ran through the gears getting to 4th gear for his roll-on tests.
Ahh, gotcha. But you never noticed it before that?
It seems to slip under hard acceleration.
I want to make sure I'm understanding the problem... In second gear ONLY, there is a regular slightly lurching as you accelerate hard, but not in any other gear at all, correct? Not a slipping at high rpms where the rpms rise faster than the bike speed, but a sort of mild lurching that happens as a regular cycle and increases with engine speed, and would be pretty fast compared to rear wheel speed.
I have talked to 2 mechanics since my last posting and both suspect either worn dogs or gear shifter fork, I'm just not sure.
Either of those things would result in not engaging a gear fully and having it pop back out, or engaging it and having it pop back out to neutral or a false neutral (or possibly even the next gear) under hard acceleration or deceleration. The problem you're describing does not sound like either forks or dogs.
With this kind of work I do not want to get screwed when I do take it in to get repaired.
Woest me
:(
Well, the "good" news is that any of those things will require splitting the cases, so you're not going to be any worse off labor-wise no matter what it turns out to be. And regardless of whether it's bearings, dogs, gear teeth, or forks, you'll be able to see the problem visibly without trying very hard once the trasmission is out of the cases.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
espresso said:
Either of those things would result in not engaging a gear fully and having it pop back out, or engaging it and having it pop back out to neutral or a false neutral (or possibly even the next gear) under hard acceleration or deceleration. The problem you're describing does not sound like either forks or dogs.
That makes sense! The bike has never popped out of gear, it may have been hard to shift into second. I have noticed in the past under hard acceleration that I have missed a shift to second, but never have I successfully shifted to second and have the gear pop out.

Thanks, I greatly appreciate your time and thought given to this thread.:D

Damn I just got the bike out of the shop, pic enclosed.
 
1 - 10 of 10 Posts
Top