[letourneaualex]

Hi

I have a 1995 ZX750-L3 that looks very clean and actually works quite well except that when I'm in second gear and above 5k rpm - and only under those conditions - the bike feels like its 'slipping' for a fraction of a second and then starts to run normal again. Since it only happens in 2nd and at higher revs I thought for sure the second gear might have a rounded tooth or something, so I figured if I have to take it apart to fix this let's make a complete rebuild project out of this bike since the models 95 and earlier look like they're getting real collectors' bikes status.

So after taking apart the bike completely and getting to the gears, all the gears looked in A1 shape! Could anything other than a faulty gear give me that kind of behaviour when in every other gear and at any revs the bike runs pretty much perfectly, starts every time instantly, idles great???

Also speaking of the rebuild in itself, is it really possible that if some of my fairings are cracked, it's close to impossible to find some at a somewhat decent price? Engine parts don't look as hard to find but even on Ebay there isn't much so I found this product that seems to work fairly well:

Motorcycle Fairings Repair with PlastiFix Fairing Repair Kit

www.polyvance.com

Anyway in case some of you like the project I included some pics of my bike pre-surgery and the current madness state that is my garage.

Thanks for any insights, I'm sure it'll be appreciated when I try to remember how to put this majestic crotch rocket back together!

Cheers

 

[ninjanut]

Likely as simple as slipping clutch. If the gear dogs were rounded/worn, it would pop right out of gear not just slip.

 

[letourneaualex]

Why does this not happen in any other gear then, I can redline all the other gears but the second??

My logic tells me that I would have that issue with more than just one gear if it was a clutch issue.

In any case the clutch parts are in pretty good condition, I might still change the clutch plate while the engine is open, but the basket looks great.

 

[ninjanut]

Had a buddy who had similar symptom only in second. Likely due to the load in lower gears. Not in first long enough to notice. He changed clutch plates and problem gone.
I would have checked the clutch and other simple checks before splitting cases.

 

[57x]

It's a semi-slipper clutch. An older worn clutch would turn it to a full slipper, and eventually just slip. An easy check would have been to go 30 MPH, then slip the clutch with lots of throttle. My guess is it would have tach'd out like it was in neutral.

 

[92Ninjas]

Why does this not happen in any other gear then, I can redline all the other gears but the second??

My logic tells me that I would have that issue with more than just one gear if it was a clutch issue.

In any case the clutch parts are in pretty good condition, I might still change the clutch plate while the engine is open, but the basket looks great.

Wait for it

Had a buddy who had similar symptom only in second. Likely due to the load in lower gears. Not in first long enough to notice. He changed clutch plates and problem gone.
I would have checked the clutch and other simple checks before splitting cases.

I, too, had a similar issue. Replacing the steels and fibers fixed it.

It's a semi-slipper clutch. An older worn clutch would turn it to a full slipper, and eventually just slip. An easy check would have been to go 30 MPH, then slip the clutch with lots of throttle. My guess is it would have tach'd out like it was in neutral.

I did this exact technique to confirm it was the clutch. I could make the clutch slip every time in 2nd gear on a 30mph roll-on.

 

[letourneaualex]

Wait for it

I, too, had a similar issue. Replacing the steels and fibers fixed it.

I did this exact technique to confirm it was the clutch. I could make the clutch slip every time in 2nd gear on a 30mph roll-on.

And you could only do this in 2nd? Cause to be fair I just went to look at the clutch plates and they look like new, however I couldn't find the recommended thickness anywhere to confirm that they're good to go. The manual I have is the Haynes and the only thing it mentions is the warp test and couldn't find those spec on the Internet either, maybe some of you brilliant fella could enlighten me.

 

[ninjanut]

Also, if someone replaced the clutch in the past, did they set the correct stack height as per the manual?

 

[92Ninjas]

And you could only do this in 2nd? Cause to be fair I just went to look at the clutch plates and they look like new, however I couldn't find the recommended thickness anywhere to confirm that they're good to go. The manual I have is the Haynes and the only thing it mentions is the warp test and couldn't find those spec on the Internet either, maybe some of you brilliant fella could enlighten me.

If you run No Slipper Clutch, all plates should be 2.3mm
Medium slipper is 4x 2.3mm plates and 3x 2.0mm plates
Full slipper is 2x 2.3mm plates and 5x 2.0mm plates

If you run Medium or Full slipper, the thinner plates should be stacked going towards the clutch cover.

To answer your question, yes. 1st gear didn't have enough torque and load to trigger it. 3rd gear required me to go way beyond the posted speed limits to trigger it. Plus, I run 17f/40r for sprockets. You might as well replace your steels and fibers since you have it open. Check your springs too. I don't remember the specs off-hand. But, it's worth looking into.

Also, if someone replaced the clutch in the past, did they set the correct stack height as per the manual?

I couldn't find a recommended specs for the pack height other than 3 different configurations for how much slipper clutch you wanted. E.G. None, some, and all.

 

[letourneaualex]

So I showed the gears to a mechanic and eplained him the issue and he was able to get through my thick skull how the clutch issue you guys mentionned is very likely the problem and not the gears, actually he thought they probably got changed not long before I bought it cause they looked new.

Looking at my Haynes manual the clutch spring standard free lenght is 34.7mm and minimum lenght is 33.5mm, all of my springs were between 34.5mm and 35mm so technically all within specs which doesn't explain why I have that problem.

I'm thinking I'll just change the plates and springs anyway since it's pretty cheap. Not sure what the OEM springs specs are - unless it's the standard lenght stated in the manual - be but on Ebay there are 44mm springs which I'm assuming are longer than OEM and might therefore make it a lot less likely for the clutch to slip, but then again maybe they'd be too stiff or even wouldn't fit. Any opinion on this?

Otherwise I'll just order both set of springs.