Jerking under heavy load (9KRPM+)

[carlo]

Hello,

I'm experiencing the following symptom on my 91 katana 750 (53k miles):

Under heavy acceleration at the higher end of the rpm the bike jerks as if something disengages and engages momentarily. I haven't been able to recreate this problem in 6th gear.
Here's a little history about the bike:
I'm the original owner of the bike and maintained it well. The bike was in storage a couple of years ago, once out of storage we noticed that it was home to rats . We discovered that the rats chewed on the signal generator wires. I attempted to reattach the wires but since it was such a tight area not sure if the wires were reattached properly. Nevertheless the bike seemed to start and run ok except for the jerking problem. If I ride the bike gently the problem does not occur.
I'm wondering if the problem has to do with the signal generator wiring. Another suspect in my mind is that I may have a worn clutch? BTW, the bike is 100% stock with 53k miles on it.
About a year ago I replaced the chain and the sprockets which did not resolve the issue.

Can anybody help me identify what's causing the issue? any help or clue will be greatly appreciated. Let me know if you need additional information.

thank you,

Carlo

[5forty2]

I'm kind of new to bikes, so I could be wrong but sounds like clutch slippage to me.

[kevin2502000]

I would check to make sure the side stand switch wires are good, intact, and functioning properly. If it hits a certain resonation it could be vibrating and making the switch cut out momentarily. If it's not that, clean the carbs especially since it has been sitting awhile.

[squiggy]

I would say rev limiter, as that's how my Kat acts when it hits it as well, verrry jerky. However, 9,000 RPMs is too low for the rev limiter to kick in, at least for mine. With my Kat, the rev limiter engages 500 RPMs below the redline.

[carlo]

Thank you all for your responses. I will pursue these leads and report on the outcome.

Carlo

[ckenwright]

Drain and refill your tank, check your fuel lines and backflush them. If you have a fuel restriction or bad fuel you could get these symptoms.

[JHILDE]

With a worn clutch you should just get slipping, not jerking. I would look at the side stand as well.

[carlo]

So I removed the fairings and inspected the sidestand switch wiring. It all looked good. Then I realized that there's a side to side play in my sidestand. I suspected that maybe during heavy acceleration the sidestand's side to side play would trip the switch. To prove/disprove my theory, I temporarily locked the side stand switch in the depressed position (side stand up) with a cable tie and went for a test run. During the test run I was able to recreate the symptom while in 2nd gear, where the RPM was as low as 6500. I also remember hearing a grinding noise during jerking. I wasn't able to recreate the symptom in the other gears, but I probably didn't try hard enough because it dark out (9pm); didn't want ot be a sitting duck for some lucky cop. I have ruled out the sidestand switch being the issue.
I think I'm going to get professional help unless if there are other things I can check out. Checking the fuel line and carburator is way above my skill level. Thanks again for all your suggestions.

Carlo

[brentwoodkris]

Grinding sounds like a clutch issue.

[carlo]

So a mechanic took it for a test ride. He says that it's the tranny, specially the 2nd gear. The bad news is that it'll cost too much to fix it, but the good news is that it's in its early stages so if I ride it conservatively it may last quite a while. That works for me because I was using it for commuting anyway and I can be a little more conservative on the throttle.
If it gets to be unridable soon, I may be looking for another kat with low miles to swap out the motor/tranny. I'm ok for now, thank you all that responded.

Carlo

[TypeZXRs]

I wouldn't ride it.

On my last bike, I was riding in a 30mph zone and as quickly as I noticed a tranny noise the back wheel locked up... scary think was I was on the motorway shortly before. It was a major failure but not a freak situation.
I'd be careful driving it with any tranny issue as if it goes it can be unpredictable.

I'd ebay for a younger mileage engine/tranny from a good seller