Hello, all..

I'm working on a '92 GSX-1100 Katana. It starts fine, runs fine and at normal riding, seems just fine.. at cruising speed, if you grab a handful and twist, it goes to bucking and acting choppy for a few seconds, then will pick up and take off..

I'm trying to determine if it is a carb or ignition problem, and what to check for both, or how to fix, anyway.. For some reason, I am under the assumption that if it were carb-related, it would fall flat, and an ignition would cause the bucking.. It only does it under heavy loading..


Ignition side: Ive got new plugs in it. Wires and coils age is unknown.

Carbs/fuel: Fuel is fresh, carbs are clean. I thought it had a jetkit, but I pulled one of the needles out and there were no multiple clip points on the top - only a white retainer, looking somewhat original.. Airbox is intact.

When it's cold, and idling w/o the airbox on, the #1 carb will get a 'pop' or slight 'backfire', and you can watch the light mist of fuel fly out the carb, and can feel warm air out of the carb when it does it, but once it's warm, this goes away..

I cannot find anything worthwhile for servicing/checking/adjusting the carbs for the GSX1100.. Haynes manual is the closest I can find for this bike, and that book serves better as outhouse toilet paper than it does a service manual, IMO..


Any help is greatly appreciated, and thanks for reading..

 

First off, sorry to hear you're fixing a Katana. Now to serious matters - It definitely sounds carburetor related. When it does that when you go full throttle, it means it has a lean condition at that point. Usually I'd tell you that you need to raise your jet needle clips one notch, but since they're stock...maybe your main jets are too small, have you done any kind of modifications to it that would require a jet kit?

 

Thanks for the reply.
It's not my bike (thank goodness), but as far as I know, and can tell, it appears all stock, minus the pipe. Thats the only thing I can think of that isnt stock. The owner said it has a jetkit, but I've never seen one that looked like stock needles

Would the floats being set too low cause this, as well? It's just confusing, especially with the whole vac./fuel line layouts..

 

Yes, low float levels could also cause this, but I would also imagine that it would affect throughout the entire throttle range, not just gunning it off partially open throttle. I'd say your best bet would be to get a jet kit so you have some adjustability in the carburetors, if it doesn't already have one that is. Otherwise, try messing with the main jets for a while.

 

Thanks, again..

That's kinda what I was thinkin, as far as the floats..
My biggest issue with troubleshooting this whole issue, is that I cannot find anything at all, worthwhile, on this bike and/or the carbs. makes troubleshooting rather frustrating.. Clymer has nothing on the bike, and Haynes... well.. it's Haynes... [sm=lame.gif]

 

I got the bike back today, and started checking things out..
What it's doing is after running for a bit, under load, it starts to crap out. It continually gets worse, until it wont go above 4k, and about 10mph..
It starts great, runs great for awhile, and idled in the shop for like 20 minutes, and I'd snap the throttle every few minutes, with great throttle response.. On the owners way home, about 25 miles into the trip, is when it started it.. When he brought it back to me, it started doing it again about 25-30 minutes into the trip, continually getting worse, until it got to the state above, at which time he was only 5 miles from the shop, so we hauled it on in.

I checked primary/secondary resistances in the coils, and they are within spec:
Pri 3-5ohms (1/4 coil) 4.0 (2/3 coil) 4.1
Sec 25-45k ohms (1/4 coil) 39.4k (2/3 coil) 39.9k

Plugs were all wet, but #2. it looked normal. The other wet ones looked a little black, and #3 was all black, couldn't see any white of the ceramic..

I'm gonna check the ignitor section tomorrow..

 

Manual says 15.7mm float height.. It's at 16.. If anything, that would cause a lean condition, rather than a fat condition..

I'm at a loss. (and talking to myself [&:] )

 

I'm gonna stick to my guns and recommend a jet kit. This will give you tuneability to an obviously ailing machine. The problem you're describing with the choppy full throttle was the same as my friend's ZX-6R after I put a jet kit and timing advancer on her bike. I took the carbs out and moved the needle clip one notch down on all four needles and the problem magically disappeared.

 

If that happened to my CBR, I would check for a worn float needle/seat or debris blocking one from closing. Just one of them being bad will usually flood the other float chambers through the vent hoses. Could also be a leaking float, clogged air filter, or choke that is stuck in the on position.

 

Yeah, and me being a novice with carbs, makes this whole thing that much more difficult.. I found the four screws where the sync tubes connect, and bought a used sync tool, but of course, it didn't come with the nipples to thread in

chickenstrips - I may go ahead and see if the customer wants to go with a Jet Kit and try that route.. Just hate to "throw parts" at it.. But at this point, I've got no other options to try, I suppose.
I'll keep you all posted, and thank you very much for your responses!!

The funny thing is, I posted this on a GSX/R forum, and haven't gotten a single reply.. Seems to me the Honda people obviously are more proned to lend a hand!! Again, thank you.