GPz struggles at 3000+ rpm

Hey all,

My 83 GPz 550 recently had a carb cleaning and oil change. Lately, its been struggling, on and off, at anything higher than 3000 or 3500 rpms. After pulling the carbs and giving them another look over (still clean), I can't figure out what's going on.

The problem is constant now. Here are some clues; maybe someone can lend some advice.

-In neutral, the bike will rev up to 6000 rpms, if I SLOWLY twist the throttle. If I rev it QUICKLY, it sounds starved for gas, and putters until I release the throttle

-In first, second, and third gear, it'll smoothly climb up to right around 3000 rpms, and top out. I haven't been able to get up to speed to see whats going on in the higher gears.

-This bike came with pod filters, and ran well for about a year, so I'm thinking it was (hopefully) properly re-jetted. The PO had installed a pre filter in the fuel line. I've temporarily removed it and routed it stock-style, petcock to carb, to make sure there was no funny business happening in the tank-to-carb route.

-Maybe irrelevant, but I put a new clutch cable in recently. Smooth as can be, and shifts perfectly. Just noting it because things started getting funny after the last round of work (clutch cable, fork seals, carb cleaning, etc.)

I have two theories, but I'm probably way off base: There's been a minor off-and-on smear of oil on the left side cylinder head. Could a head gasket be causing these symptoms? My other thought is that maybe it's just a mixture issue? Are these pod filters in need of replacement or cleaning?

Anyway, thanks for reading and responding, Any help is always appreciated.

Always trying to ride more than wrench... someday.

Thanks,

Joe

Pic of the bike? What kind of carbs? Checked the spark advance to see if it moves freely?
Steve

And have you adjusted the valves?
Steve

Reinstall that inline filter and clean your carbs again.


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swest wrote: And have you adjusted the valves?
Steve

I haven't adjusted the valves. I suppose they're due for a check. I believe the carbs are the TK 26's. I'll double check today.

Thanks

As steve mentioned, Spark advanced would be the first thing I'd check. It may have seized up during maintenance down time.

or maybe a little hole in one or more carb diaphragms..
i had something similar in the past. in neutral the bike run well, not the same under load .

Thanks, everyone. Pulled the plugs and did a compression test and everything was fine. Pulled the carbs AGAIN and actually managed to get out the smallest jet (not sure which it is, but the one hiding under the plastic plug.)

The last time I had them off, everything looked pretty good, so I assumed the smallest jet was also fine. Also didn't have a small enough flat head to get to it. I had to grind an allen key flat on one end for a make shift flat head. Turns out they were pretty dirty.

I reckon the PO also got in there, realized he didn't have a small enough screwdriver, and left that one for the next sucker.

Anyway, thanks for the input. Bike is running better than ever now.

Next up: swapping out the clutch lever that I sheared off opening the garage door carelessly.

Oh, joy.

Im glad you sorted it out!