Rich w/ stock jets and pods and exhaust? 81 GPZ550

Hey everyone! I have been lurking around the forums ever since i got my 1981 GPZ 550 a week ago. Everyone seems really helpful and i look forward to getting your advice


It was running well on the trip home but all of a sudden its acting like it running rich. Now i cant even get her out on the road. It boggs and has hardly enough power to accelerate. The inside of the exhaust pipe is covered in soot. Why would it run worse all of a sudden? The float levels are perfect btw.

Another weird issue is that it has stock jetting and needles with pod filters + open headers and its still running rich. 32 pilot 94 main and brass non-adjustable needles. I pulled out the needles looking for washers but i diddnt find any.

Could my needles just be worn out?

Or is there a problem that causes these symptoms ^^^

Thanks for all the help guys!
Look forward to reading your responses!

LeopardPepper

If it was running well, and now suddenly seems like it is running rich, I would check you ignition.

See if you are getting good spark.

The jetting didn't suddenly change, so that would not be the first thing I suspect.

Have you ridden in the rain some time before it went bad? That can kill an ignition coil.

Have you checked individual plugs? It may only be one or two cylinders running too rich.

I know you had the carbs apart, but I've seen it happen more than once when a bike is running fine, then goes suddenly rich, after taking the carbs apart, it was found the main jet had fallen out into the bowl.

Seems strange that it ran fine with stock jetting. Did you put the pods on, or did it come that way? It's possible the previous owner drilled the jets to enlarge them. This may especially be true on the pilot jets since there are no larger pilots available.

At this point, I'd check the plugs. If there are only one or two running rich, I'd try swapping coils and see if the problem moves.

Tachrev- Good thinking thats the first thing i will do once i get home. Im just about to leave work at the bike shop (bicycle )

LoudHVX- I have not ridden in the rain but i have ridden on a couple wet roads. My bike also doesnt have that front fender so even a little puddle can turn into a lot of spray.

When im testing ignition, am i just testing for spark?

Ill check my plugs and take pictures of them when i check for spark.

Im pretty sure that none of the jets have fallen out. it has ran the same after i have reassembled the carbs the last 3 times.

the jets might actually have been drilled. Ill text the previous owner but i dont know if he will respond. If he doesnt respond, is there a way i can test or check to see if they have been drilled out? I dont know how else it would run fine with the pods and open headers. I bought the bike with the the pod filters btw. It did not come with an airbox.

Even if the pilots have been drilled out it idles pretty good. I guess i could try to track down some pilots if need be. Does the Dynojet kit come with pilots?

Im going to drop a DJ kit in when i have some money. Should be about a month.

As for now, Ill check the plugs for color and then i check for spark. ill report back in a few hours.


BTW, i want to thank yall for being so helpful, The last motorcycle forum i was on wasnt nearly as helpful. Thanks again fellas!
LeopardPepper

Hey everyone.
I just tested spark for all four cylinders and i also checked plug color.

All four plugs are sparking and all four plugs look good in color. All four plugs are white on one side and golden brown on the other. Is this normal?

Im at a loss and I seriously cant figure this one out... I even drained the tank and carbs and tried a new batch of gas. Premium this time. No dice though.

Any other help would be appreciated.

Thanks guys!

Look forward to hearing from yall

LeopardPepper

When you drained the carbs did you remove the bowls? I have also heard of a main falling into a bowl. I also cannot see how original stock jets can run with pods and open exhaust. Something is not right. They must have been drilled. Did you run an inline fuel filter?

Yeah i did remove the bowls. I tightened the jets back up too. I doubt a jet fell out but if there is nothing else to test ill go pull my carbs again. I have done it like 3 times in the past few days.

Well they jets are printed as stock but ill text the last owner and see what he says about drilling them.

I have ran an inline fuel filter and it looks clean as well.

Thanks for the response.
I might have to rip apart my carbs again if need be. Im just not looking forward to doing it!

Any other thoughts??

As long as the carbs are clean, and it previously ran fine on those jets, it doesn't matter if they where drilled out or not.

I would think the problem lies elsewhere.

Where the bowls full of fuel?

Did the spark seem nice and strong?

The last owner says that it has a jet kit but i dont believe him. he says they were not drilled out too...

The float level is good. Im about to go out and test it again though.

The sparkplugs were sparking but i dont know what a strong spark looks like. So i cant really say. Should i go out and see if they all are sparking with the same intensity? Would that be a plug issue or a coil issue?

BTW it revs fine in neutral and it acts perfect. But when you put it in gear and try to take off it bogs down and wont go above 15 mph. I have tried up to 1/2 or maybe 3/4 throttle no more that that though.

Another thing is look at the wires at night they may be arcing to engine, frame or ?.

Take it from a fellow '81 Gpz550 owner that you could be having intermittent failure of one or both of your ignition coils, especially if they are the originals. I was having all sorts of trouble last year with the way my bike was running. Old coils tested good and gave good spark, but when put in service they failed intermittently. The coils are part number 21121-1035 (#1/4) and 21121-1036 (#2/3) and are both still available from Kawasaki. I bought them from Ronayers.com for $68.45 apiece. I like the Kawasaki coils because they fit perfectly and have the correct wires on them. Consider getting new spark plug caps also, if they are original. New aftermarket NGK caps can be purchased from Z1 Enterprises. Here are the correct plug caps for your bike.

NGK spark plug caps