G'Day,
I have a 1994 ZZR600. The bike idles perfectly and I can twist the throttle in idle no problems. When I take off and accelerate above first gear the bike doesn't respond to me twisting the throttle at all. It rumbles for a while and then in its own time it kicks in and the bike takes off like a rocket, a 600cc one anyway, at which point I have to release the throttle again, so the bike slows down, and then it rumbles and doesnt respond to the throttle again. Funnily, with the throttle pulled back, and the bike going nowhere, if I release the throttle the bike immediately accelerates?? My mechanic has cleaned the air filter, and carbs, and I replaced the fuel. My mechanic mentioned possible pickup coil problems, so I tried another IC Igniter unit for testing but the problem still existed. Any thoughts would be welcome.
Regards,
Kevin

 

Usually when an engine hesitates it is due to gummed up carbs, but since your mechanic says he cleaned them (personally I dont trust anyone else's work) then you may start looking into other avenues. Since its only under load I'm thinking it might be getting too much gas, did you adjust the mix screws or change the jets? How did the problem start? have you done any mods to the ride?

I suppose the pickup coil could do it, try ohming it out per the manual and see what you get.

Let us know what you find, welcome to KF!

 

G.Day Prom,

The bike stood still for a week and it rained for a couple of days. No modifications have been made to the bike. The exhaust system was a little loose at the engine block but thats all. It has been tightened since. I tested the pickup coil connecter with my own digital multimeter and got an infinite resistence reading as per the manual. Another guy at a dyno place suggested I check for water in the spark plugs and another mechanic recommend I check for water somewhere near the fuel pump? I would have thaught that my mechanic would have looked at these. I'll keep you posted.
Thanks for the feedback.
Kevin

 

lol, never assume that the mechanic did anything you didnt specifically request. I had a similar problem after a rain, turned out to be water in the fuel but even after cleaning everything draining the tank replacing fuel filter and everything I couldnt get it running right for a while. Could have been water stuck somewhere (I doubt water in your plugs is a problem)

My solution was to run the hell out of it until I got everything cleared through the system. If you cant find anything else wrong with it, try riding her hard for a few days and see if it improves.

 

Indeed never assume anything. (Not messing with your mechanics abilities here either)

Fuel issue is normally the first as mentioned. I would clean those things again, replace the carb needle/seats, set the floats and verify carb synchronization. (a big thing even on my 90 zx7 lists to do). At the same time verify that there are no cracks or loose boot fittings. (it is a 94). The plugs should have been changed out after the carb cleaning in my opinon so that a plug chop could be done.

Welcome to KF

 

Just picked the bike up and the second mechanic cleaned the carbs again and cleaned the fuel tank and replaced the fuel filter. He mentioned that the carbs had the wrong jets but was confused since the bike has performed fine for the last few years so he then thought that it must be OK?? He is at a loss and could only suggest replacing the 4 jets??? He put the bike on a dyno and said the bike was starving for fuel as the air/fuel ratio was too high?? I told him that when the throttle is pulled back with the bike going nowhere, if I release the throttle, so I would assume less fuel flow, the bike suddenly takes off. He also asked if the bike made a knocking sound beforehand as he thought that perhaps it could be a broken link in the cam chain but I said that the bike made no funny noises and ran smoothly on its previous rides. Not quite sure what to do next other than take it to someone else again or perhaps consider getting another carb at a wreckers?

 

I should clarify that there is no knocking sound now either.

 

If it has the wrong jets that could cause your hesitation. You should be able to find the jets but dunno how cheap they will be

Yeah if it runs you didnt break the cam chain, and your mechanic knows that...

 

Hmmm, if you're on a dyno, you're usually into the main jets pretty hard. I suspect the primaries are "close" and the mains are too small. Not a hard job to replace jets. Go to (one of our sponsors), or Dennis Kirk or other big box place that still sells jets (for antiques like ours.) Look at the size of your mains, and buy 2 sizes up, 4 sizes up, and 6 sizes up. (4 each.) Or, post in the classified section here and see if anyone can help. Include the size of your current (incorrect) mains. Swap out until it runs right.

Caveat: If the bike was "running fine" the past few years, with the same jets, you need to make sure they're CLEAN, first. You may not have a problem at all. Do it yourself so you learn something (and save money.)

 

Just another update on my saga. This time I took my bike to Peter Stevens motorcycles in Ferntree Gully, Melbourne, Australia. I bought the bike from their Ringwood store more than 10 years ago. They have a few dealerships in Melbourne, probably the largest motorcycle chain in Melbourne or Australia. I told them the carbs have been cleaned twice and the bike looked at by 2 other bike shops. I was initially warned off them from a Motorcycle wreckers who said that they would put an apprentice on the job. Anyway, I decided to visit them. Their experienced mechanic took my bike for a ride and said it was the pickup coils. My first mechanic also suggested the pickup coils after cleaning the carbs but I lacked confidence in the way he handled the situation. Furthermore I thought he was taking me for a ride because he didn't even really take my bike for a thorough test ride on both occassions before telling me the bike was ok. Man I was pissed off. Anyway, I have bought another pickup coil from the wreckers here in Melbourne, which arrives tomorrow. They were kind enough to only charge me $35 for testing the IC ignitor. So I'll see tomorrow and let you know.
Kevin