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Posted

Hi guys and gals

Ive got a kawasaki gpz900r A1 (1984) rides lovely exept when doing below 50mph and revs are below 4000rpm,the bike seems to pull then back off over and over making it very jerky at these speeds,anything from 60 mph (4000rpm in top) she pulls hard and clean but below that I have to be very very gentle with the throttle and still cant get her to hold a constant speed,Ive asked on the gpz900 owners club and they seem to think it sounds like the pilot jets are blocked,does this sound right and if so would this mean Its gonna be a carbs off job or is there anything I can put in the tank that would help? The chain and sprockets are in good condition with the correct amount of tension too.

cheers in advance

Dan

Posted

as you say your chain and sprock are good and tensioned right i would look at the carbs :)


a good clean up will help also get them balanced too


just to be sure check the chain for any tight spots as this can cause jerking

Posted

Yeah I clean,relube and adjust the chain about every 2-3 weeks,its something I'm a bit picky about having had a chain snap on me some time back,I'm guessing its carbs off time then?

Cheers

Dan

Posted

I would also say it's a a fueling problem, so yes check the carbs. Complete arse on some Jap bikes, took me 7 hours on my Suzuki GSX600F a while back, but well worth it in the end as some of the jets were indeed blocked. If you've not done it before it's not a hard job. Just take your time and don't get any carb cleaner on anything that isn't metal or it'll melt it. Like Stu says it's worth balancing them afterwards as well.


That said, running a fuel additive through might have some affect on the problem. You could try chucking a couple of bottles of Redex through some tank fulls to see if it makes a difference. I tried it on mine before resorting to a carb stripping. It made the fuel economy go up slightly, but I still had an idling problem which the full strip (wahey!) cured. Worth a try with the Redex first though I'd say.


Keep us posted on progress and if you run into bother give us all a heads up.

Posted

i had a similar problem on my bandit


the restrictors were fitted and the bike was jerky at all rev's however you could relate it to your problem, it turned out the carbs weren't suited to the restrictors (age thing) but it was causing an imbalance of air/fuel, so that is probably your problem :)


Regards

Anthony

Posted

Taken from Factory pro website http://www.factorypro.com/ go to product tech and CV carb tuning ,

sounds liek its lean and if youve got a aftermarket can or K&n airfilter without changing your jets then i bet that is the case but here what they say






* If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative pilot jets are supplied when normally required.

* Pilot fuel mixture screw settings, float level and pilot jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing pilot jet size will usually cure the problem.

o NOTE: A rich problem gets worse as the engine heats up.

+ If the throttle is lightly "blipped" at idle, and the rpm drops below the set idle speed, then rises up to the set idle speed, the low speed mixture screws are probably set too rich: try 1/2 turn in, to lean the idle mixture.

o NOTE: A lean problem gets better as the engine heats up.

+ If the throttle is lightly "blipped" at idle, and the rpm "hangs up" before dropping to the set idle speed, and there are no intake leaks and the idle speed is set at less than 1000 rpm, the mixture screws are probably too lean: try 1/2 turn out, to richen mixture. Be sure there are no intake leaks and the idle speed is set at less than 1000 rpm!

Posted
Hi guys and gals

Ive got a kawasaki gpz900r A1 (1984) rides lovely exept when doing below 50mph and revs are below 4000rpm,the bike seems to pull then back off over and over making it very jerky at these speeds,anything from 60 mph (4000rpm in top) she pulls hard and clean but below that I have to be very very gentle with the throttle and still cant get her to hold a constant speed,Ive asked on the gpz900 owners club and they seem to think it sounds like the pilot jets are blocked,does this sound right and if so would this mean Its gonna be a carbs off job or is there anything I can put in the tank that would help? The chain and sprockets are in good condition with the correct amount of tension too.

cheers in advance

Dan

my zx9r did exactly the same.... needed a good carb clean and new pilot jets.


the pilot jets are the main influence at those speeds/rpm so as long as your carbs are balanced, i'd focus on that area. may just need adjusting but could need cleaning/replacing depending how you get on.

Posted

Cheers to everyone for your help,gonna book the bike in at my local independant mechanics for a carb clean and balance,probably worth getting her serviced whilst shes in bits just to be on the safe side,will keep you all posted on how things progress.

Cheers again

Dan

Posted

HI guys,just a quick update.bike is in the garage as of today,am working away for a few days next week so the garage has her for the week,bought new X-ring gold chain and sprockets,having carbs stripped,cleaned and balanced plus a full service,plugs,oil and filter etc have also got an anti dive unit rebuild kit and new fork seals and the new headstock bearings have bedded in now and need adjusting so have asked them to sort these whilst they have the bike so I'm hoping she'll be perfect when I get her back,gonna cost me close to £300 but you dont see many 25 year old GPZ900R's around so I reckon its worth spending the money to get her right,will let you all know what she's like when I get her back.

Cheers

Dan

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