gsxr 600 srad 1998 missfire

[brenster]

hey guys,i wonder if you could help me please.my srad will rev lovely up to 7-8 thou then it stutters the rest of the way.now ive put a complete new motor in and its doing the same,so had the carbs off and cleaned them and drained the tank and added fresh petrol.still the same after that so tried a new coil and checked 1-4 cylinders and no difference so i tried a new cdi unit and still no change.i would be grateful for any feedback please guys im struggling now.cheers wayne
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[dextersaurus]

Maybe a bad earth? noticed my bike wouldn't rev cleanly past 4k when it had shorted out on the frame.

Other than that, are you sure the carbs are set up properly?

If the air/fuel mixture is out on any of them it'll effect it.

Dunc

[N cee thirty]

adding on to what dunc said..


are the min jets the right size ? when did the problem happen?

is the air box connected to the carbs securely
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[dextersaurus]

Oh yeah as rob has pointed out, airbox needs to be sealed... any holes in it, or loose panels and it'll throw the mix off.

Make sure the inlet rubbers are tight too, my GPZ died on me last month and i realised i had forgotten to tighten them back up.

Dunc

[brenster]

carbs were fine one moment then all of a sudden it was missing,maybe the mixtures arnt right but it ran fine for 3 months.
il check the earths thanks.the air box seems ok no air leaks but i still get the problem with the box on and off.spent some serious money on it now.i was thinking about getting another set of carbs off ebay just to try and rule that out
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[MaybeGuy]

fuel pump. does it still do the whine when you turn the key? and does the vacuum diaphragm still work properly?
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[brenster]

yeah it makes the fuel pump whine,and i know for sure that the vacuum diaphragm is ok because i sucked on it on sunday to drain the fuel out of the tank.really pulling my hair out now
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[N cee thirty]

you put new plugs in ?
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[brenster]

in my old engine i changed the plugs and it was the same.ive used the original plugs that were in this new engine.i know i should get some fresh ones but its ending up with the same story with 3 sets of plugs
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[N cee thirty]

i'm epically bored

https://www.bikechatforums.com/viewtopic.php?t=132497&postdays=0&postorder=asc&highlight=misfire&start=25

https://www.bikechatforums.com/viewtopic.php?t=197390&highlight=misfire

have a read through
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'00 Aprilia RS50 > '92 Honda CG > '99 Yamaha Fazer > '91 Yamaha RXS > '79 Suzuki X5 > 01' Honda Cg > 07' Honda Cg > 82' Kawasaki Z200 > suzuki gsxr 400 gk73a > honda vfr 400 NC30 Mod 2 Passed 09/06/2011

Jewlio Iglesias wrote: I actually did vote BNP once

[brenster]

thanks for finding them bud,il have another good check over everything again and let you know.thanks for your time
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[Ichy]

You've changed the engine, coils, CDI, and plugs.
In one way or another its can only be fuel / mixture. There isn't anything else, is there?

Does your exhaust system have any leaks? Will the engine stall if you cover the end?

Any difference if the bike is cold / warm?
Do you get the same effect when the bike is static and revved or just under load?

What happens if you get to say 9000 rpm and ease the throttle back a bit, does the misfire remain? Same revs and half throttle? Same revs and you cut the throttle?

You need to just check if there is a difference between opening the throttle fully or holding it half to three quarters open. At full throttle opening you are running mainly on the main jet. This also works out to roughly to anything over 7500rpm. By easing the throttle back a bit your introducing the needle.
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[brenster]

right,its the same cold and warm,the only thing i havent changed are carbs and wiring loom.revs are sweet until around 8 thou is then it bogs down bit it will rev through it after a backfire or two.also been out for a spin and its the same under load.i see what your saying with the needles but if i stripped the carbs i wouldnt know what to look for.i cleaned and blew everything out on sunday but it made no difference
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[Ichy]

Sorry to sound like an arse but in the first post you said it stuttered and struggled to accelerate but you just said that it just misfires a couple of times and then its fine?

Blowing through the carbs might not dislodge everything. The best thing to do is to take the jets out and leave them to soak for a few hours in a small jar of carb cleaner.

A quicker, more costly check is to just buy new jets.
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[MaybeGuy]

carb diaphragm
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[Ichy]

I thought the same Matt but then edited it out. I've not had a problem with diaphragms so I'm not sure but wouldn't it cause problems through the throttle range?
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https://www.metacafe.com/watch/1972097/how_to_behave_on_a_forum/

[Stowelly]

mine did that until i changed the plugs, now it runs like a dream

[brenster]

right il try another set of carbs on it and il let you know.i dont want to strip mine down because il lose bits and i wont know where they go ha.i will let you know how that goes cheers guys
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[dextersaurus]

Don't waste your money on buying a new set of carbs.

Just do one at a time, it's pretty simple once you know how.

Here's a guide on youtube, save yourself some money and clean the carbs you have!

https://www.youtube.com/watch?v=USqw8tYDUbw

Dunc

[brenster]

great little video that thanks,i shall have them off tomorrow and follow your advice.thanks for your time
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[brenster]

right had the carbs off and cleaned them like in the video,one seal looked dodgy so i replaced it,everything else was spot on.trouble is the fault is still there.got to be something simple surly
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[brenster]

justed taken the tank off and the pump out and blew out the filter,it was clean anyway,also taken my battery off and put it on charge.it was reading 12.3 volts
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[brenster]

battery reading 13.6 so all good.just moved the jets back one stage to see if more fuel would help but no different.think il put them back tomorrow and go and have a long run out on it to see if it helps
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[Ichy]

[brenster]

sorry yeah its been a long day
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