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Bike Carb Fueling Problem


Guest fzr1000dave

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Guest fzr1000dave

can anyone help i have fitted zx7r carbs on my pinto it has been on the rolling road this week and at 5500 rpm it all goes to lean the jets have been drilled to 195 and it has just had a faset fuel pump and regulator fitted but its still running to lean the engine has a stage 3 head and fr32 cam its producing 120 bhp at the wheels and revs very well but just gets to lean top end.

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i have fireblade carbs on my pinto also dyno'd they fuel correctly through the rev range they have 1.3mm mains and blanked off air correctors may be the carbs are the not right for the engine i know the guy who set mine up said blade carbs were the best for the pinto (his opinion) i,ve been running them a year and half now with no issues.

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can anyone help i have fitted zx7r carbs on my pinto it has been on the rolling road this week and at 5500 rpm it all goes to lean the jets have been drilled to 195 and it has just had a faset fuel pump and regulator fitted but its still running to lean the engine has a stage 3 head and fr32 cam its producing 120 bhp at the wheels and revs very well but just gets to lean top end.

 

195 sounds huge. Is it possible you are leaking air into the carbs?

Try spraying WD40 around them to see if the engine tone changes.

Have they been stripped and cleaned?

 

Andi

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Guest woolly

what about the rest of the rev range and depends on, how it goes lean. if it never goes slightly rich at WOT then a combination of needle - jet size - air corrector size.

if it goes slightly rich then leans straight out may be the fuel flow not high enough.

the air corrector is a fine tune to the main jet but also by mixing air allows better atomization so in my mind not to be closed off completely. but it is generally done to good effect.

also air box and trumpets make a big difference to these carbs.

 

woolly

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Guest fzr1000dave

what about the rest of the rev range and depends on, how it goes lean. if it never goes slightly rich at WOT then a combination of needle - jet size - air corrector size.

if it goes slightly rich then leans straight out may be the fuel flow not high enough.

the air corrector is a fine tune to the main jet but also by mixing air allows better atomization so in my mind not to be closed off completely. but it is generally done to good effect.

also air box and trumpets make a big difference to these carbs.

 

woolly

hi woolly im not shore mate bd enginering of sittingbourne has the car he started off at 1.7 jets and now 1.95 he fitted a new fuel pump and reg incase that was the problem robin hood recommended zx7 carb said there easy to set up apparently its pulling like a train through the rev range but struggles at around 5500 revs he just said it gets to lean i was going to go for 40s . im running them without a fillter to and they still have the trumpets from the bike the to middle ones are longer than the to outside ones would this make a differance

thanks for the advive

thanks dave

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Guest fzr1000dave

195 sounds huge. Is it possible you are leaking air into the carbs?

Try spraying WD40 around them to see if the engine tone changes.

Have they been stripped and cleaned?

 

Andi

hi andi yes mate he has tryed that and its all ok.

thanks dave

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Excuse me adding to this thread as I have never played with bike carbs. Do they have adjustable floats. Low level will have more effect at WOT. Is angle of carbs important? Could one carb be a problem and affecting the lambda?

I found this little pic a while back on Locosters I think, about what does which, how, to who and where. Suggests it's correctable with bigger main jets?

 

Nigel

post-21-127383235318_thumb.jpg

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Excuse me adding to this thread as I have never played with bike carbs. Do they have adjustable floats. Low level will have more effect at WOT. Is angle of carbs important? Could one carb be a problem and affecting the lambda?

I found this little pic a while back on Locosters I think, about what does which, how, to who and where. Suggests it's correctable with bigger main jets?

 

Nigel

 

You may be better off fitting a fuel pump which matches the carbs, if you do a search on locost builders some people have had similar issues.

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Guest Robin Allison

Just put ZX9r carbs on my pinto. Had it set up at Bogg Bros. Air corrector blocked off and main jet drilled to 195. Due to a problem with the dyno set up, which i'm not happy about its the same as yours and i said it to them at the time. It pulls like a train to 5500rpm then runs out of puff.

It to is going lean.

You will find the fuel it about right to 5500rpm, it the main is drilled bigger the fuel will be too rich until over 5500rpm. What you need to do it make the needle adjustable and drill the main jet bigger. The needle then needs to be moved lower to reduce the fueling up to the 5500rpm point.

But the best thing to do is fit a dynojet kit. This gives you the adjustable needles.

Lots of info here http://justkdx.dirtrider.net/printcarbtuning.html

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