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Hi,

 

Okay, I fitted my bike carbs (GXSR600) with the following spec:

 

> in-line fuel regulator

> manifold connected to servo and distributor

> timming 8 degress

> no air filter

> jets 120

 

I've set them up as per threads I've read, mixture screw 2 - 3 turns and the car idles okay with little popping. However, when you drive the car feels a little slugish below 3000rpm and when you accelerate it just boggs down and stutters. I've disconnected the distributor, no difference. I've advanced the timming, no difference. I've increased the fuel pressure, no difference. I've increased the size of the jets and still no difference. I've seen threads that tell you to block the air correcter jets but not sure if to try this. As anyone else used this type of carb??

 

Any help would be appreciated....... :mellow: :mellow:

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what manifold - engine size type please

 

woolly

 

The engine a standard 1600 and the manifold is home made. It was designed to accept the original carb mountings (no silicon hose used). The angle was also set at 30 degres. I've just taken the car out again and what I have noticed is when driving and it starts to stutter when you press the clucth it revs freely i.e not under load.

 

Hope this is of help.....Andy

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Be careful not to damage your engine as I think you are running VERY lean. I have GSXR carbs on a 2ltr Pinto, it bahaves the same when lean.

 

If you block up your air corrector jets you can run smaller main jets (anything between 1.3 and 1.5) or if you leave them open you will need jets between 1.6 and 1.8.

 

All these sizes are approx as every engine is different!!! but best to run slightly rich untill you are sure. ie many test runs and plug reading or a couple of hours on a rolling road.

 

Good luck

 

Sean

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Try clamping the petrol pipe and if it goes well then dies its too rich, its also too rich if it runs well when cold and gets worse as engine warms and visa versa.

Are the plugs black or light pale grey.

If it has an air filter take it off and if it goes better its too rich.

I cannot think what else to suggest but good luck.

I have just this weekend replaced the jets with 1.5 instead of the 1.7 that were in there on my 38 mm Keihlins on a 2litre Pinto. The car is running much better with nice wheel spinning.

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thanks for the quick replys. How do you make the mixture richer?? I've checked and I don't think you can adjust the needles. Head is checking sore now (not sure if its the fumes though)

 

Cheers will try clamping the fuel pipe just now........Andy :rolleyes:

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Just checked the plugs and clyinder 1&2 are light grey 3&4 very light brown. Therefore I assume I need to make the mixture richer but how do I do this......

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I checked the carbs last night and the needles have the adjustment at the top. Therefore I've brought the needles up a notch but could drive the car so don't know if this has help. -_- :D ^_^ Fingers crossed........

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I checked the carbs last night and the needles have the adjustment at the top. Therefore I've brought the needles up a notch but couldn't drive the car, so don't know if this has help. -_- :D ^_^ Fingers crossed........

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Hi,

 

Finally got the car out yesterday to see if the mods had made any difference. I've rasied the needles to the max, set the timing to 10 degress and tried tuning the balance of the carbs with a hose pipe. It was driving better but would only pull to about 3500rpm before spluttering. Then I blocked the air correcter jets and she pulled good in first but again spluttered in second around 4500rpm. I don't have a filter yet but looking at ordering one with a back plate from GBS. Therefore, I'm I correct in thinking I'm drawing to much air or should I increase the size of the jets?

 

Cheers Andy

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I still think you need to go slightly bigger on the jet size, maybe 1.4 - 1.5mm, with the needles back to the middle setting, pretty certain that the gsxr carbs work best with the air correcters blocked off too. What have you done for crank case ventilation, have you connected back to your manifold or have you pulled the guts out of the valve and vented to atmosphere or catch tank?

you should be able to get it running well without an air filter, but if you fit one later you'll have to change your settings.

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Okay, I'll look at increasing the jet size. Why do you say the middle setting for the needle? The crank case breather has had the valve removed and vents to atmosphere .

 

Andy....

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If you get the mixture to somewhere near correct by changing jet size, with the needles in the middle you can fine tune it richer or weaker by adjusting them

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hi, i have a 1.6 pinto on cbr600 carbs i am running 1.5mm main jets, and have the tandard vacum dizzy just to air, and have thedizzy at between 24-28deg advande at idle, and it pulls through the revs freely under load or not. and starts first time every time and idle fairly smooth.

 

stuart

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