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Bike Carbs running rich on one cylinder
whitestu - 16/9/12 at 02:38 PM

I took all the plugs out to check the mixture looked OK today and one plug is very sooty. The other three are fine.

The carbs are balanced and all have the mixture screws in the same position.

I haven't cleaned them since I fitted them and it has been standing with fuel in so they are probably bit gummed up, but what's the most likely candidate for causing one carb to run rich?

I've had the wideband on the car and according to that the overall mixture if fine, though the car is now not running right at lower throttle openings.


Thanks

Stu

Fatgadget - 16/9/12 at 02:56 PM

Swap em!

mark chandler - 16/9/12 at 03:21 PM

When apart you also need to check float levels are all the same, if one is carrying slightly more fuel then that cylinder will be running rich, could also be the float valve leaking, you may not notice with the engine running as petrol will just be drawn into the engine when at idle on the bad one and not out the overflow pipe.

Regards Mark

maccmike - 16/9/12 at 03:32 PM

floats will be the obvious one, might be a shitty plug or ht too

jacko - 16/9/12 at 04:15 PM

Try a set of new plugs first
Jacko

woolly - 16/9/12 at 04:15 PM

similar faults and mine was a lump of dirt over one air corrector.
removed each plug and found one black one.

whitestu - 16/9/12 at 06:42 PM

Thanks

I was going to stick a new set of plugs and leads on as well.

I'll give the carbs a good clean see what happens.

Stu

maccmike - 16/9/12 at 06:47 PM

when theyre off being cleaned, make sure all adjustments are set correctly

whitestu - 16/9/12 at 07:35 PM

quote:

when they're off being cleaned, make sure all adjustments are set correctly


Other than float height, needle position and idle mixture screw is there anything else to adjust?

Just dropped the float bowls off the two middle carbs and the heights are not the same so looks like that could be the issue.

Thanks

Stu

maccmike - 16/9/12 at 07:55 PM

no thats about it, take all the jets out and see what size they are, one could be too big, unlikely but you never know.

maccmike - 16/9/12 at 07:56 PM

oh and when theyve been off and cleaned, ideally you want to resync. although i didnt on the last session

maccmike - 16/9/12 at 07:57 PM

pps make sure the float needle aint sticking.

whitestu - 16/9/12 at 08:20 PM

Thanks

Stu