carbs overflowing

[hobbo]

Can any give advise on my carbs overflowing fuel out of overflow pipes, the bike is a fz600 1987 i am useing a

small make shift tank with no breather pipe fitted to it i have balanced the carbs but when i turn fuel on it

pours out of overflow pipe, if i start the bike it stops and runs lumpy and back fires on over run and starts to

run on 3 cylinders,i removed carbs checked for any crap in float bowls but was clean, i have a diffrent set of

carbs and tried them the engine run realy good but this set of carbs started to over flow as well even with engine

running then the engine run on 3cylinders but a different one this time, i replaced the original carbs it run

lumpy but was running on 4 cylinder, new coils, leads,caps,battery,have all been replaced.should i strip my

orginal set of carbs,or use the other set, i dont know what i should be looking for to cause them to overflow

the other set of carbs i think are of a radian model i was told they have smaller jets and no mixture adjustment

factory set would it harm the engine to use them as he engine is the same,could the spark plug be getting to much

or not enough fuel if it is coming out of overflow. any help would be welcomed.

[chris66]

if the float hight is set to high it would cause this also if the float valve was not seating properly through wear or dirt i would also give these symptoms.

it sounds like your float bowl is continuously filling causing the bike to flood hence the bad running and loss of one cylinder. chris

[hobbo]

Hi chris, thanks for reply i have stripped carbs down and all 4 idle jets are blocked,main jets look a bit narrow

i checked float hight with digital vernier gauge and look spot on 20mm hight as per book,there was some more jets

under the diathram dont know what they do, float needles look good so ithink i will rebuld it and see what happens,

what do you clean the diathrams with spelling looks wrong.

thanks Dave

[chris66]

clean the jets with tin carb cleaner and compressed air if you have access to a compressor,

but not anything rubber as the cleaner is suppose to rot rubber.

my diaphragms are never dirty so not sure if there is a specialized cleaner. chris

[hobbo]

Thanks for the tip, i have rebuilt the carbs took me 6 hours reset float hight, air screw,etc ran the bike and it sounded 100% better but was still running on 3 cylinders removed the plug and there was no gap i dropped the plug a few days ago and forgot to check it, re gapped plug and ran on all 4 cylinders sounded even better, balanced carbs

with vacum gauges wish i had a better set as these ones are so hard to get a true reading, and no over flow of petrol

from carbs, the bike is still a bit hard to start hot or cold would adjusting the air screw help as i set it to 2 half

turns as the book says, if i use a little easy start it fires up every time and runs fine,i can not take it for a run

as it is not fully rebuilt i think this what it needs,any think else i can check

and the back fire has stopped hanks dave

[chris66]

i would Finnish rebuilding then give it a run see how it goes. doesn't seem to much wrong now perhaps a little tinkering with mixture and balance again would get it spot on.

if the bike has a race can on it that can effect the starting, hold your hand over the exhaust when starting and see if this helps.

i use a morgan carb tune, they are about £50 on there web site, always found it easy to use.

chris