Fuel leak in carbs

**Comrade.Lance** · 29th January 2009, 16:42

I have a petrol leak coming from a screw in my carbs. This is a rather big leak as I noticed it was running down my engine onto my fairing where it was pooling. Smelt really petrolly. Not sure what to do or if this is a big problem, any ideas? I have included a blurry picture which I hope helps. The bike is a '92 cbr 250 RR mc22 .

**wired00** · 2nd February 2009, 11:31

Originally Posted by Comrade.Lance

I have a petrol leak coming from a screw in my carbs. This is a rather big leak as I noticed it was running down my engine onto my fairing where it was pooling. Smelt really petrolly. Not sure what to do or if this is a big problem, any ideas? I have included a blurry picture which I hope helps. The bike is a '92 cbr 250 RR mc22 .

It might be the float jamming and allowing fuel to continue flowing into the float bowl.

Try checking the float bowl of the carby, in that pic its the bottom area with the large drain screw/bolt attached. Make sure the float in both carbs is free moving (especially the side where the leak is). If you don't already know the float works just like the cistern in your toilet. Simply, fuel flows in -> floats rise -> the fuel valve closes. If the floats are jammed or possibly full of fuel (cracked or become porous) then they won't float up and close the valve correctly. If this happens theres usually a overflow hole which is possibly what's happening in your case. So yeah, open it up and make sure its not filthy with dirt or fuel varnish

**vifferman** · 2nd February 2009, 11:39

You're right - it IS a blurry picture, but it appears to be the carb drain screw that's leaking. Assuming it is, and the fuel's not just leaking somewhere else and dripping off the screw, all you need to do is turn the petrol tap off, remove the screw, and make sure the washer or whatever seals it is OK, then replace the screw, making sure it's tight.

**howdamnhard** · 2nd February 2009, 11:58

Replace O-ring or seal.Check its not simply loose first.

**surfer** · 12th February 2009, 21:50

Does the leak happen on the same side as the side stand? If so, get a carb gasket replacement kit as indicated above as your carbs are probably worn (especially as you have an older bike, this is a common problem). Meantime, best thing is turn off the gravity fed fuel tap under the tank EVERY time you stop, even for gas, as also noted above.

You might also want to check where else the fuel is dripping into. It may find its way into the engine by trickling through the cylinder on that side and mix with the engine oil. After a while of this happening your bike could seize, it will make engine knocking sounds first. You can tell if your fuel has mixed with the engine oil as the engine oil will feel a bit gritty if you rub some between your finger and thumb. You might also be wondering why your oil level never goes down but seems to increase. Also, the spark plug on that side will be wet giving you some starting problems. If so, replace the engine oil immediately to save wear on your engine, and sort out the leak or turn the fuel tap off every time you are not running the bike. Good luck.

**The Pastor** · 13th February 2009, 10:29

yeah you need a new seal kit for your carbs.

word of advice - get a new set of screws for the carb as well - they round super easily.

**Filmer** · 18th March 2009, 22:07

I had the same problem, was leaking round the seals of my carb bowls, i used a fuel resistant gasket goo, think it is called hylomar, available at repco.

**MSTRS:Me** · 19th March 2009, 08:26

Originally Posted by Filmer

I had the same problem, was leaking round the seals of my carb bowls, i used a fuel resistant gasket goo, think it is called hylomar, available at repco.

Yep. Had the same problem on a GSXR1100. This bike only had 2 bolts to hold/seal the carb bowl (instead of the usual 4) and one of the threads in the carb body was stripped. Hylomar 'fixed' the leak until I could sort the bolt/thread.
Either your bowl gasket is fucked, or the bolt/thread is stripped and cannot tighten enough.
When fitted, is the threaded part of the bolt exposed on the top side of the carb body it screws into? If so, and it's stripped, then fit a bolt from the top with a nut on the bottom to tighten.

**Racin Jason** · 26th March 2009, 08:39

Yip i agree, looks like the gasket leaking. Remember to clean the gasket surface well before refitting the bowl. I would prefer to use a new gasket rather that some sealant as the gasket has probably gone hard and perished.