Carburettor overflow keeps dripping

[algaib]

I have just taken a Yamaha DT 125R out of storage. I removed the carburettor and cleaned away all the residue. It now works like a dream, except that about 10 minutes after I turn off the engine, the overflow pipe starts dripping. The overflow needle valve is in good condition (no sign of damage and looks like new) and I have adjusted the float height to make it more sensitive to the overflow, but still the problem persists. I have looked at buying a new overflow needle valve, but the cheapest quote I have found is £50, which seems rediculous for a tiny piece of alloy. Any suggestions? Or perhaps do you know a dealer that supplies these parts at a more reasonable price?

[Airhead]

Lets get the terminology right first 'algaib' Its the float needle valve you are referring to?

If you want or need to fit a new one then as you say £50 is ridiculous. Try motocarb or yambits, i'm sure they will both be able to get you one for far less than that.

When you cleaned the carb out did you remove the valve and also unscrew the seat to look for crud behind the brass seat, you really should have done. Take care there is a very fine gasket ring behind the seat.

Also dont mess around with the float height to try to correct a problem caused elsewhere, keep it to spec for correct performance.

[algaib]

Lets get the terminology right first 'algaib' Its the float needle valve you are referring to?

If you want or need to fit a new one then as you say £50 is ridiculous. Try motocarb or yambits, i'm sure they will both be able to get you one for far less than that.

When you cleaned the carb out did you remove the valve and also unscrew the seat to look for crud behind the brass seat, you really should have done. Take care there is a very fine gasket ring behind the seat.

Also dont mess around with the float height to try to correct a problem caused elsewhere, keep it to spec for correct performance.

I kept the float height within spec according to the service manual.

The fuel is coming out of the overflow pipe coming from the bottom of the float chamber. If there is crud in the valve seat or main jet, wouldn't the fuel be coming from a different overflow pipe? Or do they both go to the same place? Also, if the problem was in the main jet, wouldn't the engine just rev up like crazy? When the bike is running, it de-accelerates fine as normal.

[NE0]

Invaribly fuel coming out of the overflow is caused by the float 'stuck' in the down position allowing fuel into the carb from the tank.

My 400/4 has 4 carbs and one occasionaly tends to stick after I've stopped. But its a bugger to get at so it will have to wait until they really need to come off! keeping the petrol tap turned off after stopping solves the problem. (it only happened about twice last year hardly regular but I know the cause)

In your case stale petrol may well have gummed up the float pivot, or the float axle part.

I did say in your previous post cleaning all the fuel lines and ways is essential.I also noted that your earlier problem was caused by

the float valve in the carb was stuck from the residue of old petrol

I don't think you cleaned it enough.

As Paul says don't try correcting problems when its caused somewhere else and often the simplist explanations are the main cause.

I think you really need to clean everything inside and out. A carb strip down is just that, you strip it right down to its component parts and clean everything. If there's one bit of crud on the axle pivot the float will stick and you will have problems.

Every little nook and cranny needs to be so clean that you'd be confident you could it your dinner off it!!