Dripping carbs

[zep93]

I am struggling with strange leak and I would appreciate some wise help before digging deeper.

So it all started in spring when I first started the bike after winter. I noticed that tap was dripping after turning it to PRI. It stopped dripping after some turning but then after couple of weeks it was leaking again and what was worse - all 4 carbs were dripping seriously underneath. Leak was so bad that it formed little lake under the bike, all came from carbs. Carbs were definitely dripping when engine was running (tap was ON) and maybe also on PRI (I do not remember anymore).

So to start fixing it I first ordered complete seal kit for tap because it was obviously leaking. After changing it the dripping was gone. No dripping from the tap and all 4 carbs were dry. I have driven bike only 2 times after that and today I smelled the slight smell of petrol. Closer inspection reveled that carbs in the middle are slightly dripping again. Not so bad like before but clearly they are not dry.

Bike is staring hot/cold perfectly and is running also ideally. So what should I check next?

[hugojose]

Fuel is fed by gravity and there are two thing stopping engine from flooding when not running: the petcock, and the carbs float needle valves.

.....but if you refreshed properly the petcock, then carbs should not flood, even if needle valves leak. Of course carbs can leak through the bowls gasket.,,and even through the throttle shaft. I'd try verifying where carbs are leaking from.


Basically, I'd make sure the petcock is not leaking by simply disconnecting to the carbs when not running, and NOT ON PRIME. Nothing should come out. Then, if nothing else, I'd replace carbs needle valves and bowl gaskets,...and then see how it does.

[Freddy]

Turn the fuel tap to PRIME position. Wait a few minutes. Now turn the fuel tap to the RUN position. Disconnect the vacuum line from the back of the fuel tap, and plug it with a small bolt of the correct size.

Start the engine, and run it till it completely conks out from running out of fuel. Now turn the tap to PRIME, wait a minute, now restart the engine and see how it goes.

If all goes well reconnect the vacuum line and turn the tap to the RUN position. Recheck.

Why does the above procedure work sometimes? By completely draining the carbies (yes this can be done via the difficulty to get at 'taps' at the bottom of each carby) and then getting a rush of fuel incoming while the float valves are completely open, the gunk which may be causing the carbies to flood is dislodged.

[Richard]

I've had this issue multiple times until I figured it were rust particles coming from the inside of the fuel tank.
Long story short, I fixed the tank and I had to replace the petcock, it didn't shut fully always, also caused by leftover rust particles. Problem was gone.

[zep93]

When changing the gasket set of the tap I checked the tank - it was completely clean, no rust anywhere, nothing in the tap filters. Like it was new!

Yesterday I took closer look. Nothing drips when engine is off. That means tap is now ok and problem starts only when petrol is flowing to carbs. Leaking appears to be come from second carb. As fuel feed tube is also connecting to carbs above second carb I suspect there might be the problem. I will take closer look on weekend.

[zep93]

Draining and refilling carbs didnt help. Still small leak under carb nr 2. I can see the whole lower bottom is getting moist, cant see what is happening with the top.

[hugojose]

Have you checked if the bowl fuel level is not set too high?? ...and I mean a wet test with a clear U-tube

[Richard]

Put a toiletpaper on top of the carb and you will know if it's the carb itself or the fuel supply above it?

[Freddy]

What I would do .... remove the fuel tank, and place it on a stand or bench near the bike at a height above the carbies. Connect the fuel tap to the existing disconnected fuel line with some appropriate size plastic hose and a joiner (Sold in any decent hardware shop). You will likely have to bleed the air out the line to get the fuel to flow.

Now you should be able to get a much clearer view of proceedings (remove the regulator and coils etc. if they are in the way of your view if necessary). Failing that pull the carbies right out and do the same exercise on the bench.