Leaking fuel

[warx]

After breaking my WF motor in I went for some "hot" laps at Infineon. It was running well except I realized I was too highly geared (14:56). I could just about hit the rev limit on the end of the straight (it was the National clock-wise setup). This left me a bit sluggish out of two or three corners (down to 4000 where my clutch seems to engage). Still I won't be racing this thing there anyways. Although.. the new manager, KC, said they are trying to bring 4-cycles there... They have a 2-cycle 4hr endurance there this Saturday.

Anyways, second time out I got black-flagged due to leaking fuel. My overflow pipe was wet. I just ran it down to the ground and am wondering if I should've ran it upwards (and attach it to something on the top?!). Also wondering if the float level is a bit high with the 15-deg engine mount. I had no issues I could tell with fuel mixture though.

I also lost one bolt of of the motor mount to frame clamp somehow. Oh well the engine is still with me so all's good... I like this little motor.

[ron90]

Some of us had similar issues. Mine turned out to be float level too high. Also at one track I ran a catch container to see if it was filling it up. It was, so I adjusted the level again.

I try to light my leaking fuel on fire with a lighter if someone is behind me. That usually forces them to try and pass, or they just back off.

[RichH]

Had similar issues has you. Two things have been discussed. The float level being to high and causing the overflow. There is also some theory that on long high RPM tracks that the fuel pump can over pressurize the needle valve. Some of have a pump around tee in the pressure side fuel line back to the tank. Similar to the pump around on a shifter motor. One thing is for sure is that you have to have that overflow drain to a catch tank. I just make sure I drain it before every race. Your fellow racers will be sure and clue you in if it is spraying all over the place.

I once went out for a heat race at Dixon with the bowl drain half open. The thing ran fine all race. A lot of people told me how much fuel I leaking at the end of the race.

[warx]

Alright! Some good advice. Thanks!! I will tweak the float level a bit (since it is tilted). I'll also fit a catch tank - since I don't have a crankcase vent/catch I've got an unused tank. I'll save the pyrotechnics for emptying the catch tank - I am enough of a track menace. So nobody does anything special with the tube itself (i.e create an inverted U tube?) Someone at the track mentioned that if it was just splash in the bowl causing stuff to come out the vents not just the level. It must've been quite a bit since he was saying it was on his visor and my right-rear has that streaky doped pattern to it...

[Dan Pell]

Sounds like fun @ the track. All good advise above, Ron & Rich are on top of their game!The tube on the bottom of the bowl MUST drain, or you're encounter a overly-rich motor. I'd suggest a small catch-can, with the tube into the top, then a small hole drilled into the catch-can about an inch or two up on the bottle. This way, any excess that develops will spill out so that the bottle does not become full. If it does,the fuel can only drain into the motor, and a stumbling condition WILL develop! To set float height, Briggs suggests loosening the hose clamp, then taking the carb off at the rubber intake. After removing the floatbowl, turning the carb upside down, measuring 14mm (.551) from the carb base, to the top of the float (heel & toe the same). One can eyeball it, the float (again, heel & toe) should be level to the carb base.

[warx]

My float height measures at 14mm which is stock. I will tweak it a bit lower. I did notice there's a second overflow or bowl vent that is just a stub out the side by the choke lever. I think it was originally plugged (had a cap fitted over it). I have the plug I think when I was fitting the fuel lines I pulled off all the plugs. Should this one on the side remain covered? It's a little brass tube closed at the end but a tiny hole in it's side. When I flipped the carb over it dumped a little gas out of it so it must be open to the bowl.

But... drawing a mental line across from where the floats would shut off the fuel seems like to have the same head of water present at the main jet lowering the level is actually the wrong way to go! It's a shame the rubber carb mount does not have symmetrical bolts allowing it to be flipped. It would actually put that carb back at the original slight tilt.

I am wondering if I'd be better off with a 5deg mount. I have plenty of room since I chopped my chassis cross member when I fitted the clone way back. Still, don't want to spend more money!

[Dan Pell]

That small orifice in the brass is a carb vent, and yes...unobstructed. Is there a fuel filter in-line? Racers do make the 15 degree mount work on OHV, more do choose the 5 degree. If you raised the number to 15mm, less fuel should theoretically accumulate in the bowl. The whackin & hackin on your frame should be interesting on chassis dyn- amics, guessing it's a noodle! Do you have a rear bar, might want to test with it to increase some rigidity @ 390#? Don't spend bucks on a new mount, you can make that one work.

[warx]

I ordered a 5deg Burris mount today. I know yous guys have it working fine @15. I want a backup mount anyways so figured this would be a safe bet just in case. I guess you're supposed to move the float level up when you have the tilt and this makes the leak worse - or you deal with starvation at the end of long straights (like Infineon). I also ordered a bigger catch tank (the RLV one with a quick release strap) since my one seems a bit small for a long race!

[Dan Pell]

Good choice on the 5 degree, you'll find that the motor works well with that. As for the "long race", are you considering the SWM 4 hour gathering?

[Brad Wunder]

Oh, my, God, as I'm catching up on posts I saw this one and thought oh crap, I meant to tell you on Saturday that you are STILL leaking fuel. That one time we went out and I was following you I could see fuel coming out of the left side (from my vantage point behind) of your carb. But before I could motion you off the track you lost your chain in T6. Then I headed into the pits to send out the recovery vehicle for you.

By the time we were all in the pits together I completely forgot to give you a headsup. Then you took out your 250 (that thing sounds FRIGGEN AWESOME) for a lap before tangling with the clone and that pretty much ended the day.

Annnnyway, Houston, we still have a fuel issue...

[warx]

Oooohh... well I collected about 12mm of fuel from the overflow/drain so it looks like I'll need to put a tube on the side vent as well and Y it into the catch. All this with the reduced float level too. The Intrepid is getting the 5deg mount so maybe that'll clear it up. I'll return the float level to stock. Unless of course this is the over-pressurization thing. A pump around is going to be a PITA to do on these tanks.

[Brad Wunder]

I'm sure others can provide more help on this than I can, but, you shouldn't have to go through all the trouble of doing a Y into your catch can. IMO there is something fundamentally wrong here and the fix is most likely super simple. Unfortunately I'm not smart enough to provide the answer. Sorry.