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Carburator Questions?

Featured Replies

Assembled the bike, and upon installing the feed line and opening the petcock - I had fuel pouring out the back of the carb.

So there's this 4th outlet, that I thought was for overflow purposes, or something? But after looking at the drawings, I am at a loss. Is my '99 w/ Dellorto supposed to have the "sub-air cleaner" unit? What does it do? And also, what does the 'air vent tube' that loops around the carb do? I reckon it's supposed to have the gash in it?

Edited by ARH

  • Author

Okay, so I just stuck an extended rubber hose to the hose barb so it won't leak. Upon attempting to start it, I didn't even get a slight inkling of combustion.

This thing has ALWAYS been a second-kick-start bike, but then again I've never had it apart like this. Could the fact that I patched together (ie. sealed) the proclaimed "air vent tube" have something to do with it?

My Jeep is wrecked, my license is suspended, my finals are coming up... and I wanna ride so bad now! :D

Think you want to check the floats and the fuel valve , sounds to me like the float(s) are stuck and the fuel is just pouring through the open valve

  • Author

Hm, that's awkward. The carb has been super reliable before, and I didn't take it apart at all...

check the needle & floats these wondrfull bikes that we play with can be very upset by a a little disturbance..assume you have got sparks...

  • Author

I'll check the spark before I dissasemble the carb.

Anyone have a clue about the sub-air cleaner and vent loop line?

Yes if you sealed the vent tube it can cause fuel to come out the overflow and or starve for fuel

I assume your Dell'Orto model is PHBH26BS, right? When you say "fuel pouring out the back of the carb", which specific orifice is it coming from?

Your carb has 4 orifices. One is a fuel feed line. The 2 on opposite sides are vents, and they are connected together by a single vent hose with a gash in the middle of it (the gash is how the air is supposed to get in there). Remove that hose and blow through it to make sure it isn't gummed up. The 4-th orifice is connected to a sub-air cleaner, which is basically a tiny foam air filter. Its purpose is to feed air to the air jet inside the carb. If you sealed off this circuit, then your bike doesn't have a prayer of running. BTW, there is no overflow tube on these carbs. The fuel can overflow through the vents, but only if you lay the bike on its side, or if the float valve is stuck open.

  • Author

Mucho gracias for the replies!

It now runs and have a working clutch!

Still got that leak though, it's hard to localize, but I'm thinking it could be the output axle seal (where the chain sprocket is)? The color kinda has a motor oil color to it..?

So, I think I'm gonna try some Dexron III ATF for the gearbox. Is it a no-no to just top off the oil level without knowing what kind of oil that is in there, or should I do a complete drain and fill? How can I when it's full?

Oh, and Mr. Fastducs, it's a PHBH26BC. :blink:

  • Author

Will do. What color is the Elf stuff?

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