carbeurator rebuild

[adleeman]

79f... my experienced neighbor rebuilt my carbs...weve checked the floats 5 times... blown air thru the t's. turn on the fuel to prime and gas flow out the pilot and bowl vent rapidly. brand new parts.... no crud...... start in on position and it does the same thing...... no idea what to do any help appreciated....

[fredintoon]

They shouldn't do that, eh?

Hi Tony,
is it possible that the gas lines are run to the upper tees that the '79 has that are vents, rather than the lower tees where they should go?
If not, your floats don't float or your float needles & seats don't seal.

[boyat68]

It took me more than eleven times through my carb re-build to discover that the floats were sticking in several places. At first on the edges of the new gaskets where they extended into the bowl, then the floats were dropping too far down in the bowl and sticking. The solution to the problems was to trim the gasket edges on the inside and make sure that the tang on the back of the float is bent just enough to allow the float to fall just a few millimeters. Also the floats must be pretty square with the valve so that they fall equally. Many of the posters on this web use a setup off of the bike to check for carb leakage before they are put back on the bike. This gives you many opportunities to check fuel flow and leakage.

[DGXSER]

You got a leaky faucet...

And so do your carbs. Let me asure you I feel your pain. My carb floats never leaked a drop until after I rebuilt them.

Then it was like playing with fire everytime I put them back on. I even bench tested with Prometheus's upside down test, and the right side up air test and everything passed and worked, hooked them up on the bike and one or two leaks. I finally got to it being very small pieces of fuel line scraping off or coming loose from me using hose clamps on my auto grade fuel lines when I put the lines onto the tees and such hooking it all back together and getting into my float valve seats. I was amazed at how LITTLE it takes to have one stick open. I switched to the yellow fuel line for lawn tractors at my local Home Depot and not a drip since (knock on all the wood I can find.) HTH.

[adleeman]

carburetor woes

am using auto grade fuel lines and they are not working too good for me.
could my petcocks be malfunctioning somehow....
the fuel lines are going into the bottom of the bowl the uppers are venting to air....i tested the floats by blowing into them. its a very heavy high pressure flow. lots of gas... #1 and #4 . switched floats to try to move the problem but it stayed at 1 and 4.

[DiverRay]

REMOVE THE AUTO FUEL LINES and back away from the carbs!! You NEED the proper lines on the '79.
Clean out the needle and seat once again. I would use a spray can of carb cleaner, and pull the needles, spray the cleaner into the seat to blow all the junk back out of the fuel path. Check and VERIFY!! that ALL FLOATS are SQUARE TO THE CARB BODIES, and STOP via the tang about 4mm below the setting. If the floats are set to 26mm, they should stop at 30mm. Check the gaskets to verify NOTHING is touching the floats, and that THE FLOATS CANNOT TOUCH ANYTHING IN THE CARBS BUT THE PIN AND NEEDLE. If this is all correct, you should NOT have any "sticking" or leaking carbs.

[DGXSER]

Ohh yeah, that reminds me, I also took a razor knife and trimmed the gasket along the sides of the float bowl so none if it overhung the bowl to interfere with the floats.

DiverRay hit it, once I switched fuel lines, the problem went away for me.

[adleeman]

tang

the only tang i see is the one the pushes the needle valve? is there another one?

[DiverRay]

With the floats installed, hold the carb body upright. Looking at the float pivot pin, check UNDER the needle tab, and you should see a tab hitting the aluminum body at the seat/needle. This is the "lower" stop tab. you need to adjust it so the float only drops about 5 to 7mm.

[petejw]

turn your carbs upside down with the bowls off,
blow into the fuel inlet, make sure u wipe all the fuel away, fuel tastes like crap, you'll hear and feel the air escaping at the point where its leaking.
Ive recently had to do this with mine after fitting a dyno jet kit.
If it doesnt leak this way, place the bowls back on the carbs and tip them up while blowing in the fuel inlet, if the floats are sticking on the sides air will escape.

[CatatonicBug]

fuel tastes like crap,

But I'm sure you'll suck down plenty o' beer?? Now that stuff is nasty!

[dbeardslee]

You might check your vent lines, and make sure they are clear. I have pod filters installed on mine, and had some small fuel filters on the ends of the vents to keep crud out. They got a little plugged (you could still blow through them, but they weren't right), and every time I turned the petcocks on, fuel would run out the filters. Took the filters off, and is if by magic, no more fuel pouring out. Interesting physics there.

Also, be careful blowing air into the "T's". If you do it with the bowls attached the pressure can squeeze the floats affecting their boyancy. Somewhere up the po line somebody did it to mine and I wound up replacing all the brass floats with plastic. My $.02.

[adleeman]

bowl gaskets....

just checking is this the correct gasket orientation?

[DGXSER]

If all the holes line up wiht the holes in the carb body, you got it. Seems to me if you got them on the other way round, the hole does not line up with the vent tube.

Do you see the "tang" against the float bowl "tower" on the right side in your picture, that is the one DiverRay was talking about. And when you check your float height, make sure it is with the gasket removed.