Author Topic: bad gas leak!!!!! (Read 2922 times)

kopptl · « **on:** October 07, 2009, 09:28:57 PM »

bike: 1976 cb750.
finally got everything back on, and when i turned the gas on, after about 10 seconds, it started running out of the faces of the carbs and the overflow tubes. gas was flowing out of 1-3, as it is on its side stand (no center). any ideas or suggestions???

ekpent · « **Reply #1 on:** October 07, 2009, 09:46:57 PM »

You are going to here stuck float valve and floats which will be correct.Why do so many guys have this problem------did you give the carbs an A-1 carb clean?

Did you put any aftermarket parts in

Is it from the overfow tubes or around the bottoms of your cabs

kopptl · « **Reply #2 on:** October 07, 2009, 09:49:26 PM »

clean as a whistle!!! and all the floats moved freely when i worked on them , as well as the needle and seats are BRAND NEW!!!!!!

ekpent · « **Reply #3 on:** October 07, 2009, 09:53:40 PM »

Where is it leaking from???

ekpent · « **Reply #4 on:** October 07, 2009, 10:00:55 PM »

76??? Single feed line out of the tank is the spliter or 3 way from the tank and 2 carbs sealed well

kopptl · « **Reply #5 on:** October 07, 2009, 10:05:23 PM »

its pouring out the front of the carbs, where the air cleanre should go!! all lines are tight!
single feed out of the tand that hit a 3 way splitter and feed to 1-2, and 3-4.

ekpent · « **Reply #6 on:** October 07, 2009, 10:08:41 PM »

Do not light a SMOKE until the PRO'S CHIME in. What have you done recently to the motor ? Did you change out base gaskets of the carbs. You say gas is spewing on 1-3 into the intake cleaner side

kopptl · « **Reply #7 on:** October 07, 2009, 10:10:38 PM »

re-built the carbs!! TOTAL cleaning!!!!! Brand new needles, jets, seats, gaskets, ht=e works!!!!!!!

ekpent · « **Reply #8 on:** October 07, 2009, 10:24:38 PM »

Sorry to be so picky but when you say from the face of the carb,have you isolated the exact spot?. Aftermarket float bowl seals can be junk-never pick out or replace original if they are good and not leaking------------ WHOOO new thread.

mystic_1 · « **Reply #9 on:** October 07, 2009, 10:26:39 PM »

To what height did you set the floats when you cleaned the carbs, and how did you perform the measurement?

mystic_1

david 750f · « **Reply #10 on:** October 07, 2009, 10:29:25 PM »

Check to make sure the float bowl gaskets are seated properly (not pinched). Does the bike leak only on the sidestand? If you sit on the bike does it leak as badly?

ekpent · « **Reply #11 on:** October 07, 2009, 10:40:00 PM »

+1 or two on Davids opinion and mine-make sure the base gaskets are sealing if the are "new"

ekpent · « **Reply #12 on:** October 07, 2009, 10:45:57 PM »

Well he is gone----- Must of fixed his problem-------or ran out of Gas-

kopptl · « **Reply #13 on:** October 07, 2009, 10:49:43 PM »

still here. set the floats to 26mm!! made sure the "Tang" on touched the needle and did not depress it!! and just measured and tweaked till all were exact!!!

i did replace all of the float gasket, the floats are good!! and gaskets are not pinched!! the gas is pouring out of the bore of the carb!

Terry in Australia · « **Reply #14 on:** October 08, 2009, 03:59:48 AM »

Your overflow drains are blocked. Pull the hoses (if they're still attached) and blow them out with compressed air, and take your float bowls off and unblock the overflow tubes in the same manner.

Because your tubes/hoses are blocked, the fuel level will continue to rise until it comes out thru the carbs venturis. Cheers, Terry.

Johnie · « **Reply #15 on:** October 08, 2009, 04:13:27 AM »

Any chance the floats could be in upside down? We have seen this before.

kopptl · « **Reply #16 on:** October 08, 2009, 08:47:04 AM »

i dont believe i put them in upside down!! i would feel a fool if i did. the problem is, it was draining out of the overflowes as well as the bores. i had forgotten(Dumb mistake) to put the overflow lines on. and when i turned the gas on. the overflow lines pour as well as the carb bores!!! sounds crazy i know. but thats whats happening.

Duke McDukiedook · « **Reply #17 on:** October 08, 2009, 08:59:36 AM »

Yeah, if you did everything else right and put on a new rebuild kit, you might have put the floats on upside down.
Or, they might be bad (not float properly) and you might have to replace them.

Gordon · « **Reply #18 on:** October 08, 2009, 09:01:18 AM »

If I'm not mistaken, the upside-down float problem causes the fuel level to be too low, not too high.

Disclaimer: I'm still working on the first cup of coffee, so nothing I type can be used against me in a court of law.

mystic_1 · « **Reply #19 on:** October 08, 2009, 09:11:01 AM »

This has got to be float-related, that's the only thing that could cause this sort of leakage.

I'd do this: Drain the carbs, pull #1 float bowl, turn petcock on, lift float with finger, verify fuel shuts off. If it does, next shut off the fuel and reinstall float bowl. Remove the float bowl drain screw and jam in a piece of clear tubing. Hold other end of tubing above carb level and turn the fuel back on. Fuel in tubing will rise to same level as inside the float bowl. Level should be just below the float bowl mating surface.

Repeat on #3. Post results.

mystic_1

kopptl · « **Reply #20 on:** October 08, 2009, 10:15:14 AM »

the bike is on its side stand!! i have no center stand and cant ust the jack, i would have to remove the exhaust to get it to work! if the makes a difference. i will try the floats in a bit.

Slayer · « **Reply #21 on:** October 08, 2009, 10:27:15 AM »

Quote from: mystic_1 on October 08, 2009, 09:11:01 AM

This has got to be float-related, that's the only thing that could cause this sort of leakage.

I'd do this: Drain the carbs, pull #1 float bowl, turn petcock on, lift float with finger, verify fuel shuts off. If it does, next shut off the fuel and reinstall float bowl. Remove the float bowl drain screw and jam in a piece of clear tubing. Hold other end of tubing above carb level and turn the fuel back on. Fuel in tubing will rise to same level as inside the float bowl. Level should be just below the float bowl mating surface.

Repeat on #3. Post results.

mystic_1

Thats a great idea mystic. That might help me with my current problem. Glad I read this.

kopptl · « **Reply #22 on:** October 08, 2009, 10:53:12 AM »

ok, took off the #1 bowl, and help the float up and turned on the gas. after a bit it started streaming out of the bores, the vents at the top of 2-3, and the other drain!!!!! did i mess something up??

Duke McDukiedook · « **Reply #23 on:** October 08, 2009, 11:13:46 AM »

At least you know the #1 valve works!

mystic_1 · « **Reply #24 on:** October 08, 2009, 01:57:45 PM »

Something is rotten in the State of Denmark. $:-\$

Someone jump in here if I'm wrong but on this year 750, fuel comes into the carbs via a single hose from the petcock, to a T fitting, and then down between carbs #1 and #2, and down between #3 and #4. In order to enter the carbs the fuel must pass through the float valve.

Flooding on any pair of carbs (1+2, 3+4) should not directly affect the other pair as they do not share fuel rails or vent lines.

Since you were holding the float closed on #1 and fuel came out of #2 I'd say that #2's float deserves some scrutiny. Ignore 3 and 4 for the moment.

Proceed as follows: Remove fuel line from #3/#4 carbs and plug it. Remove #1 bowl and #2 bowl. Hold both floats closed. Turn fuel on. No fuel should flow from anywhere. If it does, find out where it's coming from and you'll have found your problem.

Repeat on other side.

mystic_1

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Author Topic: bad gas leak!!!!! (Read 2922 times)