Carb leaks out pods - could it be O ring problem?

[btxs650]

Last time I cleaned my carbs I had to replace the rubber o ring on the main jet with one that I had that was the right ID but the OD was a little large so I trimmed it with a razor blade. The bike ran like a champ almost all summer long with no problems and then started leaking out the left carb into my pod filter when it started getting cold. I'm guessing the O ring is the culprit, wouldn't you agree? I think the O ring I need is a 1mm x3mm ID. Can anyone confirm this? They are BS34s on an 83 HS.

 

[grizld1]

The O-ring is on the needle jet, not the main (which screws into the needle jet in your BS34's). Although the O-ring may need replacement, you're getting fuel in the air filter because the float chamber vents are in the back of the intake bell and that's where any fuel overflow escapes when the float valve (needle and seat) fails to seal. Your oil is likely fuel contaminated as well. Also check petcock function; the float valve is there to meter fuel, not to serve as a positive fuel shutoff.

 

[xjwmx]

cycleorings.com sells the o-ring. I don't think it's listed by itself, so you'll have to contact him. I got a pair that way. Take the petcock apart carefully, carefully, and look for tears , crud, etc. It might need a kit. Very lightly grease the rubber parts when putting it back together. Greasing the o-ring will help it go in.

 

[CDNTX650]

if you have 34's there is an oring to seal the float seat to the carb. They can fail and leak.

 

[btxs650]

The O-ring is on the needle jet, not the main (which screws into the needle jet in your BS34's). Although the O-ring may need replacement, you're getting fuel in the air filter because the float chamber vents are in the back of the intake bell and that's where any fuel overflow escapes when the float valve (needle and seat) fails to seal. Your oil is likely fuel contaminated as well. Also check petcock function; the float valve is there to meter fuel, not to serve as a positive fuel shutoff.

Sorry, I always get confused on which jet is what. I didn't have my diagram in front of me when I posted this. So do I need to replace the float valve needle and the o-ring on the needle jet?

 

[grizld1]

Replace the O-rings if there's any doubt. Floats valves can fail to seal because of debris or varnish; clean the needle and seat and bench test, if that doesn't do it replace. Check to see that petcocks are closing; disconnect the fuel line and see if fuel flows or drips.

 

[btxs650]

The petcock was new as of spring, but I guess that Ethanol didn't make the seals last long. It does drip now when it's off. Guess I'll have to rebuild it. Funny thing is that I used to leave the gas on all the time because when I shut it off, for some reason the fuel line would suck air into the line and when the air got to the carbs it would want to die out until the gas came through. If I just left the gas on, it would keep a steady flow and it didn't leak out the carbs then.

 

[grizld1]

I don't know what kind of petcock you're using, but in Illinois we've been running 10% ethanol gas for 30 years, it's been hard to buy anything else for the last 15 or so, and there haven't been issues with petcock rubber parts in old bikes. I get tired of saying it, but float valves are fuel metering devices, not positive shut-offs. Unless you want your crankcase full of fuel, you need to turn the petcock off when you shut off the engine. If you have a feed problem, check your tank vent and be sure it's clear. If you still have a problem after that, replace the petcock with something that works.

 

[5twins]

BS34 float needle seat o-rings are 1.5mm thick x 7.5mm I.D. You have no o-rings on your needle jets, that's a BS38 thing. The only other o-rings in your carbs are on the mix screws (1mm thick x 3mm I.D.) and on the float bowl drain screws (1.6mm thick x 4.1mm I.D.).

 

[bluebikerblan]

BS34 float needle seat o-rings are 1.5mm thick x 7.5mm I.D. You have no o-rings on your needle jets, that's a BS38 thing. The only other o-rings in your carbs are on the mix screws (1mm thick x 3mm I.D.) and on the float bowl drain screws (1.6mm thick x 4.1mm I.D.).

Hope this doesn't count as a "high jack" but; while on the subject..... do either you 5twins or the grizld1 have similar spec. data on the o-rings of the BS 38's, type I & II.? I and some others are having trouble sourcing them. Thanks, Blue

 

[5twins]

The mix screws on the '78-'79 BS38s are the only ones that use an o-ring, none of the other years have one. 1.5mm thick x 3mm I.D. may not be the exact size but does fit. It will be tight going in the hole so lube it with WD40 so it slips in easier.

All the BS38 needle jets use an o-ring to seal them into the carb body. The size is 1mm thick x 4mm I.D. I think it was gggGary who mentioned that every time he overhauls a set of BS34s, he finds the float needle seat o-rings are bad. I find the same thing with these needle jet o-rings on the BS38s.

I source all my o-rings from McMaster Carr in quantity. I usually get the better quality Viton type but they cost a bit more. I see that Cycle O-rings place mentioned here from time to time sells the cheaper Buna-N type. Obviously, since they've sold a ton of them without any reported problems, they must be adequate for the job. The Viton type have a higher temp rating and are more chemical resistant but are slightly harder. The softer Buna-N type may actually seal a bit better.

 

[bluebikerblan]

Thanks 5twins....precisely what I (and some others) were looking for. Funny thing about the Viton vs Buna N thing. When it comes to functioning as an o-ring........ a polymer may actually work better if it absorbs (swells) in the medium. In an o-ring groove it may not even matter much if it softens and weakens as long as it doesn't deteriorate. On the other hand when things sit, dry out and harden they'll often split etc.

Sounds strange but poorer chemical/solvent resistance is sometimes better as you say.
Depends on the application for sure.

FYI....most needle jet o-rings I've encountered have been shot as well. Best, Blue

PS....I use either & both BS 38's type I & II and have just ordered 100 each of the two O-rings I needed. Thanks for the McMasterCarr tip......very reasonable! Blue

 

[jamesgs4]

I don't know what kind of petcock you're using, but in Illinois we've been running 10% ethanol gas for 30 years, it's been hard to buy anything else for the last 15 or so, and there haven't been issues with petcock rubber parts in old bikes. I get tired of saying it, but float valves are fuel metering devices, not positive shut-offs. Unless you want your crankcase full of fuel, you need to turn the petcock off when you shut off the engine. If you have a feed problem, check your tank vent and be sure it's clear. If you still have a problem after that, replace the petcock with something that works.

Same deal here in CO, ethanol gas for the past few decades. I think newer rubber parts are being made on the cheap, I have had no less than 5 brand new aftermarket petcocks dripping because the seals swelled up and fell apart within a matter of days. I finally found a motion pro valve with neoprene seals that isn't affected by ethanol. Maybe the older oem parts are made better, but the new rubber parts nowadays suck big time.
Also, the 80's models with vacuum petcocks don't have an off position, so you can't turn it off when you shut down. .

 

[grizld1]

That's correct re. vacuum petcocks--they're supposed to turn off automatically when the engine isn't producing vacuum. In practice, they often fail to do so. The OEM vacuum petcocks are no longer available, however, so when btxs650 mentioned installing a new petcock, I drew the logical conclusion that it was an aftermarket unit. Re. aftermarket rubber parts breaking down--ain't Chinese quality control a grand thing?

Thanks for the correction, 5twins. Right, no O-ring on a BS34 atomizer. The main jet O-ring bit threw me a curve, and it pushed the carb ID right out of awareness; I didn't think of the float needle seat being mistaken for the MJ.

 

[jamesgs4]

This is the neoperene sealed valve that I use, I gave up on the petcocks and use this inline to make sure gas doesnt flow. I havent tried the $100 pingel petcocks, but this is a cheaper solution.

http://www.motionpro.com/motorcycle/partno/12-0035/

 

[btxs650]

Hey everyone, sorry I'm such an idiot. I mistakenly referred to the o-ring as coming from the main jet. It's actually the float valve piece I should have been talking about. Here's a photo with an arrow pointing to the o-ring in question. If this o ring doesn't seal properly, will it cause the carbs to overflow into the pods?

 

[grizld1]

If the O-ring doesn't seal, the float valve can't control fuel level. Does that answer your question?

 

[btxs650]

You wouldn't happen to know the size of the o ring would you? I have a set of metric o rings from Harbor Freight but none of them seem to fit correctly.

 

[5twins]

Read post #9.

 

[btxs650]

Oops, sorry about that. Guess I should have read through this again before I posted.