Airbox flooding

[thewiz]

Two things ...

the aftermarket slide diaphrams that I've seen say that they only fit the LATE style BS34s of '80 and newer .... so if you're running the 79 carbs, I think they may not work.

Secondly; don't forget to eyeball the float 'drop' as well as the float level again. Sometimes I have seen the tab that controls the drop has gotten bent allowing the float and needle to sink too far down into the valve and stick cocked sideways when trying to close thus resulting in a flooding situation.

[Ken Talbot]

I held my finger over the oblong oval shaped port that faces the filter and released the slides that were raised about an inch and could see #1,2 slowly sink closed.

That is the correct way to test, and that is how they should act. The two that snap shut have problems. Those two diaphragms might have leaks, but is more likely that the diaphragms were not seated correctly last time the top covers were taken off and put back on.

[WMarshy]

That is the correct way to test, and that is how they should act. The two that snap shut have problems. Those two diaphragms might have leaks, but is more likely that the diaphragms were not seated correctly last time the top covers were taken off and put back on.

Please clarify.
I read that there is a correct orientation for the diaphram to be seated and there is some sort of a "loaction nub" on the diaphram rubber/edge? Whould this miss location make them leak or do are you thinking the seat of the diaphram as a whole might not be sealed?

Like I said previously, I feel inclined to post a little video clip of how they react when testing so new/"seasoned" members could use it in future..?
Anyways the two that leak, when i let go of the slide, it starts to slowly sink then they seem to drop 1/4" a bit faster in a certain section than the rest of the sliding range, then slow down and come very close to fully closed... I had a mechanic work on them, he adjusted the needle height, does that require takin the tops off and exposing the diaphram? Maybe its just a bad seal, just hope he didnt pinch one. If I take the top off I will do a light check for holes. Thanks Ken.

[DGXSER]

When you hold the slide up, then put your finger over the oval opening on the carb intake bell, the slide should very slowly drop. It will get air through the small hole in the slide bottom. If it drops quickly, then there is a leak in the diaphram.

On the top flange, where the slide seals is a groove for the seal to fit into, and at oen spot there is a half circle "notch" that a correpsonding section of the rubber seal fits in to align the slide. Ken appears to be suggesting you may either not have seen that alignement and have it off, or that your did not get the seal in the groove all the way around and had it stay there when you put the top on.

[WMarshy]

Did it again!

Well, put everything back together. Here's a run down. Disassembled carbs and sprayed out everything and reassembled. Left the diaphragms alone for now. Took apart petcocks and reassembled, it still leaks but decided to proceed since the needle valves worked properly and stopped fuel prior to the tip over incident. I put inline fuel filters on and got everything back on the bike. Started it up and ran ok. After about 60 seconds the carbs sarted dumping "gas diluted oil" out the back of the carbs while still running. It started to flood out and smoke. Well the only thing I can conclude is the oil level is extremely full of gas and is some how so full that its coming out the back of the carbs? How is this physically possible? So I drained the oil, not sure how over full it was but the oil ran like water. The only reason I didnt change the oil prior to doing this was in fear of getting more gas in the new oil and having to change it again. I guess I will change the oil now since I drained it, replace filter, and pull carbs again to spray out one more time.... Any thoughts, like why/how crank case oil is pouring out the carbs? Could it be so full that the vent is pouring it in the carbs?

[DGXSER]

Any thoughts, like why/how crank case oil is pouring out the carbs? Could it be so full that the vent is pouring it in the carbs?

Yep, that would be my guess. And you do NOT want to run the engine with gas in the oil like that!! Another member recently tried it and now needs new bearings and possibly a new crank!! Not a good thing at all! To check if your carbs are still leaking, try turning the petcocks to prime, with the engine off, and bottom of air box removed, drain plug out of pan, bike on the centerstand. For me, gas always comes out the airbox when on the centerstand.

[WMarshy]

...you do NOT want to run the engine with gas in the oil like that!!...
To check if your carbs are still leaking, try turning the petcocks to prime, with the engine off, and bottom of air box removed, drain plug out of pan, bike on the centerstand. For me, gas always comes out the airbox when on the centerstand.

Point taken about oily gas. It ran for no more than 120 seconds so hopefully no harm, barely got the pipes hot.

Your suggestion about checking the carbs... Im suppose to leave the petcocks on prime with the oil drain plug out? Maybe place a jug under the drain and see if theres any gas in there say in the morning? I take it that if the needle valves leak overnight it will either leak out the back or in the cylinder. Its already on the center stand, have the bottom off the air box, and the oil is drained with plug out... Will give this a try, it makes sense and it makes my job of picking up easy.

I won free Billy Squire tickets for tomorrow night so progress may be null tomorrow. Will try see if needle valves leak over night then pull carbs to clean agian and fill with oil once I know they are ready to rock. Cross my fingers. Thanks.

[Ken Talbot]

Gas pouring out of a carb is a result of a sticking float or non-sealing needle valve. Oil dripping out of the vent on the bottom of the airbox is a result of an over-filled crankcase, whether just too much oil or from gas that has leaked back through a carb from a stuck float. If you're sure you didn't overfill the crankcase yourself, both issues point back to the same cause - stuck float/needle valve problem.

[DGXSER]

Agree Ken, if he is still getting gas out of either place, it will be the float bowl valves at fault.

My thought is that he may have cured it with the last cleaning up of the carbs, but he already had so much gas/oil in the crankcase that he got the oil/gas out the airbox issue.

Now that the crankcase is empty, he should be able to open the petcocks and see either no fuel from anywhere, or he will see the fuel flow out with the drain plug out and the airbox open. For mine when it happened, it only took seconds maybe 1 minute tops for me to see fuel coming out the boots from the air box to the carbs.

[WMarshy]

1) The amount of gas Im talking here is way to much to be a stuck float or needle
2) It only does it after it has ran for about 30-60 seconds (ie. Once the crank case pressure builds up enough to force the oil+gas up the vent hose.)
3) The “gas” that’s coming out of them looks almost like straight oil just much thinner.

No doubt I had a leaky needle at one point though, that’s how the gas got in the crank for sure. I never overfilled my crank but unfortunately I did have a tip top full gas tank prior to discovering I had a leaky petcock and stuck needle/floats. The first time I started it up and discovered I had a problem it already sat for 10 days, having plenty of time to fill the crank. At this point, even if the needles do their job, Im still going to pull the carbs one more time to blast them out with more cleaner. I don’t wanna have to go back in there more than I have to. Its not a fun job getting the back of the air box back on. Next time I post it will be “All Fixed!”… I hope. Thanks all.

[WMarshy]

I was working on my carbs in the driveway and dropped the small brass washer that goes under the 137.5 (main?) jet and cannot find it. Is anyone willing to send me one? It would be greatly appreciated. I wish it was as convenient to send a beer for thanks but postal service isnt so keen on that stuff for some reason. PM me and we can talk details. Thanks guys.

[thewiz]

Bummer ...

I'm sure I have one in my carb parts jar. PM me your address and I'll put one in the post tomorrow.

[WMarshy]

Thanks WIZ!