Gas out the air box...

[mixelpix]

Hi,
Just finished reading the various threads about what to do when gas is pouring out the airbox an wanted to confirm that I am heading in the right direction with my '79SF:
1) repair petcocks diaphramgs
2) install in-line fuel filters
3) repair octopus diaphragms
4) replace fuel lines
5) clean carbs, take particular notice of the float seats and height.

I am new to this bike and was already planning on taking apart the carbs and cleaning them, replacing the fuel lines and getting a new air filter. Since the fuel has backwashed into the airbox, I am assuming it has done so into the crankcase. I haven't tried the flame test yet, but will tomorrow just for fun... Seriously though, I am curious about the implicactions of fuel in the crankcase. Can I do anything more than change the oil and oil filter? Should I check the compression after cleaning everything up? Any other thoughts or suggestions? Thanks everyone!
-Patrick Kennedy

[Dragonrider]

You're on the right track...note that it will be either petcocks or octopus...the Special's have the octopus, the Standards have the vacuum shut-off in the petcocks.

Pay very close attention to the float valves...they have a rubber (nitrol?) tip on some models and they probably need replaced.

Good luck!

[steelcat]

The needle & floats should not have the nitrol tips on your '79sf. Make sure that you set the float hiehgts correctly & trible clean the carbs. With the special you have the Octopus, check to make sure it is working or the are ways of eliminating it. Numerous posts on that.

Fuel in the oil thins the oil out TOO much. Don't run the bike w/ the fuel in the oil. Just change oil & filter. The fuel in the oil will disolve some sluge but won't hurt the bike as long as you don't run the bike w/ thinned out oil.

After doing the carbs & changing the oil, warm the bike up & do a compression test. This will let you know if you have to do ohter work this winter. If the compression is low, check the valve clearance first before assuming rings or valve seats.

[mixelpix]

Hi, follow up question re: fuel spilling into the crankcase. Just to be on the safe side, should I worry about the cam lobes and re-lubing them? Only reason I ask is that it would appear that re-lubing the lobes would require removing the cover. I was planning on doing it anyway to check the clearances, but is there an easier way? Thanks!

[TopCatGr58]

Hey there Patrick,

You never mentioned whether you did find any fuel in the crankcase oil!? As long as you didn't actually run the engine that way, then you should still have the film of oil that was on it when the engine was stopped prior to the carb leak. And even if you did run it a short time, once it stopped, and you then drained the crankcase, the gas should be gone, evaporated, etc.. Yes, perhaps the oil film is much less and thinner, but you can still start it up with fresh oil without much worry. But , if you want to reprime the topend, pull all the plugs so the engine spins easier, and then turn the starter if you're using electric vs. kick starter for several 5 second bursts, repeatedly watching for the oil sensor light to finally go out! This is to prevent frying your starter motor. Once the light goes out, then you can put the plugs back in, and fire it up knowing you have freshly bathed the topend with oil with minimal stress of spinning engine without actually starting it!

[mixelpix]

Thanks - that's a great practical tip to know! Fortunately, no, I did not see or smell any gas in the oil javascript:smilie('') . Prior to the gas leak I think one of the cylinders stopped firing. Not sure, but the engine started running pretty unevenly. I was pretty close to home after a short run around the SF coast and I was able to make it home. while i was opening my garage with the engine off the fuel started to flow out of the air box. I was thinking maybe float needle got stuck or something? I didn't think to drop some water on the headers to see if one was cooler - it had only been chugging unevenly for a short while anyways.

I haven't touched anything except changing the oil and it ran fine last night and this morning. Any other thoughts as to what might have caused those symptoms?

thanks, pdk

[DiverRay]

It sounds like you did have a carb with an open needle. Doing a "quick" clean, and check needles and float levels should fix the problem. I'm getting ready to do the same on my just purchased 1100F.
I do need to fix brakes, and adjust 7 of the 8 valves, before I get on to the carbs.
Ray