Carbs rebuilt, gas in oil, questions....

I recently rebuilt my carbs did the following. This is my second time going through them so I have a pretty good idea what I'm doing.

Set valve clearances to spec's
Thoroughly cleaned following the guides here
New throttle shaft seals
New mixture screw o-rings and washers
New bowl gaskets
New fuel rail o-rings
New bowl drain screws
Set float heights with clear tube method
Bench synced
Set idle screws to 3.5 turns out

I put the rack back on last week, started it and after adjusting the idle it idled great and was very responsive. I only ran it for about 3 mins as it was late Sunday.

So today I go to finish syncing and color tuning it. It starts great, I ride it about a mile and it dies, won't restart. Push it home and start troubleshooting.

Rechecked the float height on the bike: OK. Plugs are sooty black and I have a ton gas in my oil. Culprit is a bad petcock.

Questions:

If the floats are set correctly how can fuel leak into the crankcase?

If the floats and mixtures are set correctly how can it run so rich? Is the leaking petcock allowing fuel to bypass the system somehow?

I've drained the oil but the bike ran with the contaminated oil for probably 15 minutes. Do you think I did any damage?

Should I change the oil again after a short amount of time to make sure all the gas is out of the crankcase?

 

Culprit is not just a bad petcock, because properly functioning floats will stop gas from overflowing. It's running so rich because gas is overflowing in through the air inlet ports at the airbox side of the mouth, most likely, and letting a bunch of extra fuel in the system.

Something has to be wrong with your float system.

15 minutes won't kill the bike, unless it was a TON of gas and you rode it VERY hard. Just think of it as running with thin oil. Not a good idea, but it's not like riding it with no oil. Change it ASAP though.

As far as why your floats are good one minute bad the next... maybe something got knocked loose from the fuel rail and got caught in there? Any way it's sticking on the needles? Take a good, long look at those needles/float/valve assemblies, the bowls, and so on. Make sure the tiny spring in all four float needles is working properly. Let us know.

 

It can't, unless the enrichment plungers are not shutting off. Still sounds like a float issue.

See above; and no, the petcock either feeds fuel or it doesn't. It would have to have catastrophically failed and be pumping gas up the vacuum tube, which I highly doubt.

Not unless you were drag racing or hammering it.

Things to check:

The condition of the seals in the bottom of the enrichment plungers.

Make sure the enrichment plungers are all "free" when the choke is OFF.

The condition of the tips of the float needles.

The condition of the float valve seats themselves.

The seals between the float valve and the carb body. I believe you have Mikunis, if so there is an o-ring on the outside of the float valve seat. Replace them.

I suspect binding float, enrichment plungers not "off" or something related to the float valve seats, as above. Or you used Hitachi specs to set Mikuni floats.

 

Thanks Bigfitz. This bike has Hitachi 33's. Floats set to 1mm below carb body.

If a float is stuck how will that show up in the clear tube method?

I have the oil drained right now and the drain plug in. Petcock set to prime and I'm going to pull the plug in a while and see if any gas comes out.

 

When you do the "clear tube method," drain each carb down far enough that it has to refill and shutoff; then drain down again and again let it refill until the float shuts off. Repeat a few times. You'll quickly discover a balky float.

 

All of us are having a problem with our car maintenance and expenses.Believe it or not, it isn't all that difficult to create gasoline from air, according to a company called Air Fuel Synthesis. The English start-up uses some fairly simple chemistry to do it, too. You can buy used car that works well for you.