FUEL IN CRANKCASE?

My thinking is that with engine running, some relatively minor fuel leakage past the float valve would likely be harmless and go unnoticed as normal fuel consumption continues, keeping the level at spec.

It's when the engine isn't running (such as parked overnight) that a petcock allowing fuel flow will permit the relatively minor fuel leakage past the float valve to continue on and on -- akin to a dripping faucet -- eventually rising above spec level to overflow level and possibly on to carb throat level due to non-existent or obstructed overflow circuit where admission to crankcase becomes a serious issue.

Am guessing this is one reason Kawasaki went to vacuum style petcock, which frees the rider from any responsibility of remembering to turn off the petcock after shutting off the engine.

Good Fortune.

All of which can be permanently remediated by the installation of a Pingel petcocok with an "off" position.Lol.bj

Memo -- The issue of fuel entering crankcase isn't limited to when engine isn't running.

Excess fuel getting past float valve for whatever reason, and rising up into carb throat (due to obstructed or non-existent overflow circuit) and on into crankcase (via airbox or combustion chamber) --- may happen while riding the motorcycle.

Using a properly functioning vacuum petcock, or remembering to turn off a properly functioning manual (non-vacuum) petcock, should indeed disallow fuel from entering the carbs while the engine is not running. And which should prevent the annoyance of fuel dribbling out underneath the bike while the bike is parked, despite a leaky fuel valve.

Good Fortune!

thanx becker, petcock is always in the on position. rebuilt petcock in the spring, i know it works well. could fuel be getting in past valves/rings? will comp.test reveal any info?

thanx jim.

thanx patton. overflow all seem to be working properly. left the valve in the pri. position and fuel came out tubes. on to comp. test?

thanx jim.

Where raw fuel is entering the combustion chamber, it will flow down past the piston/rings into the crankcase, regardless of perfect compression.

The problem isn't compression.

The problem is fuel improperly rising up into the carb throat.

And it only takes one blocked overflow circuit in one carb.

Where all overflow circuits are indeed working properly, there shouldn't be any fuel rising past top of the overflow tubes inside the carb float bowls. Hence no fuel rising high enough to enter the carb throat and from there into the combustion chamber (or via airbox into the crankcase).

Z1 airbox allows some drainage down the crankcase vent tube into the crankcase. Later airbox designs seem to direct most if not all drainage to underneath the bike.

Good Fortune!

thanx for all the ideas/help everyone. will check on carbs asap.


happy thanksgiving all.
jim.

DoubleDub wrote:

Oh, and Jim, just a heads up. It's consider polite to not use all CAPS as it is the equivalent of yelling.
:kiss: :kiss: :woohoo: DOIT AGAIN DO IT AGAIN, see how much he can take! By the way a dub is what the younger generation calls a quarter ounce of weed :ohmy: :blink: that alone will bring out the caps
Does the bike have a vacuum petcock or a just a mechanical on/off/reserve?

Here's another similar experience with my '87 GSXR 750:

NEVER LEAVE THE PETCOCK IN THE "PRI" POSITION ! Idiot me, for some reason I did this, and over 2 weeks of sitting, my engine and even my airbox filled with raw fuel. What a friggin nightmare !! I did now know what happened until I saw plooms of smoke exiting my exhaust. Luckily I only ran my engine for about 30 seconds. I drained almost 3 gallons of oil/gas ! I removed the valve cover and poured fresh oil all down the valvetrain, prime filled a new oil filter with oil, and even had to remove the exhaust to drain the residual oil in the pipe. All is ok now.

nads.com wrote:

:kiss: :kiss: :woohoo: DOIT AGAIN DO IT AGAIN, see how much he can take! By the way a dub is what the younger generation calls a quarter ounce of weed :ohmy: :blink: that alone will bring out the caps

Hmm...thought that was a "doob" as in "doobie". Ah well.

Reminds of a certain bike club's new vests proudly inscribed "Road Angles," :lol:

and the leader's embroidered name was "Cool Dud." :laugh:

holy shit i hope mine is not that bad. glad you found problem i will be cleaning mine up soon. then time to put her away for winter. i'll be going over bike front to back, thanx for info polar-bus.

jim.