Compression test OK - so why running like do do ?

[grimah1w]

Did compression test, rt cylinder 125psi, left 120psi so it is above min spec in both and within allowable difference.  27,000 miles.

So, while I know I have a minor head gasket leak (oil is seeping on right side at head gasket area) why else would it be so down on power and run like crap?  Smokey gray exhaust low power, backfire/misfire at rev.

Right plug was fouled...super black

I recently cleaned the carbs and will do again.  Petcock could be suspect, I plan to bypass if only temporarily to isolate potential fault. 

Will check float height again during carb tear down.


Other ideas???


THANKS!

[Suzuki Stevo]

When did you last check the valve clearance?

[The Buddha]

  head gasket leak = huge surprise it even runs.
Cool.
Buddha.

[grimah1w]

Valve clearance check data - rt in = .002" , rt ex = .003" :  lt in = .003" ,  lt ex = .001". 
Checked on 20 Sep 13

I would call the head gasket a seep, rt cylinder, just enough oil to discolor a few of the cooling fins...head bolts loosened and re-torqued.

Again, comp test on a cold dry engine pulling 125 and 120


Top cover tiny o-rings 1mm - 4x6mm, one of them was pinched partially over the passage....both are now replaced.    Bowl heights measured and reset to ~14mm

[grimah1w]

Also, just replaced plugs yesterday.

Believe issue is w carburation...   Seems rich just by smell.   Stock airbox and yoshimura pipe.  Fresh exhaust gaskets. 

When I cleaned the carbs, I pulled the main and pilot jets, carb cleaner and compressed air through the passages.   I am third owner so not 100% sure they are stock jets.   The needle and it's retaining clip and two plastic spacers in the slide/diaphragm assemble look exactly like stock photos.   

Anyway to be sure I have a stock main jet?   

[radodrill]

The rejetting wiki page lists the stock jet sizes and are also listed in parentheses on the parts fiche.  The actual jet sizes are stamped into the jet; so you can pull them and read what's installed.

[grimah1w]

Thanks very much radodrill!   

[grimah1w]

So, after an initial nice start up, she is back to smoking like a two stroke and super rich smell....

Come home from test ride and the oil smells like gas and is thin.   Level has increased to about 1/8" above the full hash...gas in crank case :-(

Draining oil...new oil and filter will come.

NOW
Time for carbs to come off and I am done messing around with them, time to take to a local and have them fitted with repair kits (2x $30 kit plus about 80 in labor).  Not a true "rebuild" I guess but I am not sure what else or where else to go with these.   Advice?

At this point I am certain carbs are my issue. Wrong?   

Rebuild kits and thorough professional cleaning a fix?    I do not know I f the previous owner has messed w mixture screws.   Do not expect the mixture screw would contribute to gas into crankcase...obviously something more major at issue... Like needle valve /float setting...

[radodrill]

So, after an initial nice start up, she is back to smoking like a two stroke and super rich smell....

Come home from test ride and the oil smells like gas and is thin.   Level has increased to about 1/8" above the full hash...gas in crank case :-(

....

At this point I am certain carbs are my issue. Wrong?

Gas in the crankcase is a serious issue and indicates problem with the engine itself and not the carbs.  Earlier you mentioned a head gasket leak; this is likely part of the underlying problem.  I'd suggest holding of on messing with the carbs until you have the engine itself fixed.

[grimah1w]

Rado, thanks.  What is it that you think is likely reason for gas into crankcase other than fuel through carb (carb malfunction)?

[radodrill]

The carbs themselves only control the air/fuel ratio based on throttle position.  For gas to get into the crankcase would mean there is something messed up within the engine itself.  There are actually oil channels in the cylinder walls to supply oil to cool/lube the top end; so it could be that the head is loose allowing the oil and air/fuel to mix.

P.S. oil mixed with gas produces a lot of smoke (e.g. 2-stroke engines)

[grimah1w]

Really ... Am counting on fact that carbs control fuel flow and air flow as root of issue.

Only path to engine for fuel is through the carburetors, since there is excessive fuel and apparently fuel flowing while not "running" carbs seem logical issue.

yes, lots of smoke like a two stroke one of the symptoms, fuel mixing in the oil confirmed in earlier post...way excessive fuel flow...

On top of a fresh head gasket with another compression/leak down test to verify integrity of motor, Is carb cleaning and carb gasket and needle kit the right think to seek or is there some other level of "rebuild" I should be seeking?

[Big Rich]

Actually.......

If the petcock isn't stopping fuel from flowing (left on prime position, faulty diaphragm, etc...) then the carbs become flooded. Flooded carb with no overflow tube means the gas has to go somewhere - and that leads it into the engine. Given enough time, gasoline will work past the piston rings and mix with the oil.

[radodrill]

Assuming there was nothing wrong with the engine, if the air/fuel mix was too rich you'd simply have poor performance.
The carbs simply meter the fuel, but they do not have any oil flowing through them so that is not where the oil and fuel are mixing.

Oil leaking out from the head gasket and the fact that the oil and fuel are mixing (evidenced by the smoke and gas smell in the oil) are all indicators of a problem with the engine.

First step should be to have the engine checked out; once that's all good, then if you have poor performance look at the carbs.

If the petcock isn't stopping fuel from flowing (left on prime position, faulty diaphragm, etc...) then the carbs become flooded.

The floats should still stop fuel flow once the bowl are full.  Even if this has failed, and fuel has indeed seeped past the rings, this wouldn't explain why a lot of oil is mixing into the cylinder.

A leak in the head gasket and/or slightly loose cylinder head would explain it.

[radodrill]

Also think about this:
In the case of a leaking head gasket you can expect the following:

• On the intake stroke the vacuum would pull in oil past the head gasket
• on the compression stroke the pressure would in turn push the fuel/oil out past the gasket (a lot more fuel than would seep past the rings)
      This would not only go into the oil channels, but could also be pushed out of the of the engine and be visible on the fins

Since the OP has a known leaking head gasket, fixing this should be the very first course of action.

p.s. I'm a mechanical engineer.

[Big Rich]

Ok, ok..... I see that pushed a button. First off, thank you for stating that you are an engineer. I'm not doubting your intelligence by any means.

I can tell you from experience that a faulty petcock will not stop fuel the way it is intended to. And I can also say from experience that gasoline can get past a float valve, and flood the engine. It sucks, but it happens.

I was just suggesting what appeared to me as an obvious issue that begins with the petcock.

[radodrill]

Ok, ok..... I see that pushed a button.

It's all good; no offense taken.

I'm well aware that faulty petcock and float valves can indeed flood the cylinder (and seep past the rings over time).  If the bike were spitting fuel out the exhaust and not starting, then the petcock and carbs would be the #1 and #2 items to check out.  The signs of oil burning with the fuel and known leaking head gasket point to that as the primary culprit; though that's not ruling out the possibility of a carb or petcock problem as well.

[grimah1w]

Big Rich I am with you.  I also happen to be an engineer but have very little carb experience .   Fuel injection or turbines more in my wheelhouse. 

Gas incorrectly metered into engine...seep into oil.

Really just want rebuild / overhaul advice.   Rad I got the motor.  Timing- check, compression- check, plugs - check,  exhaust - check.   Head gasket replaced torqued head - check. 

Carbs....hummm. To shop I guess. 

Thanks

[Big Rich]

The last set of carbs I rebuilt cost me around $50, but that was to replace every o ring inside of them. Interior cleaning and exterior cleaning costs were less than $10. Just have a clean / open work space and take your time.

It is odd to me that your right plug was the one fouled up, especially with gas in your oil. Usually it is the left carb to cause issues first. Could it be the float was sticking and flooding the mix?

[Big Rich]

Just thought of it Vinnie - have you checked your electrical system lately as well? You didn't mention it above, and a weak / faulty spark can foul a plug too.