# Very puzzleing starting problem



## FredT (Apr 8, 2011)

I've been messing with small engines for over 40 years and this one is kicking my butt.

2 cycle chain saw.
I've cleaned the carb.
I've verified there is spark.
I've checked for compression.

It has compression, fuel, and spark.
I can't get it to fire using starting fluid.

Can't figure this one out.
Any suggestions.


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## usmcgrunt (Sep 16, 2007)

Welcome Fred,have you checked the flywheel for a sheared key?If you have all the necessary requirements for a running engine,maybe they just are not happening at the correct time.Posting the model number of your saw may get some more responses to a fix.Hope this helps.


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## luckyvision (May 24, 2007)

Check the exhaust screen, is it carboned shut?

Is there 'wet' around the crank seals? if so, those may be shot. 2 stroke cases need to be airtight. good compression is only half of the equation... any good 2-stroke shop will have adapters for testing if a case will hold vacuume & pressure. 

--Lucky


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## geogrubb (Jul 28, 2006)

If you have fuel, spark and compression, it should make smoke and noise. Before you start taking anything apart try putting a little fuel mix directly in the spark plug hole, you might have a bad air leak and it will not move fuel from the crankcase to the cylinder. Have a good one. Geo


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## justin3 (Apr 10, 2007)

You say it has fuel, spark and compression? How much compression does it have? A 2 stroke needs at least 90psi to run, have you checked to see if the crank seals are leaking? What kind of a spark do you have? White? blue? A weak spark can be reduced to no spark while under compression, the more air in the cylinder you have, the more resistance. As other have said also check the muffler and exhaust ports.


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## FredT (Apr 8, 2011)

Yes, thanks for reply. I checked that.


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## FredT (Apr 8, 2011)

I checked flywheel key, plug, starting fluid into sp hole, and cleaning exaust, but not the max compression. I only checked to see if it "had" compression. Seems to me like it would simply fire even though it wouldn't run with starting fluid, even if compression was low.


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## 30yearTech (Sep 14, 2006)

FredT said:


> I checked flywheel key, plug, starting fluid into sp hole, and cleaning exaust, but not the max compression. I only checked to see if it "had" compression. Seems to me like it would simply fire even though it wouldn't run with starting fluid, even if compression was low.


A massive air leak in the crankcase of a 2 cycle engine will prevent it from even popping with a prime. Low compression as well, you can try boosting compression with a little bit of oil in the spark plug hole to help seal. If it starts up with a prime and some oil, then the compression is your issue.



justin3 said:


> What kind of a spark do you have? White? blue? A weak spark can be reduced to no spark while under compression


You CAN'T tell spark intensity by the color of the spark! You need a gap type tester, to check for weak spark!


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## FredT (Apr 8, 2011)

I have a gap tester, spark is good.
Must be the compression.
I'll try and check that next.


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## GoatDriver (Jan 23, 2011)

Just to add to what has already been suggested....You may want to take the muffler off and check the exhaust port for carbon build up, and be sure to check and see if you have a stuck ring due to carbon build up. If there is substantial carbon build-up you may have a scored cylinder...which like a stuck ring would cause low compression and the unit will not fire or start, even if you have good spark at the plug.


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