Rookie Mistake

[rd35]

Okay so I'm putting a new short block into this MS290 that belongs to a friend of mine. I get it all assembled and fire it up for the first time. Saw sounds lean so I immediately back out the H about a half turn. Now its rich....then lean....then....well.....kinda all over the place. My brain says "Air Leak". So, I now venture down the path of doing my first ever vac/pressure test. I already had a mightyvac for doing brake jobs and I had bought a blood pressure bulb for doing pressure tests as well...just never had used it yet. I sealed off the exhaust and intake with pieces of an innertube. Used the impulse line as a port for the vac. Pump pump pump, won't hold vacuum! Hmmm. Hook up pressure bulb. Pump pump pump, won't hold pressure either. Get the soap spray bottle. Sprayed both crank seals and pumped bulb. No bubbles. Sprayed intake boot and pumped bulb. No bubbles. Sprayed both innertube block-off seals, no bubbles. Sprayed impulse line, no bubbles. Hmmm. Sprayed compression release port bolt, no bubbles. So......where else could the air be leaking?
Spark plug? Oh no....it couldn't possibly be the spark plug could it? Well, as it turns out, spark plugs do leak air when they are only finger-spun about half way in!!!!!
Tightened the plug, reinstalled the flywheel, clutch, etc., fired it up...runs great!
Take-away.....Always re-check everything...especially the obvious stuff!

 

[jakethesnake]

I call that a win

 

[BB Sig]

Thanks for sharing the mistake you made so we can learn!

 

[berrnard]

It happens. But never to me mind you [emoji6]


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3 saw plan:
Stihl 201t
Stihl 260 pro
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Stihl ms211

 

[user 122190]

Nice ending, and you got to do your first Pressure/Vacuum test. Also called that accidentally learning something.

 

[Bobby Kirbos]

It is funny how we look right past the simple stuff and go right to complicated stuff... seals, boots, etc.

 

[user 122190]

Par for the course. There are to many negative people on this site, always warning of the absolute worst possible outcome. Months ago, a new guy had a saw with some running issues, gave a short description of the symptoms, and one of our 'experts' immediately predicted it was the "metering set level". The guy exclaimed that was a way out in left field diagnosis, and our 'expert' attacked back with accusing him of storing the saw with ethanol. WTF! After that worthless help, the new guy is now gone guy.

It is funny how we look right past the simple stuff and go right to complicated stuff... seals, boots, etc.

 

[homemade]

I bet you won’t let that happen again.

 

[rd35]

Oh and I forgot to mention that after tightening up that spark plug I re-did the vac test. Pulled 20 in-Hg and the needle just sat there....while I stared at it with a red face of embarrassment that slowly turned into pure joy over the realization that I had likely found and solved the problem....silly as it was!

 

[Mauser]

The really good thing is that now you KNOW the seals are good, where before you were just going to ignore them and hope for the best. You may have thought it was just a stupid mistake, but in my book it was a blessing for you.