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Discussion Starter #1
Attached are pics of my 1980 5000 eltigre RH jug. It cracked starting at the center of the base under the exhaust port and around the right hand side to the center of the base under the intake port.

It was still running, but would not fire on this cylinder at low RPM. I noticed this when my son started it and was letting it warm up. It would fire on this cylinder, believe it or not, at over 2000 RPM. It was LOUDER than normal, too. Lifted the hood and the problem was evident.

I guess I can count myself lucky that it didn't completely let go resulting in a broken piston and rod, or more.
 

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wow...Thats a new one. aint never seem that before.
 

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Discussion Starter #4
More info

I got the sled from my little brother about 8 years ago. Went through the carbs and flushed all the crud out of the gas tank, replaced fuel pump and lines. Replaced the cdi, coil, plugs, etc. Replaced the drive clutch and crank seal on the clutch side. It wasn't running when I got it (obviously) and the flywheel side didn't have as good of cylinder pressure. The piston had scored and I replaced it. I put it together and tightened the nuts to 25 ft-lbs.

It ran OK (not as well as when we were kids) from the time I put it together until just the other day when I heard it running on one cylinder while it was warming up.

It is possible the nuts were over tightened before I got it. I remember seeing what looked like a crack in the base when I examined it prior to putting it together, now that I think about it, but the cylinder pressure was good on both sides after all that I did to it. So, I didn't think about it any further.
 

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Discussion Starter #5 (Edited)
Back in business

Found an almost new Series 2 cylinder at a local scrap yard. The piston was like new, too. So, I put that in as well.

149 psi both sides again! Woohoo!

My engine had a Series 1 cylinder on it (aluminum jug with a metal sleeve). The Series 2 cylinder is all aluminum, i.e. no sleeve.

Now it runs like it did when we were kids. I even had to back the throttle off a bit so it isn't so fast for my 14 year old. :)
 

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Found an almost new Series 2 cylinder at a local scrap yard. The piston was like new, too. So, I put that in as well.

149 psi both sides again! Woohoo!

My engine had a Series 1 cylinder on it (aluminum jug with a metal sleeve). The Series 2 cylinder is all aluminum, i.e. no sleeve.

Now it runs like it did when we were kids. I even had to back the throttle off a bit so it isn't so fast for my 14 year old. :)
Spirit engines never used metal sleeves. The cylinder base may have cracked due to weakness introduced in the area when metal was removed in the boring process before after market sleeve installation. All Spirit engines have Nikasil plated aluminum bores.
 

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Spirit engines never used metal sleeves. The cylinder base may have cracked due to weakness introduced in the area when metal was removed in the boring process before after market sleeve installation. All Spirit engines have Nikasil plated aluminum bores.

if that is true then all the spirit engines should be ran with high grade gassoline (premium) , the sulfer found in lower grades of gas reacts with Nikasil and eats it away very quickly, my bmw (which has Nikasil cylinder linings) actually had a recall be cause of this problem that called for a compleatly new block that does not have the Nikasil cylinder linings, im shure the 2 stroke oil will help slow down the reaction prosses, and the amount of sulfur is being lessened in gassline but it is still happaning slowly im shure
 
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