Stihl 090 build

[ft. churchill]

An arborist I knew has been wanting a freshen up on his big boy saw.
It's low on compression at 113 psi, but runs like a champ after I replaced the worn out carb, and fixed the recoil.

 

[ft. churchill]

I got some rings in for it but it's going to need more than rings. Jug has worn thru the chrome plating.
More pictures to come. I've got to go chop kindling before it gets dark while the photos download.

 

[Mastermind]

Oh boy. I like those big beasts.

 

[ft. churchill]

This one run "special." It blew away most of those I saw on youtube. Far more rpm's and power even though the compression was so low.

 

[Mastermind]

I've done a few 090s.

 

[Canadian farm boy]

 

[beaglebriar]

Smells like another cool build thread brewing...

 

[ft. churchill]

Smells like another cool build thread brewing...

I hope so. Remember that I'm just a peckerwood sandlapper out in the desert. Heck we barely even have trees here.

 

[ft. churchill]

So being that this saw run so good, I measured it before tearing it down to have a reference point.

 

[ft. churchill]

I started using a dial indicator to find top dead center, it's alot faster for me than a piston stop. Taking the readings, dividing by two subtracting from the reading from the stopped position, moving the wheel and trying it all over again. I get top dead center first time with the indicator.

 

[ft. churchill]

I got this arborist hooked on my work when he came by to do a quote for stump grinding. We chatted a lil', then I had him run my ported 394. Being a stihlhead, it make to much of an impression. Then I had him try a ported 064. He' been a steady customer since.

 

[ft. churchill]

Now this saw had a crappy worn out carb and I replaced it with a chinee copy and deleted the governor. It was already wearing a midway exhaust trumpet on it, similar to what you would see on a kart engine.

 

[ft. churchill]

So for numbers here's what I got......
100 exhaust
74 intake
118 transfers
18 blowdown

I knew it had been worked over.

 

[Adirondackstihl]

 

[ft. churchill]

Instead of the ports of the jug being ground on, this one had the old school way of doing thing with a trough cut in the exhaust side of the piston dome.

 

[ft. churchill]

I dunno what that hole looking chunk is from in the piston crown. Any ideas?

 

[ft. churchill]

no damage to the corresponding squish area in the jug either.

 

[beaglebriar]

Hard to say. Piston could've been dropped before it was installed. How's the bearings and stuff?

 

[Backtroller]

Do you know approximately when that saw was originally built? Never seen one in person.

 

[Redfin]

Thanks for sharing. What was the thinking "cutting" the piston instead of jug? It doesn't seem that much easier to me.