Stihl 090 build

[Deets066]

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.

How do you set the dial indicator up for this? Pics please

 

[ft. churchill]

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

Bearings look fair, heavy wear on the piston pin.

 

[ft. churchill]

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

I don't know. Maybe in the 70's because of the piston grinding technique and the header exhaust.

 

[ft. churchill]

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

I've read some of the old school 2T motorcycle books and they did it this way because pistons were cheaper to grind on than jugs, if you went to far, much lees cost.

 

[ft. churchill]

How do you set the dial indicator up for this? Pics please

I've got a 1" travel dial indicator with a flat base and I just position it atop of the jug and let the stem protrude down into the spark plug hole. I have a degree wheel set up on the clutch side, then move up piston up towards TDC by turning the flywheel with my fingers. It's real easy to see when your exactly at TDC, Then I move the degree wheel to line up at o*TDC under the MIG welding wire I use for a pointer.

 

[Deets066]

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I've got a 1" travel dial indicator with a flat base and I just position it atop of the jug and let the stem protrude down into the spark plug hole. I have a degree wheel set up on the clutch side, then move up piston up towards TDC by turning the flywheel with my fingers. It's real easy to see when your exactly at TDC, Then I move the degree wheel to line up at o*TDC under the MIG welding wire I use for a pointer.

Oh.... Didn't notice it in the first pics. I thought maybe you had a threaded bushing that screwed into the plug hole. That looks like it works good though

 

[ft. churchill]

It had low compression because of the piston rings had worn thru the chrome. I cant believe it didn't seize or scuff the piston. Pics 1 and 3 show where it wore thru at the exhaust port over to the transfers, pic 2 shows at the top of the cylinder above the intake.

 

[Deets066]

View attachment 2053 View attachment 2054 View attachment 2055

It had low compression because of the piston rings had worn thru the chrome. I cant believe it didn't seize or scuff the piston. Pics 1 and 3 show where it wore thru at the exhaust port over to the transfers, pic 2 shows at the top of the cylinder above th intake.

She's had s lot of run time for sure

 

[Redfin]

What your plan for the jug? New? Replating?

 

[ft. churchill]

I've got a aftermarket 66mm jug and piston.

 

[Deets066]

I've got a aftermarket 66mm jug and piston.

 

[Deets066]

How much would US chrome cost to replate ?

 

[ft. churchill]

The pistons are almost identical. Except for one does not have "MAHLE" cast into it.

 

[Red97]

How much would US chrome cost to replate ?

I checked a 2" bore and it was around $200

 

[ft. churchill]

How much would US chrome cost to replate ?

I do not know if you can even get a OEM set up, and the jug is so worn that you can feel a dip in the cylinder walls with your finger. It has a ridge at the top of the cylinder as well. Like what you would see in a worn out 350 chevy.

 

[Mastermind]

You can get the top ends from a dealer. They might be cheaper than you think.

I'm interested in seeing what you do with the AM top end though.

Carry on.

 

[Ladrhog]

I have one with an aftermarket top end and it runs good. My original piston had plating missing as well

 

[huskihl]

I suppose at 137cc or whatever, if an AM jug performed like 120cc it would still be OK lol. I bet it'll pull some serious chain

 

[Deets066]

Do you have any numbers on the AM jug yet?

 

[ft. churchill]

I'm still in the process.