Is this piston normal?

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7oaks

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I posted these pictures and questions on another thread but got no responses so I'm going to repost here as a new thread hoping I can get the answers!

:help: :help:

Here are a few pictures I took of the new contra last weekend.
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I'm wondering what ya'll think of the piston and rings on this saw. They look nearly new to me, with only slight discoloration and carbon buildup on the top of the piston. However, the groove on the piston at the top running down to the two rings has me perplexed. Is this normal for a Contra/Lightning piston? Is this an original Stihl or aftermarket?
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Then there is the muffler. Looks like someone broke the bolt holes trying to get it off or back on? Can you think of a purpose for this? Do I need a new one or is there some way to repair this one?
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It also doesn't have a muffler gasket so has blow-by. Anybody got a muffler gasket? All in all the saw runs pretty strong after I discovered that the plastic carb fuel filter cap wasn't attached firmly and was leaking pressure/gas. I still haven't gotten it tuned to my satisfaction but the wife was looking over my shoulder impatiently.

It also has an after market starter cover. Anybody heard of Fairbanks Morse & Co. Chicago, Ill after market parts for Contras/Lightnings?
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Thanks in advance for any help I get and sorry for the repost?
 
It looks like the saw is junk. Send it to me, and I'll use it for parts.......

F-M starters were used on many saws back in the day

Not sure on that piston. Definately worth another look, I'd say. The muffler ears can be built back up with weld, and reshaped.
 
It looks like the saw is junk. Send it to me, and I'll use it for parts.......

F-M starters were used on many saws back in the day

Not sure on that piston. Definately worth another look, I'd say. The muffler ears can be built back up with weld, and reshaped.

Thanks for the speedy and helpful reply...I guess that means the muffler is steel. I don't have it here to test but guess that would be the norm even though it looks like aluminum. Guess I'll have to break out the welder and relearn.

If I can't get it welded and the blow-by problem fixed guess I'll just throw it in the trash dumster down the road. Hate to burden you with "junk"! :hmm3grin2orange:
 
Nice lookin saw!!!!

Wish I had knowledge enough to help you with your piston question....Nice,clean saw you got!!!!
Fairbanks Morse Company been around for awhiles....suprised
to have seen that on your cover....There is a few gearboxes where I at work made by them,,and I'm talking about big gearboxes...Never ever gave us any probs. and been running since 1969...HQ company as Stihl is...
 
The vertical groove above the rings doesn't look normal. I don't see matching marks on the rings though. I think it'll be fine. Looks like new rings might be a good idea though. Then again, those spots might wear off after a little run time.
 
Wish I had knowledge enough to help you with your piston question....Nice,clean saw you got!!!!
Fairbanks Morse Company been around for awhiles....suprised
to have seen that on your cover....There is a few gearboxes where I at work made by them,,and I'm talking about big gearboxes...Never ever gave us any probs. and been running since 1969...HQ company as Stihl is...

The vertical groove above the rings doesn't look normal. I don't see matching marks on the rings though. I think it'll be fine. Looks like new rings might be a good idea though. Then again, those spots might wear off after a little run time.

Thanks for the responses guys. Guess I'll run it some and then take a second look.

Any site sponsers out there that might have a muffler gasket for this? I'd guess it is the same as the 070/090?
 
The muffler looks like cast iron so it takes some special precaution and would probably be a better fix brazing it. The upper ring on the right side is that a ring split at the edge of the port? The other side is in a shadow so I cant tell if there is one on the other side lower ring like that, and it would lead me to believe the piston is in backwards....
 
The muffler looks like cast iron so it takes some special precaution and would probably be a better fix brazing it.

Thanks AfBlue...I thought as much. I'm not experienced with brazing.

The upper ring on the right side is that a ring split at the edge of the port? The other side is in a shadow so I cant tell if there is one on the other side lower ring like that, and it would lead me to believe the piston is in backwards....

Very observant of you - I hadn't noticed them. Here are some extreme blow-ups that might help. I don't think that the top ring looks split on the left but that is sure the way it might look and it sure could be. Note a similar slanted place on the right side where I have opened up the shadows. What do you think? I'll take a closer look next time out at the farm.

Backwards piston? Never heard of that. What effect would that have on the engine?

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Thanks for the observations/suggestions!
 
I posted these pictures and questions on another thread but got no responses so I'm going to repost here as a new thread hoping I can get the answers!

:help: :help:

attachment.php




Thanks in advance for any help I get and sorry for the repost?






It looks like the saw is junk. Send it to me, and I'll use it for parts.......

F-M starters were used on many saws back in the day

Not sure on that piston. Definately worth another look, I'd say. The muffler ears can be built back up with weld, and reshaped.

Wish I had knowledge enough to help you with your piston question....Nice,clean saw you got!!!!
Fairbanks Morse Company been around for awhiles....suprised
to have seen that on your cover....There is a few gearboxes where I at work made by them,,and I'm talking about big gearboxes...Never ever gave us any probs. and been running since 1969...HQ company as Stihl is...

We used to have FM diesel generators on our destroyers. The were nicknamed "rock crushers"


Fairbanks Morse built this coaling tower in Thurmond, WV. No starter parts that I can see though...:)



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.
 
Just hazzarding a guess here but I think the shallow groove on the piston is an alignment mark for your ring-gap placement. Could be wayyy off, but it sortta looks like its meant to be there as opposed to a gouge caused by something. It runs? Then don't muck with it :D

:D
 
I would without a doubt pull it down to investigate. It is not right and running it is risking mor damage.
 
Thanks AfBlue...I thought as much. I'm not experienced with brazing.



Very observant of you - I hadn't noticed them. Here are some extreme blow-ups that might help. I don't think that the top ring looks split on the left but that is sure the way it might look and it sure could be. Note a similar slanted place on the right side where I have opened up the shadows. What do you think? I'll take a closer look next time out at the farm.

Backwards piston? Never heard of that. What effect would that have on the engine?

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Thanks for the observations/suggestions!

My lightning has got the same groove in the piston when you look at it through the exhaust port.
 
My lightning has got the same groove in the piston when you look at it through the exhaust port.

I haven't had time to go into the guts on this saw as I've got several others on the bench that take priority but appreciate the reassurance that at least one other Contra has the same grooves.
Thanks
 
beautiful saw, I don't think your piston is in backwards. I have had expirence with this and if it is going to have a problem it only takes about 5 seconds of run time! Did you check compression? That would be my next step if I were you.
 
The groove looks machined, and is that a smaller groove, in line, above the top ring? Gas port to help seal ring against bore?
 
beautiful saw, I don't think your piston is in backwards. I have had expirence with this and if it is going to have a problem it only takes about 5 seconds of run time! Did you check compression? That would be my next step if I were you.

The groove looks machined, and is that a smaller groove, in line, above the top ring? Gas port to help seal ring against bore?

Thanks guys. Haven't pulled the piston as I have other projects demanding my time right now. I did do a compression test and it was "okay" somewhere between 130 and 150 if I remember correctly. It'll get my attention when life slows down. :msp_unsure:
 
Thanks guys. Haven't pulled the piston as I have other projects demanding my time right now. I did do a compression test and it was "okay" somewhere between 130 and 150 if I remember correctly. It'll get my attention when life slows down. :msp_unsure:

I'm bettin its fine,,, But I would do this before you run it much more,,,

Pull it down and de-carbonize thouroghly,,, fix your muffler and get a gasket,,,,

buy your self some good synthetic pre-mix,,, non ethanol gas 89 RON minimum,,,,, that will stop the carbon build up,,,,

Dont look back!!!!!!!!!
 
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