Stihl Contra Pistons

[rxe]

OK. I've been looking for Contra pistons for a long time, and there don't seem to be any about. I'm not talking about Contra-S (135 CC) pistons, I've got some of those, just ordinary Contra pistons, 58mm in diameter, 107 cc. You might think that 070 pistons would work, but they don't, as the deck height is way too big.

So, I've been looking at getting some made. I've asked a few manufacturers, and all have been unable to reproduce some aspect. Until now.

I noticed that Wiseco have dropped their minimum order to 12 pistons, and Wiseco can do it. I want 6, and I need buyers for the other 6 (or more, if the demand is there). The bad news is that the price is about $170 for a piston, wrist pin, rings and clips - so Stihl dealer prices, if the dealers could still get them, which they can't.

Anyone interested in building up an order? PM me, or reply below....

 

[Jacob J.]

Is it not possible to have a machinist turn the top of an 070 piston down so the crown height is in line with a Contra piston? Seems that would be a lot cheaper.

 

[rxe]

Here's a picture of the two side by side, 070 on the left, Contra on the right:

You'd be machining right through the crown.....

 

[Dibbs]

Is it not possible in this day and age to emerse the old piston in an aluminum based solution and electroplate it with more aluminum?
Obviously if it was possible you would need to silicone or grease the ring cut outs and pin hole.

 

[7oaks]

I might be interested in one. I have yet to check my Conta's piston and won't be able to for a couple of weeks as I'll be doing a bit of traveling...Carl

 

[blsnelling]

I don't believe I'll be needing one, but good luck in your endeavour.

 

[Bill G]

I need to pull some of mine and compare them.

Bill

 

[Jacob J.]

Is it not possible in this day and age to emerse the old piston in an aluminum based solution and electroplate it with more aluminum?
Obviously if it was possible you would need to silicone or grease the ring cut outs and pin hole.

There's a couple of plating companies that use a similar process with tin to build the pistons back up. I've used a few in older saws where no replacement parts were available and it worked well. I sent them the cylinder along with the piston and specified the clearance I wanted. For example, in an IEL Model F, I specified .0035" and they were right on the money.

 

[Gumnuts]

There's a couple of plating companies that use a similar process with tin to build the pistons back up. I've used a few in older saws where no replacement parts were available and it worked well. I sent them the cylinder along with the piston and specified the clearance I wanted. For example, in an IEL Model F, I specified .0035" and they were right on the money.

Seriously looking at getting a piston cyl (gilnsil)done. Jacob is that .0035 " clearance ,a standard for all make and model?

 

[Dibbs]

There's a couple of plating companies that use a similar process with tin to build the pistons back up. I've used a few in older saws where no replacement parts were available and it worked well. I sent them the cylinder along with the piston and specified the clearance I wanted. For example, in an IEL Model F, I specified .0035" and they were right on the money.

I thought this should be a viable option for piston repair, it could end up just as expensive as having new ones made from blanks though.

How about asking www.mahle.com is they still make them or have old stock?

 

[thomas72]

Have you tried to match a dirt bike piston to yours?

 

[Gumnuts]

Have you tried to match a dirt bike piston to yours?

. ...sounds worth looking into / thanks.

 

[barneyrb]

Depending on the bore maybe an outboard piston also?

 

[thomas72]

I do not know about the newer outboard motors, but the top of the pistons on the older ones were raised to one side to match the porting and would not work with a chainsaw style porting. Also, the rings on the outboards are twice as thick as a chainsaw piston.

 

[Jacob J.]

Seriously looking at getting a piston cyl (gilnsil)done. Jacob is that .0035 " clearance ,a standard for all make and model?

That's a fairly standard piston-to-cylinder wall clearance in the big, old saws. Some of the high speed large saws like the Mac 125s need a little more room, they're making more heat.

 

[rxe]

I'll bring this thread back to life with some good news - you can get Contra pistons again.

There is a guy on eBay in Germany (Sagenspezi) who has had a batch made and is selling them for 20 EUR. I've got one, and comparing it to an NOS Stihl one, it seems very good. I haven't installed it yet, but will take pics if anyone is interested.

I'm nothing to do with the seller, I'm just pleased that some of my Contras will run again.

 

[Chris J.]

That's good news.

This thread was on page two, I'm bumping it so that it doesn't prematurely fade into obscurity.

 

[7oaks]

I for one would like to see the pictures.

Thanks for bringing this option to our attention.

 

[rxe]

Your wish is my command....:glasses-cool:

Here is a side by side comparison. On the right is an OE Stihl piston. OE certainly wins on box quality....

View attachment 170846

Close up side on:

View attachment 170850

The replica has a ribbed finish like an 070 piston, the OE one is perfectly smooth. The good news is that it has the right deck height.

End on:

View attachment 170848

The crank journal is 1.5 mm wider on the replica, I'm not that worried as Contra pistons aren't exactly consistent in that department. Weight feels about the same (don't have any accurate scales here)

Side on:

View attachment 170847

The pins are in the right place!.

At this stage it looks very good, finish is spot on and I can't see any defects.

 

[belgian]

I've bought parts from saegenspezi before and have had good experience with him. Good to know that there are pistons available for the Contra. Thanks for the tip, rxe !