44mm Piston Dimentional Data Wanted - Stihl + Husky

[Brewz]

Hi Folks

I am after the following dimensional data for 44mm Stihl and Husqvarna pistons from the 026 and 246 respectively.
Stihl OEM pn: 1121 030 2001
Husky EOM pn: 503 73 02-71

If you have, can get or know someone with access to datasheets it would be FANTASTIC

Piston height.
Skirt width.
Ring groove heights.
Wrist pin center height.
Wrist pin diameter.

I have an idea in my head for my 026 and I need this data to see if it will work.
@drf255, have you looked into this already?

http://www.hlsproparts.com/Husqvarna-246-Piston-and-ring-kit-44mm-p/h31246.htm

I recon you know what I am thinking

Cheers

 

[drf256]

I can try to get you some 026 piston measurements tonight.

Interesting for sure. I'd love to know the pin diameter on the above 246 piston.

 

[Brewz]

Yeah the whole 288/660 thing got me thinking on the 026.
I have an OEM 026 piston sitting in the garage so it is mainly the Husqvarna 246 piston dimensions I am interested in I guess.

If the piston sits a tad lower like a 288 piston does in a 660, it could be something to explore.

 

[Brewz]

@Gentleman

Would you be able to pull one of these 246 pistons out of a box and get some measurements with a set of verniers?

 

[awol]

I have used both the 026 and 246 piston in my 3 cube saw, they have the same size pin.

 

[Brewz]

Hi awol
Do they have the same wrist pin height from the bottom of the skirt, and skirt width?

glad to have you in this thread!

Is there another (better) option for the 026 other than the Stihl 026 piston?

 

[Brewz]

I am planning to machine the 026 cylinder squish flat which is nothing new, so a flat top piston is preferable.

I would like to experiment with being able to drop the exhaust port without getting 250+ psi of compression

 

[Brewz]

Here is another piston of interest



I have emailed Meteor pistons for data sheets on the Dolmar 111 and Stihl 026 pistons for caparison.

I would love it if @awol could give us some specs on the 246 piston

 

[drf256]

I am planning to machine the 026 cylinder squish flat which is nothing new, so a flat top piston is preferable.

I would like to experiment with being able to drop the exhaust port without getting 250+ psi of compression

I'm looking at it as an option on an 026 to save a step I'm machining plus have a thicker piston crown. Plus a longer and wider skirt would be nice, as would a central piston ring pin. IIRC, an 026 piston skirt's width in less than 60% of bore stock, so the option of going wider on the ports may exist.

I'm Glad you bought this up.

I'm going over port geometry in my mind, it's early here. To get a lower port you HAVE to raise the chamber. So you're making it smaller either way.

If you have more compression height on the piston, you may not need to cut the base as much to arrive at the squish you want. If you have less, you'll need to overly this the base to make it work.

I'll grab one and check it out. I don't know if it will solve the problem of getting a low exhaust on The 26 without the massive chamber cut.

 

[Brewz]

The big advantage of the 288 piston in a 660 is that the piston top sits lower.
This means a lot needs to be machined from the base and minimal from the squish to get your squish set up.
This means the exhaust port is lowered a lot, with minimal compression increase.

I am hoping to find a piston for the 026 that will do the same.
I am not so much interested in wider skirts, but a lower crown/wrist pin distance, and the single higher center pinned piston ring is a big plus

 

[drf256]

I bought one. For $27 shipped, I can be a sport.

I don't think any data sheet can compare with holding them side by side. I will do a thread.

 

[Brewz]

I was thinking I might buy a 246 piston to see how it compares

 

[drf256]

The big advantage of the 288 piston in a 660 is that the piston top sits lower.
This means a lot needs to be machined from the base and minimal from the squish to get your squish set up.
This means the exhaust port is lowered a lot, with minimal compression increase.

I am hoping to find a piston for the 026 that will do the same.
I am not so much interested in wider skirts, but a lower crown/wrist pin distance, and the single higher center pinned piston ring is a big plus

I'm trying to wrap my head around this.

So if I leave my chamber uncut and I add a flat top piston at the same squish it was at with the dome, when I turn the degree wheel, I should still see the crown at the same degree, no?

Perhaps crank angle plays a role?

 

[Brewz]

Champion!

Just add it to this thread, keep it all together.

If I had a lather I would have done some R&D myself but I dont

 

[drf256]

It may be a great option Brewz. I'm still trying to wrap my head around it. I hope a pro chimes in.

The stroke is unchanged, so in order to see the piston crown through the ex roof later, it would have to have a higher height. So the chamber would have to rise, so the same resultant cut and the same compression.

It may give a ton more latitude to a build. I can measure and see if a caber ring fits it as well.

I'm still not so sure that the piston alone will help the high exhaust problem in the 026. It may help a lot of other things though.

 

[Brewz]

No.

Piston crown will be relative to wrist pin height on the piston

Think about J's 660

the 288 piston has a lower crown when fitted to the 660 crank, making it effectively longer in the 660, even though its the same length as a 660 piston
He cut .050 from the squish, but had to cut .120 from the base to compensate for the lower crown of the husky piston.

This drops the jug more, giving better numbers without needing to machine the squish band as much.

Imaging the compression if the squish was machined .120

 

[Brewz]

I am hoping the Husky 246 piston has a lower crown relative to the wrist pin

 

[Brewz]

Then we take a ship load off the base and not so much from the squish

good numbers with lower compression

Thats what I want to achieve

 

[drf256]

I am hoping the Husky 246 piston has a lower crown relative to the wrist pin

It could be rod angle. Pistons move faster as they get closer to 90* of crank rotation.

 

[Brewz]

Hell, I might buy one while they have a sale on as well...... just in case.