288 Piston in a 660

[drf256]

Rainy weekend on the way.

I am gonna need to drop the cylinder a bit more to cover the ring pin. The cylinder has that typical large bevel on the intake roof, so the pin seems more covered than it actually is.

Bought some extra pistons for experimentation. What I noticed, on both the Hyway and the dukes, is that the pin bore isn’t centered in the boss. The meteor has a perfectly centered pin hole in the boss. Not sure if it matters or not, I’m sure they finish the hole to be perpendicular to the skirts at the time of final machining, but it kinda makes one question the overall QC on the slugs.

 

[drf256]

 

[drf256]

Meteor



Hyway



Duke’s

 

[Rich Fife]

Meteor

View attachment 375599

Hyway

View attachment 375600

Duke’s

View attachment 375602

I like the Dukes stuff... Meteor isn't too bad either...

 

[Jedd]

I like the Dukes stuff... Meteor isn't too bad either...

Meteor

View attachment 375599

Hyway

View attachment 375600

Duke’s

View attachment 375602

Interesting that the hyway and the duke pistons have the wee lug on the pin boss but not the cutout for removing those sthil wrist pin retaining clips (the ones without the ears) but don’t have the cut half moon in those lugs.

 

[drf256]

The overall construction of the dukes piston is very good. I’m just trying to figure out the offset of the pin bore on the casting. OEM not like that, nor is Meteor-which is the only AM I generally use.

 

[drf256]

Did a little lathe work in the piston.

 

[drf256]

 

[NateSaw]

Ever deal with Wiseco pistons

That's all I ran in my dirt bikes. But I never dealt with generic fitments.

 

[NateSaw]

Meteor

View attachment 375599

Hyway

View attachment 375600

Duke’s

View attachment 375602

That's a lot of offset meat. I wonder what that does for balance? Skirt wear?

 

[drf256]

 

[drf256]

 

[drf256]

 

[drf256]

 

[Brewz]

I’ve done a few of these in the past
I use an oem husky 288 piston.
I don’t bother now unless the saw is getting finger ports but even then I just rotate the piston and leave exhaust width stock.
The single ring is nice but added weight not so nice and wider exhaust and fingers just makes the saw peaky which is not ideal here in Aus.
Too much width on the exhaust just results in more bypass from the fronts of the uppers direct out the exhaust port.
A closed front cover with rearward side outlets each side helps stop that some.

288 piston does work but is it worth the effort over a 660 piston…. Mmm I’m not convinced

 

[thompsoncustom]

The single ring is nice but added weight not so nice

Stock 660 piston is around 92grams and his 288 piston is at 76 grams which should be around 17% less weight which seems like a good thing.

Is it worth the effort IDK but i'm hoping we are gonna find out when he's done.

 

[drf256]

I’ve done a few of these in the past
I use an oem husky 288 piston.
I don’t bother now unless the saw is getting finger ports but even then I just rotate the piston and leave exhaust width stock.
The single ring is nice but added weight not so nice and wider exhaust and fingers just makes the saw peaky which is not ideal here in Aus.
Too much width on the exhaust just results in more bypass from the fronts of the uppers direct out the exhaust port.
A closed front cover with rearward side outlets each side helps stop that some.

288 piston does work but is it worth the effort over a 660 piston…. Mmm I’m not convinced

Thanks for the reply. Wanted to try one for myself.

I’ve heard it’s a lot of work for not much more gain. I’m only at 65% bore width on the exhaust, which is where many take their builds without a lot of short circuiting. In addition, I’m right on the edge of the stock piston‘s skirt, I probably coulda gotten away with it, especially with a the winged skirt type slug.

I didnt do fingers, hard to make them not just push the flow circuit back towards the exhaust. I am making sure to have at least 40-45* of case compression and to keep the transfers as tight as possible to prevent short circuiting. In addition, opening the transfers at the ex side first gives them a better chance to push charge away from the exhaust.

The piston is already lighter than an 066 one. And it’s gonna lose even more weight when I clean up the casting flash and add a 395 pin.

As for the exhaust, I always do rearward placed side exhausts. Front openings don’t allow the sounds waves to collide and cancel each other out. It’s just loud without a lot of gain.

Guess I’ll see if the lemon was worth the squeeze.

 

[Hinerman]

Guess I’ll see if the juice was worth the squeeze.

Fixt...

 

[redline4]

Mofo work juicers?
I'd assume available at Macy's, Nordstrom's, etc..

 

[smokey7]

The overall construction of the dukes piston is very good. I’m just trying to figure out the offset of the pin bore on the casting. OEM not like that, nor is Meteor-which is the only AM I generally use.

Could you try to measure off the pin or something to the face of the skirt to see if they are centered on the piston not on the boss nescesarrlly.