Stihl ms 460/660 Hybrid. 469e

[NateSaw]

@Mastermind, if you say it'll come apart, it will. I have three more. I'll make another. Your input on what to do with the skirt/pin supports would be greatly appreciated. How would Randy treat the bottom of this slug? (other than to not use one of these lrb's)

 

[Mastermind]

@Mastermind, if you say it'll come apart, it will. I have three more. I'll make another. Your input on what to do with the skirt/pin supports would be greatly appreciated. How would Randy treat the bottom of this slug? (other than to not use one of these lrb's)

Did you start with a full skirt piston? I missed that part.

 

[NateSaw]

Did you start with a full skirt piston? I missed that part.

I did.

 

[NateSaw]

@Mastermind
That's fresh from the box.

 

[NateSaw]

Did you start with a full skirt piston? I missed that part.

I didn't like they way they were blocking the lowers... However, I didn't try it.... So maybe they don't matter. I was looking for anyway to shave weight. I never did however, measure the thickness of the top. Perhaps I could mill out some underneath, after turning flat and measuring.

 

[Mastermind]

I didn't like they way they were blocking the lowers... However, I didn't try it.... So maybe they don't matter. I was looking for anyway to shave weight. I never did however, measure the thickness of the top. Perhaps I could mill out some underneath, after turning flat and measuring.

288 piston

 

[NateSaw]

288 piston

Won't work with 36mm crank. Too short... I think I'd have to remove the base completely to get any semblance of squish. However, I have one. I'll put it on the crank and see if I can get a measurement.

 

[Ketchup]

Does a 288 pin need the husky bearing? Isn’t it 13mm?

 

[NateSaw]

Does a 288 pin need the husky bearing? Isn’t it 13mm?

If I recall, it needs a different bearing anyway, as the space between pin bosses is wider. Same here with the echo cs900evl slug. I had to source a wider one.

 

[NateSaw]

288 piston

288 left, 660 right. As you can see, it's going the wrong direction.

 

[NateSaw]

Here's all 4 lined up, illustrating compression heights, skirt lengths. The pins are all (sorta) lined up.

 

[Mastermind]

Remember when I said that just before you can do something.....

But I see why you used the slug you did.

 

[Ketchup]

Trying to get my head around this.

Looking back at the beginning, you added 0.018+” with the 900 piston, and still cut 0.12+” off the base? So you had to overcome 0.3+” difference in squish height. Did I get that right?

40mm -36mm = 4mm x 0.040”(to convert) = 0.16”

So your deck height was 0.14+” higher than 660? Ooch.

 

[NateSaw]

Left to right:
288,660,cs900evl, 385
The 385 shows some promise... But I'd need another 660 jug. The different dimensions require different machining and port timing. It's not as tall as the 900 slug. Nor are the skirts as long. But the pin bosses look good, and it's not a full circle. It's already flat on top.

 

[NateSaw]

Remember when I said that just before you can do something.....

But I see why you used the slug you did.

That's why I love you brotha. No homo.

 

[NateSaw]

Trying to get my head around this.

Looking back at the beginning, you added 0.018+” with the 900 piston, and still cut 0.12+” off the base? So you had to overcome 0.3+” difference in squish height. Did I get that right?

40mm -36mm = 4mm x 0.040”(to convert) = 0.16”

So your deck height was 0.14+” higher than 660? Ooch.

Something like that.... Lemme find my math...

 

[NateSaw]

@Ketchup ,i believe this was before machining... And I had 0.110" helf way into the crown where they were closest... That's why I knocked 030" off to get a reading at the edge of the slug.

 

[NateSaw]

Remember when I said that just before you can do something.....

But I see why you used the slug you did.

Right or wrong, I measured compression heights from center of pin, to edge of crown...
660 slug:
compression height =23mm, crown to skirt=43mm
Cs900evl slug:
Comp height=27.8mm
Crown to skirt=49.86ish mm

 

[Ketchup]

@Ketchup ,i believe this was before machining... And I had 0.110" helf way into the crown where they were closest... That's why I knocked 030" off to get a reading at the edge of the slug. View attachment 411318

So 0.09” squish cut?

At 0.016” you might be compression bound, not carb limited.

 

[NateSaw]

So 0.09” squish cut?

No sir. I used the echo slug so I could take a minimal squish cut, and leave the rest for the base. I took 035" from the squish. I wanted the chamber to be nice nice.