Stihl ms 460/660 Hybrid. 469e

[NateSaw]

385. Naked

 

[NateSaw]

385 compression height = 26.5mm
Crown to skirt=46.3mm

 

[NateSaw]

I'm eventually going to do some math on using the 385 slug. But I KNOW the jug will land a good bit lower. I think that'll be more tweakage than the intake boot can handle. One good thing about the 660 jug is the fat a**Ed base flange.

 

[NateSaw]

OK so I looked hard through all my post it notes. Total from base was 0.1525".
Total from squish was 0.035"

 

[NateSaw]

@NateSaw , would you mind sharing what pin bearing you’re using?

I'm not reading these carefully enough. The pin bearing was supposed to be a 12x15x17.5 I ordered from treat land, the ultimate hipster owned moped supply hut. It came short. I have two good numbers for what would be better. I was choosing based on preventing the bearing from walking. I believe however, what would be ideal would be thrust bushings to prevent bearing and rod walk. I don't want to restrict the small end too much though. So I started with wider bearing.

12x15x17.5 mm pin bearings
KTM bearing #: 4603004000
Malossi#: 66 4151B

 

[Powerstroke Cowboy]

Very neat build! I will be following this to see what you use to overcome the piston hurdle. These kinds of builds are part of the reason I've gotten so interested in chainsaws. Very cheap to experiment with and build compared to a pickup or car engine.

I've got nothing to add other than I agree with Randy, that piston looks like it's not a matter of if, but when it's exploding.

Also, I can't imagine case volume is a factor here. Port size and timing yes, case volume, no. Take the dolkita 64xx, 73xx and 79xx series saws, they share the same crankcase and crank, but they have a 15cc difference from the 64xx to the 79xx. They all run good and make.good power stock and ported. Same with the Solo 665, 675, and 681. As the bore size goes up, so does the case volume. Your setup is only adding 6cc of volume. I can't imagine case volume is a hold up.

Carry on!! I'm learning and enjoying watching!

 

[NateSaw]

Very neat build! I will be following this to see what you use to overcome the piston hurdle. These kinds of builds are part of the reason I've gotten so interested in chainsaws. Very cheap to experiment with and build compared to a pickup or car engine.

I've got nothing to add other than I agree with Randy, that piston looks like it's not a matter of if, but when it's exploding.

Also, I can't imagine case volume is a factor here. Port size and timing yes, case volume, no. Take the dolkita 64xx, 73xx and 79xx series saws, they share the same crankcase and crank, but they have a 15cc difference from the 64xx to the 79xx. They all run good and make.good power stock and ported. Same with the Solo 665, 675, and 681. As the bore size goes up, so does the case volume. Your setup is only adding 6cc of volume. I can't imagine case volume is a hold up.

Carry on!! I'm learning and enjoying watching!

Awesome! Yes I agree about case volume. Depending on what the goal is, case stuffing has been a thing on 2 strokes for decades. If I had been thorough, I'd have measured the volume of a 440, 460, and 660 case. I will one day. Again, using the 446 hybrid as my reference, adding 2ccs of displacement to that case makes a ripper. Also, the well known swap of stuffing the 12mm 440 crank, I to a 10mm 044 case has gains. I also agree about playing with saws vs. Autos. I was an auto tech for 2.5 decades. I don't miss the overhead. No punn... I haven't whacked my head on a lift arm in years. It's been great!

 

[NateSaw]

I'm going to try the oem 660 pin with this next lrb slug I machine...

Lrb weight

660 weight

The 660 pin will be fast and loose. Fits tighter in the oem slug.... This will further reduce longevity.. I don't think the poor quality of the lrb slugs will tolerate a loose pin for very long. But 3 grams is 3 grams.


Oem 660 is 0.041" shorter...

 

[NateSaw]

 

[drf256]

FWiW, you can’t easily run a 13mm pin in an 1128 crank. A 395 bearing will fit an 1122 crank small end and allow the use of a 288 piston, but the thinner bearing is still too big for an 1128 crank.

I learned the hard way when I tried using a 52mm 281 piston in a 440/460 hybrid. No worky.

 

[NateSaw]

FWiW, you can’t easily run a 13mm pin in an 1128 crank. A 395 bearing will fit an 1122 crank small end and allow the use of a 288 piston, but the thinner bearing is still too big for an 1128 crank.

I learned the hard way when I tried using a 52mm 281 piston in a 440/460 hybrid. No worky.

Amen. Another selling point to this echo slug. 12mm pin.

 

[NateSaw]

We've come a long way, this slug and I.. I might turn it into a necklace. Lemme see if I can get the one on the left close to the one on the right, with ought weakening the pin boss supports. @drf256 , this time I'm measuring the tops thickness. I might ball the end of one of my end mills. Perhaps I can take some meat out of the top. Also, @Ketchup , I'll compromise with you... I'll take a little extra off the crown and set the squish to 0.020"

 

[NateSaw]

 

[NateSaw]

 

[Maintenance Chief]

I'm loving this thread! Plus I always assume that a hybrid might blow apart in the experimental stage, learning doesn't start with perfection.
Nate I had a lazy saw with my 3.3 craftsman/036 hybrid with the piston crown blocking some of the exhaust port. I filed the piston to a slope into the port which really helped.
I know that people have filed the crown in all sorts of ways, transer timing ,exhaust, even the intake.

 

[Ketchup]

FWiW, you can’t easily run a 13mm pin in an 1128 crank. A 395 bearing will fit an 1122 crank small end and allow the use of a 288 piston, but the thinner bearing is still too big for an 1128 crank.

I learned the hard way when I tried using a 52mm 281 piston in a 440/460 hybrid. No worky.

Pretty sure 385 slugs are the same.

 

[ManiacalMark]

2lbs. is a lot, but there's a reason for it...

A 460 feels like a toy after running a 660 all the time, but it takes a pretty stout 460 to compete with 92cc on the stump.

 

[NateSaw]

I'm loving this thread! Plus I always assume that a hybrid might blow apart in the experimental stage, learning doesn't start with perfection.
Nate I had a lazy saw with my 3.3 craftsman/036 hybrid with the piston crown blocking some of the exhaust port. I filed the piston to a slope into the port which really helped.
I know that people have filed the crown in all sorts of ways, transer timing ,exhaust, even the intake.

I've been looking forward to an excuse to try some of this crown nipping I've been reading about. I plan to get an am slug for the bosses 661 I did, and nip the exhaust side till it stops gaining power. Thanks chief! This thing might get it!

 

[NateSaw]

Pretty sure 385 slugs are the same.

Yes they're 13mm

 

[NateSaw]

@Ketchup
Because that really is where it belongs.