262xp R&D

[paragonbuilder]

We don't have enough build threads. I have 2 262's I'm going to be building, and I want to try some things. This will take me a while but here is a start. I tore them down today, one is an 87 carb with a KS non decomp jug, the other is a 120 carb with a Mahle decomp jug.
Here they are torn down ready for cleaning.

 

[paragonbuilder]

Does anyone have a junk 262 jug that I could cut in half to aid in my research?

 

[Canadian farm boy]

 

[Landmark]

Does anyone have a junk 262 jug that I could cut in half to aid in my research?

I might. I will ck tomorrow and let u know.

 

[paragonbuilder]

I might. I will ck tomorrow and let u know.

Cool! Thanks. The 262 is a factory hotrod, and I'd like to see if I can find some patterns in saws like this, and the 346xp will be next.

 

[dustinwilt68]

Always interested in these builds, but the 346xp is always my favorite, so I can't wait.

 

[drf256]

Cool! Thanks. The 262 is a factory hotrod, and I'd like to see if I can find some patterns in saws like this, and the 346xp will be next.

What patterns Dan?

Excited for your build.

I have another 262 on my bench right now.

 

[drf256]

Take a looks at the tunnels in the decomp vs. non decomp jug Dan.

Also, if the uppers are equal on both sides with a ring.

Most of the 262's I've seen do NOT have equal upper timing. Very odd. I wonder why they did that and I doubt it's a mistake. IIRC, the flywheel side has the indent on it and I believe that they set that transfer higher because it flowed slightly less.

Jug design is simply excellent for performance. The lowers are right up against the piston skirts. Huge tunnels compared to an 036 Stihl.

The intake tract sucks balls though. Even with the 87 carb, it ain't enough to feed this beast. We need to find another way. @Chainsaw Jim, any ideas on this?

At least for me, the 262 doesn't want to Rev. the fastest I've done so far was happy at 13,800 to be safe. A comparable Stihl 036 will piss rev 4 stroking 1000 rpm higher. I blame the intake tract fo this, I believe it's the limiting step.

 

[drf256]

Here's a stock exhaust port inside and outside imprint.

The transverse line across the inner imprint is about where the piston lands at BDC.

There's a mile of skirt under the exhaust floor at TDC on the 262. You'll never Freeport this badboy.

 

[stihl_head1982]

readin and learnin. The 262 talk (as well as 372 talk) pulls me to the dark side.

 

[Mastermind]

I found the 262 to perform better tuned really fat.

 

[paragonbuilder]

I found the 262 to perform better tuned really fat.

That's interesting. I remember on the dyno my 55 was a little fat, I leaned it some and it made less power. So I made it slobbering rich just to see, and it was strongest there. I wonder if this means that these saws need carb tweaks to get more mid range fuel, like Rich does on the dolmar Zamas?

 

[paragonbuilder]

What patterns Dan?

Excited for your build.

I have another 262 on my bench right now.

I'm not totally sure. Ideas will be great. But for now I'm going to document stock timing numbers, crankcase volume, port shapes and entry angles. What I'm looking for are what makes this a stellar saw stock, so we can use that to improve our builds. What can the engineers teach us?

 

[Mastermind]

That's interesting. I remember on the dyno my 55 was a little fat, I leaned it some and it made less power. So I made it slobbering rich just to see, and it was strongest there. I wonder if this means that these saws need carb tweaks to get more mid range fuel, like Rich does on the dolmar Zamas?

These carbs are just so primitive....

 

[paragonbuilder]

These carbs are just so primitive....

I believe this is where autotune/mtronic really has it over standard carb.

 

[Mastermind]

I believe this is where autotune/mtronic really has it over standard carb.

I'm looking forward to fuel injection.

 

[malk315]

I found the 262 to perform better tuned really fat.

This is where I'd like to measure the difference with the dyno. This happened with Dan's 55 when we had it on the first dyno it just made power more fat. Specs on the 55 say max rpm of 12500 which is 1k less than 262 and other 60 cc class saws.

My Mastermind ks87 saw seems best at about 14k but didn't get a chance to play on the dyno. Hoping the new dyno will have the sensitivity to see the difference so we can derive the fat but sweet spot!

Sent from my XT1585 using Tapatalk

 

[Mastermind]

This is where I'd like to measure the difference with the dyno. This happened with Dan's 55 when we had it on the first dyno it just made power more fat. Specs on the 55 say max rpm of 12500 which is 1k less than 262 and other 60 cc class saws.

My Mastermind ks87 saw seems best at about 14k but didn't get a chance to play on the dyno. Hoping the new dyno will have the sensitivity to see the difference so we can derive the fat but sweet spot!

Sent from my XT1585 using Tapatalk

13,200 or so seems way to fat, and it is in small stuff, but in 14 - 16" stuff it will be better I'd bet.

 

[paragonbuilder]

13,200 or so seems way to fat, and it is in small stuff, but in 14 - 16" stuff it will be better I'd bet.

I think everyone is always trying to get more unloaded Rpm, but it's really irrelevant unless it can maintain good rpm under load.
I'm beginning to find that tuned a little fat actually performs better working. And its better for the saw.

 

[mdavlee]

I ran a treemonkey 390 years ago a good bit and it was tuned to 13.2k or something like that but held 12-12.5k in wood. Unloaded means nothing in reality.

272 carb and intake could probably be adapted with some work.