Another 260 port job.

[Alaskanrocket]

Hey guys,
Been messing with a 260 for awhile, pulled the base gasket out for .017 squish, put a tank through it, ran decent. Pulled it apart and found the piston had been making contact with the edge of the squish ring. Looks like it was running rich anyways. My timing numbers are
Ex-99
In-74
Xfer-117

I’m looking for any insights as to what I should do? I’m thinking taking the squish band down some and taking some off the base? Can I get my timing better? Thanks everyone!

 

[Lightning Performance]

Go read 026/260 builds.

 

[Alaskanrocket]

Go read 026/260 builds.

I’ve read a ton of them, but it’s a little convoluted. Thanks for the help though.

 

[Lightning Performance]

Where are you going with this build?

Doc and TM or MMWS are anything but convoluted threads.

Race or work? Not much changes but blowdown and compression ratios. Good work stands on it's own and performs well. Don't expect too much your first time around doing it.

 

[Alaskanrocket]

Race, I want this to cut a cookie as fast as I can get It to. I’ll keep you posted.

 

[Basher]

I don`t know ,much, about these 260`s but I know a guy,
@drf256

 

[Stihlbro]

Hey guys,
Been messing with a 260 for awhile, pulled the base gasket out for .017 squish, put a tank through it, ran decent. Pulled it apart and found the piston had been making contact with the edge of the squish ring. Looks like it was running rich anyways. My timing numbers are
Ex-99
In-74
Xfer-117

I’m looking for any insights as to what I should do? I’m thinking taking the squish band down some and taking some off the base? Can I get my timing better? Thanks everyone!

I would clean your squish band for the proper clearance.

What have you done with the muffler?
What carburetor are you running?
What bar and chain set up will you run?
What size wood are you cutting?
What are the rules for the cookie cutting you will be doing?

For what you have posted, the saw needs more intake duration to match the other ports.

 

[Lightning Performance]

I would clean your squish band for the proper clearance.

What have you done with the muffler?
What carburetor are you running?
What bar and chain set up will you run?
What size wood are you cutting?
What are the rules for the cookie cutting you will be doing?

For what you have posted, the saw needs more intake duration to match the other ports.

There you go. Racer X has this stuff down pat, period.

 

[Lightning Performance]

First thing you need is a bigger carb, boot, intake track and serious air filter. You can't get out what you can't get in. Think giant ..., never mind. I go back go back to my corner now.

 

[cgraham1]

If you want to cut cookies fast, get a 90-100cc and port it. Don't waste your time on a 50cc.

 

[Alaskanrocket]

I would clean your squish band for the proper clearance.

What have you done with the muffler?
What carburetor are you running?
What bar and chain set up will you run?
What size wood are you cutting?
What are the rules for the cookie cutting you will be doing?

For what you have posted, the saw needs more intake duration to match the other ports.

I cleaned up the squish band with sand paper
As soon as I can find a piece of stock big enough I plan on building a mandrel for hand cutting squish bands.

Matched the port opening to the new port size, drilled two half inch holes through the top of the cover, that was just a half ass test, I figured I’d build something different later.
I have an 044 carb and 038 intake boot that’s been opened a bit for the butterfly to clear.
No clue yet but I figure a 16” .325
Random sizes, but for the sake of testing I’ll probably be cutting something in the 12-18” range white spruce.
This isn’t for competition

Thanks!

 

[Alaskanrocket]

If you want to cut cookies fast, get a 90-100cc and port it. Don't waste your time on a 50cc.

Wait, they make bigger saws than this?

I have big saws, but I like working on two strokes and I’m trying to become more familiar with port modifications and tuning.

 

[Alaskanrocket]

Here’s what I did this afternoon. If it doesn’t work out no biggie, p&c s are cheap for this.

I flattened out the exhaust roof, but didn’t change timing at all.
I widened the intake port
And sanded the squish band, seems like they’re was a flashing lip towards the expansion chamber. Thanks for all the reply’s so far. PS I know they’re *s-word pictures, I figured you couldn’t see my port jog that way.

 

[Deets066]

Here’s what I did this afternoon. If it doesn’t work out no biggie, p&c s are cheap for this.

I flattened out the exhaust roof, but didn’t change timing at all.
I widened the intake port
And sanded the squish band, seems like they’re was a flashing lip towards the expansion chamber. Thanks for all the reply’s so far. PS I know they’re *s-word pictures, I figured you couldn’t see my port jog that way.

You should square your intake some



Just did this one today

 

[Alaskanrocket]

Will do, thanks dude!

 

[drf256]

Is that an oem piston and cylinder?

Never seen a piston like that. There seems to be an outer relief edge on it for the band. Your pic shows machining marks right though the step on it (Clearly at 0600 in pic). I’m no expert, but that don’t look like it happened from the band slapping the piston. The machine marks could just be from the photo I guess.

Is it a 44 or 44.7 mm jug?

I’ve used an 044 carb and boot on a few. They are race more than Work saws, throttle response and idling better with a 194 carb.

If it’s a 44.7, no gasket squish is usually .015-017. The 44mm usually comes in too tight, around .007-009.

You can scrape the band out with a wood chisel and sand the entire band with a piston with adhesive backed sandpaper on it. You can also cut the entire band and piston flat, which is what I usually do.

You’ll need to cut the base to tighten squish again when you do that.

 

[drf256]

Here’s a sanded band. This is an AM NWP cylinder.

 

[drf256]

Here’s some flat top pistons and chambers

 

[drf256]

 

[drf256]

A lot of info here that you might find helpful, inc the 044 carb swap.

http://opeforum.com/threads/west-german-024-super-with-build-pics.346/