Ported 026 Squish Check

[Moparmyway]

Wide band, narrow band. Domed, arced. I know which one I prefer. Carry on.

Them plugs are a dead giveaway of which one you preferr

 

[blsnelling]

If your saw has 175 psi with a gasket delete ,which is good to me on a worksaw when working on a side hill and shutting it on and off often ,can't a good runner still be had without head machining or piston pop top ?

Absolutely. The hybrid for one can be a fantastic runner with no additional machine work. This one here has no machine work. I was going to offer to bump the compression for the owner until I ran it again, but it ran too good to mess with. As is, it will out cut most built 461s.

 

[Tor R]

This has become one of the best threads 2015.
Lots of learning for å newbie like me

 

[blsnelling]

I never said it's the only way, there's tons of ways and I'm interested in all of them.

I port 066/660's mostly and have done 100's of them and there's simply no way to port one of them to where they will run and have less than 200lbs. The exhaust needs to be a 100 or more and compression is a byproduct of that.

I'll give ya that one. The 066 is one that truly needs the squishband cut, just to get the exhaust down.

 

[KG441c]

I'll give ya that one. The 066 is one that truly needs the squishband cut, just to get the exhaust down.

And an 064 isnt far from being good from the factory. Its not nearly as high an exhaust as a 066/660 from factory

 

[drf255]

So is the 026. Hence the thread.

On an 036, I cut the band and chamfer the chamber junction to create a bell shaped combustion chamber

 

[blsnelling]

What's the exhaust from the factory on a 026/260? It's been years since I did one.

 

[jmssaws]

I've never done a 026 either, matter of fact I don't believe I've ever cn one in person. Small as they get here is a 460 even though a 20" tree is a good one here.

 

[jmssaws]

I could taper the band and loose compression on a 660 but the way I do one they run pretty good with over 200lbs and I've cn no issues from it.

 

[Mastermind]

Brad, I've seen 026/260a with the exhaust as high as 98.

 

[drf255]

With .060 out of the band on this early red lever jug 026, the best I did was a 104* exhaust with the factory roof. Base .206.

I actually think I prefer the later 260 jugs. The base is much thicker and the chamber is larger to accept the decomp.

So I actually got to 103.5 on my last one and maintained a .250 base with a .020 squish with .054 from the band.

The comp comes out a bit lower.

The goal here for me is the exhaust height. The compression and wide band are the byproduct.

But the saw runs good this way, real good.

 

[Moparmyway]

The goal here for me is the exhaust height. The compression and wide band are the byproduct.

But the saw runs good this way, real good.

But a taper could be cut into the squish band, closer to the chamber which would reduce the wide band to a more narrow one, and drop compression too.

This is what I have been thinking about lately, taking into account that 240 pounds compression may not be necessary .................. I am going to play around a little on a few different jugs and find out

 

[drf255]

I could easily shim my mandrel and cut a second angle.

 

[blsnelling]

Brad, I've seen 026/260a with the exhaust as high as 98.

That is indeed way higher than current 50cc offerings. Contrary to popular belief, I don't get more RPMs when raising a 346 exhaust either. They run best and make the most RPMs when left low.

 

[Mastermind]

I use a flexible rubber sanding mandrel to taper the edge of the band into the chamber. The harder you push, the more it flexes. That will allow you to bleed off some compression if you end up with too much. On the 026, I run out of piston skirt length before I end up with too much comp though.

 

[Mastermind]

That is indeed way higher than current 50cc offerings. Contrary to popular belief, I don't get more RPMs when raising a 346 exhaust either. They run best and make the most RPMs when left low.

Factual statement......

I think our friend Andre drove that home for us all.

 

[drf255]

I use a flexible rubber sanding mandrel to taper the edge of the band into the chamber. The harder you push, the more it flexes. That will allow you to bleed off some compression if you end up with too much. On the 026, I run out of piston skirt length before I end up with too much comp though.

If you leave a small chamfer on the piston crown edge, you get a higher comp height. Certainly not ideal, but it helps the skirt issue.

 

[jmssaws]

I actually think I prefer the later 260 jugs.

I prefer the later 660 jugs,there more work but there better for what I do.

 

[Mastermind]

You can cut on an angle first and then sand or change the angle and finish cutting the outer edge flatter on the band with the hand mandrels I have and sanding mandrel to finish the very outer edge.

I used mandrels to cut squish for a long while before I finally gave into using the lathe. After doing hundreds on the lathe, I can't imagine using a mandrel again. It's about a 15 minute job on the lathe.

 

[drf255]

The chamber and band on the 026 are an arc and not an angle. Adds to the complexity of the build and chamber geometry.

A small, angled band cut and a piston cut at the same angle may work well here.