tearing into my simonized 372xp

[nmurph]

Yes, a 272 is 52mm. The 268 was a 50mm and I believe some of those were CP saws(?).

 

[boxygen]

I always assumed that simonized meant ported but my untrained eye does not see any port work. Or does he just add pop ups?

 

[boxygen]

Yes, a 272 is 52mm. The 268 was a 50mm and I believe some of those were CP saws(?).

Yes, the 268xp is a windowed piston, 50mm.

 

[Cfaller]

I believe I have the part number of the piston he uses. I can post it here tomorrow if you would like the PN.

 

[SCTREEGUY]

I thought it was ported too but it's not at all you can still see the ridges in the ports.

 

[SCTREEGUY]

Yes, the 268xp is a windowed piston, 50mm.

It definitely looks like a 268 piston.

I believe I have the part number of the piston he uses. I can post it here tomorrow if you would like the PN.

Please do that.

 

[boxygen]

I thought it was ported too but it's not at all you can still see the ridges in the ports.

Sounds like you were scamonized. Was the squish or base cut on this cylinder? Why not run a stock piston if the cylinder is stock?

 

[boxygen]

A 372 (71cc) piston is 50mm. An 064 piston is 52mm. The 75cc 372 is 51.2mm.

I thought the 75cc cyls were 51.4mm, not 51.2?

 

[SCTREEGUY]

Yes I thought it was ported but this saw was no scam it absolutely rips like no other. If a machined stock piston and base gasket delete runs like this I want more. Saw has triple port muffler,unlimited coil and I'm pretty sure I remember something done to the carb.

 

[Onan18]

I was going to say 268 XP piston but you guys beat me to it.

Joe

 

[fearofpavement]

Different builders do different things to different saws to get the results the customer is seeking. If you're not that original customer, there's no way of knowing if you got what you requested. If the saw runs great like you indicated, then perhaps that mission was accomplished via the actions he took.

 

[.404]

Much of the magick in the NW Canadian saws lies in spinning a good light and effective piston indeed. I would like to see a side by side of that black cyl with a stock one. Don't over complicate things. Remember, pressure is pressure.

.....why not just fill in and reshape the combustion chamber?

 

[SCTREEGUY]

Much of the magick in the NW Canadian saws lies in spinning a good light and effective piston indeed. I would like to see a side by side of that black cyl with a stock one. Don't over complicate things. Remember, pressure is pressure.

Look at post number 5. Black cylinder is on top.

 

[.404]

OK thanks.

 

[Trx250r180]

I have one of Simons top ends,good running saw,it's not how much aluminum he removes as much as where to make it run good, mine has no squish band cut, but has. 023 squish assembled,has about 180 psi. My piston has no pop up, but it has same mods to the intake side to adjust intake timing.

 

[drf255]

If he made that popup, he had to lower the jug onto it. Unless he found a similar husky piston with a taller compression height.

I'd pop the new piston on with no rings or clips and rotate assembly. Go with the popup diameter you have and begin cutting a little at a time till you get the squish you want.

I believe every piston is a bit different. I hear that meteors weigh more and have a slightly higher compression height on some models.

Some people believe that the majority (not all) of the power increase on a ported saw comes from the compression gains. I believe it's a major player, but they all act in concert together with a trained builder.

Some factory saws are near their max in performance already and there's not much port work you can do. Realize that lowering that jug gave him an earlier intake opening point.

 

[SCTREEGUY]

I really don't think anything is done to the cylinder. I slid a piston pin into both pistons at the same time to see the difference in pin location. The machined down portion of the piston that was in it is almost 1mm higher than the top of the new 1 then there is a 1mm popup. Its hard to get an accurate measurement of the 2 because the skirts are totally different. I ordered a new oem 268 piston last night and I'm gonna take both to the machine shop and get them to copy it then put it back together with the new cylinder.

 

[blsnelling]

We're any ports widened? Intake lowered? Transfers raised?

 

[boxygen]

I ordered a new oem 268 piston last night

Make sure it is the XP piston. The regular 268 piston is also 50mm but it is not windowed. There is a difference.

 

[mdavlee]

Why not send it to someone and cut the chamber? Then next time no worry about getting a pop up cut.