Place yah bets! Whadda yah think caused this!??

[Adnoh]

Bummer about you PCP work. Hate to see that happen to anyone. The hugh squish may be a result of the clearence. Just a thought. If one was to tighten it up a little it would be more effective and less fuel sensitive. This of course if the clearnce is too great. It would be nice to now in degrees when the exhaust port closes and the deck clearences and head cc numbers to see what CR you have. Here's another thought. If one was ( if clearence allows)to tighten it up a little you could add a second angle based on the piston crown taper and increase the chamber cc for better power stroke and offset the rise in Cr or do this in and take 2 mm off top of exhaust port. This should yield a major increase in preformance with out hurting the motor. Rember just some thought for discussion on how to keep that edge on the piston.

[Adnoh]

Heres a diff head  #1  and #2 being the previous one both cut to 180 lbs with different cc's and clearences. This is the one I use on The wifes new pump gas motor. The diff in Cr is as follows before port modifaction #1  7.62 and #2  6.84 after port modifaction  #1 7.40 and #2  6.64.  #1 head is used on the wife new pump gas motor 92 oct.

I'am not saying do it just sharing info. Last pic is of the plug chop after jetting

[BDKW1]

Monkeying with the squish band is something that should be left to a very qualified person. There are about 3 people I would trust to do this. Milling the heads is never a good idea if you taking off enough to get into the squish band. I have always taken it off the top of the cylinder. I have also never liked offset chambers.
 
Also, alcohol in the fuel while making it slightly leaner will not increase the EGT's as ALGOL burns much cooler than gas. Adding some alcohol cured overheating problems in My KX500 when I used it for a hill shooter. Only problem is finding oil that will mix with alcohol. Bel-ray used to make GK1, not sure what is out there now.

[artie on edge]

I still reckon its missing an oil ring........

[b.c.bugger]

No, I don't think running race gas in a low comp motor is a good idea. I've never heard of a 2 stroke burning down as a cause of burning higher octane fuel, but it does cause both a loss in performance and in wallet thickness

[fabr]

Honestly I feel the problem is running lean. The thoughts about the squish band are valid tho.

[SPEC]

Adnoh has made really good points...
Especially about milling the block and not the heads...Getting into the squishband is bad...They make alot of different inserts to get away from milling off any thing...so If it's not what you expected you don't have to toss the parts in the recycle bin

[Adnoh]

Here is one to compare to his style of head.

[Nutz4sand]

Well the eggs on my face a good bit here. Heres a first for me.

As custom I always do a pressure and vacuum BEFORE I tear a two stroke down. Then after I button it up to check my work.

This one held 6 inches of vaccum for more then three minutes before I tore it down. It also held 6psi dropping only 1.5 psi in four minutes. (I think it was still warm/hot a bit when I did the test from a putt around the yard before I stopped it. That might have made it read good readings???) 

After bolting the new top end on it I could not get it to hold neither vacuum nor pressure worth a dam. The gasket on the exhaust manifold was leaking and after removing it and replacing it and working it for a bit I finnally got the exhaust flange sealed with a different brand gasket.

But it still was leaking pressure and vacuum.   

Being it passed the before teardown I just planned on a top end. I never removed the clutch cover just doing a top end.

There is a vent line on the flywheel side (for the counterbalancer oil reservoir) and I put it in a water container and it did not draw nor bubble. So that told me that side seal was holding inside its area. Soapy water all over the motor I could see no bubbles at any joints.
 
Sooooo  I borrowed a clutch puller and popped the clutch off and the seal on the clutch side was blowing lil bubbles!  :P   (You can't see the clutch side seal with the drive clutch on.) 

The cranks shaft could also be wiggled up and down JUST the slightest...

Sooooo I yanked the motor and gutted it and got all new bearings and seals coming and the whole motor will be "fresh" before she sees fire.

(Side note I am also upping the jetting just for sakes sake. I can drop it if need be after break in.)     

I gotta admit I have never had a motor pass the "before teardown" vacuum and pressure test to find this later. Still thinking it passed as OK cause it was warm from driving it around a bit before I tested the motor the first time for vaccum and pressure.  From here on out they will ALL be cold tests. Maybe even a cold test then a warm one If I can.

The bearings are out. The three main bearings on the crank all have a tiny bit of slop. (Scramblers have two big bearings on the clutch side and one on the other. Then a larger diameter but skinnier bearing past the counter balance area to support the flywheel. That bearing is solid but its getting replaced too. 
More as events unfold. 

[artie on edge]

Well, while you have it apart you can fit an oil ring.......

[fabr]

I am glad to see you found the problem.

[fabr]

Well, while you have it apart you can fit an oil ring.......

I gotta ask,WHY??? 

[SPEC]

Artie thinks it needs Oil rings...
Wants it to be a 4 stroke....
Just a bit of a dill

[SPEC]

That's strange that it pulled well with a crank seal out...My experience has been crank seals run way lean and won't get up to R's with out choking the piss out of the motor...But I guess that is the difference between the twins and tripples I run VS. the 1 lungers :-\

[Adnoh]

Glad to see you found the colpurt. It was fun guessing thu.