125-200cc CR150 squish band

Nah I pulled 84 mph on Garmin once but that was a very quick roll on an off the throttle. On an Abandoned airfield too.
No cases are fine but it's dam close too swingarm.
An don't forget my rear tyres are smaller than most. They stand 2" shorter in height so that reduces gearing.

The head's back on, so I'll be riding tomorrow.

Squish is now at .77 mm (.030") and it will probably stay there. The nice thing is, with these bikes, I can have it off and back on in under 10 minutes.

Modded head


Stock head

Yeah baby, recessed into the cylinder just like mine. Keep us posted on the front wheel action, more grunt everywhere you will be smiling like a maniac

It looks like I hit the right combination.
Back to the 50T rear sprocket and the bike flies!
If you have a 125 or 144, you probably know why I put the 51T rear on, but it no longer needs it. In fact, it revved too quickly with it on after the motor work, and I not only was I was shifting constantly, but could have used another gear. The other interesting thing is no more spooge. This bike always spooged, even though the jetting was as good as I could get it, and now since the motor work, nothing. Must be getting a better burn.

So I've done a bunch of riding, and racing and written everything down.

Last test was to take the squish band recess right out of the head, making the squish same as the deck height, .6 mm and it did something really odd. With no other changes, the bike would no longer idle. Backing out the idle air screw, it would idle but was so rich it was burning my eyes in the shop. Until now, every other reduction in squish made it start easier and idle much more stable. At .75 squish, I could start it up cold, walk away and it would sit there and idle perfectly forever. Power was good, though no better than before and it just wasn't right down low, right off idle. So I put the stock head back on at 1.2 mm squish. Predictably, power down low was weak, much less snappy, but it did have excellent top end pull, and the spooge is back. As I reduced squish, low and midrange power got significantly better, and power seemed to change on the top end. It didn't seem to make as much power right at the very top RPM's, but it pulled so hard and so fast down low that it made it feel like it was running out of revs sooner. At the track, though, it was really fast, and I ride a high speed, natural terrain type MX track. In fact, I've never been faster on that track. Pull out of the turns was so much better. In the woods, it was incredible.

I just re-machined that (no squish band) head to give a 1 mm total for my final test, and likely run that for the fast MX. My recommendation, if you ride mostly woods with your 125/150, have that head machined down to a total squish of .8 - .9, with a maximum of 1mm. For fast MX, and general use, go 1 mm. The increase in low and midrange power, ease of starting, and idle stability are incredible.

If anybody wants me to machine their head, it's a simple procedure, and I would be happy to.

Another update:

So I rode it after this with the other head, and it still wasn't quite right. After dumping it in a creek during a HS, I tore it down, took some measurements and discovered that my ring gap was .075" - almost 2mm. That would explain the hard starting and mediocre power. The ring had only about 6 hrs on it, so the only thing I can think is that I must have installed the air filter incorrectly, and a bunch of dust got past, since I'd run a few dusty rides/races.

So with the new ring, and this head on, I've been riding it for a few weeks. Since I'd removed about .7mm from the head originally, then had to cut in a new squish band, compression was up. It still runs fine on 91 gas, pulls like crazy on the bottom and overrev is as good as it's ever been, maybe better. There's no downside. In fact I rode my buddies 08 KTM SX150 last week back to back with my bike. It has an FMF pipe, and VHM head with high compression insert. He told me, this bike makes 250 power! Well, my Husky makes way more power down low, through the mid and although his bike felt stronger on top (probably the hit), I pulled him out of every corner, and down every straight.

It was nice riding another 144 and seeing just how much better the Husky is