I have a 400 Scrambler 4x4 with HDP pipe and roller clutch. I have just got a Pro Design Cool Head (Very nice product) and I want to replace the piston and rings when I have the head off.

Can anyone recomend what piston I sould use. Stock, Wiseco or something else. Also what size. Do I stick with the standard size, or bore it out slightly and go .020 or higher oversize?

This will be the first time I have cracked open a two stroke, so any help would be appreicated.

Merry Christmas

TheJoka
400Scram 4x4

 

I think you'd be better off with a .20 over wiseco. The pistons is much stronger than stock, plus the bigger size will complement your other mods(plus boost your compression a whisker), and you wouldn't have too worry about your motor for awhile. Besides if you break something, I think you can go up to .80, so you have plenty of beef left in the cylinders after a .20 overbore. Plus, the slightly thinner cylinder wall will allow the coolant to pull more heat outa there, too.

 

I put a Wiseco in mine when I did my other mods. I went with the standard size. It was a lot easier than I had imagined.

 

I'm about to do the same thing as you. From what I hear, the Wiseco .20 is the way to go. While it is apart, I'm going to send my cylinder and head to Rick Ritter and let him do the porting, head mod, and bore. He can match the piston to the cylinder and send it back with all the parts to finish.

I already have the HPD trail pipe and clutch kit, but have interest in the HPD roller clutch. How do you like yours? Worth the money?

 

Only got the clutch Monday, and have to get the grinder and drill press out to fit it. I will let you know how I get on when I have fitted it.

TheJoka
400Scram 4x4

 

I went 0.040 o/s when I had the engine apart this summer, I just wanted the extra displacement. Definetly bore the cyinder and give the rings a fresh surface to work on.
The Wiseco is the best piston readily available.
Pair of 98's, Rick does some very nice porting work, you'll be pleased with the results.

 

TheJoka, Is a cool head the same as a Billet Head? I bought the HotSeat 12:1 Billet Head and going to install it after the winter. Does this actually add power?

I have a Roller clutch in my Scrambler, the Aaen model, and it is amazing what difference it made. Power hits a lot harder, acceleration is better and that obnoxous lag in throttle response at moderate speeds is gone! HPD's must be just as good.

Doesn't a .20 over make the machine less reliable? That is what I have heard a few times...

Brian

 

WISECO is the only piston readily available for the polaris's.

Brian,

Overboring should not cause reliability problems. Its something that is going to take place over the long run. Every time you tear down your machine, you probably (hence, you might get away w/ just honing) are going to need to go up a notch in piston size. (pending you do this annualy).

From my understanding, a billet head is a cool head. Billet is just what it is made of. YOu should get better cooling characteristics and more HP/grunt down low. You should really be able to tell the difference.

Good Luck,

EC

 

The Cool Head is the same as the Billet head. Pro Design make the best ones, and I have been told they make most of the cool/billet heads for most of the other suppliers.

The Pro Design one is a fantastic looking device. I almost want to take it to bed with me. It is to good looking to get oil on it and get it dirty (and that is just taking it to bed!) I have got both the standard dome and the high compression dome for use with 108 gas. I will be usung the standard one most of the time, but speedway season will see the high compression dome fitted, and the good gas used.

I hope I don't have to use grinders and drill presses to fit it like I have had to do with most of the HPD stuff I have purchased. I fitted the roller clutch last night - cow of a think. I had it clamped to the drill press, and the holes still drilled uneven, and required filing to get the bolds through. I hope it is worth it.

TheJoka
400Scram 4x4

 

EC

This is the first time I have so much as looked at the motor since new. For a nearly 5 year old bike, I think this is stunning. The bike has been given death every time it has been started. It has been raced in MotoX, TT, Enduros, speedway, hill climbs and lots of full on trail riding that is just like been in a cross country race. I have never had a problem with the motor in this time.

TheJoka
400Scram 4x4