big bore polaris 8oo cfi

[minecat]

Why has nobody else tried to do a 860 kit for the 800 cfi motors yet, i know that carls has one but they are using different cylinders not the monoblock cylinders I see that there are a few companys making skidoo 860 kits for far less money as carls and a couple of them run pretty good as well, so why doesnt anybody else make a kit using the stock cylinders for the Poos, or have i just not been able to find them yet

 

[Volvokvaloya]

This norwegian shop has are porting specialist and builds custom pipes,but they have 850 and 975 kits for the cfi engine.

They also have their own turbokits for the 800cfi,and they have a 800cfi kit for use in the 600RR

www.x-tech.no

 

[BB454]

860

I believe the CFI cylinders are too thin to overbore. Only other option would be to sleeve them and that is about as expensive as new cylinders plus you get into the argument of sleeved verses nicasyl. Also Carl's cylinders allow him to do more with the porting than the stock. His 860 is a little stronger than his 910 big block kit.

 

[minecat]

Thanks for the reply BB454 I thought that this might be the case

 

[mountainhorse]

Ya know... I've always wondered about Needing to go with individual cyls as well..

Is it truly needed or is it a need to "standardize" the same cylinders that they are using on the Carbed 600 conversions for the 860 Carbed kits And the 700 CFi 840 kits...

Both Ski Doo and Polaris went to Monoblock cylinders to increase the transfer port area....the bore centers are so close on the 800 CFi motors that the factory "siamesed" the cylinders. How much thinner would the cylinder walls Actually be?

Stock bore is 85mm... 860 @ 70mm stroke is about 88.5... Is the 1.75mm (0.135") thinner wall dangerous?


Looks like the Scandi's are using the factory mono-cyls in their setup.

 

[63nova]

big bore CFI

There's some sort of deck plate on top of the crankcase in that picture. What's up with that?

 

[mountainhorse]

Gasket....#15

 

[63nova]

deck plate/gasket

That's possible, but the Polaris base gasket is black. If it is in fact the gasket you see on top of the crankcase, then it is made from different material, possibly silver/grey colored paper.

 

[IMBROKEN]

Is it possible they are using a base plate and adding stroke instead of bore? I thought it looked like a plate too, but I could be wrong. Can they add the stroke by getting pistons with different pin placement, or maybe longer rods? It's cool regardless. I need to learn Norwegian.......

 

[indydan]

stroke

Is it possible they are using a base plate and adding stroke instead of bore? I thought it looked like a plate too, but I could be wrong. Can they add the stroke by getting pistons with different pin placement, or maybe longer rods? It's cool regardless. I need to learn Norwegian.......

You can not add stroke by moving the pin location alone, Moving the pin location and adding rod length
changes the angle of attack of the rod and reduces power loss and piston wear.

In order to increase stroke you must move the rod pin out from center on the wheel.

IMO the OEM cylinder is a poor option for a big bore.

 

[AndrettiDog]

Check with F-Bomb, I'm sure I read that he tested, or installed a Struthers 860 kit somewhere. I'm not positive, but his D8 might even be a 860 kit.

 

[mountainhorse]

Maybe it IS a base shim...to change port timing or accomodate a different wrist pin/dome dimension??

 

[Volvokvaloya]

Mountainhorse:I can translate to you from x-tech site if you want,but it doesnt say anything about that baseplate.

 

[FTXMOTORSPORTS]

Base plates and/or welded shelf mods are installed on some motors to increase base gasket area and available upper case port area when the porting in the cylinder/case grows to far into the oem base gasket to allow effective sealing.
They may have done this and are using a custom base gasket. A lot of our UBR motors are done this way.

 

[Red Dog]

Well?

Please do not let this thread dwindle.Cheers Red Dog.

 

[Red Dog]

O check with the Rabitt he's already there. Cheers Red Dog

 

[FTXMOTORSPORTS]

O check with the Rabitt he's already there. Cheers Red Dog

Hey Red, where's he at?? I've been biting my tongue so he could tell his own story!!


curt

 

[Red Dog]

Hello Curt, for some reason he says he can't register on the forum,must be wanted by the Law.His # is 509-948-1361 he would like to hear from ya. Cheers Red Dog.

 

[63nova]

Base shim

Maybe it IS a base shim...to change port timing or accomodate a different wrist pin/dome dimension??

True.....last winter some guys were experimenting with old Polaris 800 big block pistons in the 800CFI. The old piston is taller and a shim about .060" thick was needed to get the port timing right.

 

[hobbes]

Carl's uses Crankshop cylinders in his 860 kit, this is the reason for the money difference when compared to the Doo kits. And also the reason for the performance difference too...

I own one. It's probably the most impressive running big bore kit I've ever owned, and I'm still dialing in the clutching for the high elevations we ride.