I am in the market for a IRS quad and because I like to modify my motors to the max I have a problem. I was told that Polaris Sportsman motors more over the cranks can't handle the extra power. I have found that Polaris has always been a strong contender in the mud and pulling areas. Now I am leary about purchasing a Sportsman dumping a bunch of money into the motor to find out it will not hold up. For instance I have super charged my Kawi with wonder results and would like to do the same with an SP to make a Super Mudd Slinger. The Polaris motor is a basic design can it hold up the riggers of heavy modding??

 

Hey there alltoys...

From what I know, the Polaris ATV twins did have a few crank problems back when they were first introduced. But I do believe that if you used a late model twin as a base, modding won't be a problem. But you must remember, as with ALL modding, you'll be making a hand grenade. Especially if you go to the extreme. (ie: forced induction) It won't be a matter of "if", but "when" will things go wrong. Will it hold up to heavy modding? With proper R&D I see no reason why it wouldn't. But what of the drive train?

The Liberty engine is a very basic design with a TON of "built in" horsepower there for the taking. Even in a normally aspirated configuration, I can honestly see being able to DOUBLE the horsepower without sacrificing a lot of reliability. You just got to know where to look.... [img]i/expressions/face-icon-small-happy.gif[/img] I'm in the paper stages of a build up myself and my goal is that very figure.

Stay tuned for further updates....

 

Moosehunter,

Have you tried any head porting, cylinder boreing, that sort of thing? Are there any larger pistons on the market, does the motor have a sleave or is it nicklesiled? Has anyone tried a different ignition, it does fire on 180* rotation so there would be a greater amount of ignitions that would work on the SP to get higher timing advances and more rpm. It would be interesting to see if the motor would support 10,000 to 12,000 rpm!! Then like you say would the drive train handle the extra ponies!!!!

 

Hi Gary,er alltoys.I'm certainly no engine expert,but I'll tell you what I know of my own experiance with my 02.(by the way,my 04.5 EFI test bike with 195 miles on it is for sale 8000cdn if you are interested).
In 02 I turned my sp700 into an 800(780)
It is a much less than perfect way that we did it.Used the crank from a 780 frontier sled.it is way too long on the pto end,so you have to cut it off and put a clutch taper on it.(then of course you have a non heat treated taper,but like i said it was not perfect).This is a very tedious job,and you could of course ruin the crank easily by cutting only a fraction too much on the taper.
Use the head from the frontier snowmobile as well,it has bigger ports from the factory for less porting work(the temp sensor IS on the wrong side(but again...). Dont use the sled pistons,but use your own bike pistons for higher compression(they are not dished out as much as the sled pistons).I cant remember for sure,but we had to releive the counterbalance shaft to clear the crank. You can cut 15 off the heads easily,and still have tons of valve clearance. The cam I used was one of the early ones fron Olav Aaen. Offset timing key helped,as this 02 only startd out at about 8 degrees and ramped up to 27,i think. I used non ebs clutches for a lower starting ratio and it was awsome in its day.

Polaris finally made one(sp800),but I have no idea why it is 760,or why it is even heavier than before(760 lbs).Glad to hear you are all moved and healthy again.

 

10,0000 to 120000 rpms ... i really doubt that would hold up that long, thats double what they put out now. thats like taking a truck and running it in a nascar