Are there any real dangers in modifying a non H.O. sp500 into an H.O.? Polaris and all of the dealers say this should not be attempted and that you can't get any real benefits and the risk of tearing up your motor isn't worth it. I would love any feedback from those who have added the H.O. cam and piston etc. and have had some long term results. Thanks!

 

We have built several HO motors before the HO came out. The oldest ones being over 1 year and 4 months ago. No problems what so ever yet. In fact we are going to start build 425 HOs.

 

I thought the only differences between HO and non HO, was a cam and carb?
I was doing some reading and it seems to me that you could bolt the 500HO cam into the 425. Will this work? I don't see why not but, I have never held the two cams in my hand to see if they would interchange. From everything I have read though, it would work.

uflg95, you are a Polaris parts manager? Where, Marienville? I live in Titusville. Usually get my stuff from Linemans(LCR) or ST&T.

 

Fourlix did it and said it was not worth it.Not enough difference between the two,for the price it will cost you.

 

The reason Polaris and some of their dealers advise against converting a Non H.O. to an H.O., is the fact that they would like you to trade in your non H.O. for a H.O.

 

I only differance is a higher duration cam,a larger carb and lighter clutch weights.Polaris did not make a different crank,piston or main bearings for the H.O.

 

I do not know if there is any truth to this... maybe uflg95 can help. I was told that the pre-HO cases were not built as strong as the HOs. Apparantly the crank bearings are wearing the case out... I was told this by the tech at the Polaris dealership in Marshall Texas. Give him a call if this concerns you.

Greg

 

I did the H.O. treatment on my son's 425 Expedition and it was worth it. What I wasn't able to do was get any more out of my H.O. But the cam from the H.O. fits right in the 425, add a flatslide 42mm TM Mikuni, and a little porting out of the muffler finished it off. On the 425 the limiting factor was the rev limiter, which we never figured out how to defeat. Scrambler guys told us about the red/yellow wire coming out of the left grip, but on the EXP that wire controls the reverse solenoid. Acceleration was way up, top speed, about 50, was unchanged.
....We sold them both...and got the Raptor and the DS-650. I think the point is... Once you start looking for speed and performance, sell your utilities and get sport quads. Once you get the need for speed, the utilities will never satisfy. Even our new Grizz, which is light years ahead of the H.O. or the EXP "H.O.", pales in comparison to riding the DS or Raptor fast. They are all good quads,
but going fast should be left for the quads that were designed to go fast. It's that Apples and Bowling ***** thing again. Bowling with
apples just doesn't work very well.[img]i/expressions/face-icon-small-cool.gif[/img]

 

Hold on guys, before you go spend that money I HAVE MADE THIS MISTAKE FOR YOU
MY 96 sp wore the cam so i figured why not put in a scram cam
the cam is alright but not much gain because the arms arnt there
i also aded a high compression piston to make upfor the bottom end loss i got from the higher lift longer duration cam
when i finally realized that polaris DOES HAVE A HIGH SPEED REV LIMITER at 6000 rpm min is at 5800 they are all a little bit different
while apart i ported it matched everything biger carb
every thing i have done has been to improve power for on the top end that i can never have becaus of the cdi box rev limiter
easilly fixed by a scrambler cdi but i asked polaris tech after being on hold for 20min they said that the older crank (they make i believe about 3-4 versions up trough the different years and models)when turning the ho or scram cdi 6800 rpms will last 15HOURS then the berings in the conecting rod will burn up on the crank and seize hopefully, the alturnative is that the connecting rod will come apart and ruin the base and or the cilinder
SO GOOD LUCK
IM PUTING MIN BACK TO STOCK
THE BEST RUNING SPORTSMANS ARE THE ONES THAT HAVE THIS COMBO AAEN MUFLER ONLY K+N and jet kit stock cam for low end non ebs primary for lower starting gear and an ebs secondary for the back shift ho clutch cover with heal clickers
YEAH,,,, THATS THE TICKET

MAYBE NEXT TIME WE CAN BEAT THE GRIZZ

 

First off I have yet to see any of these problems.

Second the rpm limiter is above 6500rpms. Mine and my port guys '97 runs a constant 6400-6600.

Third the cases are different for strength reasons, however we have yet to see a problem. Not saying there is not one but we haven't seen it.

Fourth the several we did feel stronger than a factory HO. Why? Not sure but we used Scrambler jetting on the ones we built, that is the only difference we know of. I am going to run the Scrambler jetting in mine hopefully soon and see.

elroy, just on the north side of Marienville on the way to the ANF Trail system. How about LCR's new building, that's pretty sweet.