There has been alot of talk about putting parts to increase the Hp of the SP. Here is the scoop.
Scrambler and Sportsman part differences.
Cylinder, piston, head, valve springs, and valves share the same part numbers.
My conclusions is you can put the 40mm carb on with a manifold change and install the cam with no problems. The crank assy' and the rod have different parts numbers and I am sure they are heavier on the Scrambler. However the crank may be the same because the assy' comes only with the rod and maybe the rod is only different. The air intake is larger on the Scrambler so some jetting problems may arise. The part comparisions are for "00" machines and may alter for other years.
If anyine else know of any promlems that may creep up let us know.

 

talk to jack schultz or check out his website (www.godigital.com/schultzmotorsports/). he has turned his sportsmen into a HO. good luck

 

Chopperbill,
I know that a 36mm carb will flow much more air than the SP500 needs. Why can't you just go with a larger jet and a scrambler cam and get the same results? I also spoke with my Polaris Mechanic and he said that the scrambler crank has a different part number but it is the same as the SP500HO. He says as far as the motor goes, the only difference is the cam and carb. Someone else told me that I might need to change my CDI to a scrambler CDI. Is there any truth to this?

Greg

 

The way I understand it the oil holes on early model 500 cranks are larger. This gives them a higher tendency to break off the end at high RPMs that they can now turn with HO parts. The *cut off* RPM I here on a old style crank is about 6700 to 6800.
Jack has a 96 , it probably has the old style crank in it . Jack seems to have no trouble whatsoever . And I think he spins his even higher than 6800 I think by what I have seen him post .
I do believe Polaris had trouble with cranks when they were developing the HO motor , and therefore changed oil hole size .
The way I understand it all newer model 500's (All HO's and the latest standard 500's) have small oil hole cranks in them to keep things more reliable.

ChopperBill , do all 500 standard engines (all years) use the same crank ? I know you have little time to do recreational reading in parts fiches , I don't have the first hand experience on this issue , I was just told this by someone I think really knew the answers .
The oil hole thing being different and Polaris having trouble developing the HO I am pretty sure of though .
Your input is very welcome on this . Thank you .
Rick Ritter

 

The rod and the crank assy' both have different part numbers, so how can he say they are the same. You may be talking about microscopic difference. Would guess the old motor would live with out changing the crank. The lift and duration on the cam is going to give more fuel at intake and the larger carb is doing the same, so bingo more H.P. You can always use your 36mm carb I am sure it would work.

 

The Polaris mechanic that I spoke with said that Polaris will sometimes use different part numbers for the same parts on different bikes. It didn't make sense to me but he has been a Polaris mechanic for a long time and he has a reputation for being the best in Texas. I drive an extra 70 miles just to have him do my service. The Guys at Highlifter also bought the Big Dod there because of reputation for service. That is a good hour and a half away from Shreveport. Anyway, the guy has a reputation for know his stuff. Now, whether he is right on this issue I don't know. AND, he may have just been refering to the crank in my late model 2000SP500. It is only six weeks old.

Also the point came up in another post that maybe the 36mm can flow enough air, but can it flow enough fuel. I read my manual and it appears the 36mm can accomodate a much larger jet than the 152.5 that comes stock. What do you think about the fuel issue, and I know the scambler cam is around $200. What after market would you reccomend?

Thanks,

Greg

 

I don't know exactly what to think Bill. Did you hear of trouble at the factory when they were doing the HO motor that called for a crank change ?

 

OK here goes(wish I was getting paid for this
97-00 Sportsmans used the same crank by part number.
98-99 Scrambler cranks are the same by part number, the 97 uses a different numbered crank.
In all I found 3 different cranks.
The crank case part numbers are different between the Sportsman and the Scrambler.
Why I dont know, I dought that Polaris would keep 3 different cranks under 3 numbers if they were the same. Can't order in a couple of thousand dollars worth off cranks and cases for curiositys sake.
If everyone who put in a different cam and carb worried that the crank wouldn't hold up there would be no after market high performance manufactures around.
I'm sure Polaris by uping the HP would give thier machines a little margine of safety by beefing up cranks.
If I was overly concerned I would just buy the Sportsman HO and get the other extra goodies also.
I also think you could use your smaller carb with the cam, you just arn't going to get the full effect.

 

Greg: Almost forgot CDI is the same on both machines.

 

The evolution our 1999 Sportsman 500 into the SP 500 H.O. took a while. Initially we started off just trying to get a little more performance for the 500. Here is how it went . . .

Stage I –
DynoJet Kit; K&N w/Outerwear; Supertrapp IDS1; EPI ebs clutch kit. Installed on machine when it was brand new (15 miles).
Results: The low end and mid range were improved, but the top end still was lousy. In addition the EPI clutch springs were no improvement by the clock, in performance. Engine braking was so severe that when letting off the throttle at 35 mph, it could put you right over the handlebars when backing off the throttle. Also the EPI kit “increased” the engagement rpm, which made the SP500 a real beast on tight trails that might require log and/or rock climbing. The clutching had to be addressed first.

Stage II –
EBS clutches & belt were removed. Replaced with factory stock Indy-type drive and driven clutches. In addition we added an Aaen drive spring and an Aaen Roller clutch assy, Aaen cut helix, blue spring and Dayco belt. Also added a Westach tach to get a handle on the clutching rpm’s. The results were outstanding with this setup.
Results: Performance improved in low-mid and we gained a couple mph on top end. The backshifting was so good that even without ebs we had what felt like 60% of ebs engine braking. There was no engine braking below 5 mph when the clutch disengaged when decelerating. There was a dramatic improvement in acceleration with the roller clutch. We could get it up to shiftout rpm very fast. We knew we were on the right track now. The engagement rpm was still not what I wanted but it could be used for log/rock crawling now. We tried several different flyweight setups with the Thunder Shift Kit and felt that we could still improve with more testing. There still was that performance wall at about 35 mph, which occurred after shiftout in high range. Acceleration was very good up to that point.

We felt that the wall we were hitting at 35 mph was just a case of the engine wanting/needing more fuel/air. If you have ever seen a dyno chart, these engines hit a certain rpm and then fall off dramatically. That made us go onto Stage III.

Stage III –
Added a 40mm CV Mikuni carb off of a ’99 Scrambler 500. This was a no-brainer since Chris Picciotto offered his for sale. I weighed getting the 36mm carb from Hot Seat, but felt that the 40mm was really the way to go. To accomplish this change I bought the Scram 500 manifold, throttle cable and a new airscrew adjustment setup for the carb. The one I had was busted. Found out later that the stock SP500 throttle cable will work fine with the 40mm carb. The carb cross brace must be removed and left off. We were thinking about making another but I don’t feel we need it at all anymore. To hook up the carb to the K&N in the airbox we just turned the carb boot around and it fit snugly but nicely over the end of the carb and onto the airbox.
Results: The low end and mid range and top end were all improved now. The only problem was it was still rich in the mid-range. Not quite as crisp and sharp as it should be. We were on the last (leanest) clip on the needle. I called everywhere trying to find the next leanest needle for this carb, but because Mikuni, makes it as a proprietary item just for Polaris, there is not other needle available. The IDS2 end cap came out so we put one on . . . the difference was quite noticeable. I was surprised and did not think it would add much except more noise. The end hole is considerably larger, and the noise is also. It helped quite a bit. It was rich in the middle but very runnable in this condition. The wall at 35 mph was slowly disappearing, but was still there. So on we went to Stage IV.

Stage IV –
In an effort to get rid of the 35 mph wall and improve performance in all ranges we felt that the Scram 500 cam was the only answer. It provides more lift and duration and uses the same valve springs. We felt that this would be the only way to get the correct mid-range flow corrected with the new camshaft. In addition, we talked to the people at Wiseco about their new 10.5:1 forged piston and decided to do both the cam and piston at the same time. Both were installed along with a new gasket set. A ProLine Supercooler was added along with the required amount of RedLine Water Wetter to our 50/50 mix of water and coolant to eliminate the future possibilities of overheating. We have never had a problem, but I wanted to play it safe.
Results: This is what it needed. The top end was 4 mph faster and the quickness and mid range response was outstanding for such a heavy machine. The wall at 35 mph was gone. We were forced to keep the needle on the leanest clip and it seems to like it there. With the flyweight setup we had the rpm’s were topping 7,200 on shiftout. That was a little bit too much we felt. It would tail off to 7,300-7,400 on top end. We changed the flyweight setup to bring the operating range down to a 7,000 shiftout and 7,200 top and we picked up 4 “more” mph on top end. I guess sometimes less = more.

Since we started, we picked up a total of 10+ mph on top end and the quickness and throttle response is truly outstanding now in all ranges. The only thing I’m not completely satisfied with is the choke. It works, but does not want to idle for more than a minute or so with the choke halfway on. It starts up real good and I have noticed that I don’t really need the choke to start it. I now put it on half way, start up and run for 1-2 min, take the choke off and go. As it gets colder we will see if any adjustment is in order here. It seems to work fine, just different from a stock SP500.

To keep the rpm’s down a little more, we first changed the Thunder Shift Kit flyweights to 2 gr. heavier, and then 4 gr. heavier. This worked and did not affect the top end at all. All those revs on top were being wasted I guess. Our shiftout is now at 6,800 and it will tail off on top to about 7,000. We also changed the drive spring to engage lower by using a stock Green Polaris spring. It helped, but I still want a lower engagement. I may swap the Polaris Green drive spring from the 400SS to the SP500 to see if this does the trick. I believe that the spring in the 400SS might be slightly worn (age) and this is what allowed the engagement to be so low on our 400SS. I want to verify that. I should mention that the engagement on the 400SS (with the Super Torquer kit) is now at an unheard-of 2,000 – 2,220 rpm and is the nicest engaging clutch I have ever felt on an ATV.

I should mention that these changes were done so we did not jeopardize the reliability and runability of the SP500H.O. We use the quad during hunting season and for lots of plowing in the winter. I believe that you can in fact, have both performance and reliability. I did not want to make a missile that would launch an engine from time to time.

I will post updates as we make changes to our “Original Sportsman 500 H.O.” It’s getting close to archery season here in Pennsylvania and I need to get some range time in with my new bow setup this year.

Jack Schultz
www.godigital-design.com/schultzmotorsports