id like to know just as long as its not too much money to do
thanks

 

Well you are going to have to start typing. We are wanting to know the magic.











Jeff

 

Walexa,
I suppose since the Sportsman was their 'premium' machine, they felt it needed a 4 cycle engine. Didn't want to have to be replacing pistons every 5-6000 miles on your 'premium' machine, when no other maker required it of you.
Kind of like the Sportsman/Magnum thing they had. Brother-in-law bought both a 500 Sportsman and 500 Magnum, I think in 2000, the last year before the HO. To make a long story short, the Magnum would outrun the Sportsman every time. He asked the dealer about it, and all they really said was that they had a LOT of comments to that affect (why pay more for the slower machine) and said a fix was already in the works (the HO engine). According to them, that is also why you never saw the HO engine in the Magnum frame, because the driveline was slightly more efficient, it would outrun a HO Sportsman, and the Sportsman owners didn't like it.

Seriously, though, the HO engine would give you all the power (or more) of the stock 400 engine. It is just that the 400 is soooooooo easy (and cheap) to modify for MORE POWER it isn't funny.
My Xplorer is basically stock, for reliability reasons, but I have driven a modded Scrambler 400, and it was a bear trying to keep the front end down wherever there was traction.

 

I put the AAEN cam in my old Sportsman H.O. and saw little to no gains. I sold the H.O. to a friend who gave it back to me to sell for him after a year of not riding it very much. The AAEN cam came apart and blew the motor! Actually what happened was the compression release ball bearing and retainer were thrown out of the cam and into the lower end, wrecking the lower rod bearing. Upon "mic" ing the cam we found the bearing journals were 50 thousands out of round. This could have led to the retainer letting loose. All in all, the cam was a piece of SH!+, did almost nothing performance wise and very much overpriced, especially figuring in the price of rebuilding the motor.
......Leave the H.O. alone. It is what it is. If you want to go faster get a 600 or 700 Sportsman, or a sport quad. I went from the H.O. to a DS, and haven't looked back.....

 

Okay here we go. First off, I am below 3000 ft to sea level, using a White Bros. E-series slip on and Uni-Filter air fliter.(Foam is for me!!!) Order a Dynojet jetkit for a Magnum 425. Yes, Magnum 425 '98. Install the needle with the c-clip on the third groove. Install the 160 main jet. You have to adjust the air fuel mixture. The screw is located under the air intake side of the carb. It is covered by a brass plug. You have to drill this out with a 5/32 bit. Go slow and be careful. The screw is right underneath. Turn the screw all the way in and then out 4 full turns. This will make an extremely rich mixture and requires air box porting. Start with the air inlet snorkel. Trim the bottom of the snorkel down another 3/16 of an inch. Right behind the snorkel on the top of the lid there is a semi-flat section about 2 inches by 3 inches. Cut a 2 x 3 hole here. Velcro an outerwares water-proof pre filter over the hole. It's an easy and cheap way to gain power. You will have to drop down to a 155 main jet in the summer. With my setup my Scrammy dynos at 47.5hp. It sounds great an turns many heads at our local ring area. I love to "Scramble" 400ex and z400 riders! Had a Raptor beat me by about 1 1/2 bike lengths in a drag race. Still not to bad for a 600lb sport 4x4 quad. Somebody give me some tire ideas for sport riding!



Note-------------- Your stock jet is a 155. You can not compare it to Dynojet's 155 and 160 jet. Their design is totally different and much more potent!!! Same thing with needles. If you use the stock parts over again you will cut performance gains tremendously.---------------

 

ok i got two questions
1) what if i don't have any aftermarket pipe??

2) what do you mean by Trim the bottom of the snorkel down another 3/16 of an inch??? cut the top off or take the whole thing off??
thanks

 

You must use a more free flowing exhaust. That junk coffee can Polaris uses as a stock muffler chokes the engine with exhaust. Get rid of it! Dont take the snorkel off, just trim the top underside.

 

ok thanks man ill see what i can do maybe ill do it this summer when i get some extra money


another thing is that all you have done to your scrambler??
is it ture that you gained around 17 horse power just from a pipe, jets and air box mod?? because the stock horse power is about 30 right??

 

The stock HP is around 37-38.

 

ok thanks i was wondering because in the sport section some one posted the horse power to weight ratios and they only said 28 i think which didn't sound right