Well, we finally got the SP 90 out on the trail. It did rather well for a 90 and what is expected of them. For some reason I think they should do better, but it's just a freakin' 90. Because of the 2 stroke, Psychmike Jr. had to keep it reved up a bit to maintain momentum up the hill. Because of this, he smacked a few rocks on the under carriage. This was his first weekend out on the trails too. He's rather tenative too as he is learning how to drive this machine. We got into some mud and snow. It did especially well with it. As well as my SP 335 did while in 2wd. It's rather zippy and fun for him to drive. Jr. got it stuck in a rut, it couldn't generate enough power to turn out of it once it was stopped in the rut. I had to gas it and push it out before the CVT could get the wheels going. He got high centered in a two-wheel rut. That 5 inches of clearance is good, but always wished for more. It did well going up moderately steep grade hills.

It starts easily. However, the starter makes a aweful noise if the starter button is pushed too long (more then 2-3 sec) when starting cold or hot. A grinding noise. I'll have the dealer look at it. So far, so good.

What I want to know, is how do those 4 strokes do going up hills?

 

i still have the Throttle turned down on the grizz 80....We didnt hit many hills on our last ride...but its seems to pull them quite well...I know for sure that it will not be a problem once i can open the throttle up a little...it has lots of torque even in 2nd gear....
And ground clearance does stink on these mini's ..

JP

 

Again....Keep me posted as you experience differing terrain.

 

The 2-strokes are really choked in stock form. You can almost double the power fairly easily with bolt-ons.

Can't say that about the 4-strokes.

 

The only way I'd want to double the power is on the bottom end. Not for quickness or speed, but for maintaining momentum over slow-go rocky hils.

Are the bolt-ons better for speed and racing? I wonder if they'd fit my needs? What are they?

 

There are easy mods to help low end. I'd start out with slightly lighter rollers in the front variator half, a high compression head and new reeds. If you ride in mud, I'd keep the stock intake. Otherwise I'd slap on a bigger carb and a K&N/Uni.


WRH Racing was working on a pipe to fit the pred, but I'm not 100% sure it'll fit the sportsman too. You might give Billy Holt a call.

 

would a different size sproket make that same difference regaring transfering more power to the low end?

 

Some say it will. Haven't tried it. I wanted power all the way accross.

But keep in mind with anything that alters how many rpms you turn, you need to adjust the cvt to hit that optimum rpm. Otherwise you won't rev enough to hit the powerband. The lighter rollers hold you at a "lower gear" as well. You can play with it by removing one or 2 (6 total). You can remove them in about 20 minutes if you have an impact wrench.

 

How mechanically oriented does one have to be to make the changes? Where do you get the rollers? From WRH racing? I don't really understand the mechanics of it, but it sounds like a great help for the two stroke to negotiate rocky hilly trails at a slower speed. That's the purpose, correct? Is it best for a mechanic to do this, or can I do it in my garage.

 

I am no mechanic. With a little patience and a manual anybody can do it with the right tools. There is nothing to it but turning a few screws and bolts. I do like to tinker with stuff though.

Stuff to have on hand:
impact wrench - wouldn't want to try changing rollers without one
impact driver - not necessary but the screws are soft and easy to strip with a normal screwdriver.
philip's screwdrivers
good metric socket set
copper gasket spray if you decide on the head.
liquid silicon gasket if you find a pipe
6 pack of beer - not sure how this helps but it puts a smile on my face! [img]i/expressions/face-icon-small-wink.gif[/img]

WRH or Hetrick would have rollers.
More power makes anything easier to get up and over.