I bought my son a sportsman 90 and am surprised at the power and agility of this little machine. I've been pretty careful and cautious in the training of my son and am pleased to see he's taken to ATV riding like a natural and handles the machine like an expert (doesn't mean he rides outside my eyesite, though).

I've only one problem...speed. I've clocked the thing with my 'Cat' and it tops out at about 35mph. As my son progresses in his skill, I can see he will rapidly reach the point where this isn't fast enough (mostly to keep up with me on trails).

Does anyone know of anything I can do to eek another 5-10 mph out of this thing? I don't need it to be a speed demon, but it'd be if it could be tuned a little faster.

There is no exhaust restrictor on the spark arrestor and the throttle limiter is all the way out. Am I missing anything?

Any help would be appreciated.

 

change the sprockets to different sizes. bigger one in front(more teeth) or smaller sprocket in back(less teeth). that should give you the amount of speed you are looking for at the expense of acceleration and torque for climbing hills.

hope this helps.

laterz

 

Ummm...where would one find such sprockets?

How about tires? Anyone try going up a tire size or two on these things?

Any engine mods I can make?

Keep in mind this is a kids machine and I am not willing to break the bank here, I'd just like a little more oomph.

 

you might be able to find a sprocket at your dealer( i'm assuming they make different size sprockets) bigger tires would make it go faster but would slow acceleration just like the gearing and rob HP. you might try to have the top end ported and polished. if you do that, the extra power would probably overcome the loss of HP due to the bigger tires. good luck.

 

Thanks, yamahagye, for your suggestions. They seem a little more extreme than I was hoping I could get away with. I guess I was thinking more along the lines of changing the jetting, or air intake in some way. Something simple and basic.

You see, his two younger brothers occasionally ride this machine and will be growing into it as he gets a bigger one, so I don't want to do anything too extreme.

If no other idea's pop up, we may have to live with it as it is until I can swing him another ride.

I am checking into larger tires anyway, though. It comes with 19s, but I bet I can squeeze 20s or 21s in there, maybe even 22s. I am looking into ways to widen it too, seems too narrow for the agressive riding he does with it.

 

On all of the newer 90cc atv's, I have done the research and have made some very fast models. It is easy and does not cost too much $$.

 

Umm...care to tell me how then, Raptor720?

What can I do and how much?

 

i guess you could also get a better flowing air filter, cut a few holes in the airbox while you're at it. and don't forget to change the jetting. if the jetting is too lean you could burn out your piston which would suck. glad i could help

 

my dad bought me a sportsman 90 I think it has plenty of speed
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Well, my son would like a little more speed. And a little more power. And a little more power.


But mostly, he wants me to replace the plastic front face and rack as they got totally trashed this weekend in collisions with the rear end of my Arctic Cat 400. What really steams him is NEITHER of those were his fault. He was not even on his machin at the time. It's his brother and cousin who did it.

I sure hope that plastic don't cost me too much!![img]i/expressions/face-icon-small-sad.gif[/img]