Hi guys. I am new to the site. I have looked through the posts on the polaris 90. There isn't a ton for someone who is racing it. I thought I would post what I have done and ask for suggestions. So far: Hetrick pipe and clutch kit, wheel spacers, 31 rear sprocket, smaller rear tires, new CDI box (no rev limit). Here's my questions: Some of the other guys running my same tires are running a 27-28 rear sprocket...and I see that on this board a lot. Would it be much of a difference over what I have? I am also assuming it would really benefit from a better intake. Is it necessary to go ahead with the reeds at the same time? If I do get a filter, how much do you need to jet up? I can't seem to find out what I should cut the head safely. I also see they offer aftermarket head gaskets...would this be the better way to go? If I would cut the head, how much? Finally... Can I do better on my clutching? I keep seeing wrh racing mentioned on this board. I plan to call them, but I thought I would see what you guys have for suggestions. Sorry for so many questions, but I thought it would be better to get it all in one post!! Thanks for any help!

 

Billy at WRH racing is really good. Aswell as Hetrick. You can get a new billett head for about $100-120 or Hetrick does a good rechamber and mill on your head for about $70 works very well too. I would get a new carb/intake as soon as you can as this will kick butt with your pipe even a 20mm Keihin carb has better than twice the size throat as the stock 16mm mikuni jetting is much easier and starts when cold makes a huge difference in power 20,24,26,28mm Keihins all work good on the 90s.

 

Welcome to the forums. [img]i/expressions/face-icon-small-smile.gif[/img]
Ok, the rear sprocket may be correct as you didn't mention the tire size. Yes, going from a 31 to a 27/8 makes a difference.It'll be faster (physically).
Yes you need an intake, the ones I have seen come with the reeds.
Carb: I like the 20mm carbs. I have tuned the bigger ones in, but feel that they are bigger than nessesary.
Head: shave it .030. That's safe. I have rechambered the heads, but the stock design sucks thus you cannot make the squishband shape the same as the aftermarket head. The chamber design (rechambered) results in an ancient squish/dome shape, but it seems to work.
Clutch: hard to say, but I'd suspect more could be done. The wording "clutch kit" could mean so much or so little whatever the case may be.
My advise:: As you see, doing this and that one thing at a time, just dont cut it.
Send your motor to a builder that makes a "motor kit". A combination of motor and clutch mods that work together. You'll save time and agrivation plus get more smiles faster from your rider.
[img]i/expressions/face-icon-small-smile.gif[/img]

 

Thanks guys. It sounds like I could wake it up a lot with a air intake, gearing, and head cut. I like to tune snowmobile clutches, so I think I will play with that end. Like you said a lot less headaches to take it somewhere, but what fun is that? [img]i/expressions/face-icon-small-smile.gif[/img] Thanks again for the responses. Any others are appreciated.

 

welcome to the forums

 

If decide you want to do the head mod let me know I have 2 used ones for pred 90/52mm we only used for a short period. You could get 1 or the other cheap. The 20mm would be the best carb IMO. You said you thought there wasnt much for them. But theres butloads of mods for them. Carbs,intakes,reeds,porting,pipes,clutching, 3 different stroker cranks, ultralight rear clutches,heads(cast and billett), cylinder spacers,ported cases,aarms,shocks,swaybars,and a whole bunch of stuff I'm forgetting.

 

hi snowdust and welcome

have you been to either statelinemx(pecatonica il.) or storm mx (warren il.)
just wondering what the turn out has been. my son is racing storm at the beginning
of aug. he ran there twice last year and loved it.

 

Get your gasket to gasket cylinder measurement to 77mm. Then set your squish to .040 or less. Port timing somewhere around a LT500 Suzuki port timing. Get one of Fastest dad's heads!
There are more crumbs of info you could do at this point but...... I don't want to take the fun out of it.
Just remember your kids only stay young for so long.

 

I have been to Pecatonica and the turn out varies. I wish it was a little better. It is actually my nephew that does the racing. We try to make it to most of his races. We were at Walnut last weekend.

I think my first post was misunderstood when I said there wasn't much on mods for racing. I meant I didn't find many posts on here from people that were actually racing the quads. [img]i/expressions/face-icon-small-smile.gif[/img] Oh I know there is plenty you can do ...and plenty of money you can spend...

How much for the head? I don't see a way to send private messages on here. I am definately interested. Is there a reason why you did not keep using it?

A little more information. My tires are 16.5's. Any suggestions for gearing? I don't want to have to change it for every different track, so just looking for something faster all around. It seems like it can pull the 27-28 rear sprocket with the mods done. I just want to be sure that's what you guys think too. Again thanks for the info!!!

 

We now use WRH's bigger motor pkg with the stroker crank and a 54mm head with the 54mm piston and stroke its about 109cc. So I have sold my old cyl, 20mm carb and just have a few odds and ends for the 52mm motor like yours. Thats why I said the 20mm Keihin from WRH/Billy Holt Kicks a$s it's alot faster now than it was before but man was it fast with that 20mm carb,pipe,porting and all the other mods.