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raptorobbie
05-21-2009, 06:22 AM
ok - I picked up an 01 sportsman 90 last night for cheap - bike is in pretty decent condition but won't start. They say they had it running a few weeks ago, it stalled and hasnt started since.

1. It is getting gas.
2. carb has been cleaned and blown out - looked very clean inside already.
3. w/ the airbox and tubes completely off and a shot of starting fluid the bike doesnt even sound like it wants to hit.
4. there is spark w/ both old and brand new plug - but the spark seems weak to me - I'm not sure about it.
5. Have no compression check tool yet - but what concerns me is how easy the kick starter goes thru its stroke. I can just push the kick start real easy w/ my hand - (are these all like that or does that mean the top end is wasted?)


I'm thinking of trying a new coil - or the compression is just way too low - any other input would be great. Thanks!

dericsdad
05-21-2009, 07:40 PM
Stock compression on the polaris 90's was only about 100 psi. They were colded blooded starters even when new. Just upping the compression to around 120 made a HUGE difference.

Start by checking the compression, hold the throttle wide-open while kicking it over several times. Should be about 100 psi.


Stators comonly go bad on these also. Just because you get a single spark doesn't mean the cdi and stator are good. Best way to check the stator and coil is by doing an ohm's test.

Check out this article for more on Stators:http://forumsminiatv.proboards.com/index.cgi?board=techarticles&action=display&thread=1513

Let us know if you still need more help.

Dan

raptorobbie
05-22-2009, 06:26 AM
Oh yes - more help definitely needed - lol!!

I picked up a compression tool/guage last night - screwed it in - kicked it a few times and got 0psi - a big nothing! The needle never budged.

I can move the kick start lever through its entire cycle w/ one finger! and the resistance of the kick starter doesnt change w/ or w/ out the spark plug installed! So I think Im ready for the top end to be redone - correct me please if I'm wrong.

Can someone steer me to good step by step instructions for the top end re-build (I have someone to do the bore for me).

Thanks!

ps - how did you up the compression from 100 to 120psi?

dwhst9
05-22-2009, 11:26 AM
Originally posted by raptorobbie
Oh yes - more help definitely needed - lol!!

I picked up a compression tool/guage last night - screwed it in - kicked it a few times and got 0psi - a big nothing! The needle never budged.

I can move the kick start lever through its entire cycle w/ one finger! and the resistance of the kick starter doesnt change w/ or w/ out the spark plug installed! So I think Im ready for the top end to be redone - correct me please if I'm wrong.

Can someone steer me to good step by step instructions for the top end re-build (I have someone to do the bore for me).

Thanks!

ps - how did you up the compression from 100 to 120psi?

Are you sure the kick starter is even engaging?

05-22-2009, 11:37 AM
Does it have a crank in it? I believe Dwhst9 is correct it has to do with your kick starter the spring maybe broke and the nut might of came off the crank which means your kicker gear on the end of the crank fell off try to take your cvt cover off then let us know thanks Toby

raptorobbie
05-22-2009, 11:37 AM
yes its engaging - w/ out the spark plug you can feel a little suction on your finger - same at the inlet of the carb. I had the same thought too!

05-22-2009, 11:47 AM
Does it have rings in it or is there a hole in your piston it should suck from carb and blow from plug hole dont sound good at all!

raptorobbie
05-22-2009, 11:52 AM
I have no idea!

I need to tear into the top end and find out - nothing would suprise me!

tell me if there's something else i should do first.....

Thanks for the replys!

05-22-2009, 12:14 PM
Put a little screw driver in plug hole and VERY easily push down on kick starter to see if the center of your piston is blew. Move it around on piston very easily. Thats prolly your problem or it has no rings did you ever ride it? Sounds like it was ran lean no oil prolly cause oil injection wore out and smoked your motor.

raptorobbie
05-26-2009, 08:20 AM
yep, tore into the top end this weekend and found a 1" section of one of the rings was missing - found all the pieces in the bottom of the motor. Piston was scored real bad at the ring failure point too. Will have to have it bored and new piston.

sparks1032
06-02-2009, 09:15 PM
where did you get the parts for you top end rebuild? hopefully not polaris....

raptorobbie
06-03-2009, 06:36 AM
Nope, took it down to Shawn at SMS Motorsports and he bored it out and replaced it w/ a Wiseco and took care of the crank seals that were wasted and the drive shaft seal that I had a question about - I stuck the motor back in over the weekend and it fired right up! Great work from SMS - he also just rebuilt my other sons DRR 90 - wow didnt know a mostly stock DRR could rip that hard!!!


Now for the Sportsman - I just have to get the air cleaner, install it, and tune the bike.

dericsdad
06-03-2009, 07:43 PM
SPARKS,

Why do you hope we don't get our parts from Polaris??

sparks1032
06-03-2009, 08:09 PM
my experience is that the stock stuff is not as good as the aftermarket especially for the top end. Plenty of places will sell you the piston and such but why not get a wiseco set up that will last longer and have higher compression?? for close to the same price??

My experience is that dealers mark it up from Polaris and the stuff is marginal quality and for close to the same price we can get it from aftermarket and add reliability and performance!

dericsdad
06-04-2009, 05:06 PM
The stuff from Polaris is all oe AEON parts. Nothing wrong with the seals, bearings and gaskets.

There are better cylinders and heads that are more suited for racing, no doubt about it.

Just adding a wiseco piston will NOT raise the compression on these cvt engines. The pin location and dome height are exactly the same as the oe piston.

BUT... the wiseco piston is a LOT heavier than the oe piston also.
It is a better piston being forged, which will make the engine rev slower. I have never had a piston failure using the oe pistons.

Hopefully for those on here that don't know all of this already it will be useful information. I prefer to explain things rather than just make blank statements.

Dan.

raptorobbie
06-09-2009, 06:47 AM
OK got the stock air box over the weekend and installed it last night. The bike is completely stock except for the piston which is larger than stock by wiseco & oil inject is removed.

The bike idles fine but wouldn't rev - traced it down to the throttle switch, and defeated that switch. Now the bike revs sometimes but not always, it stays running though. When it does rev it pulls me (200#s) just fine - but when it wont rev, it wont even pull itself on the driveway and sputters real bad.

It seems like the longer you let it idle the better chance you have of it reving (like its waiting for gas to fill the bowl?)

I dont know if I have the carb tuned right or not - Im at about 1-1/2 turns out on the mix screw (and yes the carb was tore down and cleaned completely & blown out).

Fuel is fresh and clean, plug is new - dont know if this is electrical or fuel related. Let me know what you think! Thanks!

dericsdad
06-09-2009, 06:15 PM
loosen the fuel cap and try it. Maybe the fuel tank vent hose is plugged/kinked.

raptorobbie
06-12-2009, 08:09 AM
OK, I tried the fuel cap trick and it seemed to help - but I think the bike was just cold - so I'm not sure.

Anyhow, got the bike started and warmed up, and it idles fine. When you sit on the bike and try to go it bogs like a real bad miss and just sits there. I jacked the rear tires up, blocked the front of the bike and it revs and spins the tires w/ no problem - but on the ground its a no go.

I have to check back on some old posts but I think I had the same problem w/ my DRR when I was messing w/ the jetting. I think I was running the air filter directly off the carb, and then put the snorkel tube on, and the bike did exactly what this Sportsman is doing right now. I'll have to check....

Tires spinning off the ground tells me electrically everything is good and that fuel delivery is not an issue (put the gas cap on for this test), and I'm thinking I'm too rich right now. After trying to get the bike to move on the ground w/ no one on it for a while, I pulled the plug. The plug color didn't look too bad but it was slightly wet w/ gas.

Does jetting always have to change w/ a larger bore?

thanks!

raptorobbie
06-15-2009, 11:33 AM
OK - i got it finally. Just didnt play w/ the mixture screw enough. I still need to go through the carb tuning process step by step to make sure its jetted properly but the bike seems to run real strong. Now I need to work on the twitchy front end!!!

m0t0xk1d
07-09-2009, 09:28 PM
ok well i have a highly modded 01 sportman 90 (it was the only thing when i wanted t race) the fuel mixture screw is either 2 1/4 or 2/14 turns out try that it will probly fix everything for you