Hey y'all! I'm new here and I hope i am posting in the correct area!

Anyways... I recently purchased an 1990 polaris which was probably due for the bone yard. I bought it in non running state...flat tires no brakes.. and a lot more problems.

I checked compression, spark and fuel. The carb seemed to leak out the tail. The spark was okay, the compression was okay too. I sprayed some carb cleaner in the inlet and the motor fired and ran away! Even with the throttle completely closed! I tryed snuffing the carb but it kept running away (full throttle). So i suspected a bad seal/gasket and went ahead to rebuild the engine.

After new rings, gaskets, seals bearing. The damn thing won't run.

Compression=110psi
spark= okay
fuel=???

I adjusted the float and cleaned the needle and seat which corrected the carb leakage completely but it seems the motor is not getting correct mixture.
-With the carb off spraying fuel in the intake the motor will fire for a few and keel over... as soon as the carb goes on nadda, no power pulse at all..

The carb had three lines off the side a brass one a plastic elbow(top) and a plastic elbow (bottom).
-The lines where off, where are they supposed to go?
I feel this might be an issue but am unsure.
-What is initial mixture (the small brass screw) suppose to be set to on startup...it was turned 1.5 turns out..
-What is idle suppose to be set to?
..Throttle plate is about 1/8" open

I'm just really at a loss here, I figured I could get this thing going relatively easy but it definitely kicking my ***. I'm a 22year old mechanic and I learn everyday, read the manual piece meal but I can't seem to resolve this one. Any help would be appreciated greatly, I would like to get riding haha! Thank you in Advance.... Matt

 

New rings on an old piston on a two stroke doesn't always work.110 psi is still kinda on the low side even with new rings. Air screw is fine at 1 1/2 turns out.The lines are just atmospheric vent lines.Two vent tubes on the sides just run up under the tank is fine. The bottom one is just the drain/overflow tube. If you replaced the crank seals along with rings and it still wont pull fuel on its own,then might be time to do it right and have the cylinder bored and honed to the next over size piston.

 

OPT thank you for the quick reply!!

Okay if that is the case, what is your recommended oversize piston and which type of kit? How big does the bore have to be bored to? My uncle is a machinist and I can definitely get him to bore it out.
Also can i take the top end off in the quad, don't feel like pulling the whole engine again lol!
Thanks....Matt

 

First off you need to see what size the piston is that's in it.. Could be stock I guess since you installed only rings. Stock bore is 72mm (2.8346) Piston to cylinder clearance new is between .0011-.0021 by the manual. Plus on most piston to cylinder clearances .005 is considered worn out. Usually a good Wiseco first over .50mm (.020) will clean up a stock bore. Here's a good video on piston to cylinder clearances and even how to use feeler gauges if you don't have a set of micrometers.

 

THANK YOU OPT!
Today i put the breather cover back on gave it a shot of starting fluid and it was idling!!
As soon as i rev the engine with the thumb throttle, the engine takes off maniacally and i frantically hit the kill switch..Of course one step forward two steps back..
I Suspected throttle plate was sticking but thats not the case...There is ALOT of play in the thumb throttle(you can pull back on it)... any ideas why the engine would keep reving up like this..? Thanks in advance..matt

 

Adjust the slack at the throttle housing.Just pull the rubber sleeve back loosen the cable adjuster lock nut and turn the adjuster out to where there is very little play at the thumb lever. Then tighten the lock nut. If engine still races, then that's usually caused by an air leak.Seals,head or base gasket, or the engine case itself can suck air causing engine to race.Wrong jetting size,not enough fuel in the carb bowl can do the same thing. Plus always have the air box and filter installed. That in itself will cause it to run lean.

 

ok OPT ill Try that tomorrow.
The steady idle up until I touch the thumb throttle leads me to believe that there isnt an air leak somewhere but perhaps a fuel problem and thumb throttle problem...

Also the ground cable on the crank case...where does this go? it was just hanging when I got the quad...thanks..matt

 

Ground strap just hooks to the top motor mount bracket on each side of the isolator(rubber mount). Items 1,5. Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse The negative cable from the battery hooks to the engine case behind the clutch cover backing plate.

 

Thanks once again opt..
But i have the small strap hooked up to the engine mount already. The other small strap is off the frame into the battery. There is a third cable about two feet long coming off the crank case. Where does she go? It was just dangling when i got the quad..thanks..matt

 

Top strap is the engine to frame ground. Cable off the engine case is the major ground back to battery negative post.