Drain the crank case bolt like I mentioned earlier to remove all the fuel from the bottom end,also shut the fuel valve off. I'd normally say hold the throttle wide open with the plug out and use the electric starter,BUT probably might be dangerous in your case unless you have all the excess fuel removed that you can. Just use the recoil starter with the key off and throttle wide open to clear any residue. Then you can reinstall the plug and see if you can get it running. Order a carb rebuild kit from ebay if you have to. Cheaper than just a needle and seat from the dealer. This kit for an 89 model and up should be ok,just check the jet sizes against yours.http://www.ebay.com/itm/Polaris-Trail-Boss-250-2x4-1989-1999-CARBURETOR-Carb-Rebuild-Kit-Repair-P250-/171565173208?hash=item27f214c9d8&vxp=mtr Plus here's the fuel section from the manual that really can help on carb settings and repair. https://www.google.com/url?sa=t&rct=...,d.aWw&cad=rja

 

I went out and drained all fuel from crank case and exhaust. Checked compression and it was reading approx. 95-100 cold. Fired it up and let it idle for about 5-10 min. Checked compression again and it was approx. 118-120 warm.


That being said, I still have no idea why this thing won't start cold now in +10C without flooding the crankcase and it fired second pull in -15C temperature. I am baffled


Forgot to mention, I am not sure if I am running too much oil/gas mix. I ended up mixing 32:1 this time and at the same time I still have oil injection hooked up. Could too much oil cause this not to fire? I don't know why I even pre mixed as I have already done the break in. Ooops

 

Compression is getting close to the limit to where you start to have problems. Plus 32/1 is way too rich on mix! 40/1 is good enough on this low compression engine.We only ran that ratio of gas to oil on Ktm dirt bikes with way more hp and compression..

 

Going to drain out the remainder of gas and go with no pre mix as the oil injection is working. Didn't run any premix during winter and had no problems. I goofed on this run.


Thanks for the help to this point .. will update

 

I know this is a bit late based on the date of this thread, but I have had this experience with a couple small engines that I have on spreader boxes for plowing snow. I own two of these and they both had the same issue. The float stuck open and the crankcase would fill with fuel. This is a potentially engine killer at least on a 4 stroke engine. Once we got the float cleaned and cleared out the crankcase and such they ran great. It really sounds like to me you have the same issue with the float sticking open. Otherwise there would be little reason to have the crankcase fill with fuel. I know you said you put on a new carb kit etc. but it still sounds like a float issue to me.

 

Recommended that he install a new carb kit at the top of this page and listed the link to the fuel section on carbs that would help on float level settings,adjustments,etc.He installed a carb kit last year,but let it sit. Doesn't take long for ethanol fuel to mess things up.Whether he installed a new kit or got the float level set right or not,cleaned the needle and seat? Sometimes people don't post back as to their findings or repairs which can help others with the same problem.Hopefully he'll chime back in as to what he's done..

 

I'm still here. Had some plumbing issues to take care of. I did drain all premix out of tank, crank case, and exhaust. Just need to get some fresh unmixed gas and give it a try.

I haven't had a chance to pickup a carb kit yet, even though the Polaris dealer is across the field from where I work. Soon though.

 

Haven't rebuilt carb yet, but I have drained all pre mix from Trailboss. Today while I was working on everything I have (mowers, weed trimmers, snowblower, ect....), I topped up Trailboss with a fresh tank of umixed fuel.


Turned the key, without choke, and it fired up instantly. I tuned it up to idle the best I could and let it run for about 15 min.


The only thing I notice now is it hesitates when giving it throttle. Like, I have to go half throttle before it revs up. It just climbs slow like it's under load (in neutral).


Once I have the revs up, the throttle is more responsive when I give it a quick shot.

 

Once it's able to take throttle when the revs are up usually is a sign of either too much fuel(float setting off,needle sticking,etc) or could be from the lower range of compression you posted. Best to take it out and see if you can blow the cobwebs out of it and see if starts running better.Sitting around is tougher on em than riding them daily.Plus I wouldn't forget the cheap carb kit that may help.

 

I was going to order up the carb kit from the link you provided. However, as far as I know this thing is a 1988 model. Cannot verify that 100% other than what PO told me it was. I cannot find a VIN on the frame or engine to verify.


When I was comparing the 88 to 89 carb parts, not everything matches. I don't want to purchase something that is not going to work.


Is there anywhere I should be looking that I might have missed for a VIN that might be hiding?