Well I just got this older 88 Trail Boss. It Takes me about an hour of pulling and switching plugs to get it to stay running. the plugs keep getting wet. This weekend I'm gonna turn the air/fuel screw in a half turn and see if that helps. I'm gonna adjust the choke, that seems like it's not working. I bought it from someone that lived up in a much higher altitude than me. I'm hoping the adjustment screw will help. After it starts, it runs like a champ, then you turn it off and the plug fouls again!
I was looking around to get a carb rebuilt kit for it....I can't find one anywhere for a 1988. They seem to go from 89 up. Supposed to be a VM38 Mikuni.
Any thoughts or ideas that may help??
OH, and does anyone have an opinion on the OEM Champion Plug RN4YC compared to a NGK BR8ES. I was having trouble finding the Champions Local, so I went with what the NGK called for. I'm wondering if the Champions would work better considering that is what Polaris says to use.

 

First you need to do a compression check.Needs over 100psi to start and run.If that is good take the head pipe off and check for raw fuel build up in pipe.then clean the jets in the carb

 

ON the plug, see if you can find or order a platinum plug - BR8EVX (Platinum) or BR8EIX (Iridium). They can help slow the plug fouling while you are getting things sorted out. NGK's are typically much better than Champions.

Like ftwflh said, you need compression. If you don't have that, it is time for a rebuild. Don't fret though, 2 strokes are easy.

You don't necessarily need a rebuild kit to rebuild the carb. Just go to your local dealer, and order a needle and seat, pilot jet and main jet. They can give you the stock sizes. You can start there.

Higher altitude requires less fuel, so you may be running lean. Is your 88 Oil injected? If so, you might need to adjust the oil pump (Pumping too much oil).

 

OK, good to know. Thank you both. I'll start with the compression test before I start messing around with other stuff. Now if I could only get a day off work to check it out, I'd be set.

 

OK, today I checked the compression. Its fine. I turned the mixture screw in all the way and backed it out only a half turn. then adjusted the oil injection. It was a bit rich. I took off the air cleaner to make sure it was clean, It was brand new. Checked the choke adjustment and pulled the the starter without the air cleaner on and it started up 1st pull. Ran good, warmed it up and put the air cleaner back on and it was hard to start again. NOT as hard as it was, but a heck of a lot harder than without it. I do think the jets need to be cleaned in the carb. I think it was sitting for quite some time.
I was adjusting the idle, because it seems to take a long time for the rpms to slow down when you rev it up, and turned it in a bit too far and the friggin motor started winding out, the kill switch and key wouldn't shut it down, had to chock it. Talk about loud.
That's another thing I'm wondering about. why are 2 strokes so much louder than 4 strokes. Our 4 stroke quads are nice and quiet. I've had 2 stroke dirt bikes when I was younger but I don't remember them being as loud as this thing. I don't see any leaks in the exhaust. Is it just mine or are they all this loud?????
I hate to ask so many questions, but this is my 1st Polaris and my only 2 stroke quad. I have nothing to compare it to. I'm just wondering if this is all normal.

 

If it ran great without the air filter it means it's running rich, because removing the filter adds more air to the air/fuel mixture

 

It could also mean that the air filter has been water logged (Either from getting wet, or running when very damp outside) at some point.
I've had that issue with paper filters in the past. They look clean, but won't flow well. They seem to get clogged just from being old and exposed.

Try replacing the filter and turn your mixture screw to 1.5 turns out from gently seated and adjust from there. A high idle that slowly comes down is typically a lean condition. Replace the 2 jets as a minimum (using original OEM sizes as specified from your dealer - unless you have an aftermarket exhaust, different intake, etc.) and let us know how that works.