I have a 2003 Polaris TBlazer and recently had issues getting it running. Replaced the stator (extremely expensive...) and still wouldn't fire (though it did test bad). I had spark so I did a compression test and had 80 psi.

Pulled the jug and bored/honed .020 over (.5mm), new Wiseco piston. I also shaved the head .028" to increase compression.

Put machine back together this morning and fired it up (took a few pulls). I am trying to break this in so I let it run about five minutes varying the throttle but never went close to full throttle.

After I shut if off I let it sit for about 20 minutes and fired it up to take around the yard. Now it will get to about 10-15 mph and kind bog/sputter. It will go slightly faster but sputtering and fighting it the whole time. Now, since this is a brand new top end I did not go full throttle.

I didn't have any of this type of issue prior to this work so I'm surprised I have it now. I will look to make sure I hooked up the carb hoses and everything correctly but if anyone has an ideas in the meantime please shout 'em out!!

I am wondering if I should be using high-octane fuel but would this be the result if I needed high octane but didn't use it?

 

Find a stock head and try it.Also more comp means more heat with too low of octane you could have stuck a ring. .020 is norm for milling a head for trail use.

 

on the 2 strokes I`ve built i run 50;1 in the tank as well as the oil injection for 2 full tanks and drive it like i stole it, with the extra oil mix makes for a softer brake in. takes a bit longer but rings seat nice.
Do a compression test find out whats going on in there if all is good I`d try some higher octane fuel and add 2stroke oil to the tank. then do a plug chop and see what the motor in doing the spark plug tells many tails.

 

Defiantely needs a compression test

 

Piston in backwards?

 

I am positive I put the arrow of the piston facing the exhaust. But...doesn't mean I haven't made mistakes before when I was positive I did it correctly.

I also recently replaced the stator on this machine. While I'm "positive" again that I line up the timing marks, I can't help but wonder if the timing is off slightly or if it should be slightly adjusted due to the higher compression.

I will test the compression this week because I too am curious where it is.

Thanks for the ideas guys, keep 'em coming!!

 

Ok, finally got a chance to toy with this thing...but really just started.

Compression (after bore/hone, new piston/rings and decking the head .028"): 128 PSI

I would have expected more like 140 or better!!! This was tested holding the throttle full open! 125 is enough to run but after milling the head I expected it to be much increased. Should check with Cometic to make sure my gasket was not oversized (thicker) compared to stock!

So, I fired it up and rode it around and got on the throttle this time and got a huge backfire through the carb. Was able to repeat this 2 or 3 times going around the yard. I took off the air filter and the same result but I think it happened at a slightly higher speed.

I am thinking either too much fuel (wasn't an issue before) or the timing may be slightly retarded with the new stator.

Ok, guys whatcha got??? Looking to pull the cover and check the timing first to at least eliminate that!

Cleaning the carb will be next but not likely the issue (IMO).

 

you may be to lean on the pilot jet might want to go up a couple of sizes

 

OK, here's what I've tried so far:

Removed side cover. The timing indicator mark on the stator us JUST to the left (to the counterclockwise side) of the pointer inside the casing. I believe this would be slightly advanced timing.

So, I moved it just to the right side of the mark. So now the stator mark is just to the clockwise side of the pointer. I believe this retarded the timing just slightly from what it was. I realize this are stampings and castings so I don't know how accurate they are to begin with.

Took it for a ride around the yard and it helped just slightly. Still just a bit of a backfire and still a bit of the bogging.

I pulled the plug to find a BPR7HS (I have several quads here so this may or may not be the correct one). I replaced it with a BR8ES (I think from the 800). NO more bog and no more backfire!!!!!! Now, that was with the air filter off, twice around the yard.

I'm not expecting miracles here but think it should pull just a tiny bit harder than it does. It's been SO long since I rode that machine that I honestly can't remember how fast it was. So, I'll wait until the daughter gets home today and ask her to take it for a spin!

So...anyone know what spark plug SHOULD be in there and why this made such a difference?

Thanks!!

 

BR8ES is the correct plug for the 250. If you used a BP plug,it has an extended tip which could cause some problems as you described because the plug extends too far into the head, OPT