250-500cc Help me decide on WR250

I would rejet as good as you can with the standard pipe. Check to see if there is an air restrictor in your air filter as well.

Air restrictor?! How does it look? Airfilter retainer looks really weird to me. Hope it is not air restrictor.

Inside the air filter there is either a plastic cage (no restriction) or a inner shell with just a little hole for air to go through. I couldn't get mine to run because I forgot to remove the restrictor. It's the holder for the air filter.

Hope I'll figure out how to remove it.

Did I remove the right thing (air restrictor)

I can tell you that my bike didn't have one of those and it looks like a restrictor to me. What does the filter look like?

Filter looks like regular filter:

And bike still won't start even after changing the jets to power up spec.
May be I'm missing anything else!

Yes that is the restrictor. Did you change the "starter" jet? It's really small and it was in the same bag as the new needle.

Yes, I've changed the starter jet. From 50 to 80.
Should I change "restrictor" to the regular air filter holder( which I don't have)?
May be I can cut the bigger hole in this restrictor to make it look like regular air filter holder?

I'd say it would be WAY too rich if you put that restrictor back in. Strip it down as far as you can as the replacement one is just a thin plastic cage. Like less than 1% restriction. It won't start at all?

After running it with all that emissions junk on it it may have fouled the spark plug. What does the plug look like? Also check the float height, mine was too high and I had to lower it a little. The carb should pee out of the vent hose when you lean the bike to the left and the peg is about to touch the ground. If it pees when you barely lean it it may need adjusting.

I've tried to start it without air filter at all without any achivments, no it won't start
This how the spark plug looks:

I don't have br8eg, is it ok if I try to start the bike with b8eg?

According to the float height it starts to pee when the bike is 45 degree. Should I adjust it? I don't have the idea how to make it.

Yes that's fuel fouled, if it's wet it's done. Yes you can use a B8EG the only difference is that it is not a resistor plug. Next chance you should buy a half dozen plugs, you will need them for the jetting process. Once you get the jetting right a plug will last a very long time.

It is jetted to the service manual. How I can jet it now if it is not even starting?
My next gues is that smth wrong with a spark. When I take the spark plug off it rarely sparks and only when I push kick starter hard. On my old yz it sparks even with the light kick. Any suggestions?

You can't jet tell about the jetting until you get it running. It should have fired right up with the new plug. There may be so much fuel in the cylinder that you will have to clear the flood by holding the throttle wide open while you kick it several times with the choke off.

Phooo I have it started New plug and wide open throttle make it run.
hope tomorrow I'll finish barke in then some minor jetting work, hope it will be not needed. Looks like I have chance to ride it

What's the difference between resistor and not resistor plug? It's hard to find br8eg is it absolute ok to use b8eg instead.

Well? How did it run?

Unfortunately I haven't try it at full potential((( the racing pipe is still not here.
I've tried it with stock pipe and it runs like a 50cc scooter. The stock pipe restricts exhaust flow more than you can imaging!!!
At this point handling was better than I expected so far. But there is not enough impressions for ride report.
Next time I'll have the bike out only in 5 month or so((( it's very snowy already here.

During winter I'd like to upgrade it with some parts like pwk carb, radiator braces and lightless rear fender.
Where I can find oem parts diagram? I didn't managed to find online oem parts store.

The catalyst is quite easy to remove from the pipe. It is the 'corrugated' plug in the pipe where it joints the cylinder and is clearly visable. To remove it simply cut approx 75mm off the pipe so that you can then knock the cat out of this section. Once it is removed weld the section back on. Unfortunately it is very difficult to remove without first cutting the end off.
There is also a vent pipe on the restricted pipe which is part of the emission control, again cut it off and weld up the hole.

Good advise + you can use as a spare pipe in case the aftermarket pipe gets smashed.