1982 250WR...for vintage motocross?

Yeah see you guys might get some snow!

420 doesnt sound too big. different motor but my 88 250 takes a 460. the smaller bores tend to take bigger mains in these bikes. would go bigger on the main till it loses power then go back a size. i only say to settle on the main first as it tends to throw your needle settings out the window, but changing needle setting wont affect your main jet choice.

Okay...spring has sprung and I am back on the race track. And back to jetting. I went from a 420 to a 430 to a 440. The plug is somewhat darker, but I would still call it 'yellow' rather than brown. I am running race fuel, Golden Spectro 55-1. Wondering how big to go with the jet? I have to order them, so wondering if I should skip the 450 and go higher?

You go big on the main till it's blubbery, too rich. Then go down one size till she responds clean and crisp. How's your pilot and balance screw?

First your float level is the correct height, the needle and seat isn't leaking.
I set the balance screw between 1 to 2 turns open were it's smooths out, 1 1/2 turns out is perfect if that's were the pilot jet balances. I put the needle in the third slot. Then it's the main jets turn. I go larger till it's blubbery then go smaller till it's smoothed out. Now it's the needles turn. Up or down till the slide movement is clean not rich, not lean. The slide should move up bringing up the rpm's with no hesitation. Now it's the pilot skews turn again to clean up the bottom. Now your carb jetting and setting is correct.

Note, as your balancing the screw for the best idle if it's a higher rpm, lower the slide by the idle screw for the best idle. You don't want the slide to be higher so the needle and the main jet effects the pilot jet and idle setting.

It takes some time to learn jetting 101 but it's not hard to learn.

Installing the UFO in the bottom of the slide does change the jetting. But it smooths out the reaction of the engine as the throttle is turned. The UFO is a ramp that installed in the uneven bottom of the round slide. Without the UFO installed the gasses hits the wall on the bottom of the slide. It causes a turbulence that effects the rest of the gas flow that's below the slide opening too.

But the pilot jet gets addressed first. Once the balance screw is near 1 to 1 1/2 turns and we have the best idle. Then go to the main. The balance screw must have some adjustments to go either way to tweeking the last setting when the main jet and needle is set. Sometimes we need to do it twice if something was way off. We can get it adjusted to about 90% that last 10% is the hardest.

Check the float level first.
Make sure the needle and seat isn't leaking.
Make sure the air filter is clean.
Make sure the intake boot isn't cracked
Make sure the reeds are good and sealing, if open flip them.
Make sure there is some play in the throttle cable.
Make sure the throttle goes to wide open(static test) visual.

Now your ready to jet.

Okay...this update!

I've raced this old Husky a few times now...took the advice and went back to regular fuel and a 420 main jet. Can't say that I notice any difference in power...and much less expensive!

I've had the Ohlins shock rebuilt and had the spacers removed. Swapped out the rear fender for a CR fender and most folks think its a CR.

Now...what is next?

I would like to look at the gearing. First is very low, second is good...but third seems pretty tall, or at least quite a jump from second. Any thoughts on experimenting with different sprockets?

Thanks.

Kent

Gear it so you do a motocross start in 2nd and dont even use 1st, essentially make it a 5 speed. That will close up the gap between 2nd-3rd and you will still never run out of top end in 6th.

Okay...the winter has passed and racing season is underway. The Husky seems to run strong...I re-packed the silencer and, unless it is psychological, I think that made a difference. I do want to tackle the gearing next!

packing a silencer can make a big difference..better flow. when packing is loose or missing, flow goes out of the core into the packing area instead of passing thru. an extra bonus is better sound and lower decibels..