makin a trail friendly yz250

You have several options, be absolutely sure you know where you need to reduce power and where you need to increase it. Increasing bottom end can also inrease the power band hit and make the bike harder to ride, If you try to get more top end at the expense of midrange that can smooth out the power and leave you with some up top for unexpected surprises on the trail. If you decide you want more power below the band you can retard port timing but that may increase the hit as well. Vortex makes a multi curve ignition unit which will help a lot but you may have to get all your mechanical mods soughted first. Eric Gorr's book has good info, Motorcross & Off-Road Performance Handbook.

Forgot to mention, Most good 2 stroke woods trail bikes for normal riders have wide ratio transmissions. Pro riders prefer close ratios. If your riding speeds vary from walking pace to 80mph you'll struggle with the standard ratios.

I've got my '06 YZ250 very trail friendly, while still maintaining a wide spread of power for when I want it. It just takes some knowledge, fine tuning, work, and not too much money, really.

Let's start with your jetting. You'll need to order some brass; what is in your carb. now? (You'll need to know what to get, but don't order anything yet.) What is your location & elevation? What will the temp. be when you plan on riding?

Search & read up on the two-stroke jetting threads.

Then re-read them, again.

Now adjust your air screw as they describe.

Write down what all of your carb. variables are.

When you get all of this information, re-read the jetting threads again, and then post again, with your best educated guess of what one step you might want to take next.

You can order a Steahly 13 oz. flywheel weight, but don't put it on yet.

One change at a time.

I'll watch for your reply.

Ken

Flywheel weight, FMF Gnarly pipe.

I am a lardass, but my nearly stock 05 YZ250 is perfect after a heavier rear shock spring, and re-valved front forks w/heavier springs. No need for FWW and pipe. I think my bike has the perfect power delivery. Much better than the possessed 2001 YZ 250 I had. That was a scary bike in comparison.

97 CR250R :
I rejetted mine (as Ken mentioned) and then added a flywheel weight, larger rear sprocket, promoto billet kickstand, and quiet silencer along with a DB Snorkel to quiet it down. I may be wrong, but the DB Snorkel and silencer combo seemed to give me a little more bottom end also (backpressure helps the torque on the bottom). Handguards added after bashing against a tree last month.
I just got the front forks back after having them reworked/rebuilt by a local shop. I rode it last weekend and the bike glides across rough stuff in the woods.