Any Tips On Making A Yz85 Better For Trails?

Maybe a fly wheel weight possibly a new heavier fly wheel. The FMF woods pipe(not sure if they have it for a yz85), i think boyesen makes reed vavles tuned for low end power. And a smaller sprocket(front or rear or both), but i think the best bang for your buck its have it ported for low to mid power.

cycle trader....sell it and buy an RM85 or KX85. No really those motors have much better bottom end. Other than that you can have the cylinder ported for more bottom end at a reasonable rate from eric gorr. The flywheel weight will help if you can find one. Smaller sprocket in the front will give you more umpfh down low but less up top. smaller in the rear gives you more top less bottom. they are inverse proportional and changing 1 up front is about 2.2 in back.

i bought a yz 85 not to long ago like a couple months ago anyways i mostly trail ride to so all you really have to do is take two teeth off the front sproket and take off two chain links that gives it a lot more bottom end and also if you just keep it in the power band you can climb any thing you could on a four stroke just make sure not to get it out of the power band or youre probably screwed. and remember when you take the chain links out get a new master link cuz i didnt and my chain cam eoff going up a really steep hill. keep youre old sprocket too just in case you want to race or something keep the old sprocket cuz it gives it a lot more top end.

I recently got the same bike ,a 2002 Yz85 for my 11 yr old son, and a 99 Yz400f for me (Dad). The Yz400f is just fine for trails. I put a bigger sprocket in the back , thats it! Ready to fly! That bad boy will climb almost straight up at low speeds. Ok, not straight up, I just feels that way .Especially for an old man with little experience.
"Big nads" , little experience. I never knew what "Slow" was. Anywho...

What "oil/gas" mixture are you using for trail riding in that Yyz85? I've already dropped his mixture to 40:1 and that bad boy still smokes like the dickens at lower, slower type trail riding speeds. We have also been using NGK BR9ES plugs-$1.77 at Advanced Auto What brand oil should we use? Also, what "plug"? And, what "jets" if you changed them? It fouls plugs pretty quick if you dont keep it in the pipe. Its fine running it in the pasture while in the pipe, but I'm sure trail riding will foul the plug with the setup that our bike came with. Suggestions! I also heard "AMSOIL" was good. They said you can mix that stuff 100:1 .(Not that I'd try it in my bike, maybe 50:1)
Sign ,
51 yr old Rookie on a Yz400f...
Froggie

Thanks for your time!