Yz85 Trail Riding- Need setup info,gas/oil,plug,jets


Apr 18, 2007
I recently a 2002 Yz85 for my 11 yr old son,

We already changed the front gear...
What "oil/gas" mixture are y'all using for trail riding in that Yz85? 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 also dropped the needle all the way down. 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 need to change them?
It fouls plugs pretty quick if you don't 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??? Is there a safe proven setup for trail riding? We definetly dont want to blow it up running it to lean.
I also heard "AMSOIL" was good. They said you can mix that stuff 100:1 .(Not that I'd try it in my sons bike, maybe 50:1)
Sign ,
51 yr old Rookie on a Yz400f...

Thanks for your time!


Aug 21, 2006
asking people what jets to use with your bike is really inpossible. it all depends on how hot it is where you live .and how high or low you are to sea level.as for a quick guide i would start with standard jetting and then drop one or 2 sizes at a time to get the jetting right . smoking isnt the mix your using its the jetting . and as far as your mixing . i would stop at 40.1 . 50.1 is a bit much for a 85


Dec 26, 2005
Two steps higher compression dome Y03 5.9cc (Phathead Racing)
V Force 3 Reed Valve
FMF Pipe w/ Turbine Core 2 silencer (spark arrester)
VP race fuel (straight)
Timing stock
Steahly Flywheel weight

48 Pilot
NAPE needle
3.5 Slide
135 Main

This is what I have done to my son's bike for offroad use. It now has some low end where there was none before. It still has a upper powerband rush but is also a nice trail bike.

Advancing the ignition timing to 1.2mm BTDC is also supposed to help. This will be my next mod.

The NAPE needle and 3.5 slide are stock KX85 items.

Stock 2006 KX85 jetting:
Slide 3.5
Needle NAPE
Main 140
Pilot 45

Stock 2006 Yz85 jetting:
Slide 3.0
Needle NBKF
Main 138
Pilot 45

With my current jetting the exhaust pipe no longer has oil dripping all over the pipe and swingarm


Dec 26, 2005
2 strokes for life said:
husabutt, yeah we have done this befor. I would hate to drop that bike in the rocky sections.

Its not quite as pristine now. A bunch of desert trips and my kid flung it off a 20 foot drop off. Oh well at least I have the pictures of what it was.


Dec 26, 2005
biznizzle60 said:
husbutt, Youre using a 140 main? ona yz? Im using a 290 on my yz80. Should I drop it down for trail riding?

Griff is correct. Different carb on the older YZ's. I am using a 135 main. Any jetting info should be regarded as a recommondation or starting point for further tuning/evaluation. The lowest I went on the main was a 132 but as soon as I installed the V-Force reeds it needed a 135. 138 is stock BTW.

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