250r jetting

[Rocketman]

In my quest for a new atv I have found a 86 250r.
It has been bored out 90 thousandts over, has had some port work done, but I have no idea to what specs. It also has a DG pipe on it. and a 38mm Keihin PJ series carb on it. Thing is I don't think the carb is any where close to being jetted right. It has #48 slow jet in it and a 153 main jet. When I check the plug it looks like it is running very lean. Any one have any jetting suggestions?

Thanks
Randy

[r00sty]

Read this, expecially the tips section, I hope this helps.... http://www.keihincarbs.com/home.html

I had a 86 R and my slow was 48 and my main was 156 I had to move my needle all the way down and run my gas at 32:1 using Klotz to get it looking good!! Remember every machine and location are different!:demon: :D :demon:

It was 80 over, mild port and polish, boysen reeds, Paul Turner High Rev Pipe and FMF Power core silencer! Stock 34mm Keihin Flatsider Carb!

[Mr. Richard]

i'm running a 55 pilot and am 170 main in my 250r,,, 38 mm carb porting and fmf pipe ,,,,,,,,,,

[Rocketman]

rOOsty, thanks for the link. Yea I know each engine is different. And the only way to get it jetted right is to work with it and keep checking the plug. I'm just trying to start with an educated guess.
This motor is modified, and has a larger carb than stock, but is running the stock carb jets. The kid that had it already melted the motor once, because it was running so lean.

Kasey, just exactly what kind of 38mm carb are you running? Is it a Keihin PJ series?

I am new to two strokes, so still a lot to learn. Like how does your oil/gas mixture change your jetting needs? Or does it matter?

Randy

[Fuzzy]

Moving to tech section

[Rocketman]

Fuzzy, sorry for posting this in the lounge first.

[Caterpillar]

I would HIGHLY recomend running synthetic 2 stroke oil such as Bell Ray MC1 or Amsoil. I use the MC1 at 40:1, and it works well. Basicaly, you can run a leaner mix if you use a high end oil without worrying about jetting to much, (once it is jetted in properly) Make sure you don't mix different premixes together. For example, if you are using MC1 at 40:1, don't top off your tank with your buddies Amsoil even tho it is also 40:1. Burn off one batch before switching to another brand. However, you can change the pre mix ratio no problem with the same oil. If you keep an eye on that plug when you play with your jetting, you really can't go wrong. Just start rich and work your way down. Try to jet it in with the needle in the middle, that way you can fine tune it with the needle setting. Good luck, sounds like you have a torqey beast!!:headbang: :demon: