2 Stroke Jetting Info

[2 stokes for life]

I think its about time you should get a Jetting sticky because i just spent 30 mins looking up jetting infor for my friends 2002 RM 250 and came up with nothing barely. So Mods please make into sticky.

Here is the set-up or format in wich to follow please.

Year:

Model (RM, RMX, 125, 250):

Main jet:

Pilot Jet:

Air screw (turns out):

Needle model/Clip position:

Altitude where you ride:

Temperature where you ride:

Other mods (pipe, reeds, head carb mods, ect...) :

Degree of satisfaction:

So please add in your jetting. I will add my friends jetting as soon as we get it good. THANKS!!!

[mihylo33]

Good idea! But my experience with this mod is that he doesn't respond very well. I asked to have something posted for a sticky and never even got a response.

Contact Vetmxrider, he seems to have all the charts.

https://www.thumpertalk.com/forum/showthread.php?t=685121&highlight=

[2 stokes for life]

Well lets just try this and stick with it. So please add your jetting.

[mihylo33]

06 rm250 with Keihin carb

48 pilot

170 main

stock needle 2nd position from the top

air screw 1.5

PC pipe and silencer, Hotrods crank

93 octane pump gas, Silkolene comp2 premix at 32:1

0 to 1500 ft above sea level 50-70% humidity at 75 degreesF

[ghrocketman]

1)

94 RM250 w/ Keihin carb

170 Main

55 Pilot

needle 2 sizes LEANER than stock with the clip second from the top position

(R1471M Suzuki needle)

Air Screw 1.5

fuel: 50/50 110 Octane Torco Leaded Racing fuel and 94 Octane Sunoco Ultra mixed 32:1 with Klotz R50 or Klotz Super Techniplate

Stock Suzuki Pipe with FMF shorty silencer

2)

94 RM250 w/ Keihin carb

172 Main

55 pilot

R1471M Suzuki Needle clip in 3rd position

Air screw 1.0

fuel: AV100LL leaded 100 octane Aviation fuel mixed 32:1 with Klotz R50 or Klotz Super Techniplate

Stock Suzuki Pipe with FMF shorty silencer+

Riding Altitude: roughly sea-level to maybe 400' above max.

[Uncle Alpo]

Year: 1989

Model (RM, RMX, 125, 250): RMX with Mikuni VM38SS carb

Main jet: 360

Pilot Jet: 45

Air screw (turns out): 1.5

Needle model/Clip position: 6AEJ1-64 / 2nd

Altitude where you ride: ~700'

Temperature where you ride: 50-100+ F

Other mods (pipe, reeds, head carb mods, ect...) : PC pipe, Boyesen RAD valve, RM head & base gaskets, mild porting, Uni filter, 4.0 carb slide, float height 15mm

Degree of satisfaction: 100%

Oh, and on 87 octane gas mixed 53:1 with Golden Spectro

[ghrocketman]

Uncle Alpo, for shame !

87 octane and Golden Spectro at 53:1 ???????

C'mon now !

Are you serious here or is that fuel/oil mix some sort of joke ?

I wouldn't run an 87 octane/Golden Spectro mix at any ratio even in my weed-whacker !!!

Every engine I have seen using GS oil fouls plugs like mad even when correctly jetted.

[Uncle Alpo]

Yep, it's true. One bottle of GS in five gallons of gas. I've been running it like that for years and have never had a problem. If 87 octane is good enough for my 11.5:1 street bike with advanced timing, it's fine for a little two-stroke. I've never fouled a plug on the GS, either.

[2 stokes for life]

Thanks guys and keep them coming.

P.S. i dont even run 87 in my lawn mower man.

[mxjosh]

Not a good idea to base your jetting specs off what someone else is running. Even if everything is the same, its still only a baseline. Bikes respond differently sometimes. Check the YZ 2stroke forum for an excellent jetting guide. Applies to all 2 strokes. Its a sticky by the way, haha.

[Vetmxrider]

Here are my notes for the 2002 RM250. This should give everyone a good starting point when trying to dial-in the jetting for this bike. I hope this helps out.

[2 stokes for life]

That helps a bit. I wiould still think a jetting specific sticky here would be good as well.

[Uncle Alpo]

P.S. i dont even run 87 in my lawn mower man.

Then you're just throwing your money away. Unless the engine requires higher octane it will run better on lower octane.

[Vetmxrider]

That helps a bit. I wiould still think a jetting specific sticky here would be good as well.

Sounds good…. I agree… I hope they make your post a sticky. If you think / feel that my reply takes anything away from your post, or hurts the chance of it becoming a sticky, just let me know and I’ll be happy to remove it. No problem, no worries. Just jetting.

[2 stokes for life]

No works for me. Keep it just incase it is not a sticky.

[mihylo33]

Sounds good…. I agree… I hope they make your post a sticky. If you think / feel that my reply takes anything away from your post, or hurts the chance of it becoming a sticky, just let me know and I’ll be happy to remove it. No problem, no worries. Just jetting.

DUDE! all of your charts should be up on a sticky!

It took me a while to find a link that was close to one of your charts.

I have tried contacting the mod before and never even received a response.

Put together some charts and I'll forward it to Brian requesting a sticky.

[zig06]

Year: 2002

Model: RM250

Main jet: 160

Pilot Jet: 50

Air screw (turns out): 1.5

Needle model/Clip position: 2

Altitude where you ride: 0 to 1,000 ft

Temperature where you ride: 50 to 100 degrees

Other mods (pipe, reeds, head carb mods, ect...): FMF Gnarly, FMF TurbineCore2 (just purchased), Boyesen Rad Valve.

Degree of satisfaction: Very happy, seems to have plenty of snap.

Also, I do run pump premium (92 or 93) and BelRay H1r at 40:1

I am a big proponent of not using too much octane. The local gas station actually sells 115 because there's so many hot rodders around. I tried it once straight up and another time 50/50 with less than stellar results. Clearly, in my case, because I did not have a hot rodded engine, the higher octane was just a waste of money.

In UncleAlpo's case, I believe that it's possible that he is getting great results with 87 octane. His main steed is an RMX and those work best in the low to mid rpm range, and if he's keeping it there, he may really be doing better than he would with 92.

Bonus points for AP in discovering this!

[Yamajeb]

Don't you guys adjust your airscrew for the conditions of the day? For some reason very few people - here and elsewhere - seem to take advantage of the airscrew adjustment.

If you don't you ARE missing out in some circumstances.

Maybe I'm being presumptuous but because most list their A/S settings I'm guessing they keep them there.

The main and pilot are your "gross" or macro adjustments and changes come with changes in the seasons (or large changes in temps/altitudes as Vetmxrider's chart shows so well - nice job!).

But the airscrew is a "fine-tune" adjustment. Your fuel/air mixture can get thrown off a tad if weather conditions change enough if you run <1/2 throttle most of the time. And enough doesn't have to be all that much to make a noticeable difference.

Temperature, humidity, and altitude play a role in the adjustment

For example, with a 45 pilot my '02 250 ran best with the airscrew at roughly 2 turns out when the temps were mid 70s on Saturday. Yet the very next day it was mid 80s and a bit more humid and it didn't run as well - until I readjusted the airscrew by turning it out another 1/4 turn.

The good news is once you figure out what's best at a given conditions it's easy to adjust when the conditions change.

Try it out sometime, you'll probably think, "Why didn't I do this before?"

[JAMRACING21]

one thing on jetting everyone is leaving out, is the rider ability, and the terrain/track they are mostly riding, my son has the same bike as a couple of other kids here, and i have had to jet all the bikes different from each other just based on the rider let alone where they are actually riding the bike,

is it just a bigger factor on the smaller displacement engines?

maybe its also since kids skill levels vary more widely then adults?

[JAMRACING21]

Don't you guys adjust your airscrew for the conditions of the day? For some reason very few people - here and elsewhere - seem to take advantage of the airscrew adjustment.

If you don't you ARE missing out in some circumstances.

Maybe I'm being presumptuous but because most list their A/S settings I'm guessing they keep them there.

The main and pilot are your "gross" or macro adjustments and changes come with changes in the seasons (or large changes in temps/altitudes as Vetmxrider's chart shows so well - nice job!).

But the airscrew is a "fine-tune" adjustment. Your fuel/air mixture can get thrown off a tad if weather conditions change enough if you run <1/2 throttle most of the time. And enough doesn't have to be all that much to make a noticeable difference.

Temperature, humidity, and altitude play a role in the adjustment

For example, with a 45 pilot my '02 250 ran best with the airscrew at roughly 2 turns out when the temps were mid 70s on Saturday. Yet the very next day it was mid 80s and a bit more humid and it didn't run as well - until I readjusted the airscrew by turning it out another 1/4 turn.

The good news is once you figure out what's best at a given conditions it's easy to adjust when the conditions change.

Try it out sometime, you'll probably think, "Why didn't I do this before?"

i have found the air screw to only "fine tune" the idle to 1/4 throttle range