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Help on jetting a RM250

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Hello, I have a 2000 RM250 and need help with the jetting due to it being so confusing and there being so many variables. I’m at 1900 to 2000 feet and the temps are usually from 60 to 80 degrees Fahrenheit. The bike also spoodges bad, I just put a new top end in along with new crank seals and a replated cylinder. I took a look at what the jets are now in the carb and the main jet is a 167 and the pilot is a 47 the needle is also at position 1. I also have a aftermarket exhaust which includes a fmf fatty and a pro circuit silencer, I run 32:1.

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Posted (edited)

Other variables of interest:

 

-do you ride trail / off-road or motocross?

-what premix oil do you use?

-have you measured/set your float height?

-how old are the reeds?

-what needle are you using?

Edited by mlatour
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1 hour ago, mlatour said:

Other variables of interest:

 

-do you ride trail / off-road or motocross?

-what premix oil do you use?

-have you measured/set your float height?

-how old are the reeds?

-what needle are you using?

I ride off-road/Trail

I use Lucas oil semi synthetic 2 stroke oil at 32:1

havent measured my floats (how would I go at doing this?)

dont  know how old the reeds are look stock from factory

And the needle I’m using says N0ZH with the clip at the second position below the top.

 

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It being a Keihin carb, there's no such thing as 167 and 47 jets. If you look closely, they're probably 168/48 or 165/45.

Is 32:1 the ratio the owners manual states? To me, your jetting seems a little rich, but that might be what's required for that lean 32:1 ratio at your elevation.

There are lots of YT videos on setting the float. If you don't have a shop manual to know the specific float height setting, then set it so it's parallel with the carb bowl mating surface.

You check reeds by looking holding the reed cage up to the light and looking thru the inside of the cage, look to see any light getting thru around the reed edges because they're not seating. Very minor light bleed is usually ok but the reeds can become warped and light bleed is severe. Look for chipped and frayed reed petals and any damage that isn't allowing the petal to seal with the cage.

image.png.347e11dd5133e4850cb91d644d7f523d.png

image.png.dddb8f232c773c53dd1b1fd3099940b6.png

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9 hours ago, Trailryder42 said:

It being a Keihin carb, there's no such thing as 167 and 47 jets. If you look closely, they're probably 168/48 or 165/45.

Is 32:1 the ratio the owners manual states? To me, your jetting seems a little rich, but that might be what's required for that lean 32:1 ratio at your elevation.

There are lots of YT videos on setting the float. If you don't have a shop manual to know the specific float height setting, then set it so it's parallel with the carb bowl mating surface.

You check reeds by looking holding the reed cage up to the light and looking thru the inside of the cage, look to see any light getting thru around the reed edges because they're not seating. Very minor light bleed is usually ok but the reeds can become warped and light bleed is severe. Look for chipped and frayed reed petals and any damage that isn't allowing the petal to seal with the cage.

image.png.347e11dd5133e4850cb91d644d7f523d.png

image.png.dddb8f232c773c53dd1b1fd3099940b6.png

Yea i didnt know about the jets, I really couldn’t read what was on the jets. The manual states to run 32:1. My reeds look ok there is a small amount of light bleeding through but it’s not that much and the reed pedals look good with no chips or anything. Ill still have to set my floats and check that.

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Alright I took a good look at everything again. The pilot jet or slow jet is a 42 and the main jet says AB165 on it. I checked my floats and there good and the reeds look good, I think the previous owner put in new pedals.

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