What's the stock jetting for an 87 250X?

[wilkin250r]

I've got a 1987 250X that I am going to play around with the jetting, so I want to go buy a few sizes smaller and larger. The project will eventually become a technical article (I hope).

The problem is, I didn't have enough time last night to take the carb apart and find out the jets, so I don't know what sizes I need to buy, and I'd like to go buy them today (since I'm going to the dealer already to pick up some other parts on order).

Can anybody tell me the stock main jet and pilot jet sizes for a 1987 250X?

[300exOH]

I think they are 38 pilot and 122 main. That's what they are on my 300ex anyhow.

May I ask what your plans are for the 250x?

[wilkin250r]

I'm not going to make any major modifications to the 250X right now. Eventually it will be a 350X conversion, but that's not what this technical article will be.

The technical article will be about jetting and spark-plug reading. I've seen lots of jetting questions, so I figure I'll help out. I just recently got a very expensive camera microscope here at work, so I'll use it to show detailed pictures of different spark plugs. I'll first get a spark plug with perfect spot-on jetting, and take a picture of it. Then I'll change the jets to create an intentionally rich condition, and show what the spark plug looks like, as well as a lean condition. This will give people a real-life detailed look at what the spark plugs actually look like for different conditions, rather than a description with no pictures.

[sickmojave]

Hey that sounds great. are you going to chop the plugs so we can get more detail ?

[wilkin250r]

Possibly. I don't have very good equipment here to be cutting spark plugs to expose the insulator. I'll try a few and see what I come up with.

[300exOH]

Sounds like it'll be a good article. I'll be sure to check it out.

[sickmojave]

Originally posted by 300exOH
Sounds like it'll be a good article. I'll be sure to check it out.

I agree ;)

[wvspeedfreak]

Actually the 87 250x had a 125 main jet.That was the only year they used a 125.After that it was a 122 main on all 250x's and 300ex's.I am not sure on the pilot though.

[wilkin250r]

So nobody has the definitive answer on the main and pilot? I suppose I'll have to take apart my carb to find out. This forces me to another trip to the dealer solely to grab a few jets. That sucks.

[wvspeedfreak]

Maybe I wasn't clear in my other post but it definately has a 125 main stock.