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yz 250 jetting issues


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I have an '01 yz 250 and since it was new, after I ride it, it pukes up black goo from what I assume is the power valve drain hose. (It hangs off the left side of the cylinder) It's just been rebuilt (top and bottom end) I run yamalube at 32:1 on 92 octane pump gas. I switched the main jet from 172 to 165 and move the clip to the top slot on the needle. Nothing. The air screw seems to be useless too. I put a Pro Circuit platinum pipe and factory sound (not the shorty) silencer on it. Temperature doesn't seem to affect it either. It also sprays out of the pipe/silencer junction and occasionally runs out the end of the silencer (also since day one). It runs great. While not as arm ripping fast as my 450, it is still very fast. I'm not sure if this is just a Yamaha thing or what. Any one have any idea how to keep it from leaving black turds all over my garage floor?

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What you are talking about is your vent hose... its quite normal to get a couple drips of spooge every now and then from it (left over oil).

If you have it dripping from you silencer then you are still jetted too rich, these smokers can be very tricky to get the jetting dialed in on. If you dont feel like spending countless hours playing the jetting guessing game I suggest you just spend the money and get a JD Jet Kit, the kit will come with everything you need and take 98% of the guess work out of jetting.

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What you are talking about is your vent hose... its quite normal to get a couple drips of spooge every now and then from it (left over oil).

If you have it dripping from you silencer then you are still jetted too rich, these smokers can be very tricky to get the jetting dialed in on. If you dont feel like spending countless hours playing the jetting guessing game I suggest you just spend the money and get a JD Jet Kit, the kit will come with everything you need and take 98% of the guess work out of jetting.

plus one

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What you are talking about is your vent hose... its quite normal to get a couple drips of spooge every now and then from it (left over oil).

If you have it dripping from you silencer then you are still jetted too rich, these smokers can be very tricky to get the jetting dialed in on. If you dont feel like spending countless hours playing the jetting guessing game I suggest you just spend the money and get a JD Jet Kit, the kit will come with everything you need and take 98% of the guess work out of jetting.

how does the JD jet kit work?

it looks like its just a bunch of needles?

why not just get the needles?

serious question, im wondering what else is involved before i throw them $75

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how does the JD jet kit work?

it looks like its just a bunch of needles?

why not just get the needles?

serious question, im wondering what else is involved before i throw them $75

If you search this section on the topic you will find that the needle has a proprietary triple taper design. The main and pilot jets are Keihin products. You'd be hard pressed to find someone unhappy with JD needles. Make sure your float height is where you'd like it and possibly lean the slide to an 8. RB designs grinds slides and JD sells both 8 and 9 slides. Stock is a 7.

Also, what about your reeds? Did you check/replace those?

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If you search this section on the topic you will find that the needle has a proprietary triple taper design. The main and pilot jets are Keihin products. You'd be hard pressed to find someone unhappy with JD needles. Make sure your float height is where you'd like it and possibly lean the slide to an 8. RB designs grinds slides and JD sells both 8 and 9 slides. Stock is a 7.

Also, what about your reeds? Did you check/replace those?

so its more than the jets?

do the needles need to be replace? im just trying to see if its worth it, seeing as new jets are $3.00

i haven't checked my reeds, ill see if my bike runs better after i fixed the idle surge.

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Needles need to be replaced to dial your jetting. They effect the largest jetting circut on your bike. 1/4 to 3/4 throttle range.

Check for chipped or cracked reeds or if there's air gaps between the reed and reed block. If so, time for replacement reeds.

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Needles need to be replaced to dial your jetting. They effect the largest jetting circut on your bike. 1/4 to 3/4 throttle range.

Check for chipped or cracked reeds or if there's air gaps between the reed and reed block. If so, time for replacement reeds.

ah,

thank you for the info man,

ill def check this wknd. ­čĹŹ

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