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meyer1son

07 WR250F to YZ250F conversion

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I have an 07 wr250f that I just converted over to a yz to make a green sticker yz for Cali. The entire bottom end is all yz and so is the electrical system. The head is the only thing that is still wr. The bike will not start with the choke, but does with out the choke. I have a bog on the first 1/4 of throttle. And the bike does not run consistent. The temp where I like is 85-105 rite now. I have changed to a NFPR needle, 175 main, 55 leak jet. And the crab was done by ZipTy about a year and a half ago while still a wr. The wr and yz don't share the same carb. Do you think I can get this carb to work ok with it now being a yz? Below are the specs for an 07 yz and07 wr carb. Airbox is opened like yz, yz header pipe and FMF Q4.

WR YZ

I D Mark 5UME EO 5XCG GO

Main jet 170 178

Main air jet 115 2.0

Jet needle NJRU OBEPQ

Cutaway 1.5 1.5

Pilot jet 42 42

Pilot air jet 70 105

Pilot outlet 0.9 0.9

Bypass 1.0 1.0

Valve seat size 3.8 3.8

Starter jet 68 72

Leak jet 70 72

Float heigtht 8mm 8mm

Intake vacuum 31.3-36.7 kPa 29.3-34.7 kPa

Thanks,

Chris

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needs more like a 40 leak jet and the o-ring mod.

Thanks for your time Eddie! A few questions, Why won't the bike start using the chock? I thought I wouldn't need the Oring mod since ZipTy did the carb . And why is my idle so erratic? 1 more LOL Do you think the vacuum difference is a problem?

Thx,

Chris

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If a bike never needs a choke to start, it can be a few things.

1) Ambient temp is like 100 degrees. For example, where I live in VA, I do not need the choke in summer for my WR. I always need the choke for my DRZ. Once the temp drops to 60 or less, I need the choke on the WR too. I am sure I could close my fuel screw or possibly go down in pilot but the bike runs Ok and I am a Lazy SOB and do not ride much when the temp is 100 and the humidty ia 99%. I float in the lake instead.

2) Choke is not fully closing. If the choke plunger does not fully seat, the choke will always be activated, so even though you think the choke is pressed in, it is not. Keep in mind, a choke adds both fuel and air to the mix.

3) Float too high. This can make the bike be jetted to rich, again, removing the need for choke.

4) Too thin a needle (rich). This is extremely rare, but if you use a needle that is super thin and the emulsion tube is not stock or worn, it can bleed fuel.

All of these will mess up pilot jet choice and fuel screw setting. It will also make the bike hard to start when ral hot sometimes, even with the hot start engaged.

Bottom line: Either it is so friggin' hot where you live that a choke is a joke or you have something causing the jetting to be too rich at idle.

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If a bike never needs a choke to start, it can be a few things.

1) Ambient temp is like 100 degrees. For example, where I live in VA, I do not need the choke in summer for my WR. I always need the choke for my DRZ. Once the temp drops to 60 or less, I need the choke on the WR too. I am sure I could close my fuel screw or possibly go down in pilot but the bike runs Ok and I am a Lazy SOB and do not ride much when the temp is 100 and the humidty ia 99%. I float in the lake instead.

2) Choke is not fully closing. If the choke plunger does not fully seat, the choke will always be activated, so even though you think the choke is pressed in, it is not. Keep in mind, a choke adds both fuel and air to the mix.

3) Float too high. This can make the bike be jetted to rich, again, removing the need for choke.

4) Too thin a needle (rich). This is extremely rare, but if you use a needle that is super thin and the emulsion tube is not stock or worn, it can bleed fuel.

All of these will mess up pilot jet choice and fuel screw setting. It will also make the bike hard to start when ral hot sometimes, even with the hot start engaged.

Bottom line: Either it is so friggin' hot where you live that a choke is a joke or you have something causing the jetting to be too rich at idle.

Thank you sooo much for the detailed information!!!!!!!!! :thumbsup:

Wish I could give you gas but you tank is full:worthy:

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Actually, it can hold more. Why does everyone not want to 'top it off'?

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Well after spending countless hours try to fix my problem. I finally figured it out. I had the wrong type of fuel screw. It was for a quad or something else.

:thumbsup::worthy::):D:p:smirk::ride:

I had a ZipTy fuel screw in my sons bike compared it to mine. Noticed the tip was different. Installed his and it runs like a champ!!!!!!!!!!

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