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Bought 02 yz250.. Some Problems

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Tonight i picked up a 2002 yz 250. The bike is pretty clean but it does have a couple of problems i was hoping you guys could help me out with.

Problem 1.When i arrived to check it out i hoped on it and got it started. With the choke pulled out it starts up fine. I let it warm up for a little bit and shut the choke off. When i closed the choke, the bike stopped running. Repeated this a few times. I would try to rev it to keep it going, but it would just want to die.

Also, I took it for a spin to down the street. Again, the bike wanted to die in the low rpms.When i kept the rpms up, it seemed fine.When i let the rpms dip to around what would have been idle, the bike wanted to die. When i tried to get the rpms up, it would want to bog, but then it would come up and be fine..

Any ideas on what this could be??

Problem 2. I noticed some oil dripping from where the expansion chamber meets the silencer. Also, there was some spooge and spray on the side number plate .

Any thoughts here?? I know its a jetting issue. I have to admit this is the first 2 stroke i have had since a was 11 years old(about 10 years ago). Back then i didnt know anything about jetting and i still really dont..

My goals are to get the bike jetted spot on to avoid oil dripping and to prevent me having to change the plug alot.

I know there is alot of info here on jetting but sometimes it can be alot to sort through. If you guys can give me some info that would be great.

Some info..Bike is an 2002 yz 250, stock pipe, Elevation is 46ft according to google( Brandon, Florida.).. Thanks for any and all info:ride:

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Pilot and/or air screw is too lean. JD jet kit if you don't want to experiment with brass.

Pilot/ air screw too lean is causing what??Brass??

Also, what is a good mix ratio?? I always thought 32:1 was good but im thinking maybe i should thin it out a little??

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Pilot/ air screw too lean is causing what??Brass??

Also, what is a good mix ratio?? I always thought 32:1 was good but im thinking maybe i should thin it out a little??

Causes fuel starvation. Brass refers to brass jets to experiment with (pilot and main jets but also the needle jet too). Turn your air screw to 1.0 or 1.5 turns from seated. If no better, go to 0.75. If still no better, your pilot jet is too lean.

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Causes fuel starvation. Brass refers to brass jets to experiment with (pilot and main jets but also the needle jet too). Turn your air screw to 1.0 or 1.5 turns from seated. If no better, go to 0.75. If still no better, your pilot jet is too lean.

alright..thanks for the info.. will do..

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A new pilot jet would be my first move (they become clogged and sometimes cleaning does not get all of the crud out) and make sure the air screw is out about a turn as previously stated. I would also drain the tank and start over with new fuel and oil. Install a new plug, clean air filter, and see what pilot is in there. A 48 would be OK, I would think for sea level, maybe a 45. Regarding the spooge, it is not terminal I would not worry alot about it. The JD jet kit is something I will endorse 100%. Yeah I know it is expensive but his settings work awesome, and I am lazy.

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Pilot and/or air screw is too lean. JD jet kit if you don't want to experiment with brass.

alright.. I think ill go with the brass. What does the jd jet kit do exactly??Does it just tell you exactly what jets to use depending on your mods and elevation??

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classic symptoms of a bike that has been sitting and the gas gummed up. Carb clean and it should be back to 100%

yea, thats exaclty what i was thinking when i was riding it. When i was asking the previous owner he said he had no idea why it was acting like that. He said he had ridden it a week before and once it was warm it ran fine and would idle fine as well..

From what i can tell it has to be clogged jets.

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A new pilot jet would be my first move (they become clogged and sometimes cleaning does not get all of the crud out) and make sure the air screw is out about a turn as previously stated. I would also drain the tank and start over with new fuel and oil. Install a new plug, clean air filter, and see what pilot is in there. A 48 would be OK, I would think for sea level, maybe a 45. Regarding the spooge, it is not terminal I would not worry alot about it. The JD jet kit is something I will endorse 100%. Yeah I know it is expensive but his settings work awesome, and I am lazy.

Alright, will do the plug, filter, and fuel, as well as the pilot jet.

I know the spooge is not a huge problem. It would really like to get the bike spot in...

Is the spooge related to the jetting or is it just a pre mix issue??

I assume going lean with the jets would decrease the amount of spooge or would you need to go richer to decrease the spooge??

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Alright, will do the plug, filter, and fuel, as well as the pilot jet.

I know the spooge is not a huge problem. It would really like to get the bike spot in...

Is the spooge related to the jetting or is it just a pre mix issue??

I assume going lean with the jets would decrease the amount of spooge or would you need to go richer to decrease the spooge??

Go leaner to reduce spooge. Have a higher combustion temperature to vaporize spooge rather than have it come out unburnt as a liquid.

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Go leaner to reduce spooge. Have a higher combustion temperature to vaporize spooge rather than have it come out unburnt as a liquid.

so do you have an idea on what a good premix ratio is?? is 32:1 a little rich??

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Sometimes those YZ junction sleeves leak. Mine was spraying crap everywhere. I bought the TM Designsworks No Leak Exhaust collar. Great piece.

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so do you have an idea on what a good premix ratio is?? is 32:1 a little rich??

32:1 has not and will not hurt a YZ. You need to lean the jetting circuits and make sure you have a good top end/muffler packing AND use an oil with a low flash point (Maxima SuperM injector oil or Amsoil Interceptor). However, many others use far less with good results so it's up to you.

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32:1 has not and will not hurt a YZ. You need to lean the jetting circuits and make sure you have a good top end/muffler packing AND use an oil with a low flash point (Maxima SuperM injector oil or Amsoil Interceptor). However, many others use far less with good results so it's up to you.

man, you have got all the answers. Thanks. I was not worried about 32:1 hurting the yz. I was thinking maybe going with a little less oil???

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There is not reason to replace jets. Buy a can of good quality carb cleaner and squirt enough in the lid to submerge the jets in.....and let them sit for a couple hours. S100 bike cleaner works really well too!

Another trick for really clogged jets is pick it up with needle nose pliers and het the jet with an open flame.....when it flares up the clog just opened.......of course do not do this near flammable liquids.

I have been using 50:1 with Golden Spectro ......for 20+ years....with zero engine failures.

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There is not reason to replace jets. Buy a can of good quality carb cleaner and squirt enough in the lid to submerge the jets in.....and let them sit for a couple hours. S100 bike cleaner works really well too!

Another trick for really clogged jets is pick it up with needle nose pliers and het the jet with an open flame.....when it flares up the clog just opened.......of course do not do this near flammable liquids.

I have been using 50:1 with Golden Spectro ......for 20+ years....with zero engine failures.

Thats a good cleaning technique for the small jets...I will remember that one.

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The map gas torch method works real well for cleaning silecer cores before repacking , but I have never tried it on jets.

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