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Need help on full top end kit

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Hey guys I'm new to the forum. I have an 04 yz250 that ran great the first month I had it, now it has a hard time starting, and is leavin a little bit from the top of the head where the spark plug inserts in. I am guessing it needs a top end. I have looked on rockymountainatv and found a couple kits. Which kit should I get? Wiseco, pro-x or vertex? I do a lot of sand riding and also trails.

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Hey guys I'm new to the forum. I have an 04 yz250 that ran great the first month I had it, now it has a hard time starting, and is leavin a little bit from the top of the head where the spark plug inserts in. I am guessing it needs a top end. I have looked on rockymountainatv and found a couple kits. Which kit should I get? Wiseco, pro-x or vertex? I do a lot of sand riding and also trails.

 

All 3 kits are good. I've used Wiseco for 15+ years now without a problem.

 

Leaking plug hole has nothing to do with a bad top end.

 

How many hours on that piston? What's the compression?

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All 3 kits are good. I've used Wiseco for 15+ years now without a problem.

 

Leaking plug hole has nothing to do with a bad top end.

 

How many hours on that piston? What's the compression?

 

You're right.  Leaking plug is probably due to the plug not being snugged up.. that happened to a guy I knew, he felt pretty lame when we diagnosed his bike's problem not as ignition failure, but as "Loosened Pluggy Syndrome"

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Kits may come with different base gaskets.  Pay attention to thickness and don't change from what you have unless you do it on purpose.

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I'm not sure how many hours on the piston or the compression. The guy I bought it from said he just did the top end but who knows. I have tightened down my plug pretty snug. It also doesn't have any power when I do get it to start.

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Definitely change the piston no matter what the previous guy told you. I just got done with a full engine rebuild that had "new bearings all around, fresh plating and a new piston" that proceeded to die on me after 4 rides.

No power off the start could be a plugged pilot jet and no power up top could be a sticking power valve or plugged main jet. Hard starting could also be bad reeds or a plugged choke and/or pilot jet.

But try changing out that piston and inspecting the cylinder first. Then move on to the other things. A piston should be the first thing done when buying a new bike.

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Ok thanks. I just pulled the carb off and it looked pretty clean already but I'll clean it and then inspect the piston and cylinder. Thanks for all your guys help.

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Just an FYI and I see no one else mentioned it but if your spark plug is backing itself out, that is a tell tale sign of detonation. 

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