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engine rebuild question

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I came across a 300ex for the wife that needs some engine work.

Figured since it is similiar in design to a xr engine I would post here.

All I was told is that it just quit running. There is no compression and the starter apparently free spins. They did try pull starting it to no avail.

I have no doubt of my mechanical capabilities to rebuild it, but havent done a 4-stroke atv/bike engine before and dont know what to expect for costs for parts for a engine overhaul. They want $1000 for it. I dont want to end up putting as much or more money into it than I would just buying a nice running one.

From the pictures I have seen it appears to be in very good condition overall

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300ex is this an atv ?? what yr is it?

without any more details here's my take

does the piston go through its stroke?

do you feel some sort of air movement out the exhaust pipe or at carb inlet??

how does the spark plug look?

if there is no compression, it can due to valves not closing , which can mean alot and/ or nothing, if the timing chain went the valves most likely got whacked.

Or the owner never cleaned the air filter in which case it ran extremely rich and the valves are carbon-ed and stuck open

or they never adjusted the valves and they are burned

here's an idea what parts costs

ex valves $50 ea,in valves $30

valve guide seals $5.00 ea

valve cover gasket $30

head gasket $20

timing chain $70

you have to have the valve seats recut, the head work with the valves and seals installed is like an hour of shop time.

stu

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I will get more details, I havent actually seen the bike in person. It is about a 2-3 hr drive and I am trying to get a better idea of what I am getting into before going to see it.

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I don't think I'd waste my time rebuilding it, look on ebay you can find these engs for just a couple hunderd. Although the parts 98xr250 listed are cheap, trust me you will almost always find more wrong than org. thought, not to mention the time issue. It's all something to consider, I just loss my xss rebuilding my xr eng, would have been better doing the ebay thing. Good luck, also personal experiance on 300ex is great bike, alot of fun.

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I would never give that much for a non running 1995 300ex. You can find one that year for about $1200 in good running condition I think that $500-700 is more what its worth.

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That sounds pretty hight for a 300ex that doesnt even run. My friend just got himself a used suzuki lt250 two stroke quad for 800 that had a complete motor rebuild with less than a hour of riding on it. I would keep looking else where unless you can get him to sell it for 500.

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You guys are probably right on the price. Probably worth more around $500-$600.

i did check out ebay and complete running engines can be had for around $500-600.

I did talk to the owner some more on it. He bought it and it was smoking, so he put a new top end in it. The local bike shop told him the head was fine and didnt need rebuilding. When he reassembled it, it had a tick and it still smoked. He left it alone as it was the wifes bike and it worked fine for a month or two until he got on it and started riding it hard and it quit running. Everything rolls thru fine, but no compression.

I will probably offer him $500 and see if he bites.

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