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LEM Help, doesn't like to re-fire when warmed up

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So here is the deal.  A friend just gave me a pre-2000 LEM 50 that has been in his shed for a very long time.  His son used to race it.  I know nothing about the bike and frankly we don't even know the model year or model.  It has also been modified.  My buddy bored the cylinder and it runs a .60 over blaster piston and Mukini carb and R&D brass pipe.  The bike does not have reeds/reed valve.  To start I found I have to hold the throttle wide open, not sure if that means anything.  

 

I got it running this weekend and holy shit it screams like a raped ape.  The carb seems to be jetted perfect, it idles very nice all though a hair high but not bad.  Throttle response is crisp and clean and this thing absolutely rips.  

 

My boy rode it for an hour or so yesterday and then took a break.  I couldn't get it to refire after kicking for what seemed like 20 minutes.  Once we got home and I killed some time the bike fired right up.  My boy rode in our back yard for another 20-30 minutes and then stopped.  Again, I couldn't get it started to save my life.  It has something to do with the temperature.  I know this because when working on it yesterday there were a couple time where I started it for just a minute, fiddled with it and restarted it a few minutes later.  Just to see when it was running I choked it and the bike died so all seems well in the carb.  

 

If the bike runs great once started what could cause it to not want to start when up to operating temp?  I took off the magneto/stator thing.  It looks like a bunch of plates riveted together and from it runs the spark plug wire and kill switch wire.  I had it off and inspected the wires closely and all seems well.  One of the outer plates is bent on the side opposite of where the magnet is.  Considering how great it runs when running I'd like to figure out the problem.

 

Any insight is appreciated.  I threw everything out there I can think of so let me know if more info is needed.

 

 

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Wait, he stuck a 200cc Blaster piston in a 50cc jug?...................your problem is probably stator, BTW........

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+2 on a bad stator. Common for them to fail only when hot. If you kept running, no doubt high rpm opertation would slowly get worse until it stalled. However, a bad spark plug, coil wire can behave the same. Go cheap first.

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Simle & cheap test:

 

Take a cold compression test with throttle wide open.

 

Get it hot (to your re-starting issue temp) and re-test compression.

 

Older jet-ski's had this issue; essentially things expanding unevenly and hot comp starting problematic.

 

All the best.

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I'm new to thumper talk and I know this is not the right place to post this but I'm not sure where to go.

I have a 2010 Polini X3r h20 I've recently purchased for an awesome price I believe. I was aware that it needed work but not a clue as to the extent.

the bike won't engage unless almost wide open then it takes off like a bay out of hell.it seams the Tomar clutch should engage way sooner though. I've pulled the tranny cover off and noticed metal shaving and score marks on the inside case. a small circle score mark from the spring and "brass washer" that lost the circlip.

the other score mark was more severe and it came from the clutch rubbing on the inside of the case. I'm not sure why it's doing this.

the primary gear next to the clutch is also loose. any help would be greatly appreciated. thank you

-Corey

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