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I bought a used ZRT600 with an extended track that had sat for a couple of years and the mechanic went through the motor and replaced what needed to be. It ran great last season and I put a few hundred miles on it. At the beginning of what I had hoped would be another snow filled year I could not get it started. I got it into my shop pulled off the carbs, cleaned them, replaced plugs, replaced fuel lines and oil lines, primed the oil. It now starts fairly easily and runs great when it is cold. If you take it 1/4 of a mile it overheats and backfires and will not run without the choke on. I have checked compression and I have 110 per cyl on all three. I have replaced the thermostat and cap. I checked the old thermo and it worked fine. Does anyone have any ideas on whats going on here and how to check it out further? I would like to at least have this working right before I put it away for the summer again........... HELP!!!!
 

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My sled did the same thing, except for the backfiring. It was a vapor lock in the cooling system. Somehow a bubble got in the system. I popped the cap when it was nice and hot and burp, been fine then sold to Boss Hoss.
 

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I have had it suggested that its the stator. Anyone know if thats possible or sounds right and anyway to check it?
 

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take the water pump cover off and spin the clutch by hand ... make sure the impeller it locked to the shaft and spinning with the clutch . what I have seen on more than a few times is the oil pump bearing/ bushing siezes locking the shaft up (the same shaft that drives the waterpump ) it also takes out the bronz gears on the crank when this happens . also the impeller itself is prone to wear on the shaft so the shaft spins but the impeller stays stationary . good luck and ask away if you have more Q`s . M
 

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would that cause the backfire and having to have the choke on to get anywhere after it turned the hot light on? If indeed that is the case how do I check the brass gear and would the oil pump also stop pumping oil because I don't believe it has.
 

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would that cause the backfire and having to have the choke on to get anywhere after it turned the hot light on? If indeed that is the case how do I check the brass gear and would the oil pump also stop pumping oil because I don't believe it has.[/b]
take the cover off and see if the w/p is working ...if I`m wrong you are out 15 min and have 1 less thing to check lol M
 

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Well, my 96 zrt 600 is doing the same thing... overheating bad... Ive changed the thermostat (it was broke) and it still overheated so i looked at the waterpump and it spins with the clutch both directions so i would assume thats good... Ive also tried burping it and nothing... any other advise??
 

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yes it will backfire with the problem that Mark is talking about,,, your are starting to run hot, therefore getting your backfire, Mark has this exact sled and knows it inside and out,,, take his advise and check it out,,, he can help you get it running again.
 

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If your heat exchangers are hot, could your waterpump still be gone? This does not look like a 15 minute job to check on a 2001 zr.
 
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