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I have a 98' ZR600 that I bought last year. I rode it 8-10 times last winter but the last time I tried to go out riding it would not turn over. It was near the end of the riding season anyway so I didn't bother looking at it at the time. Fast forwarding to the present, the snowmobile will still not start (not surprising). Here is a long story short checklist of the things I have already checked.

new plugs that have good spark and are wet
compression is around 135-140 in both cylinders
getting fuel flow before and after carb
found that it does need a new exhaust gasket and extension spring

The previous owner disconnected the kill switch because it got messed up somehow but I rode it like that already so I know that's not an issue. It did start leaking antifreeze on me (slow leak) due to a bad hose but I made sure that it never ran dry so I don't think that's part of the issue. The most confusing thing to me is that even with starting fluid it won't start (even for a second or two) or really even act like it want's to. Same results when putting a little fuel directly into the cylinder. Also, after a few pulls on the pull cord it will all the sudden "freeze" while pulling, enough that it rips right out of your grip and kills your arms and hands. Any help/thought/suggestions would be greatly appreciated. I feel like I'm overlooking something obvious. Thanks in advance.
 

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If you truely have good spark and fresh fuel it should start.

Did you clean your carbs before last season?

Start with emptying the fuel tank
Remove and disassemble carbs and clean the passages
Then remove the reed cages and inspect for daylight through them
Remove and clean at least, the fuel pump
Replace all the fuel lines including the pick up in the tank
Remove the bar pad and Fix the kill switch (most likely your problem)
 

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Discussion Starter #3
If the kill switch was already broken and non operational and the sled was used quite a handful of times like that do you think it could all of the sudden affect it starting? It does kinda make sense, the snowmobile has the 3 things you need to start, spark, fuel and good compression and with starting fluid not making it fire it has to be something keeping it from starting. Also, the carbs have been gone through but I guess that doesn't mean that there's not a clog or something elsewhere. Although if that's the case, shouldn't it at least fire up for a second or two using starting fluid? Anyway, I have all kinds of fuel hose laying around and it wouldn't hurt to change it all out so I will definitely be changing all the hoses, thanks for your input.
 

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I'm wondering if the crank has twisted out of phase... If you're getting good spark at the plugs and the compression is good, it should at least pop when using starting fluid. The snapping back when trying to start may indicate that, as well.



If the stator plate has slipped, that may not allow the timing to fire the plugs when they need to fire. I think that would be pretty unlikely, as there's not a lot of movement in that plate. But when grasping at straws...



Another thing to check would be to pull the carbs and the exhaust and look at the piston skirts. A broken piston skirt would still show compression but would not allow the engine to run...
 

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It seems like you have what you need as far as fuel, spark, compression.

though i wonder two things or three. my first thought was its flooding. if its flooded starting fluid wont help. simple is shut off fuel, drain carbs and try and start only with starting fluid or just a bit of fuel mix directly in spark plug hole. do the cats have a engine base drain plug like the polaris fuji engines used to? it allows you to drain fuel that has collected in engine in the event of a severe flood.

2nd thought. your wet plug is water and not fuel. over the years there have been tons of people that have sworn their gas was clean and why wouldn't there sled start. well. maybe its mostly water. you can test in same way as above or run rubber hose from fuel pump into 1 gallon can.(of course you have to drain carbs as well as dry spark plugs first.)

third thought. on the engine locking up when pulling... is something hydro locking your engine.? like water in fuel or too much fuel or coolant fluid (which is also contaminating your fuel mixture) tons of water in the system also makes it look like you have great compression when you actually might not have much.

have you tested your fuel pump? can they leak thru the vacuum line into the base engine and flood everything?
 
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