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Im hoping to borrow some of the knowledge that is floating around here. I have an 04 500 Predator. I was in Oregon at the dunes last week. She ran like a bat out of hell on the first day. Towards the end of the day it started getting some backfiring. I found the ideler screw fell out of the carb (and somehow managed to wedge itself under the starter! So I still had it when I got back to camp). On the second day I went out turned it on to warm up while I was putting on riding gear. It started right up and purred like a kitten for about 2 minutes then all of the sudden shut off. I went to restart it to take off but it just turns over and over but wont fire. While at camp I pulled the carb and cleaned it although it was already clean, replaced the fuel though it was new, checked my plug, it was light brown and blue spark but i still put a new plug in anyway, air filter was just cleaned, oil had just been replaced and was full, battery tests great and is always on a trickle, checked all connections, and tried pull starting it several times throughout the whole process only to have the wheels lock up each time the clutch was dumped. So we packed up camp and drove back to WA so I could get it in my shop out of the elements and open it up.

At home I retested the battery (yes, under load) and its perfect. I pulled the starter and disassembled it. The brushes seem fine to me. They are about 1/2" long id say and had just a little slag built up on one side of each. The armature looked fine, plenty of copper elevation still, just coated in a real thin layer of powder. I wiped that all down and put it back together. Next I opened the starter cover to expose the fly wheel. No metal shaving in there (except tiny little flake/specs in oil, normal wear?). All of the teeth on the exposed gears look perfect as well. The visible portions of the fly wheel don't show any cracks, dents, or dings. I can put a 3/4" socket on the nut and roll the motor no problem. My next step would be to pull the fly wheel so i can get to the bendix. But I don't want to do to if I don't have to. If the one way was toast wouldn't I expect to see larger shavings, or chunks when I opened the cover?


Sorry if that is long winded. I'm getting to that point of not knowing what else to try. I thought about the cdi being bad to. But I have good consistent spark. And the starter seems to be spinning fine. So that kind of leads me to believe that is not the problem. But I am open to any and all suggestions.

If it helps, here are mods that might be pertinent to this issue; K&N cone style, Voertex CDI, obviously rejetted, FMF exhaust
Mods in general; custom +4.5 swing, 13/40 gears, nerfs, front and rear bumpers (front removed for dunes) 22" tires (full set for trail and for sand) vinyl wrap...yes i did it myself for $150, skid plate (also removed for dunes), steering, gas cap, fresh wheel bearings, custom oil tank
 

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I guess im confused because if it turns over, and has spark, why would you try to pull start it and why would you take the starter apart?
 

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If it was cranking why did you mess with the starter? All that does is spin the engine, it won't keep it from starting. Are you sure it's getting fuel? If the spark is working the only two things you need are air and fuel. Will it fire on a shot of carb cleaner? If it's cranking and cranking but won't start I would expect the plug to be wet with fuel when you pull it out.
 

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Discussion Starter #4
took the starter apart to see if the brushes need replaced. I was making sure there is enough there to make contact. Or see it the armature is wore out. It acts like it just doesn't have enough juice to turn the motor
 

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right off the bat id change the woodruff key sounds like you sheared it off or just enough too mess up everything, after that if it dont start adjust your valves........... if its turning over its not your starter, now if it turns and dont spin anyrhing your timing went off and crushed your valves into your piston therefore you locked up and then broke loose while pull starting
 

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It sounds like you have a fuel issue. Did you try to get it running on starter fluid to at least see if it will fire. You said you have spark, so you are either missing fuel or air. Before tearing everything apart guessing what it could I would try to get it to fire on starting fluid then if you get it to at least fire you know where to begin.
 

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and compression. you need fuel, air, spark, and compression. the starter is optional. Its always possible that you sucked in a bunch of sand through the idle circut when your screw was out and trashed a piston.....which would also lead to low compression.
 

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Discussion Starter #10
Thanks. Compression test is where I'm heading now. I've tried starting fluid, just forgot to mention that. I can see fuel when I push the throttle and look in the carb. Just got done doing another full tear down on that. Everything is clean there. I had thought about the sand issue. Just crossing all of the other bridges before I get that far. I didn't even think of the timing chain. Thanks for all of the fast replies.
 

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Checking compression can also lead you to timing. If the timing is way off, the compression will be down also so that might give you two answers with one test....but on the flip side, just because the compression is down doesnt the timing is off either. A trashed piston or rings will do the same thing. By it backfiring before it bit the dust, that would make me lean towards a timing issue but anything is possible.
 

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Discussion Starter #13
Well it'll be next week now before I can get back to this project. To much other stuff going on. But I've been waiting all winter for season to roll back around so this is going to be a priority. I'll post up what I find. Thanks again for the insights.
 

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Discussion Starter #14
UPDATE.

Finally got some solid time to dedicate to the problem. I started with the basics again.
1 Tested compression; A OK
2 Tested spark with spark tester; Perfect
3 Removed valve cover and the top inspection hole on the magneto cover to inspect timing; spot on
* I used a 3/4 socket and rolled it by hand to line up the mark by the T...yadda yadda. valve cover is still off at this point and everything moved as it should
4 Next, just for giggles i pushed the E Start with the inspection cover off of the left cover. Everything spun as it should but i finally saw the problem. When the flywheel spun at normal speed I could see a slight wobble in it.
* I pulled the magneto cover, again everything is nice and clean inside. Pulled the fly wheel and bingo. A stupid bolt backed out of the clutch and wedged between the gear and clutch. It allowed it to still spin but forced a wider gap than should be. The key was intact but had rolled slightly, wedging itself at 45* off. that is what produced the wobble effect i saw through the inspection home. My next concern was that the crank warped to. So I put a sensor on the shaft and rolled it over again. It had some play but it was inside the suggested amount listed in the manual. So I feel good about that.

Now I am ordering the new flywheel, clutch, gear, needle bearing, key, and gasket. I have been scouring the web looking at everyones prices etc... don't worry, I'm not going cheap just looking for the best deal on good parts. But my question now is are the parts I just listed interchangeable between say an 05 and my year (04)? I have looked all over the web and haven't found a definite yea or no. Some retailers have 03-06 listed as acceptable years for the parts while others say 03-04 or just 04. The reason I am asking is more because I happen to all of the sudden have access to these parts for a killer deal out of an 05. I'd still replace the key and gasket obviously but if I can save $300-400 on the rest that would be awesome.

Thanks again everyone for the help
 

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Discussion Starter #16
That's what I was looking for. Thanks. I tried looking at that last night but could only see the diagrams. The list with the part numbers just kept saying loading. The only part numbers that don't match up are the clutch bolts. Otherwise everything looks golden so I'll be putting the 05 assembly on Tuesday.
 
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