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Discussion Starter #1
So this quad has good spark, compression is about 92 psi. I gave it a shot of starting fluid, but, it doesn't start. The "cranking" speed seems to speed up a bit when the ether goes in, tho. But it won't fire.
I checked the valves and the ex seems to be good at .009/.010. The intakes are tight at .003/4. I think spec is ex ..010 and int .006. Also, when I crank it over, I can hear a loud clack that comes from what sounds like the R side and kinda low and back on the motor. It seems like it does it about once per engine revolution. NOt sure on that, tho. Would the tight intakes make it not start at all?
Thanks!
 

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If the intake valves have clearance (any clearance) it will not affect starting - I would suspect, weak spark or park at the wrong time - start with a new spark plug and use a timing light to verify spark with the plug in the cylinder - if the spark does not jump the gap, the timing light will not flash - once you have verified spark and spark at the right time, you are down to compression, fuel, air and fuel and air in the right ratios.
 

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Discussion Starter #3
I have a spark tester and it has very strong spark. Is it a timing thing? How does one adjust the timing? Or is it even adjustable?

If the intake valves have clearance (any clearance) it will not affect starting - I would suspect, weak spark or park at the wrong time - start with a new spark plug and use a timing light to verify spark with the plug in the cylinder - if the spark does not jump the gap, the timing light will not flash - once you have verified spark and spark at the right time, you are down to compression, fuel, air and fuel and air in the right ratios.
 

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The only way timing can be off is due to a faulty component - most frequent cause of the timing being off is a sheared flywheel key. Timing can be easily and quickly checked by removing the spark plug and using a soda straw to check the position of the piston - using the straw, rotate the engine to determine when the piston is at TDC - when the piston is at TDC, the mark on the flywheel should be visible in the inspection hole - if the mark is not visible, rotate the flywheel until the mark is visible and recheck the position of the piston - if the piston position is more than 5 degrees off of true TDC, then the flywheel is out of position and needs to be investigated.
 

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Discussion Starter #7
That's on the L side of the engine. The noise is coming from the R side. I think.
What is the "recoil cover?" Did you mean starter rope? There isn't a pull start on this machine.
Maybe the pulse coil fell off and is bouncing on the flywheel under the recoil cover?
 

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OK - I didn't check the particulars and most Polaris models have the ignition and stator on the R side - the predator is on the L side - I stand corrected.

The cam drive is on the R - perhaps the cam chain has worn out and is jumping teeth - maybe it has to do with the auto-decompressor - it's on the RH end of the exhaust cam?

Let us know what you discover.
 

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Discussion Starter #9
I did the straw trick and the timing marks lined up at tdc. When I crank it over with a ratchet, right before tdc it tightens up and doesn't feel very smooth. I gotta change the oil and filter anyway, so I'm gonna drain the oil and pull the clutch cover.
 

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Getting tight at TDC coupled with the clunking from the R side, I suspicion the cam jumped time and you have a valve kissing the piston. If that's what's happening, you will need to check the cam chain tensioner mechanism, install a new cam chain and possibly (more likely than not) you will need at least two new valves. You will not know the situation until the valve cover is removed and the cam timing checked.
 

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Discussion Starter #11
I will. I have the clutch cover off, but the battery is dead. Doh! So, its on the charger. The cam chain seems very tight, but, I'll know more when I can crank it over.
Thanks for your input! (y)

OK - I didn't check the particulars and most Polaris models have the ignition and stator on the R side - the predator is on the L side - I stand corrected.

The cam drive is on the R - perhaps the cam chain has worn out and is jumping teeth - maybe it has to do with the auto-decompressor - it's on the RH end of the exhaust cam?

Let us know what you discover.
 

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Discussion Starter #12
So I found the source of the noise. I started to suspect the starter one-way clutch. Seen this many times. The polaris tech told me that it's most likely the tight intakes is why it won't start. He said they will start at .004, but probably not at .003. And with a new plug in it, and a shot of ether, the cranking speed picks up noticeably like it's really trying to start. Those are both steel and alumnum bits in there.

137225


137226
 

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Polaris tech is wrong - they will start at -.0005 clearance, but they are hard to start - at -.002 the engine can start, but it needs needs to be spun faster than the on board starter motor will turn it. On a manual transmission machine, they can be pull or push started. I have seen YZ250F Yamahas (5 valve engine) run with a valve at -.004 (that's open 4 thousandths of an inch when the engine is cold ans at rest). When the engine is spun at a higher speed than the starter motor will turn it, the compression rises sufficiently to get it started and once running, compression will blow the valve closed, but eventually the clearance will decrease to a point where even push starting will not get the job done and the valves have to be adjusted to get adequate clearance for ease of starting.
 

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Discussion Starter #14
I wonder if the desintegrating starter sprague is slowing the starter down and therefore not starting? But, regardless, the valves need to be adjusted and the starter clutch will need to be replaced. Ordering parts momentarily.
 

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Discussion Starter #15
I have about 7 different pullers. And at least 3 are for Polaris machines. Buuuuuuut, not for this one! :poop:
I have one for an old yamaha dirt bike and it fits at least 100 other models.
Rant over. :cool:
If I ever post up here that I'm thinking about buying a Polaris quad......somebody find me....and shoot me! ;) :ROFLMAO:
 
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