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truckcap22

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Reply with quote  #1 
Hi there, I'm new to the forum, but have been lurking for the past several weeks as there is great information on the site. I recently purchased a new to me 2005 predator that didn't run when I bought it. Former owner mentioned that it started bogging down when he would give it gas. He thought it was in the carb, so he ended up buying a new carb and throwing it on there, still wouldn't start for him so he decided to sell it.

Well first thing I do is open up the valve cover and notice that the timing is off @ TDC on the compression stroke. So I set the timing and check the valves to make sure they're in spec. They're not, exhaust valve on the brake lever side was .03 and intake valve on the brake side was .013. Both exhaust and intake on the clutch lever side weren't far from spec and were re-shimmed to within spec no problem. The exhaust valve on the brake lever side was re-shimmed within spec no problem. However, the intake valve will not change from the .013. It originally had a 1.77 shim in it so I bumped it up to a 1.95 shim and the measurement stayed the same at .013.

All the valves are in spec now with exception of that intake valve which is being stubborn. I also noted the decompression on the cam seems to be completely broken as it just spins around on the cam freely, not sure if this is a huge problem that would cause it not to start or not.

Thoughts on where to go from here would be appreciated. I'm almost to the point of just digging into the motor to visually see the head, valves, piston etc.

Thanks!
05pred500

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Reply with quote  #2 
Welcome to the site! Check the essentials, are you getting a good, hot spark? Getting fuel delivered to the cylinder? How is your compression?
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2005 predator 558 - falicon supercrank w/ knife rod, ss valves, 12.5:1 wiseco, hpd 558, HMF full system, uni, CFM oil tank, pro design tether, suspension work by Monster Performance, HID light kit, ODI Rouge, Kalis Racing riser, Flexx bars, razr/razr2
truckcap22

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Reply with quote  #3 
Quote:
Originally Posted by 05pred500
Welcome to the site! Check the essentials, are you getting a good, hot spark? Getting fuel delivered to the cylinder? How is your compression?


Hey thank you and thanks for the reply. I should have mentioned spark is good and I've pulled the plug on several occasions and it's wet after trying to start. So I assume it's getting fuel. Sometimes you can see a bit when the intake isn't hooked up. Compression test kit is on its way. I tried renting one from an autoparts store, but they didn't have the right connections in stock to make it work.

Anything else to look for while I wait?
LEOGM5150

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Reply with quote  #4 
I am guessing that the timing chain skipped time and the piston made contact with that exhaust valve and it is bent.
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FROM: POWELL WYOMING USA

MY GREATEST FEAR IS THAT WHEN I DIE MY WIFE WILL SELL MY TOYS FOR WHAT I TOLD HER I HAVE INTO THEM...

2014 POLARIS RZR 4 900 EPS
2012 POLARIS RZR 4 900 XP
2008 POLARIS RZR 800
2008 POLARIS OUTLAW 525S LE
2007 POLARIS OUTLAW 525 IRS
2000 400 RCR TWO STROKE SCRAMBLER
2001 400 TWO STROKE SCRAMBLER
2005 SKI DOO 1000 TWO STROKE SAND SLED
truckcap22

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Quote:
Originally Posted by LEOGM5150
I am guessing that the timing chain skipped time and the piston made contact with that exhaust valve and it is bent.


Thanks Leo, I've been temped to just open it up and get it over with. I figure I could freshen some things up while I'm in there anyways. Just wanted to make sure I wasn't overlooking anything before I take the plunge. :/

thanks for both of your help!
LEOGM5150

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Reply with quote  #6 
No matter what you find I would replace the timing chain.
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FROM: POWELL WYOMING USA

MY GREATEST FEAR IS THAT WHEN I DIE MY WIFE WILL SELL MY TOYS FOR WHAT I TOLD HER I HAVE INTO THEM...

2014 POLARIS RZR 4 900 EPS
2012 POLARIS RZR 4 900 XP
2008 POLARIS RZR 800
2008 POLARIS OUTLAW 525S LE
2007 POLARIS OUTLAW 525 IRS
2000 400 RCR TWO STROKE SCRAMBLER
2001 400 TWO STROKE SCRAMBLER
2005 SKI DOO 1000 TWO STROKE SAND SLED
truckcap22

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Reply with quote  #7 
Quote:
Originally Posted by LEOGM5150
No matter what you find I would replace the timing chain.


I will certainly plan to do that along with the tensioner for safe measure!
ORION

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Reply with quote  #8 
Put your thumb over the spark plug hole, and crank it over. If you can keep the hole sealed with your thumb, there is a compression problem. The pressure should blow past your thumb when cranking, no matter how hard you try to prevent it. A bent valve or bad rings could cause low compression. I would highly recommend finding out what the compression is BEFORE tearing the head off of the motor. Once you take it apart, you cant check the compression. 
truckcap22

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Reply with quote  #9 
Quote:
Originally Posted by ORION
Put your thumb over the spark plug hole, and crank it over. If you can keep the hole sealed with your thumb, there is a compression problem. The pressure should blow past your thumb when cranking, no matter how hard you try to prevent it. A bent valve or bad rings could cause low compression. I would highly recommend finding out what the compression is BEFORE tearing the head off of the motor. Once you take it apart, you cant check the compression. 


Thanks for the reply. However, I had some time to dig into it last night (the compression wouldn't blow my thumb off btw). But I tore down the top end and sure enough both intake valves had made a little contact with the piston and were bent. One worse than the other, but both bent none the less. At this point with the fact that the exhaust valve on the brake lever side took a 1.45 shim to get within spec I'm probably looking at doing all 4 valves while it's off.

I'm also planning on looking into how the cylinder is worn and potentially replacing the piston because of the dent, along with the timing chain. Is there anything else that I should look to replace while everything is torn down?

Any recommendations as far as replacing the valves go? I'm assuming the seats don't need cut, but may need to be lapped?

Also what seems to be the best place to buy parts? I've noticed ebay, and partzilla seem to be some of the only places to get parts from at a decent price.

Thanks again!
ORION

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Reply with quote  #10 
I have rebuild a bunch of motors. At this point, I would just buy a good used head on eBay, get it resurfaced, and bolt it on with new gaskets. Ya, replace the timing chain and tensioner, but that's about it. Rebuilding the head will cost a lot, take a long time, and you might not wind up with a very good head after its all said and done. The last one I had rebuilt cost a lot, and the jackass did not do the valves correctly. Then I wound up getting a great price on a newer model Outlaw a month later. The newer quad cost less than that damn head rebuild. Then after all that, I sold the quad with the new head. Just my $0.02
truckcap22

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Reply with quote  #11 
Update*

4 new valves, valve seals, gaskets, and timing chain and it's running again. However I have to give it a little throttle to get it started after its warmed up a bit.. Thoughts? I've yet to open up the carb to see what jets are currently in it. I've turned the a/f screw 3 turns out to get it to start without throttle cold.

Also noticed the spring is completely missing from the cam decompression mechanism.. It completely spins and rolls around on the cam and makes noise.. Can j cut the decompression mechanism off without ill will? I don't really feel like taking a small loan (exaggerating) for one exhaust cam.

Thanks for all your guys help so far!
ORION

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Reply with quote  #12 
If the throttle effects the starting procedure, I would look at issues in the carb. You may be priming the carb via the accelerator pump if you have to open the throttle to get it to start. Or, you may need to raise the idle. Clogged air filter? Either way you look at it, it probably has something to so with the carb/throttle/choke.. something to do with intake/fuel. It doesn't look like timing, compression, or spark - so it must be intake related. 

New valves? Sweet. Did you have it done, or do it yourself? 
truckcap22

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Reply with quote  #13 
Quote:
Originally Posted by ORION
If the throttle effects the starting procedure, I would look at issues in the carb. You may be priming the carb via the accelerator pump if you have to open the throttle to get it to start. Or, you may need to raise the idle. Clogged air filter? Either way you look at it, it probably has something to so with the carb/throttle/choke.. something to do with intake/fuel. It doesn't look like timing, compression, or spark - so it must be intake related. 

New valves? Sweet. Did you have it done, or do it yourself? 


Agreed, it's supposed to be a new carb, but it looks like a cheap oem knock off. I still have the original carb I think I'm going to clean it up and give that one a try. It currently doesn't have an air filter, so I know that can't be clogged [smile]

I did everything myself on the valves (I'm kind of that way) the two intake valves were bent one way worse than the other. Cleaned the seats off real good and lapped them myself. The surface on the head looked brand new.

I'm still curious on this cam decompression mechanism. I'm leaning towards cutting it off since I need to do a final shim on the valves as it is. From what I know the aftermarket cams don't have the decompression on them, so theoretically I should be alright to just dremel this while I have it off the bike, yes?
ORION

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Reply with quote  #14 
It might be worth putting the air filter and lid back on, just to test it. It probably wont make a difference, but some engines wont run properly without those parts. I have a Polaris Sportsman and a Seadoo Speedster, both of which won't run right without the filter and lid installed. 
05pred500

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Reply with quote  #15 
I have heard of a few people running without the decompression and they haven't had much issues with it.
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2005 predator 558 - falicon supercrank w/ knife rod, ss valves, 12.5:1 wiseco, hpd 558, HMF full system, uni, CFM oil tank, pro design tether, suspension work by Monster Performance, HID light kit, ODI Rouge, Kalis Racing riser, Flexx bars, razr/razr2
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