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post #1 of 10 (permalink) Old 04-19-2019, 10:22 AM Thread Starter
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Help with Predator Valves

I have an 04 predator 500. Measured and adjusted valves. Middle intake valve was still tight. Removed another .048" shim so there is no longer any shims left under the bucket and still can not get a feeler of any size under cam. Now what. Do I need a new valve? What is the process. Is it better to pull head and bring to dealer?

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post #2 of 10 (permalink) Old 04-20-2019, 10:25 AM
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If you run the engine without any shim on the valve, the keepers can come off the valve and the valve will fall into the cylinder.

Now, you say you removed "another .048 shim" - where are you getting these shims? The thinnest shim available from Polaris and KTM is 1.45 mm (0.05708661 inch) - the thinnest available on the after market is 1.20 mm (0.0472441).

Yes, when you can no longer set clearance because no thinner shim is available, you have to install new valves or get the valve seats repaired or both - always a good idea to do all 4 if one needs to be done. Curious, but it seems the RH intake valve always wears faster than the rest. Same can be said about Honda's, Kawasaki's and others.

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post #3 of 10 (permalink) Old 05-08-2019, 02:07 PM Thread Starter
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It is a Hot Cams shim kit. Maybe it was .047. Anyway I bought new valves. Interestingly enough the seats don't look hardly warn. I will try to lap in if that don't work will get head seats repaired.
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post #4 of 10 (permalink) Old 05-14-2019, 04:29 AM Thread Starter
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Well I bought all 4 valves and were able to lap them in and get a nice even grind around the surfaces of the head and the valves. Still not sure how a steel valves wears but the seats are still fine. Any way got it back together yesterday and it fired right up. Wouldn't even start before I tore it down for the adjustment. Now it fires right up.
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post #5 of 10 (permalink) Old 05-14-2019, 05:39 AM
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Good deal!

As to how a valve wears; the seats are a hard steel - the valves are hard, but not as hard as the seats - without the cushion that leaded fuel provided, the constant contact between the valve and the seat wears both, but the valve being softer than the seat, the valve wears fastest. The intake valves get absolutely no cushion - the exhaust valves run hotter, but are smaller and get carbon and other byproducts of combustion to contaminate their faces and seats, therefore they do not wear as fast as the intake valves. The life of the valve can be extended through the use of fuel additives (such as oil and lead substitutes), but the additives also raise octane. If you are running the recommended octane fuel and use additives, you should compensate for the change in octane proportionately. If the additive raises octane 2 points, use fuel 2 points lower that the recommended octane - using fuel more than 3 to 5 octane points higher than recommended by the engine manufacturer will result in a loss of power, lower fuel economy, higher exhaust temperatures and accelerated engine wear.

My CRF had Titanium intake valves - the valves were light, but wore out very quickly - I did not ride as hard or as often as some other CRF owner's (I rode most every Sunday for about 2 hours in the woods) and I stretched the life of my first set of intake valves out almost 2 years - for the guys that rode every day for about an hour a day on an MX track, they had to replace their valves once a year.

While I got away with adjusting my valves 2 or 3 times a year, the frequent riders had to adjust their valves every one or two months.

It's pretty easy to know when the valves need adjusted - when the engine becomes harder to start than normal, adjust the valves. For the guys kick starting; if the cold engine usually started in 2 to 5 kicks and got to where it had to be kicked more than 8 to 10 times, adjusting the valves would get it back to starting in 2 to 5 kicks.

Is this as clear as mud? If you want more info or a clearer explanation, search valve wear and octane articles published by scholars specializing in those subjects. I'm just a layman mechanic.

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post #6 of 10 (permalink) Old 05-14-2019, 05:55 AM Thread Starter
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Quote:
Originally Posted by latebird View Post
Good deal!

As to how a valve wears; the seats are a hard steel - the valves are hard, but not as hard as the seats - without the cushion that leaded fuel provided, the constant contact between the valve and the seat wears both, but the valve being softer than the seat, the valve wears fastest. The intake valves get absolutely no cushion - the exhaust valves run hotter, but are smaller and get carbon and other byproducts of combustion to contaminate their faces and seats, therefore they do not wear as fast as the intake valves. The life of the valve can be extended through the use of fuel additives (such as oil and lead substitutes), but the additives also raise octane. If you are running the recommended octane fuel and use additives, you should compensate for the change in octane proportionately. If the additive raises octane 2 points, use fuel 2 points lower that the recommended octane - using fuel more than 3 to 5 octane points higher than recommended by the engine manufacturer will result in a loss of power, lower fuel economy, higher exhaust temperatures and accelerated engine wear.

My CRF had Titanium intake valves - the valves were light, but wore out very quickly - I did not ride as hard or as often as some other CRF owner's (I rode most every Sunday for about 2 hours in the woods) and I stretched the life of my first set of intake valves out almost 2 years - for the guys that rode every day for about an hour a day on an MX track, they had to replace their valves once a year.

While I got away with adjusting my valves 2 or 3 times a year, the frequent riders had to adjust their valves every one or two months.

It's pretty easy to know when the valves need adjusted - when the engine becomes harder to start than normal, adjust the valves. For the guys kick starting; if the cold engine usually started in 2 to 5 kicks and got to where it had to be kicked more than 8 to 10 times, adjusting the valves would get it back to starting in 2 to 5 kicks.

Is this as clear as mud? If you want more info or a clearer explanation, search valve wear and octane articles published by scholars specializing in those subjects. I'm just a layman mechanic.
Thanks. I used the smallest (1.20) hot can shim I had when I installed the intake valves. Ended up close to perfect at .007". So next time it need adjustment may need new intake valves again or headwork.

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post #7 of 10 (permalink) Old 05-14-2019, 06:17 AM
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You can always take the valves to a automotive machine shop and have the valve stem tip ground to reduce the overall length of the valve - much cheaper than a new valve and allows for many more future valve adjustments.

Valve seats that are re-cut effectively lengthen the valve the amount that was removed from the seat. If the seats are cut too much or too many times, the valve is effectively longer than designed. Options an this point? Have new seats installed, tip the valve or get a new head. If you have the valves tipped so you can use thicker shims, keep the records and pass them along when you sell the vehicle so the new owner will what needs to be done if the valves have to be replaced again. It's a courtesy.

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post #8 of 10 (permalink) Old 05-14-2019, 07:16 AM Thread Starter
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How much is ground off and dies the groove need to recut further down?

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post #9 of 10 (permalink) Old 05-14-2019, 02:39 PM
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The valve stem has to remain a few thousandths of an inch above the cotters - I don't have any of those valves handy to make a measurement - but a machine shop can use the valve and cotter to advise you how much can be removed.

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post #10 of 10 (permalink) Old 06-02-2019, 05:01 AM Thread Starter
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Seems pretty easy to figure out. Here is a video on my work.

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