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Timing Issue

2380 Views 32 Replies 5 Participants Last post by  shadetree, 
984man
I am brand new to this forum, just thought I would seek some assistance with what I have going on. I purchased a '98 Foreman 450S, and just the other day, it "pecking." Adjusted the cam chain both clockwise and counter clockwise. Turning it counter clockwise caused it to smoke, so I turned it back clockwise and it continues to smoke. Took the valve cover off and spun it over using the electric start and noticed that only the intake push rod is moving. Could it have jumped time and bent a valve? Strange thing is that it fires right up, rides fine, and lacks no power, just pecking loud and smokes. Any help would be appreciated! I would think if it jumped time, it wouldn't have any power, or would run rough. None of this is happening.

Thanks!
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R
The cam chain tensioner is automatic. DO NOT try to adjust it as you'll only cause it to jump time if you back out the retractor screw.

As for a reason a pushrod is not moving is difficult to guess with any hope for accuracy... because I suspect all of your problems were borne right here (someone "repaired" it? LOL) though:

Going to have to tear it down I guess. It just had a top end rebuild right before buying it.
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Get yourself a copy of the service manual before attempting to work on it anymore. We are here to help if you get in a bind.

Welcome to the forums!
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R
Took the valve cover off and spun it over using the electric start and noticed that only the intake push rod is moving. Could it have jumped time and bent a valve? Strange thing is that it fires right up, rides fine, and lacks no power, just pecking loud and smokes.
Click to expand...
Check for proper operation of the decompressor on the camshaft. (see the attachment below from the FSM, section 7, page 23)) You can verify that it releases the exhaust lifter when the motor starts by watching the rocker arm motion the moment the engine starts. Don't run the motor with the valve cover off though... only for a few seconds to test.... motor oil should be flying!

If the exhaust valve is hung open... either by the decomp, or stuck or bent valve, busted valve spring, etc... a running motor will suck oil past the exhaust valve seal constantly and smoke a lot. A hung valve or hung decomp can be quite noisy too.

I'm not buying any claims that the topend has ever been rebuilt. It sounds like its gone about as far as its gonna go...?

Specs are in the FSM that answer your questions about the wrist pin and rod/crankshaft clearances. Wish you the best.

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R
If the auto-decomp releases (the exhaust rocker/valve open/close fully) when the motor starts it is working. If it does not release (the exhaust rocker/valve does not open/close fully), it has failed.
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R
The decomp cam assembly should not show any damage. The FSM explains how to check it. I can't see your photo well enough (bad eyes) to tell what I'm even looking at, so its your call. If its damaged and sticking you'll have to fix it though.
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