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basspond

04 Foreman 450es Timing Chain and Tensioner

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My 04 Foreman appears to have jumped time.  The timing chain feels tight so, I'm not sure how it jumped time.  The tensioner does look like it is probably be fully extended.  I trying to decide my next step.  So, does a fully extended automatic timing chain tensioner have to be replaced or can it be reset? Even though the timing chain does not appear to be loose, should I assume I need to replace both the chain and the tensioner?

 

Thanks

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 What makes you think it jumped time ?  And the chain is still tight  !!!   Running bad ?  Maybe you have valve troubles , rocker arm problems , a bent pushrod , or bent connecting rod ---some thing else that will make you think it is running out of time , the diaphragm in the carb 

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Not running at all.  It died suddenly while I was cruising up my driveway (maybe going 3 mph).  When I try to restart, the motor turned over but, would not start and I have a noticeable clanking noise as the starter spins the engine.  I pulled the front cover off and can line the indicator mark on the timing gear with the mark on the case but, over on the Flywheel the "T" is about an inch below the mark.  I can't turn the flywheel 360 degrees in either direction and can't get the "T" up to the mark on the side of the bell housing.  Something is stopping it.  I assumed a valve might be hitting the piston as it near TDC. Another thought is something broke up top (the same things you mentioned).

I was going to take the head off tonight to look at the valves if somebody suggested that could still be the problem.  I open to all thoughts or a process of elimination.

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sounds to me like you either snapped a valve stem or the keeper camee loose on the spring , the valve dropped and hit the piston 

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Thanks for the thought.  I'll pull the head tonight and find out what's going on up there.  It had been kicking out of gear and freewheeling down hills when I let off the gas and I needed to pull the front cover anyway to get to and test the one way bearing.  It will turn both directions so, I've got a new one ordered.  While I've got it stripped down, I want to fix everything that might need fixing.

 

I'll update with what I find out with the valves, rockers, and push rods.

 

Thanks.

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I found the problem.  A half inch piece of the valve seat broke off and was sitting slightly embedded in the head.  The little flakes flipped right off and I ground the indentions smooth.  The piston had no damage.  The push rods looked good. Now I've got to figure out what to do about the valve seat(s).  Can I replace the valve seat or would it be better to just buy a new/used head? (or do I send it to someone who does that?). I'm guessing if I get new valve seat(s), I'll need to get new valves?

In the meantime, I'm going to replace the cam chain since it looks like the tensioner is fully extended.  Can I get the tensioner to retract back or do I need to replace that?  I was hoping to avoid pulling the cylinder.

BTW, after I pulled the head and I got the piston to TDC, all the marks line up like they're supposed. So, you were right in questioning if it ever really jumped time.  Now seeing what the problem was, it makes since that the engine just shut off.

I appreciate your time and advice.

Head.jpg

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2 hours ago, basspond said:

I found the problem.  A half inch piece of the valve seat broke off and was sitting slightly embedded in the head.  The little flakes flipped right off and I ground the indentions smooth.  The piston had no damage.  The push rods looked good. Now I've got to figure out what to do about the valve seat(s).  Can I replace the valve seat or would it be better to just buy a new/used head? (or do I send it to someone who does that?). I'm guessing if I get new valve seat(s), I'll need to get new valves?

In the meantime, I'm going to replace the cam chain since it looks like the tensioner is fully extended.  Can I get the tensioner to retract back or do I need to replace that?  I was hoping to avoid pulling the cylinder.

BTW, after I pulled the head and I got the piston to TDC, all the marks line up like they're supposed. So, you were right in questioning if it ever really jumped time.  Now seeing what the problem was, it makes since that the engine just shut off.

I appreciate your time and advice.

Head.jpg

you can not replace the valve seats, they are pressed in the head from the factory, you either have to buy a new head ?, or a used head. no, you do not need to replace the valves..UNLESS !!!, they are bent or damaged ?. the cam chain adjuster is automatic , remove the screw/bolt from the end, use a small screw driver to twist it back into the body, once you do this, you will see how it works.

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11 minutes ago, basspond said:

Awesome.  That's what I needed to know.  Many thanks!

yw :-).

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