[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!

 

[shadetree]

welcome to the forums. i'm confused here, you say you adjusted cam chain clockwise and counter clockwise, how is this posb ?, you can't turn anything to adjust the cam chain, least not from what i know ?!. if the exhaust valve was bent/broken ?, it won't run..period !. so both valves are working if it runs. as for the smoking ?, this has nothing to do with adjusting the valves. it's smoking because odds are, rings and cylinder are worn out, maybe from age ?, maybe from being sunk from who ever owned it before you ?, bottom line : this will need a top end rebuild. UNLESS !!!!!!!, the valve guide seals are bad ?, and oil is leaking past the valve stems ?, and this is where your smoke is coming from ?. this i can't say is your problem, only a tear down will answer this .

 

[984man]

There is a cam chain tensioner adjustment under the exhaust pipe right at the head. I removed the plug and used a flat head screwdriver to turn it both directions to try and get rid of the "peck" from the chain. It didn't help the sound, so I am thinking it needs a chain. Just trying to figure out why the exhaust rocker is not moving, and the pushrod is not traveling. Going to have to tear it down I guess. It just had a top end rebuild right before buying it.

 

[retro]

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.

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!

 

[shadetree]

retro ^^^ nailed it !. that is NOT the way you adjust the cam chain, they all are automatic, UNLESS !, you install a manual cam chain adjuster ?, which from what i know of ?, there is no manual cam chain adjuster for that model.

 

[shadetree]

There is a cam chain tensioner adjustment under the exhaust pipe right at the head. I removed the plug and used a flat head screwdriver to turn it both directions to try and get rid of the "peck" from the chain. It didn't help the sound, so I am thinking it needs a chain. Just trying to figure out why the exhaust rocker is not moving, and the pushrod is not traveling. Going to have to tear it down I guess. It just had a top end rebuild right before buying it.

been posted above ^^^, clearly you should have got your hands on a service manual before turning things..lol. we'll let it slide this once..just don't let it happen again, or its the time out corner for you !..lmfaooo. i'd be willing to bet, its been sunk ?!, that was the reason for the '' so called top end rebuild '' ?!. soooooooooooo..step one, get the service manual !, step two, tear it down, step three, do an inspection, compare the specs from manual to what you find, step four, replace, bore, what ever it takes to get the engine back in good shape. final word : replace cam chain, replace all oil seals and gaskets ( where it calls for gaskets..USE THEM ! ) do not use any rtv sealant..ANYWHERE ON THAT ENGINE !. step five, come back here, give us an update, and thank us for saving you thousands of dollars in dealership repair bills !..lol.

 

[984man]

I have taken the head and jug off. Found no issues. Removed the front cover found no issues. Checked can lobes no issues. No issues with lifters or push rods and no issues with the cam chain. How do I know of it jumped time? Can't see the crank shaft with the clutch in the way.

 

[984man]

The rings LOOK fine. The cross hatch was gone from the cylinder for sure. But its just weird that it is all of a sudden. The exhaust valve was coked from the oil of course but no major issues to the naked eye.

 

[shadetree]

The rings LOOK fine. The cross hatch was gone from the cylinder for sure. But its just weird that it is all of a sudden. The exhaust valve was coked from the oil of course but no major issues to the naked eye.

did you check the piston to connecting rod for play ?, in other words, does the wrist pin have any play at the top of the connecting rod ?.

 

[984man]

I'm trying to figure out how to post a video to show you.

 

[984man]

It has side to side, like front to back but not vertically. Sliding in between the two retainers some.

In these engines is there supposed to be ANY movement in the rod on the crankshaft? Slight aide to side movement like the wrist pin but not much

 

[shadetree]

It has side to side, like front to back but not vertically. Sliding in between the two retainers some.

In these engines is there supposed to be ANY movement in the rod on the crankshaft? Slight aide to side movement like the wrist pin but not much

very side to side at bottom is ok. what you don't want it lift on each side of the piston, or, with wrist pin installed in the top of rod, lift each end of the wrist pin, there should not be any movement at all !. should be a solid fit.

 

[retro]

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.

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.

 

[984man]

So if I check the decomp, what exactly am I looking for? I mean if I make sure it locks and unlocks, how will I know if it is bad?

 

[retro]

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.

 

[984man]

I checked the timing last night (putting the engine to TDC and checking the cam sprocket to the mark on the case). Everything was as spot on as it can be. I am thinking about pulling the cam tonight and check the decomp to see if it is hung up because there was a little bit of rattle when the engine was running before the tear down. The service manual is kind of vague to me as far as how to check the decomp with the cam removed. Any special or weird instructions that I am not aware of?

Also, it looks like the crank and rod have a little "blu-ing" from where maybe it had been hot before? Any pointers on checking the bearings to know if they are salvageable? Other than trying to rock it up and down and back and forth?

Just want to hit as many issues as possible before putting it all back together.

 

[984man]

Is this considered "failed?" There is one straight edge and one jagged. Almost looks chipped. Moving the springs up and down it seems like the decomp gets hung up. Normal or no?

 

[shadetree]

Is this considered "failed?" There is one straight edge and one jagged. Almost looks chipped. Moving the springs up and down it seems like the decomp gets hung up. Normal or no?

normal, bluing on crank is normal to, this is from being heat treated.

 

[retro]

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.

 

[984man]

Well I'm not sure what else to check at this point then. I guess I'm going to put new stem seals and a set of rings in it and hone the jug, new can chain and tensioner lifter, and run it.