Honda ATV Forum banner

Timing Issue

2389 Views 32 Replies 5 Participants Last post by  shadetree
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.

1 - 11 of 33 Posts
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 :).
  • Like
Reactions: 1
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.
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 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 !
See less See more
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 ?.
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.
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.
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.
stick a ring down in the cylinder, check the end gap, if the end gap is too wide ?, more than likely a hone and new rings won't solve your problem ?, you will need to have it bored over, new piston kit ( has rings with it ), cam chain is always a good idea. top end gasket kit, new spark plug, then see what ya get ?, keep us posted on your progress !.
Does it help if I mention that I mic'ed the cylinder? Almost perfect at 90mm.
if the spec's call for 90mm ?, then get a new set of rings, and it should be fine :). but !!!!!!!!!, the $64,000 question is, is the cylinder out of round ???, if it is ?, then new rings won't solve the problem. get new rings, run one down in cylinder, hold the cylinder up to light, look between the ring and cylinder wall, see light between it ?, if so ?, then the cylinder will need to be bored over/up, new piston kit with rings :).
the catch here is, if and when you get new rings to fit it now ?, and you discover that the cylinder is out of round ?, just wasted cash on a set of rings that won't fit it if it has to be bored over ?!. soooo..what i would do, is have it bored over, then get the piston kit to fit the new bore job, this is the correct way to do it.
Measured my ring end gap have stroke. .028" on wiseco rings. I'm going to say it probably needs to be bored.
agreed ^^^. please keep in mind, ONLY WISECO RINGS WILL FIT A WISECO PISTON !!!. you can't use any other rings with a wiseco piston.
  • Like
Reactions: 1
Update on the situation:

Removed the engine from the frame to get a better look at things. Tore the engine down and checked the hard parts. Did not split the case though. Checked for play in the rod, and play on the crank. All looked good in the lower end. Used oil/gas mix to flush out the case as best as I could. Replaced the camshaft due to the decomp ring hanging up, along with the cam chain, and clutch pack on the change clutch. Had the cylinder bored to 90.5 and put a 4825m9050 Wiseco piston and rings in. Lapped the valves, changed the seals, and reinstalled. Fired it up for the first time yesterday and all seemed fine. Quiet, except the HMF exhaust being loud (LOL). Going to put the plastics and all back on and take for a spin.

Thank you all for the help that you've offered. Definitely helped along the way!
yw, and ty for the update !.
1 - 11 of 33 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.