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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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shadetree
984man said:
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.
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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 !.
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984man
Does it help if I mention that I mic'ed the cylinder? Almost perfect at 90mm.
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shadetree
984man said:
Does it help if I mention that I mic'ed the cylinder? Almost perfect at 90mm.
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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 :).
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shadetree
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 ?, well..you 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.
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M
984man said:
Does it help if I mention that I mic'ed the cylinder? Almost perfect at 90mm.
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If the cylinder is almost perfect and the cross hatch marks are gone I'd guess you measured it wrong. Measure the ring gap at the top of the cylinder where the rings never make contact. This will be an almost zero wear point. then push the rings down in the cylinder perfectly square using the old piston to the half way point of the stroke. I'm almost positive you will see 10 to 25 thousanths difference. Another way to check is to measure the piston skirt against the same spot at the middle of the stroke in the cylinder. A really quick method I use is to put a feeler gauge between the skirt and the middle of the stroke. This is usually accurate enough to see if it is completely worn out.
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984man
Measured my ring end gap have stroke. .028" on wiseco rings. I'm going to say it probably needs to be bored.
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shadetree
984man said:
Measured my ring end gap have stroke. .028" on wiseco rings. I'm going to say it probably needs to be bored.
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agreed ^^^. please keep in mind, ONLY WISECO RINGS WILL FIT A WISECO PISTON !!!. you can't use any other rings with a wiseco piston.
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M
984man said:
Measured my ring end gap have stroke. .028" on wiseco rings. I'm going to say it probably needs to be bored.
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What was the measurement at the top of the cylinder where the rings haven't touched? I'm just curious to see the actual wear numbers.
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984man
I did not get a measurement at the top. Dangit. I took it to the machine shop to get it bored over. Going with a 4825M09050 Wiseco setup. So far its getting complete gasket kit top end and front cover seal. New can chain and tensioner and lifter. Getting new cam and bored over.
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fishfiles
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I just went thru a very similar situation , Wiseco .050 over 10.25 piston in a 300 Fourtrax , very low hours on the jug and it started smoking , took it a part and the walls were smooth , very little hone marks visible , measured the cylinder top , middle and bottom and it looked good , got a new set of Wiseco rings and honed the cylinder and gapped the new rings as per the chart that Wiseco sent with the ring set and didn't go with the OEM specs , all is good so far , think I am at about 30 hours now since it was re-ringed

I think the problem I had that caused early smoking was over fueling from a larger carb that was putting too much fuel and unburned gas washing the oil off the rings

I think you done the best thing getting it freshened up with a boring , the egg shape thing is very common , especially if you have play in your connecting rod -------- you are doing this upper job , be aware if you have play in the lower end , your upper isn't going to last long , the piston will wobble around and egg shape the bore quick

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984man
Fish, thank you for the information. I checked for side to side and wobble on the small end and the crank end. Barely side to side on the crank. No "rocking" on the small end.
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984man
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!
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shadetree
984man said:
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!
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yw, and ty for the update !.
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