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Discussion Starter #1
I've been reading several posts on here about other 350 Ranchers smoking and have gotten some good info on what might be wrong with my '02 350 Rancher.
Let me start by telling about how this all started this past weekend. Went on a camping trip/atv ride in the NC mountains with some friends and rode all day on Saturday with no problems (no smoke). Sunday morning, got up and had to ride up the trail a short ways to take care of some paperwork if ya know what mean. After taking care of business, started up the Rancher to ride back to camp and my 350 Rancher started smoking pretty bad upon start up. Just start smoking all of a sudden!
I haven't started any tear down as of yet, just getting info first before I do. I've read that it may be in the head (valve guides/seals) or it may be a broken piston ring.
I did check the oil before going on the ride and oil was up to proper level and was nice and clean. Now the oil is slightly low and is now black and dirty. I haven't noticed any power loss but I haven't really got in the throttle real hard since it started smoking.
I've also been looking on ebay at prices of possible parts I may need, head, cylinder jug & piston kits, and so on.
One of my main question is, how good are these aftermarket heads and cylinder jug kits? Aftermarket head is $150 and aftermarket cylinder/piston kits are $80 to $100. I like the price but I don't want to buy cheap junk that's not going to last.
 

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I'm not a fan of aftermarket parts made in china, but check your crankcase vent hose for kinking or a plugged vent before buying any parts for it. I would change the motor oil & filter right away too... do a valve adjustment on it, change the fuel filter, make darn sure the carb is clean and float valve is not leaking raw fuel into the cylinder while sitting, and any other routine maintenance that might have fallen behind in these past 16 years... you may not need to rebuild it after all.
 

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Discussion Starter #3
OK I have done a compression test on the Rancher 350 and everything I have read is that the psi should be between 90-97 psi. First test I was getting 150-155 psi!! I thought maybe my gauge is reading wrong (it is an old gauge). I borrowed another gauge that I knew is good and ran the test again...same thing 150-155psi. Just to make sure I'm doing it right here, I am spinning the engine over with the throttle wide open and getting 150+ psi. With the throttle closed it reads around 90psi,
What would be giving me these high compression readings??
 

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Lots of motor oil in the cylinder, along with lots of thick carbon buildup in the chamber and on the piston crown can cause high compression test readings. I'd yank the head cover and have a looksee... you might have a broken valve spring, a broken valve seal and/or a broken valve guide.
 

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Discussion Starter #5
Tore the engine down today on the 350 rancher. Found NOTHING out of the ordinary broken that will be causing it to smoke heavily. Valve guides look good, piston looks good, cylinder has no scratches or gouges. Ring gaps are in spec. I do not have a repair manual on hand.
Can someone give me the exact cylinder bore diameter and its wear limit size. I'm taking the cylinder and piston to the machine shop next week for them to measure
 

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Ya, see the attachment below from Chapter 8 of the FSM.

Was the crankcase vent clear when you checked it? Motor oil clean and at the correct level, not black with carbon particles, saturated with gasoline or water? Keep us posted on what you find.
 

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