2004 350 rancher knocking

Need more info.

Has it been sunk? Was top end bored and honed by a competent machinist?

Mr Crankshaft has a good reputation. If you have play in your crank rod bearing or the wrist pin you need to have a rod kit installed on your crank.

Yep, Mr crankshaft will fix it. Side to side play is fine but up/ down play is not, and neither is any slack in the wrist pin to rod fitment.

I had a 420 crank that had no play on either end, but was tweaked just a hair. Tore the motor down thrice before I figured out the rod was barely tweaked/ bent.

Tear it down, send the crank to Mr Crankshaft, CLEAN THE BOTTOM END OUT REALLY, REALLY well, and reassemble with a bored top end with new piston and rings.

Google "youtube 420 crank" and there's a 4 part video showing the process on a 420 motor. Very similar to a 350 Rancher motor other than the timing chain is in the back on the 350 and the front on the 420.

Do you have a local machine shop that does boring and honing?

Your cylinders likely aren't perfectly round due to wear. Even though they might look good, we're talking 1000's of an inch so you won't be able to tell without measuring with the proper (very precise) tools.

Once they measure your cylinder, they may say "it just needs a hone" but more likely you will need to bore the cylinder oversize (thus making it perfectly round and matching the size precisely to the new oversized piston, which the machinist will use to determine the exact size to bore the cylinder out.

So, take cylinders to machinist, have him measure. If it needs to be bored, ask him how much oversize it needs to be (a lot of the time mine have had to go straight to .5 over as the wear was too much for .25 to cover), and then buy the appropriate piston and take it to the machinist with the cylinder, and he will bore the cylinder to match that piston.

Make sense?

Manny said:

I wouldn't stop there, I would take the cylinder head as well to have a 3 angle grind done, valve guides checked, along with fresh valve stem seals.

kinda pointless to do everything below that and not finish up with the head.

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Good point.

Definitely have this done too. My machine shop charged $30 to do it before they went out of business. Now I just remove the valves, put some grinding compound on the seats, spin it a bit, clean it up, and put in new stem seals.

Well worth it.

shadetree said:

YellowRancher said:

Thats a good idea i have cardboard boxes im probably going to use and do the same thing. Hopefully i can get this all done before newyears

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ya got 2 months, its gonna take ya longer than that to rebuild the motor ??..holy crap, I've pulled my '05 trx500fm motor out, split the cases, changed out the bad gears, put it back together, back in the frame, and running in 9 hours !..lol.

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Bet you were slap worn out after that 9 hours though!

Google "420 Crank youtube". Good 4 part series of videos that will show you what you're going to have to do.

The 350 motor is a little different but everything is more or less the same. Close enough to see what you need to do.