Questionit started smoking real bad, burning about a quart of oil in 3 hours, suspected broken ring, but it isnt (tore it down) lots of grainy carbon on the valves and piston (looks like beach sand) oil is clean, cylender wall is smooth. my plan is to bore it 25 over and have the jug and head re-done, is there something i'm missing? i ride weekly 3-5 hours on the weekend and this is a bummer. any help or suggestions would be greatly appreciated. also any idea where i can find the torque specs on line? this ride has less than 1500 hours on it.
AnswerNot really one of my specialties.... new ATVs, however engines are engines....
You need to look carefully at all of the top end parts and have them measured for wear. Check the ring end gap, bore for roundness, taper and finish. Check the piston clearances at the skirt against factory tolerances. Rings should have minimal side play in the grooves and should be the same thickness and width all the way around.
Sounds like dirt or some kind of abrasive has entered the engine through the intake system or through the fuel. Check the whole intake system for leaks that can let in contaminants.
Once you get everything back to factory clearances, be sure to inspect the fuel system, crankcase breather system and drain the oil, check the filter by cutting it in half to see if something was put into the lubrication system.
Pistons wear from overheating, lack of lubrication, abrasives or crankcase pressure backup for the most part.
Look at the cylinder head carefully, checking valve guide wear and observe if there are deposits in the intake and exhaust ports.
Get a shop manual for specs, so you don't have to do the job twice... www.helminc.com www.motorcyclebooks.com
or Ebay auctions.
Bill Silver
