Well, it's not mine but I have ridden it a couple of times. When I have it ran fine, as it is a clean quad with not a lot of hours. I would guess it's a 2000ish model.

It's my father-in-laws.

The bother in laws fired it up a month or so ago, when it was very frigid out (below zero). They were pulling tubes down the road, I am assuming at a pretty good clip.

I guess the quad just quit.

He replaced the plug, obviously checked the fuel and fluids. It will crank for a while, then "BANG" big backfire through the exhaust.

He has not done a compression test yet.

My fear is that being so cold, the fuel mixture was lean and the oil injection oil very thick. Pulling a load for an extended period, could he of put a hole in the piston? What are the symptoms? It almost sounds like fuel is building up in the crank and then it ignites and backfires big time.

It ran really smooth prior.

Other thoughts? Ignition issues? Can timing "jump" on these?

Thanks!~

 

Try the compression test as you mentioned first. Could have very well run lean during this time.Backfiring can mean compression is to low to atomize the mixture properly and sometimes excess fuel explodes past the cylinder in the exhaust pipe. Just test it to see where you stand on the top end first.