On Sun, Jun 01, 2003 at 01:46:10PM -0400, Jim & Nadia Higgins wrote:
>
> Hello all,
>
> I have a Polaris ATV that has a 2 cycle engine. There is a reservoir for
> the 2 cycle oil which is then automatically mixed with the gas. I stupidly
> let this reservoir run dry and now the engine will turn over but not fire.
How dry is "dry"?
Did it seize?
> I plan to check the spark plug first (maybe I'll be lucky to get off so
> cheap)
It won't be the plug.
If you find bits of aluminum on the plug then
you know the piston is toast. But damage from
lack of oil doesn't usually result in aluminum bits
on the plug until it's pretty severe, and it usually
seizes then.
> but what other damage might I have done? Burned valves?
No valves on a two stroke.
The piston and rings are usually the first thing to get damaged when a
two-stroke runs out of oil. The piston will scuff, leaving deposits
on the cylinder wall and clogging the ring gap or 'smear' into it.
With the ring(s) no longer able to move in the groove, they won't seal.
Combustion pressure starts leaking past the rings which heats up the
poor piston even more. At this point it will not live much longer.
My guess is that you will need to replace the piston and rings and clean
up the cylinder. If it has an iron liner it can be bored and an oversize
piston and rings installed. If it has a 'nikasil' or similar liner,
it MAY be ok. If there are aluminum deposits, you MAY be able to etch
them off using muriatic acid. If the coating is damged, you can get
it recoated. US Chrome is an outfit that does much of the re coating
work in the US.
You should also replace the small end bearing and wrist pin. I recommend
using a stock or Pro-X piston, not a Wiseco (except their "pro" series).
I won't go into the metalurgy reasons since this post is already too
long...
Working on two-strokes is not difficult, but you need to be pretty
careful about your work. Sloppy or dirty work often means failure.
The shop manual should tell you how to take the top end off, and it may
give you enough info to do a decent rebuild. If you decide to do it,
I'd recommed leafing through A Graham Bell's _Performance Tuning in
Theory and Practice- Two Strokes_ before you assemble your new top end.
BTW, run, do not walk, away from a re-coater or machine shop that does
not require your new piston in order to get the bore diameter correct.
Eric
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