So we decided on ATV’s on our family toys knowing full well that we would have to learn mechanic’n because there is no way we could afford to drag them to the dealership every time something broke. So, we bought this one knowing full well of the issue that I speak of with the assumption that it was a simple carb clean or rebuild. OOPS, what an idiot I was. I’m too embarrassed to say how many hours I have in this thing thus far but suffice it to say I’m at my wits end.
Through the help of the factory service manual and these forums previusly as a spectator only, this is where I stand:
2004 Polaris Magnum 330 4×4, apx 2000 miles.
Starts, idles, perfect (even when blipped or WOT is cut it drops back to perfect idle) but very boggy (not missing like rev limiter? IMO) under throttle from idle and or WOT.
Does not backfire or die unless you simply don’t let off throttle at deep bog, but doesn’t smoke. You can at times nurse it up to a fairly high rev but soon will begin to bog and not run smooth. This is not an intermittent issue, it happens consistently every time the machine is run, hot or cold.
Determined (IMO) a rich condition exists; removed air filter, condition improved, partially covered air intake and condition worsened, gas could be smelled coming through back side of carb…
Replaced spark plug (2x). It comes out black, somewhat sooty but not wet looking at all that I can tell.
Emptied tank, rinsed (with fresh gas), blew out with compressed air, filled with fresh 100% gas.
Cleaned air filter.
Replaced fuel filter.
Vacuum tested fuel pump and it bled down from 5" to 0 in 10-15 seconds so fuel pump was replaced and tested solid.
Vacuum tested needle and seat at fuel inlet fitting, solid.
Carb rebuild kit and cleaned (factory jets, settings, float height= .55 inches, level).
Tested with 120 and 117.5 main jets, no difference, maybe worse.
Then went the other way (just to say I tried everything even though it ran counter to all the signs) and tried it with 125 and 127.5 jets and the boggy condition worsened. Finally just returned to factory 122.5 main jet.
Each time I’ve removed carb for cleaning or adjustment I’ve re-clamped all lines and boots and tested both with and without air filter attached and condition absolutely worsens when air filter (K&N) is attached.
Adjusted valves.
Removed muffler drain/cleanout bolt, no exhaust restriction but did discover a couple minor holes at rear of muffler.
Cleaned all ignition/electrical push plug/connectors with contact cleaner.
Checked all battery/other electrical lugs & connections for tightness, investigated for broken /damaged wires.
Battery tests 12.80V at idle, 14.30 at 1/2 throttle, 14.40 at WOT.
Compression test jumped to 90 PSI on 2nd or 3rd stroke, then to 160 PSI steady after 5-6 strokes.
Removed valve/head cover and checked every component for wear or damage, none present and camshaft mic’d out perfect.
I have not replaced any electrical or ignition parts, but battery faithfully spins the starter strong every time the ignition is engaged.
Sorry for marathon post but I just figured I’d include my entire journal in order to save a few Q&A volleys.
Really the only thing that I know left to do is to replace the ECM but I question whether that would help me out at all on a normally aspirated engine (Carburetor, no EFI)? Hate to spend the money on a no return part only to find out my condition still exists … Any ideas?
