not firing on left/drivers two cylinders

[gauthierdustin]

ok so the carbs are spotless, not a drop of gunk or dirt, plugs are getting wet, small spark off plug wires, is it possible motor is screwed?  it doesn't seem to have any leaks such as head gasket, etc, it seems to fire on all 4 cylinders around 2500 rpm, is it possible it just needs to be driven, hasn't moved in two years?

[tqmx1]

Next step is run a compression check on the engine. and then run a valve clearance check. It sounds like you might have a few tight valves.

[Klavdy]

Hmmm, good idea Kim but for now, maybe try to answer a couple of things before you start with the valves and compression tests.

How do you know the carbs are clean?
Did you take them apart and clean them or just look at the outside of them?

The more info you can provide, the better the prognosis.

Cheers

[andyb]

ok so the carbs are spotless, not a drop of gunk or dirt, plugs are getting wet, small spark off plug wires, is it possible motor is screwed?  it doesn't seem to have any leaks such as head gasket, etc, it seems to fire on all 4 cylinders around 2500 rpm, is it possible it just needs to be driven, hasn't moved in two years?

So far, so good.  As above though, you mean the insides of the carbs are clean, rather than just the outsides, right?  Clean on the outside doesn't mean clean on the inside.  Rember that rule or you'll eventually catch gonnorrhea, but that's another problem entirely (penicillin helps).

If the carbs are internally clean, with particular attention being paid to the pilot jets (the little bastards buried next to the main jets with a really, really small orfice size), the choke circuit (the hanging down brassish tube that sticks out when you remove the bowl), and the idle mixture area (the screws normally covered by plugs on the top, nearest the engine side), then the carbs qualify as clean enough to run decently.

However, what you're describing if it's running on all four at 2500rpm and up is an absolutely perfect example of plugging pilot jets.  Like I said, the metering orfice in them is on the order of "really goddamned small", it's a hole with a diameter of perhaps 0.018" or thereabouts... I've got reasonably young eyes, and I require sunlight to be able to see if it's clogged or not.  Reading glasses and one hell of a light source are helpful, but if you're in your 30's your friends will wonder about you if you store them in plain sight on the workbench.  Don't ask why I know this.

Most likely, a few hours spent with a can of carb cleaner and this guide will correct the problem.  Get two cans of carb spray, incidentally, it's not uncommon for me to totally drain one and not quite finish.  Do not use wire to clean the jets, they're made from brass and really easy to scratch internally, which screws the metering up.  Nylon bristles pulled from a brush work, compressed air works better, but just blowing the hell out of them with a concentrated stream of carb cleaner usually swings it also (explaining why I use so much when I do mine).

Alternately, if they're clean internally and you don't catch gonorrhea from them, I struggle a bit to troubleshoot from there.  I'd start with draining the tank and using absolutely fresh fuel from a known good source (BP, Mobil, Shell), making sure the plugs are new or damn near new and gapped appropriately (if the spark is weak, dropping the gap some can help you figure out where the weak link is), and failing that, break out the compression tester.  If the motor fails a compression check, a leakdown check will help explain what's wrong.