Poulan Pro with a Tecumseh engine

[sbushman46]

Working on a Poulan Pro now with a 8.5 Tecumseh flat head motor, Model LH318SA/156551H.Motor was difficulty starting then at one point wouldn't start at all.First thing I did was took the carb apart soaked it in an ultra sonic cleaner twice cleaned it good and installed a carb kit.Replaced the old gas with fresh and a new plug. Got it to start and had it running at an idle but once i gave it full throttle it would bogged down and stall popping some flames through the carb.Tried starting it again but the same result more popping coming from the carb and very hard to start..So i figured bad carb and replaced it with a new one but same result.Figured the timing was off so popped the flywheel off and checked the key way but it was fine.Thinking now a stuck valve so pulled the head off but both seemed to be seating good. Had some light carbon build up but not much.I checked both valve clearance figuring it was .008 on the intake and .012 on the exhaust but both were way to tight.Seemed like .004-.005 fit snug on both..Also changed the plug twice but nothing..Any suggestions ?

[RoyM]

Did you get the valve clearance to spec?

[bgsengine]

Figured the timing was off {snip} Seemed like .004-.005 fit snug on both..Also changed the plug twice but nothing..Any suggestions ?

timing IS off - valve timing that is. get clearances set to spec might solve your popping issue.
you may also need a valve job - you'd have been better served to do a leakdown test before even pulling it apart but I would bet you have some "dished" valve faces (worn) causing the narrow clearances so you may need to eventually do a valve job.
Did you also check your valve seats? (while you had head off, roll engine til a a valve opens and then use a screwdriver to see if you can wiggle/wobble/rotate seat)

then again you could also have not done the carb up right, could have a plugged muffler, loose ignition grounding wire, bad switch, etc.

- I can think of hundreds of things that can cause a pop/misfire on these
- you need to follow a logical step by step troubleshooting method - *verify* things like spark, compression, leak down test, fuel quality, fuel lines, etc rather than just guessing or "figuring" - for example, suspect spark, disconnect the machine's grounding system at the terminal where it connects to engine and re-test (Had an ariens with one of those round "transistor" safety switches drop spark intermittently - quickly isolated that by unhooking machine's shut-off wiring at the engine.)

But since you have obviously located a flaw in the system that does indeed point at a cause for your popping out the carb, I suggest fix that first and try again.

[RoyM]

Did you check valve clearance at the top of the compression or the exhaust stroke? To get an accurate reading move the piston to the top of the compression stroke + another quarter inch.

[sbushman46]

Ok thanks form the input your right i should have down the leak down test first. Motor isn't that old figured at first it was something other then the valves. I'm going to try a leak down test in the morning.

[KE4AVB]

Do you have a spare ignition laying around you could try?

I had several 2C ignition coil packs lately where the spark advance had failed in such a way that the ignitions triggered at full advance too soon. Two of them literately set fire to the air filters as I tried to accelerate.

Just thinking out loud.....

[sbushman46]

Took your advise KE4AVB and dug out an older model ignition that fit just to see if it would work..Bolted it on and started right up and ran great.Needles to say went out and purchased a new one ( 57.00 ) and machine is running perfect...Thanks for the help..