Are you using Ethanol
fuel and using an additive as Stabil or Etc to treat the fuel to reduce the
Ethanol related problems (deteriorating fuel lines and swollen seats? I
had one experience of a mower stopping as if it was out of fuel until I learned
the Carb’s needle seat was swollen. Otherwise, I have found very
defected loose leaking fuel lines affecting starting and running from the loose
fuel lines (sucking air).

History: Has the
engine had a general check-up, tune-up in the last few years? Mainly
compression test, plug, air filter, fuel filter if present and checked the
valve adjustments X Specs. If there is no fuel filter, look close in
the fuel tank for small debris as wood Etc that could have gotten in the
tank. Without an inline filter the debris can travel into the Carb’s
fuel screen that is probably present and restrict fuel.

If you ck the compression,
turn by hand 1st to know the piston w/n make contact with the gauge. W/O a gauge you should not be able to hold
the compression in the cyl with your finger or thumb. My rule of thumbs w/o specs is 100 psi on an
eng that size.

Good Luck On Your
Investigations!!! Please Share what your
find. Oops Any Errors.

No, engine has not been checked. No reason; always starts on 1st or second pull and runs for hours. I do have a nice compression tester (and a handheld that probably won't reach) but I suspect I don't have a small plug fitting. I always use stabil. Again, this carb has only one gasket/seal and needle tip that are rubberized and not deformed. Bowl seemed to have appropriate fuel volume. No fuel filter; line is ~3" direct; heavy auto type tubing. Air filter was off for this test. On my perhaps three carb blow/clean outs in my 10 years of ownership, it has appeared completely clean and new and like I wasn't doing anything.

Even though I gave extra info in original post, I was mainly asking whether weak spark could be explained by a resistor rather than standard plug!? I had asked since a round trip to town for a plug is 25 miles.

Fire/Fuel/Compression is the
formula for it to run: Looking at the
age, d/n rule out checking valve clearance for clearance if not to spec. if the
compression is not good. The valve has
to have clearance to seat in the head to get compression.

1. Do you have an
in-line-spark-tester (attached)

to check for spark with the plug installed? The advantage
is to prove the plug is firing in the compressed cylinder (vs in the open
air). They are cheap (approx 6-7.00) at your local Auto
or Harbor Freight. A known good spark
plug from another engine should be just as good to prove you are getting fire
in the cylinder.

2. You said the bowl had a
good level of fuel but is it getting into the Cyl? I’m not looking at your post. Did you try
priming and it try to start or fire??
Did you ck the passage on the bolt Hor & Ver that hold the bowl on
with fine wire to prove it is open?

3. The Eng has to have
compression to run. The exhaust valve can stretch due to heat over a period of
time, “even if the Eng is running good.
If the compression is “Very Low” (bad), your resistance of pull starting
“Might” detect less resistance.

I used to do the priming thing on older engines, but I forgot all about it. I drove 25 miles for a plug, but it didn't help me so I decided to take it in since the sooner it got in, the sooner (a week or two) it would get back. Before we took it off my truck, the mechanic gave it a yank and it fired up for him. It still wouldn't run off choke. Mechanic thought it was likely an air leak, but after spraying carb cleaner at gasket without effect, and finally realizing that this engine has a Nikki carburetor, he told me that they almost never have good results cleaning/rehabing them. So, I took it back home; gave it one more air and probe clearing; changed the apparently good fancy internal gasket; and still wasn't able to get it to start or fire. The mechanic was 20 years my junior, but I thought I was pulling almost as well, but no cigar.

So I ordered up a new (hopefully the same) carb from Amazon. Then I read your post. I can see how middling compression might draw low fuel. I will see if I can find my tester and I will check the valves. But remember, until last weekend, and even two weeks ago, this engine always started easy for (apparently weak armed) me and ran fine for at least two hours.

I found my compression tester right where I left it 11 years ago. I had only used it for autos. The highest value I got was 68psi on first pull. I never found an increase with extra pulls and I found no increase with a little oil. I know that is a lot lower than loger's estimate. However, it feels and sounds as resistant as any other small engine that I use. I also see that B&S cams are designed to keep intakes open a little late to assist with pull starts. I also see that some posts think 60psi is OK. Of course, others say the government is hiding aliens in Utah and New Mexico.

I checked the valves and the clearance appears to essentially be correct. Specs are .004 to .006". The exhaust may have been .007. I'm not going to mess with that. I hope our local parts store has valve cover gaskets since I tore it.

While I''m waiting for this carb or while I would have a chance to return it, does anyone have a practical way to do and analyze a leak down test? I have an air compressor and lots of tools.

EDIT. but I suspect I don't have a good way to keep the engine at tdc. There is a clutch so the chipper can start without the chipper running so probably never mind.

The compression is not a big
concern if you have some form of compression release (for ease of
starting). IMO! If you have a good spark and fuel (primed or
choked) you should have a backfire at least if the Eng does not run.

I feel you could lock the
flywheel to hold the Eng at TDC but what would you measure? With a Sun Eng Analyzer in the 70s we had a
percentage leakage gauge on it (adding compressed air into the plug hole). If we lost over a certain percentage we
checked by listening at the exhaust and carb to see if we had “Excess” air
escaping past valves and in the radiator for air bubbles past a head gasket.