Hey guys .......just ran the first 2 tanks through the SPE 40. I tuned the needles a little and she runs great..............low idle and a vary fast transition to wide open throttle. My question......while I removed the plug to put my cowl on I inspected the plug(just for fun) usually I don't unless she not running right.........what I found was a little strange half of the plugs ceramic was light tan.....looked good, but the other half of the ceramic black , almost a perfect line between the 2.

What do you plug readers think?.................appears to be late timing and the flame front dying out before complete burn ...but this is only my second gas airplane so what the heck do I know. The engine runs great, plenty of power, smooth mid range, smooth WOT, and a vary good idle. Should I would fiddle with it or run a Gal or 2 first.

Checklst,

There is no need to run a lot of fuel through a gas engine to break them in like you do on a glow engine. What prop are you using and what rpm's are you getting? Lean the High speed needle out to max rpm and back off 1/8" turn. Lean the low end needle until you loose a good transition and back off 1/8" turn. Go back to the high needle and repeat as before.

Thanks zippi I will run a gal or 2 in the air........................you are right no need for break in on the ground with these engines...............I set my needles after about 4 oz of fuel went through her, and the rings seated in just fine after the first few oz.........the compression on the second start after 4oz of fuel took me by suprise.....I really had to put some arm into the flip. I did not have her balanced her yet or I would have flown her on the first tank.

The engine is running great so I think all leave it alone, but I just thought the plug look strange with it's half black, half tan burn marks in the ceramic insulator.

Thanks again

Here's a good tuning guide for walbro carbs http://tech.flygsw.org/walbro_tuneup.htm
It has never failed to work for me yet works on chainsaws, weedwackers and blowers too
The float diaphragm adjusts for air pressure changes as the airplane go up and down in flight to keep the mixture correct
that's why you don't need to run them rich at all if your engine breaks into 4 cycle anytime during accelleration you are out of tune
while it won't hurt the engine it could be a bummer if your trying to punch out of trouble and intead of power you get blubber and hit the ground ouch
I know this to be true form years of cutting firewood out west we lived at 2000 feet where we tuned our saws and cut from 3000=5000 feet and the saws never missed a beat
that's the nice thing about a pumped engine that the float system you can tune for the best mixture setting and it shouldn't change if it does you have a problem that can be fixed
Take some time learn your carb and how it tunes soon you will be the one everybody comes to for help tuning their engine
rebuild kits are cheap so don't be afraid to get one and take a look inside just take your tie and keep it clean the only adjustment if needed is to the flaot lever there's a tool you can buy for a few bucks or you can eyeball it with a straight edge.