NT Carb Help

I have a PK 80 from Ozark Cruisers. Has an NT type carb. I read somewhere that I should open up the stock muffler. I cant the tube inside of the muffler down to a nub. I drilled it out and put another hole in the bottom cap as well.

Now I have read that when I open up the muffler for less back pressure I should now allow more air to enter the carb?

I removed filter from carb and found a black dust like material in the bowl and on the back side of the carb itself. It easily washes off. I am guessing it comes from the air filter as this motor only has a couple or three gallons through it all on clean roads.

Should I wash the filter? Should I change it out? Should I replace with one that allows more air to enter?

Am also considering trying different sized jets.

The motor runs well, but rarely reaches top end. Usually you can feel the motor bag down, or lag perhaps at all throttle. Let off the throttle slightly and she picks up again. Seems to me its not getting enough gas? Maybe not enough Air?

When it gets really hot it seems to work better.

Advice?

Thx for reply. I do have a mug welder and acetylene torch. Will that work?

I know what 4 striking sounds like. This is not 4 stroking. The motor simply lags at full throttle and then picks up as I let off the throttle slightly

TheNecromancer13 said:

Sounds like you are 4 stroking at full throttle. You need to lean out the air/fuel mixture, either by moving the needle clip up higher, or using a smaller jet. As for the black stuff in the carb, do you have a fuel filter installed? Also the stock exhaust is a piece of **** in my opinion. If you or any of your friends own an acetylene welder, or are really good with tig, you could make your own expansion chamber. Otherwise buy a decent one (not the cheapest one, general rule of thumb, the bigger the better). Drilling holes in the stock exhaust gives you a minimal performance boost, when compared to how much more noise it makes.

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Played with the motor again today. I believe you may be onto something with the 4 striking. It goes from a nice Bzzzzzz sound to a Blaaaaatt sound.

BUT I moved clip from second to first notch and did not improve. Then noise was similar, but I think power was less.

Moved clip to third notch and power was definitely diminished. Looking at the plug after running with clip on the 2nd notch it looks about right to me. After running it with clip on the first notch the plug is not white, but it is VERY clean.

Did not bother looking with the 3 notch setting. Low power.

Will getting a smaller jet do something that moving the clip did not do?

This jet is not marked. I have no idea what size to go to?

BTW I am AT Sea Level in South Carolina.

ALSO: What should my plug gap be set at?


THANKS!

crassius said:

cut a small piece of plastic into a trapezoid and ziptie it to the seat post so that dirt from back tire is blocked from going into carb

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I do believe your right about the tire. Although I can not see where the tire is being rubbed down, the material looks just like it would be tire.

Is there any point in getting a different air filter or carburetor? Like a carb that has two needles on it so I can tune it properly?

P.S. I fly RC planes with gas motors. They have adjustable needles for the low and high end

OK, more info:

I messed with the needle as described above and stuck with the original position. Noticed that the head bolts were lose. Tightened them up. Took filter off carb and got a bit of improvement.

I had the carb on a short, aluminum billet intake. looked up in the hole into the head and noticed that the gasket was protruding into the hole. Took it apart to find that the gasket is made to fit the standard Z shaped intake. The aluminum intake has a much wider hole that appears to match the port on the head better. But the gasket was messing it up.

Took the aluminum intake off and replaced with stock using the same gasket. ZING! I got speed now! BIG difference. No more 4 stroking or gasping.

Question: should I leave it alone?
Should I get a gasket to properly fit the short, aluminum intake?
Should I just use permeated gasket sealer with no gasket?