possible carb issues

GoldenMotor.com

6ty_six

New Member
Oct 16, 2013
6
0
0
Illinois
Hello, I have the run of the mill black unmarked motor with NT carb and for some reason about a week ago fuel was pouring out of the intake and soon stopped since then I can hit about 50% speed at WOT just fine until it just stops gaining speed and makes a different sound. This will happen randomly sometimes it runs great sometimes it don't. Also blows whiteish blue smoke.
 

fatdaddy

New Member
May 4, 2011
1,516
4
0
San Jose, Ca.
Take off the float bowl, the round white float will be in the bowl.leave it there..slide out the pin that holds the brass float tang assembly to the carb. be carefull, the float needle just slides into a slot and may just fall off, Dont lose it. unhook the fuelline and blow it out from there. the needle valve is not seating properly, probably because of dirt and crap. when you put it together you can see how it works. the float pushes the needle valve up to close off fuel flow. for some reason the valve is NOT closing the flow. (Dirt and crap.) Then, get an inline filter!!!
fatdaddy.
 

6ty_six

New Member
Oct 16, 2013
6
0
0
Illinois
the float and bowl are both totally clean but after further research i know now it is four strokeing, and I'm not sure why. I have the inline filter and the tank is clean the plug says its not rich or lean just tan to choclate brown on the ngk plug (it says b4-L on it) i did notice a scratch on the inside of the cylinder about the width of a grain of sand and the full stroke of the piston
 

FMB42

New Member
Sep 27, 2013
107
0
0
Idaho
Did your engine run well before you had these problems?

If yes; exactly what, if anything, did you do to it before these problems began?

If not; then I suspect that your carb needs to be carefully checked out (see link below). Like others have said, it sounds like you might have a bad float or that the float level is mis-adjusted.

Also please tell us the pre-mix oil brand/type and ratio you're running.

im thinking about soldering and re-drilling the jet to a smaller size. Is this a bad idea or no?
I'd first consider lowering the carb needle jet by raising the "E" clip a notch at a time (the main jet more or less only comes into play at full or very near full throttle). But before you do that I recommend that you read through this very good NT carb install/rebuild/tune "how to" link (compliments of Norman):

http://motorbicycling.com/showthread.php?t=195

Good luck and keep us posted!
 

rustycase

Gutter Rider
May 26, 2011
2,746
5
0
Left coast
Just to re-state the above...

Your problem, at this stage, is not the jet size, it is the float mechanism.
..and they ARE fiddly ! Just a tiny bit of adjustment may make the difference between working properly, or not.
A good cleaning is most important.

Only difference I would say from the above is that I would BEGIN resolving this problem with an inline fuel filter.

Best
rc
 

6ty_six

New Member
Oct 16, 2013
6
0
0
Illinois
again as previously stated I do have a fuel filter and this is not in any way my first build. Just my first unsolved issue. I found a leak on the intake manifold and thread seal tape works wonders. it works a bit better but still 4 strokes at half speed. My NT carb is just a few degrees off level but it makes no difference pitching the bike from side to side. could a scratch in the cylinder wall cause this as well? its not too deep maybe a few thousandths of an inch deep and the full stroke of the piston.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
If the scratch is deep enough, it will cause a loss of compression which can cause symptoms like you describe. You may have a broken ring or piston pin circlip.
I would look for the cause and go from there. New top end is not too expensive.
 

6ty_six

New Member
Oct 16, 2013
6
0
0
Illinois
yes but if I remove the cylinder jug what do I replace the gasket with and can the head gasket be re-torqued? At least for inspection purposes.