about main jets for the NTs & clones
- Thread starter crassius
- Start date
Crassius,
The numbers I see posted referring to jet size are all arbitrary at best. Like you I have yet to see a designation on a jet. I use a small drill bit index and solder and drill my jets to coincide with bit diamater. Example: At my altitude of about 6000' above sea level I use a drill bit that is .0225 in diameter after soldering the jets closed using NT carburetors. That's pretty small but at this altitude we need to go lean because of the thin atmosphere. Sea level folks will need a bigger drill bit.
I'm not sure where people get jet sizes and what those sizes are actually supposed mean in jet orifice size. They don't reflect numbered drill bits and they are nebulous as far as I'm concerned.
Tom
The numbers I see posted referring to jet size are all arbitrary at best. Like you I have yet to see a designation on a jet. I use a small drill bit index and solder and drill my jets to coincide with bit diamater. Example: At my altitude of about 6000' above sea level I use a drill bit that is .0225 in diameter after soldering the jets closed using NT carburetors. That's pretty small but at this altitude we need to go lean because of the thin atmosphere. Sea level folks will need a bigger drill bit.
I'm not sure where people get jet sizes and what those sizes are actually supposed mean in jet orifice size. They don't reflect numbered drill bits and they are nebulous as far as I'm concerned.
Tom
I've been drilling at .025in which is .635mm, then playing with the float level a bit. A .026in would be at .066mm, but not sure if the numbered jets are that size. I don't have a measurement of jets that come with the carbs, but suspect it is around .68mm to .70mm.
Just seems something that would be good to know.
Just seems something that would be good to know.
The jets we sell are marked and are in mm. So a 68 jet is .68 mm and the stock jet on an NT carb is .70.
thank you so much - have been assuming that to be the case, but it is good to know I'm on right track
been looking at diffs in motors, and why the needed jet size is so diff - finding a correlation between cold compression value & jet size
the higher the compression, the larger the jet needed
been looking at diffs in motors, and why the needed jet size is so diff - finding a correlation between cold compression value & jet size
the higher the compression, the larger the jet needed
The only thing I know about Jet sizes is SBP sells what I need for my cold weather climate @ 65ft above sea level. I have their sizing figured out and it makes sense. Low # = smaller jet hole. When running pit bike pipes and NT carbs jet needed is a 62 or 63. Seems small but I get the best throttle range with this size. Running the non EPA stock muffler the stock 70 seems about right. Although I like the quiet- I avoid the EPA mufflers cause they do restrict low end tourqe. My perception that's all.
Also meant to say the Dax clone runs excellent with a 62 jet from SBP. This bike also runs an EXP ch from pit bike motor with a screw in small engine muffler welded on to the end.