How Hard is it to modify the jet?

Randog707 · #1 (**permalink**) 11-27-2009, 07:55 PM

I hear people posting about modifying your jet,well what does it acually do?,and is it hard to do.what are the thing you need to modify it?....Thanks for you time guys....Randy

Nashville Kat · #2 (**permalink**) 11-27-2009, 08:35 PM

I ordered a jet with some other things, because it was just a dollar or two thrown in-

I'm very surprised at just how miniscule it is- I've put the kit on and reamed an alloy billet to be installed, and I might ream the ports on the ends, but haven't much fiddled with the carb- I may try to slightly enlarge this andput it on- but in no hurry, and it will have to be wth something very small and very little more opening- i'd like to remove theidlescrew- because it seems to leak gas there- and maybe the slightest little port on the slide would let it idle otherwise, but that's a risk.

The new NTS carb comiong out for the 66 motors claims a slightly larger jet, and justmay wait until I eventually get one of those.
Motorized Bicycle Carburetor

Randog707 · #3 (**permalink**) 11-27-2009, 08:47 PM

thanks Kat for the reply,I also wanted to let people know what I have on my MB,I have a 80cc raw kit with a ada proformance air filter,36t sprocket,ngk spark plug,everthing else is stock on the motor,engine is fully broken in. running 25:1 ratio.top speed 31mph.what else do I need to do to get a high top speed?

tyrslider · #4 (**permalink**) 11-28-2009, 12:36 AM

2 strokes wake up w/ an expansion chamber!

Nashville Kat · #5 (**permalink**) 11-28-2009, 12:42 AM

Speaking of Grandfathers, here's my Grandpap, the Original Wild Man! (circa mid-60's, Canonsburg, PA)

Randog707 · #6 (**permalink**) 11-28-2009, 01:46 AM

cool pic of grandpa,took my kids to the circus once,had a great time!!

EnFlaMEd · #7 (**permalink**) 11-28-2009, 02:48 AM

Modifying the jet size is easy. Simply drill it out if you need to richen your mixture or solder it closed and then redrill if you need a leaner mixture. Tools required: flat head screw driver, appropriately sized spanners and drill bits.

Buddy · #8 (**permalink**) 11-29-2009, 05:25 PM

Drilling a jet is a terrible idea. The swirls from the drill bit make the fuel swirl which actually slows movement through the jet and will just upset the mixture. Buy a new jet for a few dollars.

**Norman** · #9 (**permalink**) 11-29-2009, 05:40 PM

Gee it works for me. I haven't had any problem soldering them shut and re drilling to tune these engines lot cheaper than 120 mile trip(for me to go to a big enough town with a cycle shop) to try to find a jet that is the right size and will fit one of these carbs.
But if you want to not do it that is fine.

tyrslider · #10 (**permalink**) 11-29-2009, 06:19 PM

Larger hole more fluid the carb atomizes the mixture anyway. Done it it works! However, if you can buy an assortment of jet sizes for cheap why would you mess around w/ drilling them.
Beyond smoothing out ports and maybe an air filter, every mod will require rejetting for a truly tuned motor!

The only adjustment you get w/ most of these carbs is from 1/4-1/2 throttle by adjusting the needle. Idle circuit stays "about" the same on most motors independent of state of tune so not really missing anything there. But if you change something i.e. exhaust, air filter, port timing, compression etc and you need to adjust 1/2 to full throttle, i.e. the main jet, then you either find'em or drill'em. Cause if you don't you'll have one sticky piston!