As promised, my write up on how to rejet the stock
Cag carb for those who are not a fan of the adjustable jet kit like me.
Most stock jets out there are roughly a 62-63 jet size although there are reports of size 60 and 68 jets, I have never came across one yet myself. The
Adjustable Jet Kit comes with a jet size of 68 or 70.
Method One (limited):
Easiest way to rejet is to drill the jet larger using
Wire Gauge drill bits which can usually be found at your local hobby store. They are numbered #1-#80. You'll only need the #60s-70s range for rejetting. The
Wire Gauge number is
NOT the actual jet size. Minimoto/pocketbike jets are measured in one hundreths of a millimeter, for example, a 66 jet has a 0.66mm hole diameter.
Below is a chart showing which
Wire Gauge # drill bit to use for specific jet sizes. As you can see, you are only limited to a certain amount of jet sizes. Although you may never need to jet higher than the 70 range, I included larger sizes anyways.
Note: Wire Gauge drill bits are for precision use and are very very small which will break easily if not careful. Be sure to drill at the lowest speed setting possible. Sometimes it may be easier to drill using them by hand speed using a drill pin vise (X-Acto No.73220). Remember, always go up only one size and test, once you drill there's no going back.
Wire Gauge #= inch = mm = jet size #73 = .0240 = .6096 = 61 #72 = .0250 = .6350 = 64 #71 = .0260 = .6604 = 66 #70 = .0280 = .7112 = 71 #69 = .0295 = .7493 = 75 #68 = .0310 = .7874 = 79 #67 = .0320 = .8128 = 81 #66 = .0330 = .8382 = 84 #65 = .0350 = .8890 = 89 #64 = .0360 = .9144 = 91 #63 = .0370 = .9398 = 94 #62 = .0380 = .9652 = 97 #61 = .0390 = .9906 = 99 #60 = .0400 = 1.016 = 102 Method Two (preferred):
This method is the best and is what I use since rejetting/drilling with
Wire Gauge bits limits you to only a few sizes. This will allow you to use Dell'Orto jets (SHA/PHBG) and will give you a wide range of jet sizes (even and odd number jet sizes).
First remove the atomizer (long brass tube) from the carb using a wrench and remove the jet from the atomizer using a flat head screwdriver. The stock jet will no longer and can not be used after the modification to the atomizer. You will need to drill out the threads/hole where the stock jet screws into the atomizer using a 11/64 drill bit. Place the atomizer in a vise or use vise grips to hold it (don't attempt to hold with with your hand). You must be fairly precise here when drilling since there is not much room for error. I recommend using a 5/32 drill bit first followed by the 11/64 drill bit. Be sure not to drill the hole any deeper than it already is and as straight as possible. Next use a M5 x 0.75mm tap (bottoming or plug style) to rethread the hole. Be sure to drive the tap in as straight as possible. Don't force the tap in any further when you feel resistance, brass is very soft. Remove the tap and check to see if you have rethreaded pretty much most of the hole. Clean as necessary and test fit a Dell'Orto jet.
Note: The Dell'Orto jet may not screw completely in and seat as the stock one did so do not force it once it gets tight. This is perfectly fine.
These instructions are very simple and should be clear enough to understand easily. If you do not understand them, my suggestion is to have some one else do the work for you who does understand. I am not liable for any damage you might do, mod at your own risk.
PS. I can also do the work to the atomizer (to accept the Dell'Orto jets) if anyone would like it done. Please PM me if interested.
