jetting trick

[deerfield]

Something I do when jetting bikes is i'll buy one jet for each carb and drill it out with number drills. by keeping detailed notes of each change, when i get to rich you only have to drill out the orignial jet to the new size. Keep you notes for future reference ,it will give you a starting point for future changes. jets get expensive when your doing 4cyl bikes, so I thought this might help someone. it's worked for me for years,maybe not worth it on a single cyl.

 

[sheeblast]

dont see how drilling out jets will be cheaper than just buying the proper size jets.
because you still have to buy the jets to drill out, then you have the time drilling them out.
it is cheaper and easier to just buy the proper size jets.

 

[OConnor Racing]

Jets are sold by flow numbers, not the size of the hole. In other words, two jets that both have a hole size of .015 will not flow the same. This is how Mikuni figures what size a jet is. They flow test it. I'm sure the aftermarket jets you can buy don't do this.

 

[Awk08]

awsome little known fact about jet sizing...flow tests !!!!!!

 

[slickerthanyou]

Have to say, i won't be tryin that. Probably cost more for the drill bit than the jet.

 

[YZ Otis]

Been drillin jets for years. soldered'em up & drilled'em in a pinch. With a little pin vise ya could twist through that solder in a jiffy. Never worried bout flow tests, just plug chops. Even if we coulda come up with the money for a good jet selection we prolly woulda bought a tire instead .... LOL ... be surprised how many peeps wanted to drill a soldered jet for the main event ... lean is mean ... almost always a bad idea ... ... ya do goofy stuff when yur underfunded & uninformed ... LOL ... Don't know bout multi cylinder cuz wobblin the drill a bit would richen'em up.

Now that I'm a member at blasterforum I'm well informed and still do dumb stuff
>>> Buy OEM jets!

 

[sicivicdude]

Well, the idea is sound. Instead of having to buy 10 jets to try you would only have to buy two of the smallest diameter holes you can find and drill one until you overshoot your jetting mark and then drill the other one one step smaller than the first.

The problem is, if you change elevation or seasons or you sell your bike/quad you nor anything else knows what friggin size jet you're running! You can't "go up two numbers" in the winter to compensate for the air density changing because you have no clue what number you're at right now.

If you sell the quad the jet in the carburetor says 130 but in reality the hole size/flow amount is like a 155 jet. Some goes to "go up two numbers" and puts a 132 in the carb and they've dropped 23 numbers not went up by 2...

 

[royalt67]

Even so, I did this on a 90 once that I couldn't just go out and buy jets for (had to order). A set of tiny little drills was 10 bucks. Worked great.

 

[deerfield]

Use to do it years ago on old streetbikes and dirtbikes when stuff was hard to find. Probly not as valid today,but was common around here at one time.