Drilling out main jet?

[yammy225ttr]

I've read of ppl drilling out their jets. Since the size I need is on back-order. I was wondering what type of drill bit this would require?? and how do I convert jet size to the drill bit size??

thanks for any help

[XRIowa]

Just wait for the order is my advise

[MathProf]

I agree with XRIowa: Just wait.

You can't drill accurate enough to get the the size you back ordered.

If you're going to be around dirtbikes get used to the words "back order"

[CRFThumper]

It's not that hard to do.If you need a 165 and have a 160 and a 170 then its a piece of cake.You will need a set of SMALL bits mac.snap-on and others sell them.Find a bit that will go thru The 170 but will not go thru the 160 and then use that size bit!While it may or may not end up at a 165 it will be close!!We have had to do it many times!!

[Silver Surfer]

I agree with XRIowa: Just wait.

You can't drill accurate enough to get the the size you back ordered.

If you're going to be around dirtbikes get used to the words "back order"

EXACTLY. would make for a good experiment though...be sure to include pictures of your fouled plug and the black smoke coming from you pipe after you've overdrilled your jets.

[dirtsquirt101]

When I was riding my TTR125 I did the airbox mod and an exhaust mod. My father went to work and drilled out the main jet before I bought a 110. I popped it in and it ran absolutely perfect. I then through in a 110 and it made no difference, maybe even worse. I wouldn't bother, but it can work.

[yammy225ttr]

yeh im just gunna wait, hopefully it doesnt take too long to get in.

[miguelitro]

its doable and done frequently by dyno techs when the perfect jet size is unavailable.

the bits are expensive fragile and if you drop one god help you finding it

[RichieGoatGruff]

You should never drill out a jet. They have a radius on them that smooths flow. If you drill a jet it will never flow correctly...just wait for the right one. Did you order from Sudco or someone that buys from them?

[CRF50Racer]

Just wait or look around at other shops

[vetplus40]

yeh im just gunna wait, hopefully it doesnt take too long to get in.

Very good decision.

[hotwheels]

These jet drilling threads are getting like oil threads ! Drilling jets is easy and fun, you need two sets of drills, #1 to #59 and #60 to #80. Find the smallest drill that WON'T go thru the jet you want to enlarge or richen. Then clamp the drill in a vise, this is neccessary with the very small drills, then with your fingers twist the jet down onto the drill until the drill goes thru the jet. Next find a drill that just fits into the reccess (or counterbore) of the jet, and lightly dress off any burrs caused by the first drill, do both sides. Install the jet and go for a test ride. I've been drilling jets for years with great results, I've even filled a jet with solder and redrilled when I went too far. I won't go into jetting theory and all that rich/lean business, if you can't tell a lean running engine from a rich running engine you have no business running drills thru your jets.