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Drilling Your Carburetor Jets to Change Size Print E-mail

Carburetor Jet Tips

12/1/00 Courtney Hook
For those of you who don't know it, you can drill your jets out for larger sizes instead of spending big bucks to acquire a vast selection. You can also solder the ends closed and redrill them smaller if you are so inclined. Of course, the millionaires among you will scoff at this, so please ignore. Those of you however like me who have more time than money can read on. :-)

After some surfing I've calculated that you can use the following drill bits to come close to the sizes needed, or actually be bang on with many of them. So here goes. Remember that a jet marked 120 is 1.20mm in size, 135 is 1.35mm etc. Perhaps those who know more accurately can correct me if I'm way out on this, but I think I'm close.

  50    #76
  55    #74 approx.    
  60    #73
  65    #71 approx.
  70    #70
  75    #69 approx.
  80    #68
  85    #66 approx.
  90    #65
  95    #63
100    #61
105    #59
110    #57
120    3/64th's
130    #55
140    #54
150    #53
160    1/16th's
165    #52 approx.
170    #51
180    #50
185    #49
195    #48
200    #47
205    #46
210    #45
220    #44
225    #43
230    #43 approx (close to 225)
245    #41
250    #40

12/5/00 Carl Bennett
Not to be a wet blanket here on everybody's enthusiasm but, before you go drilling out your extra jets there maybe a problem doing it this way. A drill will leave a spiraling grove that will cause the matter passing through that to swirl. My understanding on the carbs is that this could disrupt the normal flow. Look at the smoothness of the present jet hole and compare it to any drilled hole. How much this would effect overall operation would be anyone guess and would greatly depend on the accuracy of the hole and sharpness of the drill bit among other things. Also, are the jet holes bored or are they drilled? My bet would be towards a mill vise a drill press.

I am not saying that drilling is wrong but I have heard this from quite a few mechanics that have much more experience in this than I reccommend against it for those reasons.


12/5/00 John Dean
Both natural gas and gasoline are fluids and drilling out orifices is a common practice in the HVAC bizziness that I'm in. Actually if it swirled a little bit that would help atomize the fuel, it vaporizes when it enters the combustion chamber anyway.


12/5/00 Maans "Smitty" Smit
XS main jets are exactly the same as that for a 1600 Beetle Solex carb (old Beetles, dunno bout the new ones). Over here (South Africa) Yamaha charged me R33 /$4,25 each while the general carb shop down the road charges me R8,50 /$1,10 each for the Beetle main jets. Go figure.


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