Jetting?

bronco315 · #1 09-07-2009, 08:51 PM

Does anyone know what jets are in the grubee 60cc kits from factory? or what jets work well at 4500ft elevation?

stv1jzgte · #2 09-08-2009, 12:49 PM

Quote:

Originally Posted by bronco315

Does anyone know what jets are in the grubee 60cc kits from factory? or what jets work well at 4500ft elevation?

usually around 0.28" or 7mm factory, but im not sure about 4500ft up id think smaller.

freewheeling frank · #3 09-08-2009, 01:33 PM

my jets appeared to be about a #65 bit i soldered em up and took them down to a#80 and what a difference it made, my house sits at 7108 ft

bseelbach · #4 09-08-2009, 02:05 PM

Alright I'm a bit confused on the drill bit vs jet size vs hole diameter. I have read that stock jet is approximately #70 which is approximately 0.7mm= 0.028mm right? I also read that leaning it out makes it a bit smoother and might help my 4 stroking. So if i want to close the hole then I should use a smaller jet- perhaps a 65. So as jet size increases, the hole size increases? I take it this is the opposite since as drill sizes increase the hole is smaller (ex #70 is smaller than #65).

Appreciate the clarification as I am just confused.

freewheeling frank · #5 09-08-2009, 02:28 PM

ya higher the bit number the smaller the hole i bought my really tiny bits at hobby lobby by going to the #80 i totally got rid of the top end 4 stroking and increased response an acceleration all thru the band. you can google bit size versus bit number and you will find a chart

bseelbach · #6 09-08-2009, 02:32 PM

So bit diameter decreases as # increases. Are Jets the opposite and actually increase in size as the # increases. I want to buy a couple new (smaller) jets but just don't want to go in the wrong direction.

freewheeling frank · #7 09-08-2009, 02:50 PM

try this. wikipedia.org/wiki/drill_bit_sizes

Ghost0 · #8 09-08-2009, 03:26 PM

Yes jet size is jet size, a 65 jet is smaller than a 70 jet. But they do correspond to mm. A 65 jet is a .65mm jet and a 70 jet is .70mm.

Here is drill chart for reference.

bseelbach · #9 09-08-2009, 03:47 PM

Thanks for the clarification!

bronco315 · #10 09-08-2009, 06:42 PM

I guess its mostly trial and error. but at 3-4 bucks a piece its nice to have a jumping off point. I read another thread that said he went down to a #65 jet at 1200 and could have gone one more down so i guess im starting at #62. We will see, thanks for the help, I'll let you know how I make out. I also ordered a Dellorto carb 14-14. Any experiences with these?