DIY....re-jetting a 6.5
- Thread starter cjtmini
- Start date
- Tags diy....re-jetting
Since this old thread came back up...
If you want to poke jets out in standard Keihin sizes, use metric drills. Keihin jet numbers refer to the orifice diameter in hundredths of a millimeter. For example, a #82 jet has a 0.82mm. Inch drills are close enough for baseball, but if you are buying a set of small drills just for modifying these jets, I would suggest metric.
If you want to poke jets out in standard Keihin sizes, use metric drills. Keihin jet numbers refer to the orifice diameter in hundredths of a millimeter. For example, a #82 jet has a 0.82mm. Inch drills are close enough for baseball, but if you are buying a set of small drills just for modifying these jets, I would suggest metric.
Look up a combination inch + metric drill chart and cross-reference the metric sizes to the standard inch sizes. Like I said, the inch drills will get you "close enough" for tuning a mower engine, but will not correlate to an exact Keihin size. I find it easier to help someone that can tell me they have a #90 jet instead of "I drilled it out with a #65 drill," Which equates to an odd half-size in the Keihin system.
Another thing to be aware of is that drills commonly make a hole slightly bigger than their measured diameter(especially using a hand drill and a vice). Keihin jet orifice diameters are very precise and I suspect that they use reamers to finish the the size.
I don't really recommend drilling jets anyway just from the aspect of potential confusion unless the jet can be marked. I have to engrave mine under a microscope.
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Another thing to be aware of is that drills commonly make a hole slightly bigger than their measured diameter(especially using a hand drill and a vice). Keihin jet orifice diameters are very precise and I suspect that they use reamers to finish the the size.
I don't really recommend drilling jets anyway just from the aspect of potential confusion unless the jet can be marked. I have to engrave mine under a microscope.
ut:
This tutorial is exactly what I wanted to know, THANKS!
If anybody finds it useful, I find it easier to sometimes use an X-acto knife tool to hold small drill bits such as these. I posted a pic of the tool that I use. I can spin the tool in my fingers as I gently drill.
Another easy method of removing the idle screw cover is to simply squeeze the sides of the screw head with needle-nose pliers and the cover pops off.
If anybody finds it useful, I find it easier to sometimes use an X-acto knife tool to hold small drill bits such as these. I posted a pic of the tool that I use. I can spin the tool in my fingers as I gently drill.
Another easy method of removing the idle screw cover is to simply squeeze the sides of the screw head with needle-nose pliers and the cover pops off.
I just did this and it made an amazing difference. It runs so much smoother now and pick up is right off the line, no more bawg down after off throttle.
I just had one thing I did differently, I used a #70 drill bit for my idle jet. The #77 just wiggled around and had tons of space around it already, so it wasn't going to do anything. The kit I bought said the #70 bit is .028" and it worked really good.
Another side note I upgraded to a 140 emulsion tube during this process. If you think your 6.5 clone swap can't get any better, you are wrong! Do this and it will.
I just had one thing I did differently, I used a #70 drill bit for my idle jet. The #77 just wiggled around and had tons of space around it already, so it wasn't going to do anything. The kit I bought said the #70 bit is .028" and it worked really good.
Another side note I upgraded to a 140 emulsion tube during this process. If you think your 6.5 clone swap can't get any better, you are wrong! Do this and it will.
I did this to my 6.5 also and I also had an idle jet that was larger than #77 drill. I didnt change it, only the main jet and after things did seem better. I noticed that the idle "jet" is exposed to air. So isnt this an air bleed? Opening this would have the effect of leaning the idle mixture wouldnt it? I am far from a carb expert but what is correct here? Or isn't exposed? Once I saw it was already bigger I just put it back in.
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