- Joined
- Apr 28, 2015
- Messages
- 154
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I got a new toy tool. I picked up a relatively inexpensive Air Fuel Ratio meter on Amazon along with a small 12v battery to help me tune my MK3 after the engine rebuild. I could skip the 12v battery part if I was wired with a negative ground, which is a project for another day. I am using the MK3 crossover with a O2 sensor bung welded into it. Once tuned will ditch the cross over. I have plans to weld a bung to each of my pipes so I can tune in each individually.
Prior to the rebuild I had zero issues with the jetting that was supplied by JS Motorsport. However, after going with a larger cam (stage 2), and 9.6:1 compression, RH10 port conversion sleeves, and a more open exhaust, I had some need to refine the jetting. Changes were relatively minor.
Idle jet moved down from 68s to 60s. Needle jet went from a YY6 to a YY7, clip is 3rd position from bottom of the needle, I kept the 130 mains, and I moved the air jets one size leaner to 240s. Idle screw is roughly 1 turn out, and closer to 3/4 on the other side.
Idle sits roughly at 12.5 to 13:1. WOT is around 12.5:1, if not slightly richer. I have no throttle stutter coming off idle and the pull feels great.
This is probably the easiest way I have found to tuning a main jet without looking for the perfect road and looking over your shoulder constantly.
Prior to the rebuild I had zero issues with the jetting that was supplied by JS Motorsport. However, after going with a larger cam (stage 2), and 9.6:1 compression, RH10 port conversion sleeves, and a more open exhaust, I had some need to refine the jetting. Changes were relatively minor.
Idle jet moved down from 68s to 60s. Needle jet went from a YY6 to a YY7, clip is 3rd position from bottom of the needle, I kept the 130 mains, and I moved the air jets one size leaner to 240s. Idle screw is roughly 1 turn out, and closer to 3/4 on the other side.
Idle sits roughly at 12.5 to 13:1. WOT is around 12.5:1, if not slightly richer. I have no throttle stutter coming off idle and the pull feels great.
This is probably the easiest way I have found to tuning a main jet without looking for the perfect road and looking over your shoulder constantly.
![Tuning Keihin CR33 Carbs Tuning Keihin CR33 Carbs](https://i.imgur.com/ENhLKsC.jpg)