Great video , I for one appreciate all the effort that goes into creating this data . Any idea what the Density Altitude or Adjusted Altitude would of been on that particular day ? Which app are you using for jet selection ? and would you consider it accurate ?
Unfortunately, I don’t know what the density was. I use an iOS app called “Jetting CR125 Shifter Kart”. The app seems well designed. It can pull in local weather data and has a setting for how long the straights are on the track.
Awesome video, my shifter seized up right after I got it on my second track day. I think it was jetted too lean to get the most performance out of it. It’s getting rebuilt right now and I want to get time and reliability out of it. It looks like going with a rich safe tune in the carb won’t cost me a ton of time. Seat time is what will benefit me more than a marginal HP gain from ragged edge jetting. Thanks for the vid. Also if you don’t mind me asking what oil ratio do you run in the shifter? I ran 32:1 in all my dirt bikes and never had any issue but someone recommended me running 20:1 on the kart since it’s under so much load from the added grip of pavement and always revving high. I thought that seemed like a lot of oil but I’m probably going to give it a go.
My lifan cd 70cc byke had 72 main jet i up it to 80 85. put a con filter and a 2 tooth up front sprocket. before it did 85km/h gps than it did 90 kmph gps i did same with my ybr 125 i up it from 120 main jet to 150 but no difference it has a cv carb
Interesting question. According to my iphone jetting app, 165 would have been way too lean considering the atmospheric conditions. My original plan was to do 5 jets, so I stuck to the plan. Next time, I hope to have the EGT sensor in place. The EGT readings will give me a little more confidence to go leaner.
For kart racing, you’re never off the pipe. If you’re getting in situations where you’re off the pipe, you’re not driving correctly. Two benefits: 1. No need to worry about the valve getting stuck shut. 2. You can make that area of the exhaust runner nice a smooth. These aren’t big advantages, but plugged valves are quite common.
Thank you
Great video , I for one appreciate all the effort that goes into creating this data . Any idea what the Density Altitude or Adjusted Altitude would of been on that particular day ? Which app are you using for jet selection ? and would you consider it accurate ?
Unfortunately, I don’t know what the density was. I use an iOS app called “Jetting CR125 Shifter Kart”. The app seems well designed. It can pull in local weather data and has a setting for how long the straights are on the track.
Awesome video, my shifter seized up right after I got it on my second track day. I think it was jetted too lean to get the most performance out of it. It’s getting rebuilt right now and I want to get time and reliability out of it. It looks like going with a rich safe tune in the carb won’t cost me a ton of time. Seat time is what will benefit me more than a marginal HP gain from ragged edge jetting. Thanks for the vid.
Also if you don’t mind me asking what oil ratio do you run in the shifter? I ran 32:1 in all my dirt bikes and never had any issue but someone recommended me running 20:1 on the kart since it’s under so much load from the added grip of pavement and always revving high. I thought that seemed like a lot of oil but I’m probably going to give it a go.
Thank you 🙏 for excellent explanation very professional. Regards
Also why the race fuel if the compression isnt high, wouldnt that decrease power? Isnt premium 91 enough
My lifan cd 70cc byke had 72 main jet i up it to 80 85. put a con filter and a 2 tooth up front sprocket. before it did 85km/h gps than it did 90 kmph gps
i did same with my ybr 125 i up it from 120 main jet to 150 but no difference it has a cv carb
Since the 168 had a considerable jump. Do you think 165 would be relatively higher or more matching the 168?
Interesting question. According to my iphone jetting app, 165 would have been way too lean considering the atmospheric conditions. My original plan was to do 5 jets, so I stuck to the plan. Next time, I hope to have the EGT sensor in place. The EGT readings will give me a little more confidence to go leaner.
Why plug the powervalves? Any benefits downsides?
For kart racing, you’re never off the pipe. If you’re getting in situations where you’re off the pipe, you’re not driving correctly.
Two benefits:
1. No need to worry about the valve getting stuck shut.
2. You can make that area of the exhaust runner nice a smooth.
These aren’t big advantages, but plugged valves are quite common.