banshee400nut Posted May 20, 2011 Report Share Posted May 20, 2011 Just got done building the new shee. Took it to get dyno tuned. When it hits 7000 rpm it spikes off the chart lean. Both cylinders react exactly the same. Pressure tested system, found it to hold 6psi for 30min. I'm running 33mm pwk's and installed 230 mains to see if it would change, didn't even bog, same results. Is it possible the floats need adjusted? I don't know what else would affect both cylinders the exact same. These are brand new carbs right out of the box with cel needles. Mods: Stock cylinders/trail ported/bored .30 FAST cool head/ 19cc domes Ported cases Vforce 3 reeds Boss intake 33mm pwk's Toomey t5 Timing advanced +4 Any advice would be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
Phelps Posted May 20, 2011 Report Share Posted May 20, 2011 Just got done building the new shee. Took it to get dyno tuned. When it hits 7000 rpm it spikes off the chart lean. Both cylinders react exactly the same. Pressure tested system, found it to hold 6psi for 30min. I'm running 33mm pwk's and installed 230 mains to see if it would change, didn't even bog, same results. Is it possible the floats need adjusted? I don't know what else would affect both cylinders the exact same. These are brand new carbs right out of the box with cel needles. Mods: Stock cylinders/trail ported/bored .30 FAST cool head/ 19cc domes Ported cases Vforce 3 reeds Boss intake 33mm pwk's Toomey t5 Timing advanced +4 Any advice would be greatly appreciated. keep going up on jet sizes until it goes away Quote Link to comment Share on other sites More sharing options...
J.J. Posted May 20, 2011 Report Share Posted May 20, 2011 I run 148's on a similar set-up. Sounds like you're running out of fuel; check float heights, pet-cock screen and fuel tank cap vent Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted May 20, 2011 Report Share Posted May 20, 2011 I didnt think you could accuratly use a O2 meter on a 2 stroke due to the fact that unburnt fuel and air blows out the exhaust port. Yea the pipe's job is to create a pressure wave to force it back in but it isnt 100% efficent. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted May 20, 2011 Report Share Posted May 20, 2011 Just got done building the new shee. Took it to get dyno tuned. When it hits 7000 rpm it spikes off the chart lean. Both cylinders react exactly the same. Pressure tested system, found it to hold 6psi for 30min. I'm running 33mm pwk's and installed 230 mains to see if it would change, didn't even bog, same results. Is it possible the floats need adjusted? I don't know what else would affect both cylinders the exact same. These are brand new carbs right out of the box with cel needles. Mods: Stock cylinders/trail ported/bored .30 FAST cool head/ 19cc domes Ported cases Vforce 3 reeds Boss intake 33mm pwk's Toomey t5 Timing advanced +4 Any advice would be greatly appreciated. What does the dyno graph look like at 7000 rpm? Quote Link to comment Share on other sites More sharing options...
Coupelx Posted May 20, 2011 Report Share Posted May 20, 2011 I didnt think you could accuratly use a O2 meter on a 2 stroke due to the fact that unburnt fuel and air blows out the exhaust port. Yea the pipe's job is to create a pressure wave to force it back in but it isnt 100% efficent. good question. the unburnt oxygen would lean out the reading from the WBO2 even if the actual AFR is correct. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted May 20, 2011 Report Share Posted May 20, 2011 good question. the unburnt oxygen would lean out the reading from the WBO2 even if the actual AFR is correct. That and the oil would massivly foul the o2 sensor. Quote Link to comment Share on other sites More sharing options...
banshee400nut Posted May 21, 2011 Author Report Share Posted May 21, 2011 As far as the fuel petcock goes, I replaced it with a bigger dual out style using 5/16 line to each carb. It weird cause it just kept pulling strong on the dyno. From past experience if it were going that lean it would lose power and backfire. I have considered that the 2stroke exhaust is messing with the 02 sensor but the guy running the dyno says he's done a lot of them on there. As far as what the curve does after 7 grand we don't know. As soon as it went lean he would back out of it. It made 59 HP up to that point. I have not ridden it to see how it rides mainly cause I'm paranoid. I might just have to suck it up and do a good ole fashion plug chop and see where I'm at. Has anyone had to adjust the floats on there new pwk's before install? Quote Link to comment Share on other sites More sharing options...
Coupelx Posted May 21, 2011 Report Share Posted May 21, 2011 That and the oil would massivly foul the o2 sensor. theres ways to prolong the live of the sensor, mainly an extended bung. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted May 21, 2011 Report Share Posted May 21, 2011 Yea I have seen those, and a heat sink that moves the o2 sensor out from the exhaust. Does the O2 sensor on dyno's have a shield over the tip to keep it from getting directly sprayed? Quote Link to comment Share on other sites More sharing options...
banshee400nut Posted May 21, 2011 Author Report Share Posted May 21, 2011 Yea I have seen those, and a heat sink that moves the o2 sensor out from the exhaust. Does the O2 sensor on dyno's have a shield over the tip to keep it from getting directly sprayed? The sensor is mounted under the dyno in a box. He has a hose with a metal wand that he sticks down the exhaust. The sensor is not directly put in the exhaust. Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted May 23, 2011 Report Share Posted May 23, 2011 I'm running 33mm pwk's and installed 230 mains. Keihin 33 PWK´s and 230 mains? Are you 100% sure that you are not using Mikuni main jets? ...just asking. -Pasi S. Quote Link to comment Share on other sites More sharing options...
banshee400nut Posted May 24, 2011 Author Report Share Posted May 24, 2011 We just put the biggest jet he had trying to get it not to go lean. We took them back out. I know that they would be too big. My 421 cub has 176 mains with the same carbs. I figured with 230 mains we could get it to stumble and fall off the power and we would go down from there. But it still pulled and went lean on the chart. Gonna play with it this weekend. Quote Link to comment Share on other sites More sharing options...
banshee400nut Posted May 25, 2011 Author Report Share Posted May 25, 2011 Held 6psi for 35 minutes. Came back two days later and it still had 2 psi on the gauge. Quote Link to comment Share on other sites More sharing options...
banshee400nut Posted May 26, 2011 Author Report Share Posted May 26, 2011 Hopefully I will have time this weekend to check those things. Is there anything special that needs to be done to the pwk's before they can be fitted on the banshee? Besides the jets and needles. Quote Link to comment Share on other sites More sharing options...
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