New Rider
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Post by rsw1158 on Apr 24, 2014 17:47:19 GMT -5
I have a 2013 Jonway YY250TT scooter with the CF250 engine. The scooter is popping through the carb when it is running at 4000 rpms to 5000 rpms. It also won't hold steady at thoughs rpms and will actually surge with bigger than a 138 main jet is installed. I have been trying different jet combinations to see if I can clear it up but it will only get worse but not go away with the different jets. I don't find any air leaks at the intake or carb area but I do have a small leak at the exhaust flange I can't stop. I even tried a different cab but it still does it. I also noticed that I have very little response at my air fuel mix screw. I can turn it all the way in and it will still idle great no matter what size jet I put into it. It has always done this with the air mix screw ever since I found a tool that could get to it and that was about a 1000 miles ago or so. I've have 112 to 144 mains in it to test different combinations. Do I have a valve problems or what is going on? I have 3300 miles on it. All highway miles.
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Freshman Rider
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Joined: Apr 8, 2014 13:17:56 GMT -5
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Post by bashan on Apr 24, 2014 23:11:11 GMT -5
I have a CF 250....you have to get that exhaust leak off of the table. These engines are funny in that they have reflux into the combustion chamber from the exhaust. This is because Honda detuned them so they would last forever...and they do. The CFs will last about as long with some TLC. People think that the exhaust just continually pushes out..it does not. There are pressure waves that set up in an engine and there are actually negative pressure troughs that will pull atmosphere back into the engine through the exhaust port. That is how a PAIR unit works, pressure waves. So Honda overlapped the cam a bunch which makes for a loping mild mannered engine. It also lets the screen door open for bugs to come in. Fix the leak. Next, set your valves. The Honda people have a specific gap but all of the mechanics use the push the adjuster up against the mechanism while it's running. It's fun! I'm sure Jack has that video from Mike at BPNW somewhere on this site. Kissy wissy Jack. :-*Rich
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Post by alleyoop on Apr 24, 2014 23:21:52 GMT -5
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..BAD TO THE BONE..