Needle Size?

I bought a rebuild kit and the needle that came with it says Y63 on it. The needle that came out of the carbs sayd 5CL10 on it. Which one of there is the correct size or are these the same. I have been having trouble getting the bike to run right arter puting in the new needle so I was wondering if this could be the problem. Also what position should the clip be in if the jet size it came with is a #90. BTW the bike is a 78 KZ650 B2A.

Time for some common sense! Let's think our way through this issue... VM24 came in a ZILLION different configurations. OK, that being said, do you have a Kaw Factory Service Manual? What main jets are supposed to be in your bike? The version of the VM24 that used the #90s was about the leanest and puniest of any of them. I would not hesitate to use #102.5 main jets regardless of the configuration of VM24... The #90 version usually uses a #50 barrel jet over the pilot jet (#15). The jet needle with the Y63 MAY NOT BE THE SAME AS YOURS... the Y63 is a Keyster badge number. Unfortunately, the VM24 comes with a bunch of jet needles as well. Look at your old jet needles and the new ones. Are they the same? Length and taper? You can measure both using a micrometer if they are the same length to ensure they are the same or just eyeball them. If you use a micrometer, mark 10mm points on the jet needles (at the same place on each) and measure their diameter at each 10mm point.

Sounds like the kits you used MAY not be for your exact model of VM24 if the mains are wrong and the jet needles different. The other parts should work just fine.