Even though the 650 was completely put back together I had still been having problems with it breaking up at 4k rpm. Idle was smooth and acceleration was great right up to 4000 rpm then all of a sudden it would start to choke and stutter.
I consulted the carb bible linked from the xs650 proboards vault and determined that the main jet must be too large, thus causing an over rich scenario as the main just started to flow. This was not a huge surprise as I had rejetted my carbs with a kit from 650Central.com. The kit installed 145 main jets when I had 132.5 mains from the factory. I ordered a few more jet sizes in between 132.5 and 145 so I had some wiggle room.
As long as I was doing the jets I decided now would be the best time to replace those cheapo pod air filters I got from MikesXS. The air filters were cheap. That is the only positive thing I have to say about them. The fit is not great and the noise when at full throttle sounds more like a chainsaw. I was not a big fan as soon as I went for my first ride with them. I finally bit the bullet and just bought a set of name brand K&N air filters, RC-0982.
I fitted them to the bike and decided to take it for a ride before I did any rejetting. I wanted to see if the problem was any worse or better with the new air filters. To my delight the problem was completely gone! The acceleration is smooth all the way up to red-line. I went for an hour ride trying all combinations of throttle at various gears and speeds. It worked great. There is a slight increase in power at 6K rpm, which makes me think I might be able to slightly richer on the midrange but its not worth the effort to me.
The sound of the engine is also much nicer with these filters. The chainsaw noise is dramatically reduced, although not completely eliminated.
I just wish I had forked up the money for these originally. I would have saved myself a considerable amount of time troubleshooting. That just goes to show you get what you pay for, and sometimes even less than that when it comes to mikesxs stuff. Not that the pod air filters didnt work, just that they didnt flow nearly as much air as the K and N filters.
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| pod style air filters from mikesxs, will be replaced |
| was planning on replacing 145 main with 142 but didnt have to after installing filters |