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Old August 4th, 2022, 10:58 AM   #29
Mauricemonge member
Name: Maurice
Location: San Francisco
Join Date: Sep 2018

Motorcycle(s): bastardized ninja 250 (think land speed record with a sidecar) soon to swap a 500 engine

Posts: 34
Originally Posted by InvisiBill View Post
For whatever it's worth, I ran into a lean spot around 6-7k when I put slipons on my EX500. It would actually sputter like I was running out of gas, even though it seemed fine elsewhere in the range and before the exhaust change.

I assumed that was just the leanest spot in the stock setup, and my change had leaned it out enough that it became noticeable. I switched to adjustable Factory Pro needles using the second slot, and it seemed to be a great fix.

One of the forum oldtimers stated that a lean spot there was indicative of the valves needing to be adjusted. However, I had never heard that mentioned previously, in many years of hanging out there, even though he made it sound like common knowledge. This doesn't seem too likely in your case, but it might be worth checking.
Someone recommended factory pro needles on the 500 forum too. I never checked my valve adjustment. It feels like it runs great with the ninja 250 needles, I may just leave it as is for now.

I do have a misfire at idle, but Iím pretty itís one of my coils since it followed it when I swapped them yesterday. Theyíve got over 100k miles on them so it might be time for a replacement set
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