Hi sohcers,
I've done this to my engine -->
http://www.sohc4.net/?p=333 , which is mating the top end of a 650 onto 550 bottom, effectively stroking the engine to get some displacement less than 626cc.
Long story short, I've got my jetting to a tee with my stock 77' CB550 airbox, carbs, and a uni foam filter that fits in the same spot as the stock one. The only exception to this is 0 throttle idle, where the mixture is incredibly rich. This got me thinking after ensuring that the timing is on point, fiddling with the idle mixture screws throughout their entire working range, and syncing the carbs after getting the mixture screws the best I could.
I've narrowed down my problem to the following possibilities:
1. Idle mixture screw seals need to be replaced because they are possibly not responding to my adjustment
2. My advance mechanism for my ignition timing isn't working at low rpm, the springs aren't incredibly tight
3. Leaky rubber boots leading to carbs? Probably not significantly
4. The stock airbox/filter has a larger pressure drop than the less restrictive uni filter, maybe this is a problem similar to pod peoples'
5. My pilot jet is too small, which for me is counter-intuitive if I went up in main jet size and displacement.
I don't know much about how the fuel to air mixture ratio changes, but I know it does throughout the throttle's working range. Is it possible that I would need a smaller pilot jet?
What do y'all think?
