If your worried about Stock vs aftermarket needles, You can use a drill gauge to compare taper. Bob Wessner used my suggestion when comparing 750 needles. Interesting result, as the aftermarket was pretty different.
It seems a lot of people are under the (mistaken) impression that Keyster only makes one carb rebuild set for both the 550K and 550F. It appears that Keyster does in fact manufacture different sets with different needles for the CB550Ks vs. CB550Fs. That means there were actually different stock (KeiHin) needles as well, and our buddy Harry-the-Keyster-Man's note bears this out (see earlier in the thread).
I'm not convinced that the Keyster-woes so often reported are actually intrinsic to the quality of Keyster's needles. Someone complaining about the quality/performance of Keyster needles might not have been fully informed about differences between Keyster kits for the 550K vs. 550F. That is, assuming they were told there are two different kits, let alone that the two kits have different needles and not just different Main Jets.
But ultimately, I'm not so much concerned about the presence of differences between stock vs. aftermarket (read here Keyster) needle taper, so much as whether those very differences might actually come in handy for ultra-fine tuning.
In other words:
Keyster Needle Size: #D274, which is intended to replicate the Stock KeiHin Needle #273004 for a CB550F (which came with a slightly narrower needle taper than the K for greater fuel flow) might actually provide
too much fuel mid-range on a bike with a non-stock (less restrictive) air intake (pods).
In which case, Keyster's Needle #D26, the intended aftermarket replacement for KeiHin's Needle #272304 from the CB550K's carbs, might actually be a
better choice (performance wise) despite the fact that it's not the intended aftermarket part for the CB550F.
Crap. I think I pulled something in my brain.
