Originally posted by astoch
I'd like to know what else you did to your bike as far as the carb.
Either of the needles I mentioned will help the infamous hiccup, easily the best eleven dollar improvement I ever made, and this should be even more significant at your colder temps and lower alt.
Of course, like Holeshot mentioned, a lot of that “hiccup” effect depends upon what you are used to. But I am convinced you can improve upon stock, especially the ‘00. First get the ’01 needle, and see what you think.
Next, the Flat CR has a tab cast into the body that you can drill and tap for a screw to limit/adjust the accelerator pump stoke, it was obviously designed and put there for this purpose. Take off the plastic pulley cover and look just above the throttle stop and you will see what I mean.
I cut the pump stroke on mine almost two thirds and loved the difference. I kept shortening it, throttle response kept improving. I eventually turned the pump off, re-jetted my bike, and then slowly increased the stroke from zero until I was happy with the throttle response (the screw is accessible with the carb on the bike, barely). With the modified pump I ended up a clip (or two) richer on the needle and up one size on the pilot.
I suspect the “redesigned” accelerator pump for the ’01 does less of the same thing, I tried to get the pump diaphragm when they first came out but couldn’t. It is only eleven dollars, so my best tip may be to order $22 of ’01 YZ parts, the stock needle and pump diaphragm. Especially if you’re not into drilling holes into your carb and just want to see if you can fix the hated hiccup for around twenty bucks.
Hope this helps.