I have a 1999 Whizzer Black Classic. Only has 400 miles on it. Ran great since new. Took restrictor out at about 350 miles. Ran fine. Now I get no top end all of a sudden. Bike only does like 25 miles per hour as opposed to 40. New plug. New gas. No broken or cracked lines. Cleaned every part of carb perfectly. Reassembled. Same problem. Starts easily. Tried every possible adjustment on carb. When ice cold, will reach top end for about 1/2 mile then go back to 25 mph. Even took off airfilter to make sure engine was getting enough air. Carb is tight, head it tight. I just am at a loss here. Any suggestions? Thanks in advance for any insight. Nick