Well, for starters, dropping in a stronger engine doesn't equate to a different top speed.

Let's assume the SW .26 is a big power upgrade over what you had, and produces a similar redline to the old motor (with 7-ports, it probably matches or betters the old red line):

>Acceleration should be noticably improved.

>Top speed, which is a product of the ability of the engine to hit redline and of the gear ratios, probably would look and feel identical.

To harness the new power (the SW .26 HAS to be a good upgrade) you need to consider two things right off the bat:

1. You probably need different gearing. Bigger pinion (cluthc bell) gears...or smaller spur gears...or some combo of both. Imagine pedalling a multispeed bike in first gear. Would getting The Hulk to do it make it any faster? No, the gear would waste all the power, especially a very short gear.

2. The SW .26 might blow through first gear so fast (in two feet!) that it spends it's time pulling through second, making it seem sluggish. Find out if you can adjust the tranny to shift later (often accomplished by tightening a specific grub screw internal to the tranny. Check the manual for the right one, if it exists).

Check out current set up: Start out with very very light throttle and then see if you can notice it shift when you build revs. Sometimes when the gears are very close in ratio, it is very difficult to hear any appreciable/audible drop in engine RPM (the 'shift' sound is the engine dropping RPM as the next gear engages).