That's very good top speed for that big of a sprocket, none of m current engines will twist as high as yours is, My Kulana bike as it is right now will do 43-44 on the flat with a 36T rear sprocket, not sure what my rpms are at that speed.
base engine is a dax GenIV lower, ports just cleaned up nice, ramped piston on transfers and exhaust, 6cc Fred Head, Speed carby, exhaust is a small diameter pocket bike chamber being fed with some1" ID flex pipe that is actually to long for high rpm power I think, I think header pipe is about 13-14".
this engine maks good hill climbing power and runs comfortably smooth from idle to WOT and cruise speed in low 40's.
This same engine ran faster with a short home built basically straight through exhaust, it would hold a steady 45-46 mph on the flat and on a slight declining area of road it would stick the speedo on 48-49 mph and then level back down to 45-46 on the flat.
I wanted to quiet it down a little so I put the current exhaust on it and it knocked 2-3 mph off my max cruising speed but it is quieter.
Originally Posted by Davezilla
I've got mine up to the 41 to 42 mph range using a 44 tooth sprocket, but very true... it won't do it in stock trim because first off it lacks the power needed to get there, and it'll rev out somewhere around 7k rpm. I think the quickest I got mine with a stock engine and 44T sprocket was around 25 to maybe 28mph.
I'm running a modified KTM exhaust pipe, Fred head, and some pretty extensive porting so it can spin up to almost 10k rpm and still make plenty enough power up there. Mine does feel like it's reving out at 41mph, it gets there fairly quickly and ducking out of the wind or streaming behind a truck won't get it any faster, I did hit 42 once but I'm thinking that road may have been just slightly downhill and I was streaming behind a big truck, and it wouldn't budge over that speed on that road. On a perfectly flat road it'll hit 41 and that's all it'll give me with this gearing.