2 Daytona's why is one faster

whisnantrider · 10-05-2009, 02:40 AM

I have two 95 Daytona's one has a new SBT 644 motor while the other is an older rebuilt 639. The 644 out accelerates the 639 but the 639 is faster on the top end by I'm guessing about 5mph. It strongly and consistently pulls away from the 644. Is it just the different motors maybe? Carbs? The 644 runs much smooter than the 639 and has an aluminum prop instead of a stainless but these are the only differences that I am aware of. I guess its not really a big deal just kindda bugs me.
Thanks

donwkk · 10-05-2009, 05:45 AM

Sounds like different impeller pitch to me - one impeller is pitched for low end and the other is pitched for top end. If it bugs you enough just swap the impellers or pumps.

dank · 10-05-2009, 01:14 PM

Hard to tell without a tach but if they are doing the RPM then the impeller/pump pitch/wear would be the difference.

whisnantrider · 10-05-2009, 06:49 PM

Does it say the pitch on the impeller? What is the best impeller and pitch for all around performance? This winter I plan on tearing them down, painting, adding decals, mirrors, fixing a few things and replacing anything that looks worn. I might just replace the impeller depending on the cost.

Thanks again guys

dank · 10-05-2009, 11:15 PM

No, If it is stock it may have the OEM part number but you won't know the pitch. Contact Impros about the best one for the model.