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Old 01-18-2015, 07:25 PM
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mapbike mapbike is offline
Motorized Bicycle Elite Member
Join Date: Mar 2010
Location: Central Texas
Posts: 5,379
Default Re: what did you do to your motorized bicycle today?

put another 15 miles on the "Half Breed" running a little better business no where near what I expected from what I was told to expect from it, but we all know these engines are a rap shoot and you may get one thats a good solid runner and another one just like it that is an under performer.

it smooths out nice at higher rpm at at 39-40 mph bus it wont run that speed on the flat, it steggles to reach 35 on the flat so far, and the vibes between 30-37 mph are fairly harsh, way more than anyone of the dax Gen IV lowers I've run.

I think the biggest issue with this engine is low compression as far as power is concerned.

(Edited) Without milling .060" (.025" as I said before is not enough to get piston and deck height matched up correctly) off the jug and correcting the port timing issues there just wont be much performance to get from these engines compared to the 40mm stroke engines that have a good balanced and true crank and better port timing.

Because of the lower compression, these engines may have good reliability since the lowerend is under less stress and being 38mm stroke also helps take some pressure off the upper and lower rod bearing.

I think raising the compression on this engine and going from a 30T up to maybe a 34 or 36T might help this shorter stroke engine since it just doesn't have quite as much grunt as the 40mm stroke engine.

Seems at least the one I have is balanced well for high rpms, its butter smooth to about 28mph but doesnt get that smooth again until around 39mph and up to the max I registered at 41mph, I think higher compression and a lower gear ratio would get this engine into its sweet spot and help it to get there much quicker.

But all said and done , I got to enjoy 22 miles of riding in the 60 degree weather today after watching the Seahawks get lucky and beat the Packers, I dont think they'll be so lucky when they play the Patriots though.....

Had a good ride and watched a nail biter football game the wife and I have our health we are truly blessed so yeah.... it's been a good day and I'll get this "Half Breed" running better, I just wanted to see what it would do with nothing removed from the jug and only some port cleaning with no piston mods.
I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!

Last edited by mapbike; 01-19-2015 at 11:49 AM.
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