Thread: New (old) stuff
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Old 02-03-2016, 06:11 PM
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Agreen Agreen is offline
Motorized Bicycle Elite Member
Join Date: Feb 2013
Location: Goose Creek, SC
Posts: 627
Default New (old) stuff

Long story short, I acquired a Huffy "good vibrations" bike and a USED 66cc kit that was missing parts. The engine is in good shape, and upon inspection shows that the engine is well broken-in. Strong compression, starts without choke, and strong exhaust pulses too. The cylinder is shiny and the rings have worn the black coating off, so I'm calling them seated.

Anyway, I get the bike assembled after ordering some parts (which includes a 41t sprocket) and I went for a ride. It starts up good, runs quiet, and pulls well without misfires. The only thing is that it's just incredibly slow! I thought for sure a 66cc with a 41t would outperform a 48cc with a 44t?

I'm going to compare the ports on the 2 engine's and see what I come up with. Here's what I'm thinking:
-put a degree wheel on the crankshaft
-find TDC and make it 0*
-note the angle at which the exhaust port opens
-note the angle at which the exhaust port is fully open
-same for intake opening and closing

I also want to see if there's a difference between the two as far as magneto positioning.

If everything check out, then I'll probably port the transfers where the cylinder meets the base.

I kind of want to get to the bottom of why everyone is having different results with these engines. My 48 should not be powering past the 66 with a taller sprocket. Something's got to be amiss here.


Something else I noticed is that this engine is a center-fire head. I haven't seen one of those in a long time. Then again, so is my 48 (but it's a freakin beast!)

Maybe this is a much older model with bushings instead of roller bearings? I guess we'll see.
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