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Old 06-20-2015, 03:07 AM
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Davezilla Davezilla is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: San Antonio Texas
Posts: 2,710
Default Re: what did you do to your motorized bicycle today?

Tonight I actually made some decent progress with the road bike project... first I had to decide how I was going to install the rear sprocket so I decided to open up the center hole just enough to fit the flange of the fixie cog in thru the hole then made sure everything was centered up, clamped the 2 together then welded the 44 tooth sprocket onto the fixie cog. Problem solved, no rag joint, no adapters, perfect chain alignment, no complaints here...

I was just going to do that and go home but decided to choose an engine for the bike, temp installed the super rat then decided to go with a Dax engine instead. Grabbed a brand new Dax bottom end from the stock room, got a cylinder I previously ported, did a quick hone job to get the right cross hatch pattern, and put a piston on with the rings removed, trial fit the cylinder and the piston was protruding by about 1.5mm... I definitely didn't want to stack head gaskets so I grabbed the degree wheel and some copper base gaskets as well as a .040" thick spacer.
Stacked the gaskets and spacers until I got a 0.6mm squish clearance using a .025" thick copper head gasket, then checked the port timing to see if I needed to cut any more on the jug or not. After setting up the degree wheel I ended up with 164 degrees of exhaust duration, 122 degrees of intake and 132 degrees on the transfers so no piston ramping or cutting of the skirt will be needed or done.
I still need to take the top end back off to put the rings on the piston and then do a final assembly. The pipe of choice for this one will be a kx65 pipe since it fits really well with minimal modification and should hit where I want it to for a good combination of acceleration and top speed. For the carb I'm leaning more toward the mikuni vm18 for this engine since it's still fairly easy to tune and I want this bike to be not only fast but able to get up to speed quickly as well.
here's a pic of the progress I've got so far... this frame makes it a lot easier to work the engine without having to take it out of the frame so I've been able to set up the port timing and squish clearance, the head is temp installed so I could see what it's going to look like and to protect the internals until I can finish everything else I'm doing to it...

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