Modded 420cc Mini Dragbike w/3d manual clutch

#1
Well i sold the original designed chassis with the nitro 44 from minichopperssocal - 909 minibikes

So i shall start a build thread finally of the new chassis im currently building...............pic is old chassis at track a few weeks ago with a torque converter on it.

So far i have............

Powerland 420cc ----- NEW $160 shipped off ebay !
Custom mounted 3d manual clutch all brackets and mods done by me (first big block with 3d manual)
nr racing camshaft
arc long rod
billet lever set
billet raceseng s2 wheel with adjustable coil bracket
header
32mm carburetor (might go bigger still)
hd springs
minicup wheel and tire in route

Engine is currently getting the new crank keyway cut for clutch then off to get balanced. Then i can reassemble the engine finally and get on with the rest of the build.
 

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delray

Well-Known Member
#2
what kind of power can that 3D clutch handle. you think that big block 420 built up will still be ok for it.
i just installed a thumb control on my 10hp and under class drag bike and i really like it when it comes to launching from the start.
a reg-minibike throttle just doesn't work good for straight line racing for me.
 
#5
I already ran the engine before and the balance shaft was removed without balancing the engine. It had a slight vibration but wasn't bad. It didn't vibrate your hands off it was just annoying.

I am balancing it this time tho to be safe. While it's apart.

And not sure on what your referring to on balance factor ? But I'm having a local automotive race shop do the balancing. They said 2 days and $125 and it shall be done.
 
#6
Did you give them the reciprocating parts to use to calculate the bob weights? If so they need to take the piston, pin retainers circlips and the small end of the rod and weight them then take a percentage of the weight to calculate the bob weight. Being as you can't balance a single cylinder engine because of primary imbalance you just create a percentage of the reciprocating mass so for example if you use a 50% balance factor you are allowing the engine vibration to be divided along the horizontal and vertical planes. Here is a link to explain.

http://www.tonyfoale.com/Articles/EngineBalance/EngineBalance.pdf
 
#7
Finally found the right tire size after ordering and returning multiple tires for the front to match the mini cup tire and wheel. Also got the clutch finished. And rotating assembly will be headed to Russell at nr racing for balancing. Also got my cnc fork triple tree plates in so I can weld my own forks up............
 

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