Mike's bike... of DOOOOOOOOM!!!

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PAracer

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Sep 14, 2012
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Steelton, PA
So I'm getting a late start with my build thread, but late is better than never. This is my first attempt a building a motorized bike.

I picked up the bike from Craigslist. This was the pic that was in the ad.

Supposedly, the frame is a 1930's Elgin. The bars I believe are period, as is the fork. I can also see some vintage bmx and mtb parts on the bike.

The plan for the bike is to build a boardtrack styled, functional racer. It would be something that I can take to car/bike shows and also race when the opportunity arises.

This is where I was at a couple weekends ago:


What has been done so far?
Puch head
Pirate cycles sprocket adapter
36 tooth sprocket
#41 chain

I've got a couple things on order that I expect to recieve soon. From Sick Bike Parts, I have an expansion chamber and jets due to arrive on Friday. From Amazon, I have a leather tool bag coming. No tracking number, no ETA on that one:(

This bike needs more brakes. I can see a drum being added to the front.

I will add a bit of detail on these changes today. Hopefully this thread can be of use to folks that are planning similar changes and need help.
 
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PAracer

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Sep 14, 2012
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Steelton, PA
My Puch head notes:

I picked up a Puch 50cc hi hi compression head from treatland.tv

I runs nicely with a single head gasket. Check your plug clearances before you start the motor. If you crash the plug, you will possible wreck the engine.

I am enjoying the increased cooling capacity of the head. The casting is a much nicer quality than the HT parts. I can't comment on added performance since I never did run the engine with the stock head.

This is an all around great modification. It's cheap too.

You do need to make a couple changes to get going. The Puch head is drilled for m6 studs. If your engine has m8 studs, you will need to drill them to fit. I used a hand drill and an 8.5mm bit. the second issue is that the kit hardware will not work. The cooling fins are too close together. I solved this by getting coupling nuts and short socket head screws. I locked (red loctite) the screw into the nut, then threaded the nut onto the stud. i now use an allen wrench to remove and reinstall the head.

Difficulty: no problem. If you were able to build a MB, this will be no sweat.
 
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PAracer

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Sep 14, 2012
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Steelton, PA
Sprocket adapter, 36 tooth, #41 chain notes:

I'm putting this together since these all kinda work as a unit and were installed at the same time.

Wonderful mod!

The stock rag joint sucks, the standard stamped sprocket is crap, and the kit supplied chain is terrible. It's kindof a theme with the kits.

This upgrade makes the bike work so much better. The sprocket stays in place, runs perfectly true, and the heavy duty chain is quality.

Now, I did need to make a custom shim to fit my hub. My hub was a funky size a little bit smaller than the common Shimano size. I found a tube the right size to make a collar at mcmaster.com With the shim in place, I was able to crank the adapter down nice and tight.

The new sprocket installed nice and easy. No fussing.

The chain also went together without a hitch. I also got the chain from mcmaster.com. I bought a 6' length with a master link. The charge by the foot, $3something per foot. High quality stuff.

Another great mod. the 36 tooth is obviously faster, but at a loss of torque.
 
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PAracer

New Member
Sep 14, 2012
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Steelton, PA
Had a good night tonight. Installed the sick bike parts expansion chamber. installed it 'up' with all the pipes on the left side. The header pipe is 10 or 11 inches long. from what I've read, that seems to be ideal.

the chamber recieved a wrap of 1" header wrap. Holy crap, what a pain. I'm itching all over from the fiberglass. It looks good though.

went out for a quick ride and noticed a nice gain across the board. Big imporvement especially down low. also found that it would 4 stroke in the mid and upper rpms. i threw in a .7mm jet, but that was the end of my night.

Anyway, it's late. I should post some new pics soon.
 
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JonnyR

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May 13, 2012
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ronkonkoma, new york
PAracer said:
Had a good night tonight. Installed the sick bike parts expansion chamber. installed it 'up' with all the pipes on the left side. The header pipe is 10 or 11 inches long. from what I've read, that seems to be ideal.

the chamber recieved a wrap of 1" header wrap. Holy crap, what a pain. I'm itching all over from the fiberglass. It looks good though.

went out for a quick ride and noticed a nice gain across the board. Big imporvement especially down low. also found that it would 4 stroke in the mid and upper rpms. i threw in a .7mm jet, but that was the end of my night.

Anyway, it's late. I should post some new pics soon.
Click to expand...
lol (bucket of water with the roll of wrap inside)your supposed to wet wrap the pipe it keep that from happening and it shrinks to a tight fit when its dry:)its a old racers trick i learned from my dad i want to see the pics though
 
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PAracer

New Member
Sep 14, 2012
284
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Steelton, PA
I was able to get it nice and tight. I read about the soaking trick. I actually wrapped from the middle, out to the ends. It kinda happened by accident, but it kept both ends real tight.

One trick I found was to use zip ties as you go so that you can keep what you've done tight. A zip tie every three inches or so. That way you can mess up a bit without losing what you already have done. I put the steel bands on it at the end. BTW, the auto parts store prices wrap and bands out the a$$. Its a quarter of the price on amazon.
 
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PAracer

New Member
Sep 14, 2012
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Steelton, PA
Does this mean it's tomorrow already? In which case... weekend!!!!!! No, I'm still sitting at the office. I snapped these while at lunch. Maybe I'll try for nicer shots this weekend.



 
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PAracer

New Member
Sep 14, 2012
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Steelton, PA
Did a little carb tuning this weekend. As much as you can do I guess. Dropped a .70mm jet in on Friday. A little better but still 4 stroking a bit at the big end. One more step down to a .68mm was much better. Plug is still grayish.
 
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PAracer

New Member
Sep 14, 2012
284
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Steelton, PA
Thanks Bill!

I put a layback seatpost on it theis weekend that supposedly came off of a Hawthorne. My butt now hangs out over the rear tire. I had to move the tool bag to the right side of the CDI to keep it out of the tire. I think it looks better there anyway. It kind of balances out the exhaust that sits on the other side.
 
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PAracer

New Member
Sep 14, 2012
284
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Steelton, PA
Haven't done much with the bike lately until today. I added an inductive tach that I found on ebay. Five dollars later, I can confirm that I was able to wind out the motor to 7200 before I ran out of road in the neighborhood.

With my 26" tire and 36 tooth sprocket, that should be 37mph. I guess that's not so bad considering I'm still on my first gallon of gas mixed at 20%.
 
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