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DIY Home Built Motorized Bicycle (non kit) Post all about your home built rides here. Weedwacker motors, lawn mower engines ect. This area is for non kit builds

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  #51  
Old 01-02-2017, 01:17 PM
scrollerguy scrollerguy is offline
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Cool Re: Cannonball Builds a Briggs and Scrap Iron

How do you attach the rear large sprocket? Did you say it bolts on?
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  #52  
Old 01-02-2017, 03:54 PM
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cannonball2 cannonball2 is offline
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Default Re: Cannonball Builds a Briggs and Scrap Iron

Yes the common CG kit sprocket aligns perfectly with an 18t coaster brake sprocket. Bolt it on with nine 1\4 inch screws washers and lock nuts.

Last edited by cannonball2; 01-02-2017 at 03:56 PM.
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  #53  
Old 01-03-2017, 07:19 PM
scrollerguy scrollerguy is offline
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Cool Re: Cannonball Builds a Briggs and Scrap Iron

Did you make the engine support out of angle iron or flat steel?
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  #54  
Old 01-03-2017, 08:09 PM
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cannonball2 cannonball2 is offline
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Default Re: Cannonball Builds a Briggs and Scrap Iron

The mounts are angle iron.
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  #55  
Old 01-04-2017, 03:12 AM
MEASURE TWICE MEASURE TWICE is offline
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Default Re: Cannonball Builds a Briggs and Scrap Iron

Quote:
Originally Posted by cannonball2 View Post
Thanks Scratch!

You have a good eye on the fenders. Had to make two small extensions the extend the rear fender to get the proper spacing. Details details.

A common CG sprocket will bolt directly to an 18t sprocket on an IGH or coaster, aligns easily and runs very true.


Scrollerguy

The BB mod is just flange bearings bolted to the BB. The clutch is a 12t, mainly because I screwed up and ordered that instead of the 11t I wanted. It runs to a 28T which I had on hand. This also keeps the sprocket size small for clearance. These are #35 chain. This gets the most teeth in the smallest overall size.

The secondary side is a 9t to a 44t running a BMX chain. This gives an 11.41 overall ratio. The 3speed Nexus takes this ratio to a 15:1 for low and an 8:1 for 3rd. 2nd is direct drive at the 11:41. This gives a top speed around 43mph should I want twist the engine to 4750rpm which a stocker will do no problem.
I just put a newer used Briggs 3.5hp 9000 series in place of a Briggs 3hp 8000 series that was worn out.

I like riding with more torque, I'm only legal on trails no pedals any more. I had 20:1 ratio with 26 wheel no shift gears. It was good.

Now for how I had to fit the newer used engine I have only 13:1 ratio.

As an option I may get 14:1 ratio, but I'll have to do as mentioned below.
Option is to be using the engine to drive a jack shaft with the clutch on it with a reduction of 1.08 : 1

Then the auto clutch will not engage at 2000 to 2200 rpm ting the bell of the clutch to fully lock, nope ting the bell to lock up will be at 2167 to 2367 rpm.

Either way I was wondering how in comparison does your bike with 3 speeds do with the similar engine on hills?
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  #56  
Old 01-04-2017, 08:02 AM
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cannonball2 cannonball2 is offline
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Default Re: Cannonball Builds a Briggs and Scrap Iron

Sadly the Briggs build is gathering dust and not completed. Soon I hope!

For a single speed bike with 26" wheels I have found the 16:1 ratio best overall.
This varies with engine size bigger engines may pull a 14:1 ok. 16:1 has decent bottom end and a reasonable top speed. I have run a 12:1. Great top end leisurely acceleration and hard on the clutch. The advantage of the IGH is that it will lower and make useable a ratio that is too high to be used direct.
On paper the Briggs build has a 15:1 low gear and would be a decent hill climber in low. I live in the flats so hills are a non issue. If big hills factored in I would set the low ratio for around 18:1. If you ride trails I feel 14:1 is a bit high.


I jackshafted the 98cc Villiers build with the clutch on the jackshaft because
fitting a clutch to the engine was difficult. In order to keep the clutch engagement rpms reasonable I contacted Maxtorque for info on shoes and springs. I found a set of heavy shoes coupled with a different spring to allow the clutch to engage around 1200rpm This kept the engagement rpms for the engine in the low 2000s which is good for a 2stroke. Check the thread for info.
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  #57  
Old 01-13-2017, 01:31 PM
scrollerguy scrollerguy is offline
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Red face Re: Cannonball Builds a Briggs and Scrap Iron

When I was a mechnic, we had a lot exhaust flnges, well if you cut them at just the right angle, the are 1/4" thick and work well.
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