Cannonball Builds a Briggs and Scrap Iron

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cannonball2

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
Caproni? Didn't they make jet engines? Seems like I remember seeing one in a BD5J. But that was eons ago could be wrong.

Today was chain guard day. This should please you L2. You chided me once for a lack of one on an earlier build. I complied this time. Wisdom comes with age. Both guards will get a final trimming when removed for paint.

I also made the clutch "spinner" from a 6" mixing bowl I finally convinced my wife to part with--that's another story. Took quite a while to whittle the bowl to fit. If I can get it perfectly centered(its very close) it will appear still(or nearly so) at idle. I can polish it by putting my jeans against it while riding. Easy maintenance.

Swapped the long threaded 1/2" exhaust stub for a close nipple, exhaust fits better. In the interest of being a model citizen I will add the common Briggs "hot dog" muffler to the end of the pipe. The pipe gets precious close to where the wires exit the battery tube, the fault of building in the wrong order. If that's the biggest issue with this build I'm home free.

The word Pirouline is embossed in the battery tubes end. I will relate to on lookers that its a high end French racing oil.
 

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Tony01

Tony01

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Nov 28, 2012
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nice! that clutch cover is sweet.

The briggs muffler is pretty restrictive and makes the motor sound like a lawnmower. If you punch out the center baffle it will make it a straight through; the sound will still be quieter than an open header but performance will be way better than with the baffle. Or take it apart and pack it but its too much for me. With the straight through its noticeably quieter and the engine still has good power. I had the welders attach a 1/2" pipe female double sided fitting so I could remove the muffler if I wanted to, but I never took it off.
 
scratchbuilder

scratchbuilder

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Jan 17, 2015
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Looking good. That clutch bowl..i like it alot. Thanks for the showing of cutting the front block plate off and shaping the fins. I have done it. Sooo much better, asteticly.
 
Ludwig II

Ludwig II

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The Caproni-Campini hybrid jet flew pre WW2. A petrol engine drove a fan with fed a combustion chamber where more petrol was burnt. It worked, but inefficiently.

 
scratchbuilder

scratchbuilder

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Question, have you given any thought to losing the pull start cover and installing a pull start cup, with a safety cover that swings out of the way or is removable to start??
 
cannonball2

cannonball2

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Oct 28, 2010
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No, the main reasons being with the fake pedals being set back about 3" my right leg will rest right on the recoil starter. Its a nice safe place. I doubt I could make a decent enough shield. A cup protrudes as much as the recoil.

Secondly we have some pretty high temps in the area. Poking along the islands unimproved road for a mile or so home would probably overheat a free air cooled engine, will leave it fan cooled.

I have in the past build a few shroudless engines. A Briggs 3.5 and a Robin 5hp. They do look better/more M/C. I machined the fins off the flywheel and ran a rope start. Its a real problem(and easy to do) when you realize after a stop miles from home you left the rope!

Will have to remember this with the Villiers build as it will be a roper.
 
cannonball2

cannonball2

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Oct 28, 2010
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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.
 
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MEASURE TWICE

MEASURE TWICE

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cannonball2 said:
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.
Click to expand...
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?
 
cannonball2

cannonball2

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Oct 28, 2010
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Colonial Coast USA.
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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