Dr. Shop Teacher's Tonic le Moto--Broncco T-XL

Here's my entry....a hacked up Broncco TX-?? IMG_0072.jpg
So, the lookers will note that I'm not doing my usual Tecumseh for this build...as this is a bearing Briggs flathead.
Here's the tic list:
Frame: 5.5" stretch to fit a tall boy like me.
Sprocket and Caliper: 70t #35 with the sprocket machined to accept a DB30 style caliper.
Swing Arm Mount: to accept jackshaft and swing arm (which may be stretched).
Front Springs: internals dumped for external springs.
Seat: by manchester1.
Clutch/chain Guard: Custom aluminum
Fuel Tank: 2 qt kart fuel tank shrouded by an custom aluminum Broncco look-alike
And the fun:
Engine: Ungoverned. ARC Piston Rod, ARC Billet Flywheel (fixed at 30 degrees), 18# Springs, Dyno Super Stock Cam rated for 6500. Billet Lifters. Re-jetted Chi-Kuni 22mm Carb. Shaved eyebrows, etc.

I have the original rims with Pirellis in great shape. A few other mods up my sleeve, but we'll see what time I have this spring.

BTW, the poster is patterned after an old "patent medicine" advertisement from the late 1890s, I thought it would be cool to do.


Well-Known Member
briggs flathead will be cool pete. this will be a new territory for you. hot rod briggs..cam..mikuni carb..mods...nice
Tuesday was my first real day of fabrication for the Broncco T-XL. The fork lowers were frozen inside the upper tubes when I tore it down and no amount of heat would break them loose, so I had to cut/drive them out. I didn't want to use the internal springs because finding new boots was impossible.
I used 50 grit paper in the orbital sander to get all of the rust and corrosion off so that the lower tubes slid freely. Then I marked the uppers 6" from the lower tree to square off. A sawzall did the trick.
The new spring cups and springs came from OMB. I set up a step drill in the 'press and drilled to 0.990. A sanding drum eased the hole open for a snug fit on the upper.
On the lowers, the tube is under 7/8", so I opened up a washer to 0.800 and filed to a snug fit.
The final ride will be adjusted once the rear shocks arrive so that I don't mess up the fork rake.
Boogers and Bars--
I worked on cleaning up the major booger weld at the neck today. I was able to flap disk some of it, but mostly filed it. To get the Bondo out, I used the torch and literally burned it out.
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Then it was on to some tweaking of the frame design. I really liked the grab bar I put on the last Gilson, so I picked up another off of Ebay. This one I shaped to fit the tube contour and will weld, rather than bolt to the frame.
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