APE Fat Bob

APE Fat Bob

Get on, twist and hang on.

Part two of our Milwaukee 8 Power Build Series features a spectacular 162 Horsepower Fat Bob built by Alpha Performance Engines (A.P.E.).

The invitation came from Alpha CEO Mark Harris, “We’re running our 2019 Fat Bob build at Willowbank Dragway this weekend, Dave. Why don’t you come up and take it for a test ride in-between runs.”

Naturally I was there at bang on time and watched Mark tear up the strip with several runs around the 10.1 to 10.2 second times before he gave it a splash race fuel and said “Off you shoot”.

I rumbled slowly out of the track compound, cruised leisurely down the Champions Way until I turned right onto the Cunningham Highway where I did give it a handful. That’s when I heard myself exclaim “J-i-i-i-m-m-m-iny!!!” (or words to that effect), right out loud, as those 162 ponies and 154.55 Ft Lbs came into play.

It pulls.

It keeps on revving well beyond the point that you would normally reach for the clutch and upshift, with no diminishing of its surge – long, long, long and strong. Linear power till well past you run out of daring on the open road.

The way the bike has been set up with FXDR Triple Trees and wide off-road style tapered handlebars makes the surge even more exhilarating.

After a good session winding on and off the throttle over some of the Scenic Rim’s quieter backroads I returned to the strip with a huge grin across my dial and set about finding out how this high-performance machine was built.

It started life as a 2019 Fat Bob and the first modification was the FXDR Triple Trees and headlight assembly to change up the looks and to make the wheelbase longer for added high-speed stability.

From there XR1200X wheels were added to make it lighter and to offer a better range of drag-racing-size tyre options. The rear is a 180-55-17 and the front is a 120-70-19 running Dunlop Q4 qualifier rubber.

The engine was originally a 107 cube but is fitted with a 114cube stroked crank for starters.

Initially the build was done with the balancers removed in an effort to extract more horsepower in conjunction with the lighter crank but it vibrated quite badly over 5,000rpm so the balancers were lightened slightly and then re-fitted. There was no noticeable difference in made horsepower with the balancers removed or fitted.

Capacity has been increased to 128 cubic inches using a proprietary APE Kit which includes 4” 250-thou bore CP Pistons, Stage 2 Warflow Cylinder Heads that were milled to lift the compression to slightly over 12:1, 64mm Screamin’ Eagle throttle body with Warflow ported manifold, APE 530" cam, APE 6.2gps injectors, Screamin’ Eagle High-capacity lifters, Screamin’ Eagle extreme flow air filter kit and a good quality D&D 2 into 1 pipe. There are a choice of tuners available to suit the kit while the Powervision PV2 unit was chosen for this setup.

It’s running stock M8 Valves with the Screamin’ Eagle spring upgrade and a ported inlet manifold that has been modified for consistent flow to both cylinders.

In the early stages of development, the motor was producing 155 horsepower with the APE 530 cam fitted but some inconsistency and cross-port contamination was evident in the intake manifold.

Different cams can have varying effect on manifold flow on the M8 engine so the manifold was split, rebuild and reshaped using metal putty to achieve optimum flow. This manifold has been scanned and digitised so future builds will be made from CNC’d billet aluminium – as well as being offered for sale as a stand-alone part.

Interestingly the bike produced one less horsepower with the Extreme Ventilator pod filter removed.

Mark summed up the process by saying “The reasons we have been able to extract such impressive power and torque from this bike are all around the Cylinder Heads, the Intake Valves and the right Cam Shaft for the job. Also having the right exhaust system is crucial. The D&D we have fitted does the job really well.”

The clutch and gearbox are stock apart from Screamin’ Eagle 1275 Springs and they are handling the increased load without issue. The stock oil pump is also proving adequate for the job.

What APE have achieved is a bike that will run close to 10-second quarters and wheel stand past balance point in second gear if encouraged appropriately.

Back at Willowbank I watched the bike do a few more very impressive runs as it qualified in top spot for the final.

Unfortunately, Mark ‘Picked a Cherry’ and red-lighted in the final so they didn’t come away with the win on the day, but as a high performance Harley that is still very ride-able in real-world conditions and on the open road, this build is a winner every day.

Ape have a variety of M8 Power Build Kits Available:

Stage 1 Kit: APE Stump Puller Kit 124”/128”
• 4.250” Bolt on Pistons/Cylinders with MLS head and base gaskets
• Bolt in Cam Shaft
• High Capacity Tappets
• Screamin Eagle 55mm Intake manifold
• Screamin Eagle 5.5gps Injectors
• New head bolts, gasket kit
• $3199 parts only, $4799 ride in ride out from Stage 1
• 125-130hp, 140 plus ft lb

Stage 2 Kit:

• 124/128 4.250” bolt on pistons/cylinders with MLS Head and Base Gaskets
• Warflow Performer Cylinder Heads
• .470” Bolt in cam
• High capacity tappets
• Screamin Eagle 55mm intake manifold
• APE 6.2gps injectors
• New head bolts and gasket kit
• $4499 parts only, $5900 ride in ride out from Stage 1 (Quality 2-1 exhaust and adequate air cleaner needed to make the most of package)
• 135-140hp, 145-150 plus ft lb

Stage 3 Kit:

• 124/128 4.250” bolt on pistons/cylinders with MLS head and base gaskets
• Warflow Satge 2 heads with High Lift valve springs
• SE 64mm throttle body with Warflow ported manifold
• APE 6.2gps injectors
• High capacity tappets
• .530 lift cam
• SE tapered adjustable pushrods
• Head bolts and gasket kit
• $5799 parts only, $6999 ride in ride out ( stepped header 2-1 exhaust and large volume air cleaner a must)
• 145hp-150hp, 150 plus ft lb

For more info Contact Alpha Performance Engines.


Make: H-D
Model: 2019 Fat Bob
Owner: APE
Builder: Sam Fry

Type: M8 107
Capacity: 128ci
Cases: Stock M8
Crank: Screamin Eagle 4.5”
Barrels: Heavy Duty Bolt On 4.250”
Pistons: CP X-Forged 4.250”
Bore: 4.250”
Stroke: 4.5”
Compression: 12.4-1
Cams: .530” lift
Pushrods: Sreamin Eagle Tapered Adjustable
Valves: Stock M8
Springs: Scremin Eagle
Carburetion: Screamin Eagle 64mm Throttle Body, Warflow ported manifold, APE 6.2gps injectors
Air cleaner: Scremin Eagle Extreme Flow Heavy Breather
Exhaust: D&D Fat Cat 2-1
Power: 162.52hp 154.55 ft lb
Max revs: 6500rpm

Clutch: Stock 114 clutch pack with Screamin Eagle 1275N Springs
Primary drive:
Rear drive:

F rim: XR1200X
R rim: XR1200X
F tyre: Michelin Scorcher
R tyre: Dunlop Sportmax Q4
F brake: Stock
R brake: Stock
Brake lines: Stock


Front: Stock
Trees: FXDR
Rear: Stock

Bars: Stock
Switchgear: Stock
Levers: Stock
Grips: Arlen Ness
Mirrors: Stock
Footpegs: Stock
Gear change: Stock
Speedo: Stock
Headlight: Night Rod

F guard: Modified Sport Glide
R guard: Stock
Fuel tank: Stock
Oil tank: Stock

PAINT & FINISH: Custom APE themed paint from Mark at QMPP