Taking the Triumph Bonneville 865cc Engine to an 1100cc Beast!

With the help of Bill Gately of Bonneville Performance!

I had over 63,000 miles on my 2008 Bonneville 865cc engine and it needed a valve job. So, instead of doing that only, I decided to send the entire engine to Bill Gately of Bonneville Performance, for a complete engine overhaul and upgrade modification! My final engine will have the same spec’s as the BP 1100cc crate engine, including:

  • New bearings
  • New oil pump
  • Billet cylinders with Nikasil lining
  • BP performance head porting with BP valve train
  • BP Cams
  • Crankshaft dynamically balanced
  • All paper and MLS gaskets

The modified engine, along with the twin Mikuni HSR42 carbs and the BP 2 into 1 Exhaust system should produce approximately 94 HP and 76 ft. lbs. of torque. Bill also had a number of the engine covers powder-coated satin black for me.

Step 1 – Remove stock 865cc engine from 2008 Bonneville frame

This is easier said than done. You basically have to take the motorcycle apart! I followed the steps in my Haynes manual to remove all the parts that connect to the engine including exhaust system, oil cooler, carbs, electrical system wires and components, and subframe members.

Beginning the process.

Sub-frame basket bars… these are heavy!

In the process of disconnecting everything from the engine.

I’ve protected the intake and exhaust port holes with clean rags.

I supported the rear of the bike from a garage joists with 2 adjustable tie-down straps. With the front tire in a floor carrier, the frame is stable and suspended.

With the frame suspended I removed the rear fender, wheel and swing arm. I then removed the 2 sub-frame basket bars.

STEP 2 – Prepare engine for shipping in a crate

Bill Gately suggested that I contact Johnny Scheff at Motoworks Chicago to see if he had an extra Triumph engine shipping frame. These are angle iron frames that Triumph uses to ship its engines to dealers. As it turned out, Johnny did and was kind enough to let me borrow it.

Triumph engine crate shipping frame

Saturday, January 3, 2014 Update – Engine removal and mounting to shipping frame

I read in my Haynes manual that removing the engine from the frame is a 2 or 3 person job, because of its weight. So, I pinged a few of my Bonneville buddies, and Ernst and Lee volunteered to help me with the stage of the project.

We had a little trouble with getting the engine to drop from the frame, but once I removed a couple more brace pieces around the lower exhaust mounts, things freed up and we were able to slide the engine down free of the frame and then sideways on the floor jack. Then we were able to pick up the engine (it weighs about 165 lbs) and mount it on the bright yellow Triumph engine shipping frame.

Front view of Triumph 865cc Twin engine on shipping frame
Rear view of Triumph 865cc Twin engine on shipping frame
Wngine on shipping frame next to empty Bonneville frame

January 4, 2014 Update – Building the Shipping Crate

Here are a series of photos of the process of building the shipping crate around the 865cc engine on a shipping stand. I purchased 2 sheets of 1/2″ x 4′ x 8′ plywood, (4) 2x2x8 ft., (1) 2x4x8, (1) 1x3x8 and (1) 1x4x8 plus misc screws, etc. for about $75 at Home Depot.

I started with the base, slightly larger than the angle iron frame.

Completed base made of 1/2″ plywood with a 2×2 base frame and 2×4 base slats.

The engine frame fits inside the 2×2 frame just right.

Next I built sides also on a 2×2 framework.

Side panels and 2×2 frame connected.

Next, I added the rest of the framing and the end panels. I also put a 2×4 brace across the interior for extra support and engine protection.

Another view of the interior of the shipping crate with interior brace and exterior handle added.

Marking the top for re-assembly.
Ready for the top to be cut and added.
Top is ready to be mounted.
Final photo before sealing for shipping

January 9, 2015 – Engine Picked Up

I was able to secure a decent freight shipping rate through freightcenter.com with Pilot Freight as the carrier. I also insured the shipment through freightguard.com. I took care of everything online, and the truck and driver showed up as promised today.

Step 3 – Engine Rebuild Process

January 15, 2015 – Arrival at Bonneville Performance

I am pleased to share that my 865cc engine crate arrived safely at Bonneville Performance via Pilot Freight on Thursday, January 15, 2015. The crate was in good shape with no signs of stress or damage. Bill Gately, owner of Bonneville Performance was able to disassemble the crate, lift the engine off the skid and get it setup in his shop for tear down. Thanks for the photos, Bill!

I have been told by Bill that he will tear the engine down and then:

There is a 3-week wait on the crank and cams before they are returned to Bonneville Performance which puts the reassembly starting around the week of February 9, 2015. I am assuming I won’t see the engine back until some time in March.

My 865cc Bonneville Engine arrives safely at Bonneville Performance in Florida, via Pilot Freight Services.

The 865cc engine being lifted out of the crate.
The only mishap was the crate crossmember brace was too close to the oil pressure sending switch and broke off the tip.
The 865cc engine mounted on a work stand and ready for tear down.

Update February 17, 2015

I spoke to Bill yesterday and learned that my engine parts are in the process of coming back to him from the various shops.

My engine should be looking like this fairly soon except it will have satin black powder-coating instead of glossy.

April 4, 2015 Update

The long winter is over and work is picking up in Randy’s Garage. Today I disassembled the front of the 08 Bonnie including the front head triple trees and bearings, and worked on cleaning the frame.

The frame is fairly clean and free of parts.

April 28, 2015 Update – Engine Crankcase Reassembly

I heard today that my 1100cc crate engine rebuild is moving along nicely. Here are photos of the parts back from various machine shops and parts vendors ready for reassembly.

Closeup view of head showing valves and intake manifolds.

Cylinders with pistons, plus various parts for the rebuild, including the two BP Mile camshafts in boxes.

Rear view of upper crankcase ready for cylinders to be bolted on.

Front view of upper crankcase. The cylinders and head bolt on the 8 vertical studs.

Lower crankcase showing crankshaft (left) and transmission gear assembly

May 2, 2015 Update – Engine Reassembly, Cylinders, Head, Cams and Covers

Bill sent these photos to me today, to let me know that all he has left to do is set the valve clearances, cam timing, and button up the timing cover and cam cover – then into the crate for the Monday, May 4, 2015 pickup!

Front view of 1100cc Triumph parallel-twin engine, modified by Bill Gately of Bonneville Performance.
Intake side the the 1100cc Triumph parallel twin engine.
Right side view of engine with side cover not yet installed. One way you can tell a Bill Gately engine is that he does not coat the cylinder exterior section with the black coating used by the factory. This is done to increase cooling.
Bottom view of engine. I’ve got a black K&N oil filter just waiting to be spun on.
Bottom of engine viewed from the front. That is Bill’s 2001 Bonneville in the background. I believe it has a 1200cc engine in it.
Bottom view of the engine. The side you see will be on the right. The red seal is behind the front drive sprocket.
Bill had my left engine cover and other parts powder-coated satin black for me! Behind this cover is a Barnett heavy-duty clutch with green springs.

Front view of the engine with cams and cover yet to be installed.

Exhaust ports on the front of the engine head. A new BP 2 into 1 exhaust system will be bolted up to these.
Can’t wait to shove some premium gas and air mixture into these manifolds, ignite it with some spark and see what happens!
Left and right intake manifolds ready for twin Mikuni HSR42 carbs.
Left intake manifold and view into the ported head.

May 12, 2015

Always good to arrive home from work and be greeted by boxes of performance parts from Bonneville Performance! I received my Bonneville Performance Stainless Steel 2 into 1 Exhaust System that I will be using with my rebuilt Bonneville Performance 1100cc Triumph Twin engine. Also arrived was the Bonneville Performance Crankcase Oil Breather Canister Kit for the same engine.

As soon as some correct size valve shims arrive, Bill will finish up my final engine adjustments and ship it to me!

Bonneville Performance 2 into 1 exhaust headers down into a collector with clamps on the left, Supertrapp silencer on the right.
Bonneville Performance Crankcase Oil Breather Canister Kit

May 2015 Update

I am happy to report that my engine rebuild has been completed by Bill Gately at Bonneville Performance! Now, the planning begins for how we will put it all back together!

Rebuilt 1100cc engine – right side view
Rebuilt 1100cc engine – left side view
Intake side of the engine
Bottom 3/4 view of the engine
Another right side view
Right rear 3/4 view
Another intake side view
Left rear 3/4 view

December 2015 Update

The 2008 Bonneville frame is going back together in preparation for a road trip down to Bonneville Performance in January 2016 to be reunited with the new 1100cc engine! The task today was to install new All Balls Steering Stem Bearing Kit 22-1020 in the head and then install the upper and lower yoke assembly. The new replacement bearings are roller bearings that replace the less desirable and less reliable ball bearings installed at the factory. I followed the instructions in the Haynes manual to remove the old bearings, and press in the new sleeves and bearings without the use of a machine press.

2008 Bonneville frame cleaned and ready for re-assembly. Front head and yoke assembly completed.
Closeup of front head and yoke assembly reinstalled with new roller bearings.
December 27, 2015: After the front head bearings upgrade I added the front forks, bars, controls, brake and wheel assembly.

January 1, 2016 Update

In preparation for my trip to Bonneville Performance later this month, I am using my holiday weekend to get more of the frame and parts ready for the trip and final reassembly. This morning I trimmed 3/4″ off the sides of the rear fender, and 1/4″ off the sides of the front fender. While the Bonnie is apart, I plan to shoot some new coats of Eastwood Rat Rod Satin Black Paint (Item #21857ZP) on these parts: fenders, chain guard, side covers, front sprocket cover, and seat cover. I am considering also shooting the swing arm and the gas tank (not pictured) but leaving the frame in the original factory black.

Starting the new year by getting all the parts ready to paint.
Eastwood Rat Rod Satin Black – #21857ZP

First coat of Eastwood epoxy primer

Week of January 25-29, 2016

I loaded up my 2008 Bonneville in my 1993 Chevy pickup and headed down south to Bonneville Performance to install and dial in the 1100cc rebuilt engine.

After arriving at Bonneville Performance, we unloaded the bike, put it on a work stand in the shop, and began the process of installing the engine into the frame.

Truck loaded and ready to roll.
Road trip: 2 days, 1200+ miles
Bill Gately lining up the 1100cc engine on a jack for bolting back onto the frame.
The 1100cc engine mounted in the frame, with the swing arm and rear wheel assembly added.
Close up of engine in the frame, Mikuni carbs, oil cooler, oil pressure gauge, side panels, sprocket cover installed.
Bonneville Performance Mikuni carb kit installed.
Bonneville Performance Oil Breather Kit installed.
Bonneville Performance 2 into 1 stainless steel exhaust system – installed.
Fully assembled Bonneville on the stand during heat cycling of the engine.
GoPro view of engine and frame assembly[

January 29, 2016 – First ride with the 1100cc engine!

Having completed the assembly of the 1100cc Bonneville Performance twin back into my 2008 Bonneville frame, heat cycling the engine and doing the final oil change to synthetic Castrol racing oil, I was able to take the bike out for its first spin. I took it for few laps around the streets near Bonneville Performance. A short GoPro video clip is below.

All I can say is… Wow! Amazing! Incredible! How else can I describe the increase in performance? The most noticeable change is the instant response to the throttle and the torque! I am sure a wheelie would be no problem… and that fact that is a bit scary!

2008 Bonneville with 1100cc Bonneville Performance twin-engine after first test run
2008 Bonneville after first test run.
Loaded up for the road trip home.
Perfect weather all the way from Florida to Chicago.

February 1, 2016 Update

A little over a year since I began the project, I arrived back home with a fully functional 2008 Bonneville with a high-performance 1100cc engine. A couple of friends helped me unload the bike at home, and it is now safe and sound in my garage.

It still being winter in Chicago, I have a number of smaller projects, modifications and improvements to make to the bike to get it ready to ride in the Spring, including:

  • Install Sato Racing rearsets
  • Install 520 chain and sprocket conversion
  • Final paint color sanding and buffing, including gas tank
  • New custom badges
  • Replace and improve fuel lines – Tygon
  • Install shorter K&N air filter pods
  • New handlebar grips
  • New front gaiters
  • Sort out front brake master cylinder mushiness
  • Sort out rear shock performance issues
  • Consider changing rear wheel from 17″ to 18″ dia. to improve handling and suspension performance
2008 Bonneville back home in garage

May 22, 2016 Update – Dyno Results

I have been able to complete the items on the list above except for the last one, which I will wait another year to do. I am also happy to report that I had a chance to put the Bonneville on a Dyno and had some great results, as shown below.

The outcome is basically 92 HP and 72 ft. lbs. of torque with a power curve that just keeps building, at least all the way to 115 MPH! This matches my riding experience where I have not yet experienced the bike flattening out… at all, at any speed, in any gear. It is truly amazing to ride!

Mobile Dyno at Team Triumph, Janesville, WI. – Visit mobiledyno.net
Dyno results of 2008 Bonneville with a Bonneville Performance 1100cc twin engine: 92 HP and 72 ft. lbs. of torque. Performed by MobileDyno.net at Team Triumph in Janesville, WI.
2008 Bonneville cooling down at Team Triumph after the Dyno run.

Additional Work Done Since 2016

In the months and years since I completed this project with Bonneville Performance, I have made some additional changes and upgrades.

After more discussion with Bill Gately regarding the initial dyno results I got, he recommended that I go with the Mikuni HSR45’s for additional intake capacity. These carbs are 3mm larger in diameter than the HSR42’s, but otherwise have the same housing and connections. I went ahead and made that swap and have definitely noticed an improvement in power.

In 2019, Bill told me that he had entered into an agreement with Triumph Twin Power (in the UK) to make a custom CDI unit for his engines. I purchased the Fire Starter with the custom map for the BP 1100cc engine (https://www.triumphtwinpower.com/fire-starter-performance-igniter-unit.php). Wow! What a fantastic improvement that made!

I also upgraded the headlight to an LED unit so I can see better at dusk or at night, or during rain. It really makes a huge difference! This is the unit I purchased: Liteway Headlight. It fit right inside my stock headlamp bucket in place of the original and plugged right into my three-prong connector.

I have also purchased additional diffuser discs for the Supertrapp muffler to tune the exhaust a bit more.


A recent photo that was taken on a ride in March 2020, here in Southwestern Wisconsin.

Upgraded Mikuni HSR45’s – with custom choke arrangement I fabricated.

Triumph Twin Power custom CDI for the BP 1100cc engine.