Category Archives: Engine Placement and Drive Train

Where in the reverse trike to place the engine and how to get the power to the ground.

Reversing a Reverse Trike Motorcycle

Most motorcycles don’t have a reverse gear, unless you consider the Fred Flintstone reverse of putting your feet down and pushing. In an enclosed trike, that is not possible. How you resolve this is something I would prefer to decide early on before getting the doner bike. You basically have three choices: Use a motorcycle with a stock reverse gear, buy an after market reverse gear, or design and build your own.

Motorcycle with a stock reverse gear

There are very few motorcycles that come with a reverse gear. In fact I currently only know of three major manufacturer motorcycles with a reverse gear, the Honda GL series starting with the older discontinued GL1500 and the current GL1800 and the BMW K1200LT. These are shaft drive and use the electric starter motor to power a reverse gear in the transmission that must be engaged first. The Can Am Spider a stock non-leaning reverse trike has a stock reverse gear with a belt drive. A fourth motorcycle manufacturer is the Russian Irbit Motorcycle Works (IMZ) who produces the Ural which is a heavy sidecar motorcycle equipped with a four-stroke, air-cooled, flat-twin engine, a four speed gear box with reverse gear and shaft drive.

After market reverse gear for trike motorcycles

Below are links to several after market reverse gears for motorcycles, trikes, or motorcycle powered cars.

Non Gearbox Reverse Options

On the internet I have found ingenious solutions to getting motorcycle powered cars and trikes a reverse gear using automotive starter motors engaging a gear connected to the drive shaft or drive chain. This will require a stout 12 volt electrical system and usage could quickly drain your battery. But you have this same problem the the Honda and BMW motorcycles stock reverse gears as well

Hydrostatic Transmission

Another idea less explored would be to use a Hydrostatic Transmission. Using a bike engine with a dry clutch like a BMW or Moto Guzzi you could replace the gearbox with a variable ratio hydraulic pump and on the driveshaft at the swingarm base put a hydraulic motor. This would also work for a belt or chain rear drive by putting a pulley or sprocket on the hydraulic motor. This would have a lot of advantages like allowing more freedom in engine placement with out worry of how to get the power to the rear wheel. A Hydrostatic Transmission gives you a smooth transition from stopped to full speed without coming off the power-band, by just pushing a lever forward to go forward and faster or pulling the leaver back to slow or reverse. There is a slight loss of efficiency with hydraulics over a direct drive 80% vs. 95%, but it may well be worth it. KTM and Yamaha have experimented with 2 wheel drive motorcycles by mounting a Hydraulic pump at the drive sprocket and running flexible hydraulic lines to a Hydraulic motor on the front forks with a gear driving the front wheel. The motors are surprisingly small and powerful. For a non leaning reverse trike this would be a good solution for front wheel drive by putting hydraulic motors on each wheel

Engine Placement options for leaning reverse trike motorcycle

Engine placement is one of the first things that must be decided when designing your leaning reverse trike motorcycle. you basically have the option of front engine, mid-engined front, and mid-engined rear.

  • A front engine placement means that the motor is going to go before the front axle or over it.
  • A front mid-engine placement puts the motor just behind the front axle and before the passenger or rider.
  • A rear mid-engine placement places the motor behind the passenger but in front of the rear wheel.

All of these options have their advantages and disadvantages. An important thing to keep in mind is making sure there is space for all the other essentials that are required for leaning, steering, passengers and storage in your leaning reverse trike motorcycle.

The mid-engined rear mount is probably the simplest and most economical to implement for a leaning reverse trike motorcycle. You can basically take the front forks off of an existing motorcycle and attach the entire frame behind the passenger and just reroute throttle, break, shift and clutch controls. The downside is it makes the wheelbase very long, especially if you are building a two-seater. Because we are building a leaning trike you’ll want to keep weight centered, so having a second passenger sitting beside you means you’ll be unbalanced unless both passengers are the same weight and in the vehicle at all times together. It’s much better to build your leaning reverse trike motorcycle like a fighter jet, with passenger seated behind the driver.

The front engine placement is used by the RX3 a hybrid reverse trike. It uses a small diesel engine mounted before the front axle and uses a VW transmission with front wheel drive. This is an intriguing setup, with the advantage of having a very short distance from the motor to the wheels and keeping the bulk of the vehicle weight over the drive wheels. With this setup The motor and transmission would not tilt and would be mounted to the main frame. A sub-frame consisting of the driver cabinet and rear wheel would be the parts that lean. Because the engine will not lean, this causes several problems that would have to be dealt with. It would be best to not use a motorcycle engine. They are designed to lean and use centrifugal force to keep oil in place when the engine is at an angle through a turn. If the engine does not lean, all the oil will slosh to one side. Car engines are designed not to lean and are a better choice for this setup. Another problem is getting the controls from the leaning cab to the non leaning engine and transmission, and will require the use of hydraulics or cables. And the killer for this setup may be that the steering and leaning mechanisms may need to be located where the engine and/or transmission are located. Getting the engine to exhaust behind the riders may also get tricky.

The front mid-engine placement, locates the engine of your leaning reverse trike motorcycle between the front axle and the driver. This setup is best for shaft-drive motorcycle engines, but will require an extension of the drive shaft from the engine to the rear wheel. A chain drive is possible but will most likely require several jackshafts, or a jackshaft combined with an aftermarket reverse gearbox that can double as a jackshaft. It keeps the main weight of the vehicle close to the front wheels for better traction in cornering. You should be able to get a slightly shorter wheelbase with the Mid Engine Front than the Mid Engine Rear setup. The engine will lean with the bike getting more effect of weight transfer while leaning and keeps engine controls in line with the driver. While extending the drive shaft, an inline reverse gear box could be installed between the engine main shaft and the extension, allowing a wider range of engine choices for your leaning reverse trike motorcycle. I currently know of only two easily available production bikes with a drive-shaft and reverse gear as standard equipment. They are the Honda Goldwing (GL1500 and GL1800 Models) and the BMW k1200LT.

More on reverse gears