Honda Transalp and Africa Twin

The Honda Africa Twin is a 650cc (RD03) or 750cc (RD04, RD07) cousin of the 600cc Honda Transalp. The earlier Africa Twins are very similar in construction to the Transalp, and many parts can be put onto a Transalp. Potential improvements include a larger fuel tank, an aluminum swingarm, taller suspension, and a rear disk brake.

Model Designations

Model designations become very important when purchasing parts, so it's important to understand the meaning of PD06, RD04, RD04, and RD07.

The Transalp imported into the US in 1989 and 1990 is the PD06 XL600V.

There are several models of Africa Twin. The important thing to remember is that RD07 parts are cannot be used on Transalps. Many RD03 and RD04 parts, however, bolt straight up to a Transalp. The following chart shows years and models. Note that only models relevant to the US-spec Transalp are shown:

Year	Africa Twin
1988	RD03 XRV650
1989	RD03 XRV650
1990	RD04L XRV750
1991	RD04M XRV750
1992	RD04N XRV750
1993	RD04P XRV750
1994+	RD07

For a full breakdown of Transalp models (PD06H, J, K, PD10, etc) see Deti's page.

For a full history of the Africa Twin (RD03, RD04L, M, N, P) see this page (Japanese).

Fuel Tank

RD03 and RD04 fuel tanks, which are identical apart from color scheme, will fit directly onto a Transalp frame. An RD07 has an entirely different frame, so its tank will not fit a Transalp.

Interference

Without the support bracket, the RD03/RD04 tank's petcocks may interfere with the Transalp engine's oil lines. This does not seem to be an issue with later Transalps, which may use a different oil routing more similar to the NT650 Hawk.

Support Bracket

The Africa Twin tank requires a support bracket, which is mentioned here (image).

This item may be listed on Ebay Germany as "Verkleidungshalter" (translates as "Fairing bracket"). It certainly appears to be the exact same part as what is commonly listed as "Kühlerhalter" ("cooler holder").

It appears in the XRV650K microfiche as:

64209-MS8-000 PIPE COMP., COWL MOUNTING

and on the XRV750N microfiche as:

64209-MV1-000 PIPE COMP., COWL MOUNTING

Fuel Pump

The Africa Twin tank needs a fuel pump in order to pump the last few gallons.

Stock Africa Twin

The Africa Twin's OEM fuel pump is electric, and it's prone to failure due to internal electrical contacts which arc and destroy themselves. The pump itself can be hardwired and controlled by an external relay, which prevents the arcing problem.

Substitute Pumps

Fuel pumps are rated in flow rate (gallons or liters per hour) and pressure (PSI).

In selecting a fuel pump, the right pressure is critical. Carburetors have a float bowl which works a bit like a toilet's valve system. Sealed floats are pushed upward by their buoyancy as fuel fills the float bowl. When enough fuel has entered, the floats press a needle valve closed, stopping additional fuel from entering the float bowl.

The Transalp's carburetors are designed to accept gravity fed gasoline. Pumping fuel in with a fuel pump may overwhelm the float & needle system, pumping too much fuel into the float bowl, causing an over-rich condition. A worst case scenario would end in hydraulic lock and a severely broken engine! Even without this worst case, running an overly rich mixture would cause poor fuel mileage and increased cylinder wear as the excess gasoline washes oil from the cylinder walls.

How Much Pressure Is Needed?

The pressure created by a column of water is about 0.433 PSI per vertical foot. Assume that the fuel pump is mounted at the lowest point on the frame, the carburetor inlet is no more than two feet above this point. So, if we were pumping water instead of gasoline, we would require only around 0.866 PSI or less to overcome gravity. Gasoline has only about 75% the density of water, so we should require no more than about 0.65 PSI to overcome gravity.

A real life example can be found in the KTM 950. This post states that a stock KTM 950 fuel pump puts out 2.2 PSI (at the carburetors), draws 1 amp, and pumps 23.4 liters (6.2 gallons) per hour. So, the KTM's carburetor floats and needle valves can hold back at least 2.2 PSI. We don't know how much the Transalp's needle valves can hold back, but we can assume it's certainly no more than 2.2 PSI!

How Much Flow Rate Is Needed?

This post provides an interesting, simple method of estimating pumping capacity requirements for a 100hp KTM 950 Adventure:

Assume 100 hp, this is 75kw.

In an hour at fuel load the engine will produce 75kwh/hr of energy. Assume the engine converts 33% of the energy in the gasoline. We need to input 250kwh of gasoline. Gasoline has an energy density of about 8.76kwh/l. So the max fuel flow rate is about 30l/h. This is 8 gph.

I left a bit of slack in the calculaitons by rounding up. Made the flow rate come out higher then it actualy is. It's close to 7gph which is the output of a 40177, so close I'd go for it and see what it does in the real world.

Since the Transalp puts out around 1/2 the horsepower of the KTM 950 (50 hp versus 100hp), it would seem that 4 gallons per hour (15.14 liters) per hour should be sufficient.

• This page has Modrover asking for advice on regulating a fuel pump. Are new float needles required? He gives up in the end, returns the Transalp to stock form, and buys a real Africa Twin.
• This post on ADVRider's Orange Crush section, has tips on selecting and mounting fuel pumps.

Mechanical Fuel Pumps

Mechanical, vacuum-operated fuel pumps are powered by vacuum from the engine. Mikuni produces a compact one for motorcycles. It pumps 14 liters (3.7 gallons) per hour at 3.2 PSI, costs around $20, and is fully rebuildable. They produce other pumps as well, but the 14 liter version is the only one suitable for the Transalp.

According to this post, 'Modrover' found that the 3.2 PSI from the Mikuni pump was too much for the Transalp's float needles to handle:

I own a '88 XRV650 now, but did the AT tank mod to my Transalp awhile back. I used this pump and found it to be a bit more than the stock needles could take. It was pumping too good!  ;^)

Pros:

• Inexpensive ($20ish).
• Rebuildable.
• Automatically stop pumping when the engine stops. i.e. they won't continue pumping gas all over after a crash.
• Output may increase with engine RPM?

Cons:

• May be less reliable than electronic pumps.
• Requires a new vacuum line.
• Potential for vapor lock in hot conditions. Engine heat boils the gasoline in the tube between the pump and the carb, so the pump begins ineffectively pumping and compressing gaseous gasoline.
• Only available in a single pressure rating which, according to 'Modrover', is too much for the Transalp's float needles.

Resources:

• • Mikuni website
    • DF44-211: 1 outlet, 14 Liters/hr
• A site selling Mikuni vacuum pumps from the K&L catalog. It appears that one can choose between genuine Mikuni and a generic pump (?).

Electronic Fuel Pumps

Facet (a Purolator company) makes solid state fuel pumps, which claim to have no moving parts or diaphragms to wear out.

Pros:

• May be more reliable than mechanical pumps.

Cons:

• More expensive ($33 - $48 from Aircraft Spruce & Specialty Company).
• Not rebuildable.
• Requires a switched electrical supply, preferably one which cuts out when the engine dies so that the pump doesn't continue pumping gasoline onto the ground after a crash, leading to a fiery death.

Resources:

• Facet-Purolator's fuel pump web page.
• This post describes using the Facet 40105 electronic fuel pump from Aircraft Spruce and Supply.
• This post mentions that Purolator's filter (F10028) screws into the Facet pumps, and is much shorter than Facet's own filter.
• This post mentions that the Wix 33049 filter may be compatible.

Short list of Facet pumps (pumps which may be usable on the Transalp):

Model	Pressure	Flow Rate (gallons/hr)	Check Valve	Anti- Siphon	Comments
40105	3 - 4.5psi	30 GPH	no	no	Too much pressure, no shut-off valve
40163	1.5 - 2.5psi	17 GPH	yes	no	Great pressur, but no shut-off valve
40171	2 - 3.5	15 GPH	yes	yes	Possibly too much pressure
40177	1 - 2 psi	7 GPH	yes	yes	Good choice
40252	1 - 1.5psi	6.5 GPH	yes	yes	Good choice

I have installed the 40105, which clearly puts out too much pressure, since it starts too easily when cold, and runs worse at idle with the pump engaged. Also, it is capable of pumping around 7.5 times the volume of fuel needed by the Transalp engine! Finally, it has no anti-siphon/cutoff valve, which means fuel could continually leak into the carburetors, cylinders, and crankcase when the bike is parked!

I would guess that the 40252 or 40177 would be the Facet pumps most suitable for the Transalp. The 40252 uses a 'Packard' connector, which is simply a brand of sealed quick-connector.

Pressure Regulation

The Africa Twin's fuel pump is voltage regulated. At around 1,000 RPM, voltage to the pump is about 3V. At higher RPMs, it reaches 12V.

• This XRV.org.uk post mentions voltages.
• This thread discusses the stock Africa Twin fuel pump versus the Facet. It is indicated that the Africa Twin has some sort of regulation circuit which varies the input voltage from 3V up to 12V, and has a cut-off for safety.

It may be possible to use a fuel pressure regulator:

• This regulator might work (Mr. Gasket adjustable 1 - 6psi).

People seem to generally indicate that a motorcycle should only require 1 - 2psi.

Another option may be to use an RPM-regulated fuel pump intended for karts.

The Mikuni mechanical (vacuum-operated) fuel pump may increase output with RPM, but it's not clear whether this is the case.

Swingarm

The Africa Twin has an aluminum swingarm which is is longer than the steel Transalp swingarm. It can be fitting with relatively few problems. Notably, the drum brake stopper has to be ground to fit the Africa Twin swingarm (assuming an Africa Twin disc rear wheel hasn't been used as well), and a 124 link chain is needed.

The RD03, RD04, and RD07 swingarms appear to be identical, but in fact differ. The RD04 swingarm is slightly longer than the RD03 swingarm. The RD07 swingarm has slightly different mounting spacers and bushings and requires adaptation to the Transalp. If an Africa Twin rear wheel is to be used for disc braking, note that the disc and bracket are different on the RD03 than on the RD04 and RD07. See below, under "Rear Brake".

• Translated "Transalp with Africa Twin swingarm" (from transalp.de).

Swingarm Parts Interchangeability

This diagram from the XRV750N microfiche is colored to indicate compatibility of many of the swingarm parts between the Transalp and the RD04 Africa Twin. Green indicates that the part numbers are the same, while red indicates that the parts differ.

Chain Slider

This ADVRider post mentions two European sources which ship internationally and stock Africa Twin chain sliders.

Rear Brake With Africa Twin Swingarm

The stock drum brake housing can be machined to fit into the slot on the RD04/RD07 swingarm.

Alternatively, an Africa Twin rear wheel can be used to get a disc brake. This post provides the following information on rear brake disks:

Model	Rotor Dia.	Internal Dia.	Bolt Center Dist.	Bolt Dia.
PD06	240mm	105mm	125mm	10.5mm
RD03	240mm	105mm	125mm	10.5mm
RD04	256mm	144mm	166mm	10mm
RD07	256mm	144mm	166mm	10mm

The same post goes on to point out that the RD03 and RD04 rear caliper brackets are for different diameter disks, but they are interchangeable in terms of width along the axle. So, if you have a 240mm disk, use an RD03 caliper bracket. Otherwise, use an RD04 or RD07 caliper bracket, regardless of which AT swingarm you have.

Rear Brake Rotors for Africa Twins

EBC

• RD03 and later Transalps with disc rear brakes: MD6097D.
• RD04 and RD07: MD6103D, pads FA140 or FA140HH.

Buying Parts

Ebay

Ebay is a good source for used Africa Twin parts. I recommend Ebay Germany since shipping prices from Germany are reasonable, and German sellers have proved very helpful. UK sellers have either refused to ship, or charge exorbitant rates, and Italian sellers want nothing to do with me.

Payment

Traditionally, German Ebay sellers accepted only SWIFT money transfers. Ask your bank if they can perform an international money transfer. Get a copy of the transfer form, and look for "SWIFT" in the routing number area.

More recently, some German Ebay sellers have begun accepting PayPal. This makes the process much simpler and faster.

Make sure to get a shipping quote before committing to purchase!

German Terms

Finding parts in German can be tough without any language skills.

English	German
Fairings	Verkleidung
Tank Support Bracket	Verkleidungshalter ("fairing bracket") Kühlerhalter ("cooler holder")
Swingarm	Schwinge
Brake Rotor	Bremsscheibe
Sprocket	Kettenrad
Sprocket Carrier	Kettenradträger
Rear	Hinten
Wheel	Rad
Rear Wheel	Hinterrad

Other

• This post gives contact information for a seller in Singapore.

Substitution

Honda reuses parts whenever possible across models. It's worth finding part numbers on the microfiche and looking them up online. Ron Ayers has an excellent parts lookup facility.

Petcock

According to this page, "the left AT petcock is the same as the petcock for a 1990 NT650 Honda Hawk" ($55 at BikeBandit.com).

Microfiche

The Honda parts microfiche for Africa Twins is an absolute necessity. I have made PDF copies particularly relevant pages of the XRV750N microfiche:

• Swingarm
• Rear Wheel
• Gas Tank
• Rear Suspension
• Front cowl

Resources

Conversion Examples

• dualdogdave appears to have a very clean Africa Twin swingarm and fork conversion (called TANTAT).
• Jeff Stoess AfricaAlp: XR600 forks, RD04 swingarm, 30mm spacer on the rear shock.
• Jeff Stoess RallyeAlp: XR650L forks, stock swingarm with 30mm spacer, EBC oversized rotor kit for XR650L, Boano fairing, 1983 CR250 rear shock, IMS Pro Series footpeg copies