ROYAL ENFIELD CLASSIC 500 CARBURETTOR CONVERSION

Here’s everything you’ll need to know about converting the Royal Enfield Classic 500 from EFI to a Carburettor.

I bought a second-hand Classic 500 back in early 2011, it was an August 2010 model with barely 300 kms on the odometer. Since then, I’ve clocked over 30,000 kms (not much by riding standards) and it has been far from a painless ownership experience.

My model had the older ECU, and all attempts to get it updated have been futile. Every service centre I went to had one of three responses – they don’t have the equipment, the equipment is broken or the guy who knows how to use the equipment isn’t in. The incorrectly mapped ECU caused a lot of jerking at low speeds and often made the bike run rich. And then there’s the EFI, an excellent system that I’ve never had issues with. However, stories have trickled in from other owners about the pump failing or nozzle getting clogged due to impure fuel.

If your bike is running fine, I wouldn’t recommend you make the switch. However, if you do decide to do so, here are some advantages as I understand it:

• The overall cost of ownership becomes cheaper as the ECU, wiring harness and fuel injector are prohibitively expensive. Take note, the ECU and EFI are supposed to have a very low failure rate and should ideally last you for the lifetime of the bike itself. Even so, you’ll probably need to carry a spare for long rides (Murphy’s law being what it is) and have to buy them anyway.
• Get your bike repaired and running no matter where you are. Every mechanic in this country knows his way around the carburettor system and has the spares needed, can’t say the same about EFI/ECUs.
• You’ll be able to use aftermarket air filters and exhausts (silencers). The Indian market Classic 500s have an ECU that runs an open loop, it doesn’t automatically adjust for changes made.
• Increased power and a smoother ride.

Anyway, let’s cut to the chase and see how to go about the conversion. You have two options:

I ordered the kit for about ₹6000 and got it installed on my bike post-haste. The box contained:

1. Adapter plate for fuel pump
2. High flow Petrol tap and hose
3. 33mm Inlet manifold rubber
4. UCD 33 carb with TPS connector jetted to suit ECU models
5. Nuts, bolts and other assorted components needed.

It took about an hour with my mechanic to get it all in place. While the bike started flawlessly, some wiring changes are required that go beyond a basic swap. Once you swap out the EFI and throttle body, a lot of sensors are disconnected. Hence, you need to start the bike before the ECU runs a systems check and detects their absence. There are two ways around this, swap wires on the TPS sensor or cancel two wires on the ECU. Both methods essentially prevent the systems check from completing, I’m not sure if the benefits of having an ECU still apply though. Another issue that you’ll probably face is that of the air filter hose being insufficient in length, it didn’t bother me as I use a bolt-on K&N filter.

I opted not to make the changes and instead start my bike immediately after turning on the ignition. It worked fine and is indeed much smoother than the EFI/ECU system I was originally on. I didn’t bother checking if fuel efficiency increased as it wasn’t the reason I wanted to convert.

Complete Conversion

After running the indiMotard kit for about two months, some problems started cropping up. The bike would switch off randomly while I was riding (thankfully I’m well-versed in jump starting the bike while in motion) and the TPS sensor appeared to malfunction as it started up just fine once I disconnected it. My mechanic narrowed down the problem to the wiring harness and not the indiMotard conversion we had undertaken. Now I was left with two options – either buy a new Classic 500 wiring harness or completely convert to a TCI system. I decided to go with the latter.

One of the first references I found on the web for going about a complete conversion was from Hitchcocks Motorcycles in the UK.

They sell an Amal Carburettor Conversion Kit (EFI Models) that seems to do the job quite well. Being in India, I decided to take their kit as a reference and source the parts locally. You’ll need:

• The indiMotard kit (refer above to know what it has). Primarily because they manufacture the adapter plate for the fuel pump. Another option is replacing the fuel tank with that of a Classic 350. They also claim the UCAL BS33 Carburettor supplied is customised specifically for EFI models, I can neither confirm nor refute that. I would just go ahead and buy the kit from them. Cost ₹6000.
• Wiring harness for the old Classic 350 (rectifier mounted in front). This is the harness that fits my 2010 model. I’m not sure if later models of the Classic 500 need the newer harness. Cost ₹1300.
• Magneto and coil for the Classic 350. The Classic 500 magneto and coil have sensors and the timing doesn’t seem to match if you try to use it with the 350 wiring harness. I learnt this from trial and error. Cost ₹1625.
• TCI unit. Cost ₹1300-1500.
• Throttle Position Switch. This is optional in my opinion, many people end up cancelling this out anyway as the dual throttle wire invariably ends up jamming. Cost ₹100.
• Ammeter to replace your fuel/engine light gauge. Cost ₹350.

It took about 3-4 hours of real work to make the switch, I spent a considerably more amount of time buying parts as their need was ascertained. The bike now performs flawlessly and is an absolute pleasure to ride. The presence of an ammeter allows me to keep an eye out for shorts in the wiring, while the absence of a low fuel indicator reminds me to start using the fuel tap (which I kept permanently on reserve after the partial conversion).

I’ll update this article if anything else does crop up in the course of the next few months. Do drop me a message in the comments if you have any queries or additional advice to give.

Note: The above article has been written based purely on my understanding of the whole thing and what I have done to my bike. I don’t take responsibility for any damage/issues that may crop up if you try to do the same.