[Jamesriot]

Has anyone ever convert 500 EFI to Carburetor system? Is it easy to make changes and will it make any problems later?

[barenekd]

There is a kit available from Hitchcock's.
The swap should work fine, but then you will start battling the carb problems that show up on this forum weekly. Actually you shouldn't have that many problems, except for the ones that are inherent with a carb system. Just a few more little things to go wrong.
Can't really imagine why you'd want to.
Bare

[walken4life]

Have to agree with Bare.  Anything that could be changed on a carb (and more) can be changed on the EFI system by a shop that has the right tools and know-how to reprogram it.

Though, the built-in EFI computer should be able to automatically handle small changes like high flow air filter and less restrictive exhaust and adjust accordingly.  That is the beauty of fuel injection.

[Arizoni]

I think some people just like to frinkle with things in an attempt to improve on what they have.

With EFI there is very little that can be done besides changing the inlet filter, the exhaust system, the spark plug and the oil. 

With this limited small number of things to frinkle with,  owners start looking at their lawn mowers and gas weed trimmers.  Dangerous indeed when one considers their wives reaction to grass and weeds growing up past their knees and the man standing there with a unstartable mower! 
(For reasons that escape me, wives don't seem to mind unstartable motorcycles unless it is theirs.)

[ace.cafe]

Unless you have some internal engine modifications which require something more than the existing capabilities of the EFI, there is no particular reason to change.

[The_Rigger]

Has anyone ever convert 500 EFI to Carburetor system?

I can't for the life of me imagine why you would want to.

Can't for the life of me imagine why anyone would want to change *any* fuel-injected engine over to carburetor, as a matter of fact...

[Jamesriot]

Thank you for your help, I could not agree more.
but, Does a difference to the sound of "thumping" and low idling if the conversion is made?

[ace.cafe]

It shouldn't change the "thump" unless it's tuned improperly.

[barenekd]

The only way to change the sound of the "Thump" is by silencers. My G5 occasionally idles at below 1000 rpm. even low enough when it's cold to keep the autodecompressor open. You might be able to tune a carb to get a more consistent  low idle speed, but you'd be giving up all the other advantages, better mixture, better mileage, altitude compensation, etc, for a possibly better idle sound? Not me, mon!
Bare

[Chasfield]

I can't for the life of me imagine why you would want to.

Can't for the life of me imagine why anyone would want to change *any* fuel-injected engine over to carburetor, as a matter of fact...

It depends on what led the designer to implement fuel injection. These days they do it to get extra lean running to satisfy Euro. regulations. The EFI is set just this side of the engine quitting so that emissions are up to code and we can all sleep soundly. Back in the seventies, fuel injection was installed as a performance upgrade on prestige cars and it made them run like hot rods.

I like the second type of fuel injection but not the first - my car has the first and it manages to be gutless in the mid range, yet has a tendency to surge on the throttle. Most unpleasant to drive. Reckon the motor would run much better with a pack of Dellortos installed.

[barenekd]

I've had mine dynoed with the EFI muffler and it has a very good mixture range. Wouldn't want it any different. Mid range is the best part of it.
Bare
 

[Arizoni]

While there's no denying that the RE's fuel injection and cam timing is set up for low emissions and high fuel mileage there also is obviously a performance boost as well.

The classic 500cc Iron Barrels of 1952-1962 delivered 25 horsepower at 5250 rpm ("Royal Enfield, The Postwar Models" Roy Bacon, p 166).

The fuel injected 500cc UCE is rated at 27.2 horsepower at 5250 rpm. (20.3Kw/746 = Hp)

That's an 8 percent increase over the carbureted Bullet.
In both cases I am referring to the engines horsepower, not the rear wheel horsepower which is much reduced by the inefficiencies of the transmission and the chains involved in getting the engines horsepower to the rear tire.

[Lwt Big Cheese]

No other changes to the engine at all?

Wouldn't the the carb version liberate more hp if gas flowed? More than 10%?

[Chasfield]

Modern EFI Bullets have an 8.5:1 piston, which by itself would account for the power output advantage of new bikes over the fifties iron barrel.

[ace.cafe]

After procuring measurements for the EFI throttle body, and seeing the port and valve sizes, the EFI throttle body has sufficient diameter(32.5mm) for making good power. It's not the restriction in the inlet system if the throttle is open. It has about the same area as a 32mm carb would have. It can get enough air.
Getting it past the very low-lift valve is the issue in the EFI engine. It has short duration valve timing, and low valve lift. It was designed purposely to be low power, and have most of its torque at the low rpms. It can be modified to do more of what we want on the highway, but it isn't the fault of the EFI entirely.
The EFI does have the rev-limiter though, and that would limit the max rpm unless we can get around that somehow via programming. A carb wouldn't have that limiter on it.

If I put a carb on it, it would still be the 32mm TM32 flat-slide carb that I use on the Fireball. That's a really killer carb.

[cyrusb]

I don't think performance is what the original poster is after. Gee, a whole 27hp! If a carb befuddles you, then FI is the answer. Remember, this is the classic forum, where guys bought this bike BECAUSE it has a carb, points, cable brakes,non unit construction etc. It is these features that makes these bikes unique. And although it lacks the blazing performance of the new bikes, it more than makes up for it in it's "oil lamp" simplicity. 

[mustangdave]

I have an 05 that I just get a hoot out of tinkering with...I went through a number of issues as I've sorted the bike out...finally got the carb set up going GREAT...the bike runs like nobodies business...IF I didn't want to tinker I woulda bought an EFI model...as it is I wouldn't have it any other way...wrenchin is cheap entertainment and keeps me out of trouble.

[cassiopia]

I have been under the impression that a carb would produce more torque. 

[Adrian II]

Modern EFI Bullets have an 8.5:1 piston, which by itself would account for the power output advantage of new bikes over the fifties iron barrel.

I think the stock 500 Redditch Bullet (we can ignore the Woodsman and Westerner models) was only 6.5:1. You can also factor in the 1⅛" (28mm) Monobloc carb and the old-style hemi-head combustion chamber instead of the EFI's more modern design which RE (India) carried over from the AVL/Electra-X 500. Also the "S" cams were only a touring cam, regardless of what they have since been shown capable of doing for the Electra-X. The Big Head Bullets might have managed 27bhp, I'd have to check.

My '57 old 500 was in a lower state of tune than my old Electra-X and it showed. I gather the current owner has it running at 7.5:1.

A.

[ace.cafe]

I have been under the impression that a carb would produce more torque.

The throat(venturi) size of the carb, or EFI throttle body size, will give approximately the same torque curve results if they are the same size on the same engine. It more-or-less sets the air speeds in the inlet.
Typically smaller throats give more low rpm tq, and larger throats give more upper rpm tq, within certain limits of the rest of the engine design.

[ddavidv]

The HP gain is the result of the UCE engine, not so much the EFI though the latter may improve burn efficiency.

I come from an automotive background. It's been dyno proven that an EFI system vs a carb on a street spec engine offers no tangible performance advantage with both properly tuned. What the EFI does is tune on the fly, whereas the carb is limited to whatever the air temp or altitude is.

I've read of various bike guys going from EFI to carb for 'reliability' because they fear EFI failing on the road in a way they can't easily fix. The theory is you can disassemble a carb and clean it but can't fix a failed pickup or control module. What they ignore is the failure rate on those components is so negligible it's probably not measurable.

[eskasteve]

One of the biggest advantages to a carburetor system is it provides the owner the ability to make his or her own adjustments. These tweaks only require simple hand tools along with the appropriate knowledge regarding what you're trying to accomplish. Sure FI provides more precise fuel metering but at the cost of the owner being able to easily and cheaply make modifications. RE is the embodiment of simplicity from a bygone era of motorcycling that unfortunately is long gone. Emission standards, though, have bitch slapped quite a bit of that simplicity to the curb. Heck, my last dirt bike, a 2010 Husqvarna 450TE, was fuel injected. Because it was street licensable it had a catalytic convertor and a very annoying lean run stumble. It was unridable at slower trail speeds as delivered. Out came the cat and a Power Commander was installed. Then it was off to the DynoJet approved dealer to get the initial settings loaded into the Commander. About $500 total. Credit where credit is due, that bike ran incredible after that. DyboJet gave recommended programs that an owner could load with their own laptop to compensate for any new changes.

[Paul W]

It's a similar argument for and against points ignition as opposed to electronic; it boils down to personal preferences.

In the past I've had various cars with distributors and points. I found the weak point to be the condensers. For one car in particular I got really tired of having to buy two or three condensers at once in the hope of getting one good one. For me, modern electronics are better; they're usually fit and forget.

My 2004, iron barrelled Bullet Electra 350 has possibly the best of both worlds. It came out of the factory with a carburettor but TCI ignition so there are no points or distributor to worry about; the ignition is powered by a magneto which runs off the left hand end of the crankshaft, similar to the present UCE engined Bullets. I found a spare TCI ignition module (cost just £12.99!) and put it in my spares cupboard in case the original fails, but I'm really not expecting to have to use it.

[Adrian II]

powered by a magneto

I wish the factory wouldn't call it that, it's a permanent magnet alternator!

A.

[Paul W]

[qupte]powered by a magneto

I wish the factory wouldn't call it that, it's a permanent magnet alternator!

A.

Seeing as we both know, I don't think it matters too much. Many modern similar setups are similarly called "magneto" ignition.