Performance mods for a Royal Enfield Bullet

[BJ250]

For all you engine experts out there, I am looking at trying to improve the BHP on my Royal Enfield Bullet without doing any major modifications to the bike. So with my limited knowledge about engines, I have thought of doing the following:

1. The bullet comes with a Micab carburettor with a 28mm bore (This info is from the Hitchcocks website and I have no clue what the bore refers to!). Anyhow, I'm thinking increase the pilot, needle and main jet's sizes so more fuel pases through at the respective throttle stages.

2. Adding a free flow air filter like the K&N rc1060 pod filter to support the increased fuel flow due to the larger sized jets in the carb.

3. installing a Goldstar silencer.

A general question: how would shortening/ lengthening the header pipe effect the performance? I know its got something to do with the compression, but an explanation in layman's terms would be much appreciated.

Thanks for your time

[slofox]

You would need to balance 1. and 2.

Had a mate put larger jets into a constellation - it ran rich and farted and popped until he leaned it out again. Waste of time. And gas.

Not sure about 3.

[Edbear]

In the old days, a rough method of getting the correct pipe length was to travel on a gravel road in the dry, get to about 40mph and kill the engine in top gear, coasting down to a stop. The distance the dust was drawn up the tailpipe was where you cut it off. Never tried it of course...

A shorty muffler, (ie: less restrictive), and freer intake can help a bit. If mucking about with jets, you really need to consult someone who knows as you could waste a lot of time and money experimenting until you get it right, as bigger is not always better.

[BJ250]

thanks for replies guys..

so, there is no point installing a free flow air filter without modifying or changing the carb since it would then be running rich, right? so unless I am willing to do both modifications 1 and 2, there is no point doing just the one.

I might have to look around for a good RE workshop around here to do the job for me..

[White trash]

thanks for replies guys..

so, there is no point installing a free flow air filter without modifying or changing the carb since it would then be running rich, right? so unless I am willing to do both modifications 1 and 2, there is no point doing just the one.

I might have to look around for a good RE workshop around here to do the job for me..

The beauty of your machine is of course that it is amazingly simple to work on and play with. Brian D'marge (Or similar) seems to know a bit about these bikes, send him a PM.

[AllanB]

Header length - longer tends to offer more torque than shorter, diameter will make a difference too........ if it is a skinny restrictive header going up a size may be an improvement but no doubt introduce it's own tuning issues.....


Start with the old school mods first - a less restrictive muffler on the stock header, a decent free flowing air filter and alter the carb mixture/jets etc to suit.

The 2 mods of intake and muffler should lean out the stock carb setting requiring you to make it richer. Unless it is running very lean from stock there is no point altering the carb without the other changes.

Being a really basic motor it should give you a bit more seat of the pants omph but don't expect it to beat SV650's!

[BJ250]

The beauty of your machine is of course that it is amazingly simple to work on and play with. Brian D'marge (Or similar) seems to know a bit about these bikes, send him a PM.

Agreed. even with my limited knowledge, I have been able to switch gear sprockets, tappet adjustments and de-carbonising by just following the manual.

[ducatilover]

The beauty of your machine is of course that it is amazingly simple to work on and play with. Brian D'marge (Or similar) seems to know a bit about these bikes, send him a PM.

I second that. D'marge has a fairly extensive knowledge on most old things, plus many new ones. If he can't help, sell it.

[BJ250]

If he can't help, sell it.

sell off a Royal Enfield???? no way!! been riding RE's since '96, took a 4 year break and just got another one last week. absolutely love these bikes

[The Pastor]

talk to brain, he races them i think

[BJ250]

Header length - longer tends to offer more torque than shorter, diameter will make a difference too........ if it is a skinny restrictive header going up a size may be an improvement but no doubt introduce it's own tuning issues.....


Start with the old school mods first - a less restrictive muffler on the stock header, a decent free flowing air filter and alter the carb mixture/jets etc to suit.

The 2 mods of intake and muffler should lean out the stock carb setting requiring you to make it richer. Unless it is running very lean from stock there is no point altering the carb without the other changes.

Being a really basic motor it should give you a bit more seat of the pants omph but don't expect it to beat SV650's!

Thanks for the header explanation AllanB.

I have a short muffler on the bike right now. I'm thinking a slightly shorter conical shape would work better. The carb settings on these bikes is relatively lean as stock so can be tweaked a bit. I think K&N should be my next port of call

Dont wanna go racing on it, but a bit more oomph would be nice!

[pete376403]

3 C (cam, carb, compression) is the key to taking a nice soft woofly civilised motor and turning it into a fast cantankerous grenade.
Trouble is once you get onto the tuning merry-go-round, where do you stop? Tuned motor gives more power at the expense of narrower powerband, so needs close ratio gearbox, more speed needs better brakes, better suspension, etc. It never ends.
DBD Gold Star BSA is a prime example of this.

But if you're still keen, lots of people sell bits, eg:
http://www.royalenfieldaustralia.com...ance_parts.php

[ducatilover]

You don't necessarily have to go too silly... I imagine with head work, cam, port shape, polish and angles cleaned up, a slightly longer duration/higher lift and closer lobe center cam, with the correct carb work, you could turn it into quite a peppy beastie.

[Scouse]

For all you engine experts out there, I am looking at trying to improve the BHP on my Royal Enfield Bullet without doing any major modifications to the bike.

Forget it...............

[BJ250]

I was advised to consider replacing the stock rockers with lighter ones, but then the current carb would be useless and I would have to invest in a Mikuni 30mm or 32mm. Then I would have to look at increasing compression and so on. Like you said - it'll be the never ending story

I dont want to get a huge increase in bhp since the Enfield is ideal for my needs already as a long ride cruiser. but it would be a thrill to be able to get a bit more power out of it myself. (as i said earlier, im not engine savvy so it would be an ego booster if I could do a little something to the bike myself)