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BJ250
29th October 2010, 15:05
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!).:confused: 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
29th October 2010, 15:29
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
29th October 2010, 15:31
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
29th October 2010, 16:26
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
29th October 2010, 16:29
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
29th October 2010, 16:38
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
29th October 2010, 16:39
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. :woohoo:

ducatilover
29th October 2010, 16:40
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
29th October 2010, 16:51
If he can't help, sell it.

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

The Pastor
29th October 2010, 16:53
talk to brain, he races them i think

BJ250
29th October 2010, 19:18
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 :yes:

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

pete376403
29th October 2010, 23:52
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/performance_parts.php

ducatilover
30th October 2010, 00:01
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
30th October 2010, 00:49
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
30th October 2010, 08:47
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 :facepalm:

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) :innocent:

SS90
30th October 2010, 09:09
Lighter rockers?

FFS, be careful who you listen to there mate. Such things are really only going to make a difference on an engine that has several other modifications.

Before even considering lighter internals, consider your carb size.

By your own admission, you not really savvy with the "Ins and Outs" of tuning, so the wise thing to do would be grab a copy of Phil Irvings book "Tuning for speed" it covers stuff from that era, and if you read it cover to cover, you will decided for yourself,not only what actually makes power on an old single banger, but also what you can do for yourself.

Compression is always a place to start( that is, after measuring what you have now), and so is a camshaft.... I am sure you will be able to find a hot cam suitable for "sporty" road riding that already exist, and is well tested...those bikes have been round since Before Rossi was a twinkle in his dads eye.

It has been said already by others (cam compression carb), and with old designed single bangers, there is plenty of room for improvement in this area.

Will make it hard to start though!

BJ250
30th October 2010, 09:22
hehehe... thats why I dont want to do anything with the internals at all.. I just want to do the free flow filter and exhaust. And if changing the jets isn't gonna fuck it all up, then that would be an option too. just basic shit that i could do myself and not ruin the bike

I'll hunt for the Tuning for speed book. can never read too much, ey :yes:

I have been using the Hitchcocks website to read up on the technical stuff about RE's and nothing bad has happened to the bike yet! :blink:
http://www.hitchcocksmotorcycles.com/

calmone
30th October 2010, 10:10
You say you have been online at Hitchcocks, they also put out a vey comprehensive Manual each year for the Bullet both 350 and 500 versions. It details all that is available in the way of aftermarket bits etc and when to use them.
I have a 350 Bullet with a High Com piston and a few other mods and the small muffler option, but still with standard carb and filter. A little underpowered compared to my previous 1200,s I rode but a fun ride.
They are easy to work on, but can be a little fiddly around the carb , with mixture adjustments etc quite critical.

BJ250
30th October 2010, 10:39
I did see the 2010 manual. just gotta send them the international reply coupons so they mail me a catalogue.
I notice that most of their gear comes from India so I am trying to source the parts directly from the Indian dealers if possible. might be able to save quite a bit that way.
The Enfield is definitely underpowered compared to most other bikes but its the fact that the engine is so basic that I really like about it.
what kind of mods have you put into your bullet?

calmone
30th October 2010, 12:10
Just the Piston, and the Front Brake mod that Hitchcocks detail, Saddle Seat and Saddle Bags and the small Muffler. It is a Kick Start 2000 model ex India.

banditrider
30th October 2010, 12:22
http://www.musketvtwin.com/home.html

Paul in NZ
30th October 2010, 12:59
Look - I'll put my grinch hat on...

If you just want to make it go faster and you dont approach the project with a specific goal and look at the bike holistically. You are doomed to waste money and blow stuff up. If you dont want to do that then be happy with what you have which is a pretty good thing as is.

Taking my grinch hat off

The bullet motor can be made to go alarmingly fast for an equally alarming short amount of time) BUT build quality is suspect so before any performance mods, consider stripping it down to make sure everything is dickity pooh. I once got chased by a decrepid Bullet running a 30mm AMAL, megga and modified compression ration and it went real good (no cams or anything tricky) and toped out around 90 to 95mph! BUT the guy had rebuilt the whole bottom end properly, checked the oil delivery was correct (it wasnt) and cleaned up valves and ports.

The other option to adding horsepower is removing weight....


Hitchcocks seem to know a LOT about all this stuff - I doubt they will put you far wrong.

Grumph
30th October 2010, 15:56
Paul has pretty well covered it. Put the thing together properly first...
If yours hasn't got electronic ignition, find one & fit it - the points setup is crap.

i had one here i sorted out for a friend and even set up properly it was slow.
A Norton ES2 - 1952- here at the same time was way quicker....

BJ250
31st October 2010, 08:31
Thanks for the replies guys.. I took the old girl out for a spin yesterday. planned to go up the road and back - wound up doing a 250km round trip! :scooter:

That musket vtwin is a sweet bike. that is one dedicated biker for sure with all the work he has put into it.

Thanks Paul. I don't want the bike to go faster, she is perfect already. I'm not into speed. i just want to try and improve on the bike, thats all. Maybe i ought to get myself an old trashed Bullet and experiment on that. I cant find anybody with Enfield knowledge here in Hastings and I'm not savvy enough to strip and rebuild her myself.

Grumph, by electronic ignition, do you mean a push start ignition?

bsasuper
31st October 2010, 09:26
Have you tried mounting a J-type jet booster engine?

BJ250
31st October 2010, 09:28
hmmm. wasn't there a MiG for sale at Turners recently? :whistle: :bleh:

Paul in NZ
31st October 2010, 12:15
If you just want to improve it then rebuilding they way it should have been built is the first step. Quality is patchy - yours may be perfect but.... better carb and electronic ignition (not electric start) is a good 1st step. Or just love it for what it is...

BJ250
31st October 2010, 14:49
been reading up on the electric ignition and it does sound like a good idea. Will definitely make life easier when it comes to cold starting

thanks everybody for the replies

Flip
31st October 2010, 14:55
What a cool project.

I would say a better slip on can and air filter would be a good place to start, but keep in mind the more air you are able to feed the leaner the mixture will get. Keep an eye on your plug colour. You might find that you can get the mixture right(ish) by raising the needle, if not the carb will need a bigger main jet.

It's just my opinion, but I like points ignition, folk seem to like to fit electronics to vehicles because there are other problems with their ignition systems. I can fix points ignition on the side of the road and a spare set of points and condenser takes up no room in my tool kit and is cheap.

Also don't go past running the bike up on a dino, its the only real way to set the ignition and mixture correctly and get the best from the parts you fit to your motor.
Do a web search on performance mods to RE's there will be a wealth of knowledge out there, but don't take too seriously, 2/3rds of it will be crap.

BJ250
31st October 2010, 18:06
Thanks Flip. I spotted an Amal carb conversion kit sold by Hitchcocks. it comes with a 30mm Amal MK1 Concentric carburetter and S&B performance filter. that might be the way to go for me right now..

anybody know of any Enfield Bullets going dirt cheap? Even if it needs a bit of work no worries

Paul in NZ
31st October 2010, 18:33
..

anybody know of any Enfield Bullets going dirt cheap? Even if it needs a bit of work no worries

You dont want a cheap one - inexpensive yes, not cheap though...:innocent:

BJ250
31st October 2010, 19:00
lol :facepalm:

pete376403
31st October 2010, 20:38
Thanks Flip. I spotted an Amal carb conversion kit sold by Hitchcocks. it comes with a 30mm Amal MK1 Concentric carburetter and S&B performance filter. that might be the way to go for me right now..

anybody know of any Enfield Bullets going dirt cheap? Even if it needs a bit of work no worries

Amal MkI concentric AKA the metered leak. Mikunis are far nicer, and there's probably more knowlege about jetting them (MkIs are ancient)

Get hold of a service manual - downloadable if you use torrents (*cough*). These engines are dead simple and well within the realm of stripping down on the side of the road if need be (just like all bikes used to be). A manual, a few tools and a bit of common sense and you should be able to handle most things.

BJ250
1st November 2010, 08:15
ok, I'll do a bit of research on the MkI and Mikuni before making a decision.

Already got myself the service manual and a bunch of tech notes from the Hitchcocks website. Their guides are damn thorough with pictures as well