Royal Enfield Tech/Modifications

[thegreasepit]

Royal Enfields are the red-headed step child of British iron and not really known for their speed or ability to retain oil, but they are a fascinating motorcycle with some ingenious engineering. The neutral finders on all 4 speed gearboxes eliminated fumbling around for neutral when sitting at a stop light- patented in 1948, and is available on damn near every Enfield built. Details like that make these bikes stand out, although still shadowed by the better known Triumph and BSA, from rest of the British motorcycles.


I'm trying to compile as much information for the big twins (Meteor, Super Meteor, Interceptor, Constellation.... and Apache, Trailblazer, etc for the Indian badged Enfields) regarding modifications on keeping that precious oil where it's supposed to, making these beasts go faster, and staying in one piece. Although, I aimed this thread at twins, most mods will be useful on the singles as well and some interchangeability with parts.

I'll start off a crankcase modification that will keep it breathing right and reduce leaks.


Enfield Twin Crankcase Breather Mods


I have modified my case differently, but is still effective. The area of the case that under the magneto is drilled and tapped with a brass barbed fitting that vents pressure from the timing chest. I used a 3/8 hose barb and ran the vent hose over the transmission and next to the rear fender.
Picture of case attached.


Pistons: The 700cc models (Constellation, Super Meteor) have interchangeable pistons with the 350 and there are 8.5:1 compression pistons available, which is a vast improvement to the measly 7.25:1 stock compression. The 750 Interceptors have 8.5:1 compression from the factory, with plates at the base of the cylinders that can be removed to bump it to 9:1.

Constellation cams are a direct fit into the Super Meteor cases. The Connie had better cams for a bit extra power over the SM.


Gearbox:

How The Royal Enfield Gearbox works

I recently bought a sealed bearing kit for my 4sp from the UK. Turns out it's a Timken (will get specs later) and that I could have bought one from a local bearing distributor. Using a sealed bearing will allow gear oil (90w or 00grease suggested) without the need to pack with hi-temp grease.


Shop / Technical Manuals

** Complete Super Meteor / Constellation service manual (including Airflow model)
I have a hard copy of this from Hitchcocks. Not as detailed, but still very useful

** Complete Bullet service manual 180+ page PDF file.


Any other mods/technical information out there?

[swooshdave]

If it were me I'd drill about a .75in hole in the crankcase and put a breather (reed valve) on it. No more leaks. Well, at least from excessive pressure.

[thegreasepit]

Yeah. I should have done that mod when I had my cases split but only found about it after putting the engine together. The link I posted has you drill a hole in the flat section of case behind the cylinders. A hose barb is threaded in or a section of pipe is JB Welded in place.

[thegreasepit]

I recently came up with a modification for the older Enfields, that route the oil lines between the heads and feed the rockers, that will help keep the oil cooler.

The "newer" Enfields, such as the Interceptors, had only a single oil-feed port on the timing side case half to cure the weeping between the cases at the cross-over feed to the opposite case. Also, the oil lines are routed outside the heads to keep the oil from running hotter from being in such close proximity to them.


Factory oil feed lines for a Super Meteor:





Interceptor oil feed lines:






Notice the difference? The Interceptors were the best of the best Enfields, with most of the bugs fixed and problems solved that plagued the older models. I had to upgrade.


My plan was to make my own using all the parts found at your local True Value or Ace (had a hard time finding this stuff at Home Depot or Lowes), while also keeping my original feed lines in factory condition.


Here's the parts you will need:

- 1/8" thick walled vacuum hose - a couple feet.

Obtained from any auto parts store and very inexpensive. Make sure it's the thick walled hose!


- 5/32 Brass tube - 12" length






- 5/16 steel shaft collars - need 6






- Acid core lead solder




drill press works the best.

This mod costs under $20.


Cut 8, 1" length sections of the brass tube and rough up one end with sand paper (needs to be roughed to get the solder to stick better)
Remove the set screws from the steel collars and open up the holes to 1/8". Take two of the collars and add another 1/8" hole opposite the 1/8" as this will split the oil and feed the exhaust rocker. The 5/16 opening will need to be opened up just a bit more to fit the odd, british size banjo bolt.

Remove any burrs from the drilling and rough up the area around the holes so the solder will stick well to the steel.

Press the 1" sections of brass tubing into the shaft collars, making sure the end of the tube doesn't interfere with the banjo bolt.





Solder the tube to the collars. Install some new copper washers and viola!





Took only a couple hours on a Saturday afternoon. So far, it's working without any leaks and looks good too.












Shown with new breather fitting installed.

[bon]

There were loads of british bike makers overshadowed by the big three of triumph, bsa and norton, ajs/matchless, ariel , sunbeam and of course royal enfield, i don't know why though they are a nice bike. Weren't they built in an underground factory ? The singles seem to be more popular then the big twins , there is a guy in england doing all sorts of tuning and upgrades for them , a 750cc big bore kit and modified cylinder heads etc.

Looks like a good mod for the money greasepit, should help keep the oil where it belongs.

[CarlLaFong]

Why not make the entire thing from the brass tube rather than the brass nipples and rubber hose? Also, I'm a bit concerned about the solder joints. There is no way to get those collars hot enough with a soldering gun to get a good bond. It looks like a cold joint in the pix. Propane/MAPP and silver solder would be a better choice

[DocS]

Originally Posted by CarlLaFong

Why not make the entire thing from the brass tube rather than the brass nipples and rubber hose? Also, I'm a bit concerned about the solder joints. There is no way to get those collars hot enough with a soldering gun to get a good bond. It looks like a cold joint in the pix. Propane/MAPP and silver solder would be a better choice

Second that...

I'm partial to StaBrite silver solder and StaClean flux.


Doc

[thegreasepit]

Originally Posted by CarlLaFong

Why not make the entire thing from the brass tube rather than the brass nipples and rubber hose? Also, I'm a bit concerned about the solder joints. There is no way to get those collars hot enough with a soldering gun to get a good bond. It looks like a cold joint in the pix. Propane/MAPP and silver solder would be a better choice

The brass and hose set up is a lot easier to work with than bending some brass tube. The brass tubes are 5/32 pressed into 1/8" holes...they're in there. The brass tube/collar was heated up hot enough to let the solder be melted by it and it's more of a seal than structural. Enfields don't run a whole lotta oil pressure to begin with and the worst that can happen is they start to weep a bit of oil. No big deal. This modification was to keep the oil as cool as possible by running it outside the heads, as opposed to running in tubing between the heads as the factory feeds did.

[unclechop]

Ill copy this from my royal enfield thread: https://www.jockeyjournal.com/forum/s...ad.php?t=93360
Slipping clutch pre bullet RE
Got the modified pressure plate in tonight and it works pretty well I can now kick through the compression stroke and start it first kick( the previous 3 owners have sold it due to not being able to start it properly, I think due to the clutch slipping).
Ive since found out you can buy an indian Bullet one for about ten bucks- ah well
First up the original:

The clutch assembly:

New vs Old

And finally installed

[reverb]

...a partner of my MC have a 700cc but still (after few years!) we do not can make the OIL PUMP RUN properly.
Impossible, we have been doing all type of tests, included put a new one from the Indian s bullets and adapt the little holes.
Also, make a 1/2" thick Nylon gasket for the cover and adapt a Jap small bike pump.
No pressure at all.
All lines are clear; we checked with air pressure, etc

Where would be the problem?

thanks so much for any kind of info

[Ducbsa]

Regarding using rubber hoses, I used rubber hose for an oil return line on another low oil pressure Brit bike and over a year or two, it got swollen and leaked. I was able to find some auto trans hose that slipped over the brass oil lines. Some rubber absorbs oil and is bad news.