The Royal Enfield Bullet: Lubrication System General
The Royal Enfield Bullet lubrication system is a dry sump system. It includes an oil tank, a feed pump, oil filter system, a return pump, screen filters, internal passageways, external oil lines, and an oil catch tank for oil that is blown out of the crankcase during engine operation.
My thanks to the people who put the Bullet Workshop Manual online. I borrowed some of their .gifs to illustrate this section. I also used images from Classic Motorworks, the US importer.
Specifications
Tank/Engine capacity: 2.25 liters
Recommended type: SAE 50 or multigrade 20/50
Oil pumps: feed and return, plunger type, 1/12 (one twelvth) engine speed
Oil pump shaft: worm gear, plunger connecting shafts
Oil filter: The oil filter has a spring loaded end in the mounting scheme. This allows oil to flow to the engine in the event that the filter is completely clogged up.
Seals: Cork or neoprene oil retainer, various gaskets.
Valves, plugs, pipes: Oil feed plug in crankshaft, grub screw, external oil lines, rocker pipe.
Circulation
Feed loop:
Oil is held in the oil tank. The feed pump, which has the smallest plunger of the two oil pumps, sucks oil from the tank and pumps it through the filter element. From the filter oil is routed into the crankshaft, through the right hand flywheel into the connecting rod journal. Thereafter it is thrown around inside the crankcase and falls into the bottom in a relatively thin layer.
Return loop:
The return pump pulls oil from the bottom of the crankcase and pushes it up into the engine top end. The oil travels from the return pump directly into the external oil lines. It goes into the rocker assembly, falls out of that through the shafts that the pushrods are into the timing case, where it pools and lubricates the timing gears. Eventually the level rises to an exit hole which routes the oil back into the primary tank.
Oil flow through the engine:
Oil tank
The capacity of the tank is listed at 2.25 liters and is cast as part of the engine crankcase. The cap is a spring loaded screw on type and has the dipstick built in. The cap is located on the right hand side of the engine. It's best to use a funnel to fill it up.
Feed pump
The feed pump is located on the rear part of the timing cover.The stock feed pump has a very small plunger. There's argument on the webboards and newsgroups about whether it is adequate. It probably is for most climates. It is possible to buy an aftermarket feed pump that passes more volume than the stock. If you live in an extremely hot climate, like a desert, you might want to consider a larger oil pump, despite the controversy. A cool engine is happier than an overheating engine.
Feed pump external:
This is the feed pump side on the engine itself, with the pump cover in place.
Feed pump internals:
There are two ports in the timing cover feed pump housing.
B: The spindle from the oil pump shaft. It connects to the plunger
D: Shaft rotation
X: Delivery to the oil filter, crankshaft, connecting rod journal, and subsequently the crankcase area.
Y: Suction from the oil tank.
There are four ports in the feed pump disc.
A: Plunger, showing bore that spindle (B) above fits into
C: The pump disc
R: Delivery port (to oilfilter, crankshaft and bottom end)
T: Suction port (from oil tank)
W, Z: Internal routing holes
Return pump
This pump is located on the front of the timing cover, just above the access port for the oil filter. However the oil goes to the filter from the feed pump, not the return pump. The return pump supplies the top end of the engine -- the valve train -- with lubrication. If the feed pump is replaced with a higher volume disc and plunger, then the return pump should be changed to match. The aftermarket (but OEM) return plunger is much larger than the stock plunger.
Return pump external (sorry about the focus!):
Return pump internals:
There are two ports in the timing cover return pump housing.
B: Spindle from oil pump drive shaft
D': Shaft rotation
X: Delivery to the valve train
Y: Suction from the crankcase
There are four ports in the return pump disc.
A': The plunger, showing the bore for the oil pump shaft spindle
C': The disc
R': Delivers oil to the external oil lines and then the valve train
T': Sucktion port from the crankcase
W',Z': Internal routing ports
External oil lines
The external lines deliver oil from the return pump to the top of the valve train (rocker arm assembly). Oil flows down through the pushrod shafts into the timing case and lubricates the cam gears.
External lines:
This is an electric start model. The placement of the line is somewhat different than the white kickstart model above. The horn also blocks the view of the exit from the return pump.
Service & Diagnosis
Crankshaft seal
If the cork or neoprene seal around the crankshaft is damaged or worn oil will be pumped into the timing case and NOT into the crankshaft. Left untreated that can be a bad thing should the problem lead to oil starvation in the engine. One symptom is copious amounts of oil collected in the contact breaker (points) housing. Oil will begin dripping from the around the plastic cover of the points assembly. If you see this it's time to investigate. Small amounts of oil are permissible and even normal, as the timing case has oil in it and that oil is pushed up to the axle that runs over to the points. However if the cork (or neoprene) seal is going bad too much oil will be pumped into the timing case and pools of it will collect in the points assembly. If this happens you must remove the timing case and inspect the crankshaft seal, replacing if necessary.
cork retainer:
Filter
Changing the filter is a straight forward procedure. After draining the oil from the middle nut at the bottom of the engine case, you can remove the small retaining nut on the oil filter cover. There are various o-rings and washers that come with a filter. Be sure to keep track of the order of rings and washers when removing. The assembly is spring loaded so that if the filter is completely gummed oil will still be sent to the crankshaft and top end. Note that the replacement filters DO NOT come with an extra felt washer so don't discard the one that is part of the endcap assembly.
Oil pumps
Since I live in central Texas where the temperature soars into the high nineties and low hundreds for 3 -4 months of the year -- with little or no wind -- I decided to put in a higher capacity oil pump (but see note below). It was a quick procedure, not as complicated as outlined in the workshop manual. For one thing, I did not remove the timing cover, so all the steps outlined in the manual that are a result of doing that fell out. At first I put the new return pump in the old feed pump -- I didn't know what the plunger size relation was. Note that the small plunger is the feed pump, the bigger plunger the return pump. All the operation required was the correct size hex wrench and a gasket scraper. When I had replaced both pump covers I also changed the oil filter. It is claimed that it can be recycled, but mine was so filthy I simply tossed it. The following proceedure is what I did:
1. Drain the oil.
2. Remove feed pump and return pump covers using hex (allen) wrench.
3. Pull out stock feed pump.
4. Scrap off old gasket.
5. Lubricate replacement pump, and install on in feed pump housing, fitting the plunger bore onto the oil pump shaft spindle.
6. Replace feed pump cover.
7. Repeat for the return pump.
8. Put 2.25 liters engine oil.
9. Pump the kickstart about 20-30 times to get some oil in the system.
10. Start up, listen for bad noises, turn off and check oil level.
Est. time: 20 minutes.
Upsized oil pumps (designed for 535)
Note: many experienced mechanics believe a higher volume pump on a 500 serves no purpose because the stock pump has proven itself adequate for many years in various locations around the world, including India, where conditions can be as hot as in Texas. Doubt has been cast on whether oil flow really does increase. I bought the advertising from Enfield USA that the 500 top end runs "30 degrees cooler" with the higher capacity pumps. The high output pumps are standard on a 535, so if you are planning to increase bore diameter or "stroke" the engine then it might be worth the ~ $60 price tag.
Timing case removal
Here is a more extended proceedure, from the online workshop manual:
Remove the timing cover.
Remove the end covers from both pumps.
Remove the pump discs and plungers.
Remove the pump spindle, which can be pulled out only from the front or return pump end.
Check the fit of the plungers in the pump discs, which should be sliding fit and should be able to be moved in and out by
hand.
When matching a plunger in the pump disc, if it is found to be too tight a fit carefully lap the plunger in the pump disc, using metal polish until it is just free. If the pump disc is not seating properly in the timing cover, or if a new pump disc is fitted, it should be ensured that the
pump disc matches properly and has a perfect seating in the timing cover.
Lap the discs in the timing cover with fine metal lapping paste or liquid metal polish using special tools PED 2034 ST for feed pump disc and PED 2035 ST for return pump disc until a fine gray surface is obtained on the pump disc face.
NOTE: Replacement pump discs have a lip left at the opposite side of the lapped face. The purpose of this is to hold the disc central in the housing during the lapping-in. It should be filed off before the pump is finally assembled. Care should be taken not to damage the lapped face.
Wash all components and passages thoroughly with petrol after lapping, to remove all traces of grinding paste. Check the pump disc springs for fatigue by assembling in the timing cover and placing the pump covers in position. The latter should be held 1/8" off the timing cover if the springs are correct. The pump spindle should be renewed if excessive wear has taken place on the teeth. Reassemble the oil pumps, replacing the cover gaskets. Before fitting each cover fill the pump chamber with clean oil. Having assembled the pumps, lay the timing cover flat and fill the oil ports using an oil can. Turn the pump spindle with a screwdriver in a clockwise direction and it can then be checked whether the pumps are operating correctly. Before replacing the timing cover on the engine, fill the filter chamber with clean oil and fit the filter element.
NOTE: With the engine running, the oil feed to the big end can be checked by partially unscrewing the feed plug in the timing cover between the oil pumps. The oil return can be checked by slackening the rocker pipe banjo bolt on the cylinder head and observing the oil flow.
The Royal Enfield Bullet lubrication system is a dry sump system. It includes an oil tank, a feed pump, oil filter system, a return pump, screen filters, internal passageways, external oil lines, and an oil catch tank for oil that is blown out of the crankcase during engine operation.
My thanks to the people who put the Bullet Workshop Manual online. I borrowed some of their .gifs to illustrate this section. I also used images from Classic Motorworks, the US importer.
Specifications
Tank/Engine capacity: 2.25 liters
Recommended type: SAE 50 or multigrade 20/50
Oil pumps: feed and return, plunger type, 1/12 (one twelvth) engine speed
Oil pump shaft: worm gear, plunger connecting shafts
Oil filter: The oil filter has a spring loaded end in the mounting scheme. This allows oil to flow to the engine in the event that the filter is completely clogged up.
Seals: Cork or neoprene oil retainer, various gaskets.
Valves, plugs, pipes: Oil feed plug in crankshaft, grub screw, external oil lines, rocker pipe.
Circulation
Feed loop:
Oil is held in the oil tank. The feed pump, which has the smallest plunger of the two oil pumps, sucks oil from the tank and pumps it through the filter element. From the filter oil is routed into the crankshaft, through the right hand flywheel into the connecting rod journal. Thereafter it is thrown around inside the crankcase and falls into the bottom in a relatively thin layer.
Return loop:
The return pump pulls oil from the bottom of the crankcase and pushes it up into the engine top end. The oil travels from the return pump directly into the external oil lines. It goes into the rocker assembly, falls out of that through the shafts that the pushrods are into the timing case, where it pools and lubricates the timing gears. Eventually the level rises to an exit hole which routes the oil back into the primary tank.
Oil flow through the engine:
Oil tank
The capacity of the tank is listed at 2.25 liters and is cast as part of the engine crankcase. The cap is a spring loaded screw on type and has the dipstick built in. The cap is located on the right hand side of the engine. It's best to use a funnel to fill it up.
Feed pump
The feed pump is located on the rear part of the timing cover.The stock feed pump has a very small plunger. There's argument on the webboards and newsgroups about whether it is adequate. It probably is for most climates. It is possible to buy an aftermarket feed pump that passes more volume than the stock. If you live in an extremely hot climate, like a desert, you might want to consider a larger oil pump, despite the controversy. A cool engine is happier than an overheating engine.
Feed pump external:
This is the feed pump side on the engine itself, with the pump cover in place.
Feed pump internals:
There are two ports in the timing cover feed pump housing.
B: The spindle from the oil pump shaft. It connects to the plunger
D: Shaft rotation
X: Delivery to the oil filter, crankshaft, connecting rod journal, and subsequently the crankcase area.
Y: Suction from the oil tank.
There are four ports in the feed pump disc.
A: Plunger, showing bore that spindle (B) above fits into
C: The pump disc
R: Delivery port (to oilfilter, crankshaft and bottom end)
T: Suction port (from oil tank)
W, Z: Internal routing holes
Return pump
This pump is located on the front of the timing cover, just above the access port for the oil filter. However the oil goes to the filter from the feed pump, not the return pump. The return pump supplies the top end of the engine -- the valve train -- with lubrication. If the feed pump is replaced with a higher volume disc and plunger, then the return pump should be changed to match. The aftermarket (but OEM) return plunger is much larger than the stock plunger.
Return pump external (sorry about the focus!):
Return pump internals:
There are two ports in the timing cover return pump housing.
B: Spindle from oil pump drive shaft
D': Shaft rotation
X: Delivery to the valve train
Y: Suction from the crankcase
There are four ports in the return pump disc.
A': The plunger, showing the bore for the oil pump shaft spindle
C': The disc
R': Delivers oil to the external oil lines and then the valve train
T': Sucktion port from the crankcase
W',Z': Internal routing ports
External oil lines
The external lines deliver oil from the return pump to the top of the valve train (rocker arm assembly). Oil flows down through the pushrod shafts into the timing case and lubricates the cam gears.
External lines:
This is an electric start model. The placement of the line is somewhat different than the white kickstart model above. The horn also blocks the view of the exit from the return pump.
Service & Diagnosis
Crankshaft seal
If the cork or neoprene seal around the crankshaft is damaged or worn oil will be pumped into the timing case and NOT into the crankshaft. Left untreated that can be a bad thing should the problem lead to oil starvation in the engine. One symptom is copious amounts of oil collected in the contact breaker (points) housing. Oil will begin dripping from the around the plastic cover of the points assembly. If you see this it's time to investigate. Small amounts of oil are permissible and even normal, as the timing case has oil in it and that oil is pushed up to the axle that runs over to the points. However if the cork (or neoprene) seal is going bad too much oil will be pumped into the timing case and pools of it will collect in the points assembly. If this happens you must remove the timing case and inspect the crankshaft seal, replacing if necessary.
cork retainer:
Filter
Changing the filter is a straight forward procedure. After draining the oil from the middle nut at the bottom of the engine case, you can remove the small retaining nut on the oil filter cover. There are various o-rings and washers that come with a filter. Be sure to keep track of the order of rings and washers when removing. The assembly is spring loaded so that if the filter is completely gummed oil will still be sent to the crankshaft and top end. Note that the replacement filters DO NOT come with an extra felt washer so don't discard the one that is part of the endcap assembly.
Oil pumps
Since I live in central Texas where the temperature soars into the high nineties and low hundreds for 3 -4 months of the year -- with little or no wind -- I decided to put in a higher capacity oil pump (but see note below). It was a quick procedure, not as complicated as outlined in the workshop manual. For one thing, I did not remove the timing cover, so all the steps outlined in the manual that are a result of doing that fell out. At first I put the new return pump in the old feed pump -- I didn't know what the plunger size relation was. Note that the small plunger is the feed pump, the bigger plunger the return pump. All the operation required was the correct size hex wrench and a gasket scraper. When I had replaced both pump covers I also changed the oil filter. It is claimed that it can be recycled, but mine was so filthy I simply tossed it. The following proceedure is what I did:
1. Drain the oil.
2. Remove feed pump and return pump covers using hex (allen) wrench.
3. Pull out stock feed pump.
4. Scrap off old gasket.
5. Lubricate replacement pump, and install on in feed pump housing, fitting the plunger bore onto the oil pump shaft spindle.
6. Replace feed pump cover.
7. Repeat for the return pump.
8. Put 2.25 liters engine oil.
9. Pump the kickstart about 20-30 times to get some oil in the system.
10. Start up, listen for bad noises, turn off and check oil level.
Est. time: 20 minutes.
Upsized oil pumps (designed for 535)
Note: many experienced mechanics believe a higher volume pump on a 500 serves no purpose because the stock pump has proven itself adequate for many years in various locations around the world, including India, where conditions can be as hot as in Texas. Doubt has been cast on whether oil flow really does increase. I bought the advertising from Enfield USA that the 500 top end runs "30 degrees cooler" with the higher capacity pumps. The high output pumps are standard on a 535, so if you are planning to increase bore diameter or "stroke" the engine then it might be worth the ~ $60 price tag.
Timing case removal
Here is a more extended proceedure, from the online workshop manual:
Remove the timing cover.
Remove the end covers from both pumps.
Remove the pump discs and plungers.
Remove the pump spindle, which can be pulled out only from the front or return pump end.
Check the fit of the plungers in the pump discs, which should be sliding fit and should be able to be moved in and out by
hand.
When matching a plunger in the pump disc, if it is found to be too tight a fit carefully lap the plunger in the pump disc, using metal polish until it is just free. If the pump disc is not seating properly in the timing cover, or if a new pump disc is fitted, it should be ensured that the
pump disc matches properly and has a perfect seating in the timing cover.
Lap the discs in the timing cover with fine metal lapping paste or liquid metal polish using special tools PED 2034 ST for feed pump disc and PED 2035 ST for return pump disc until a fine gray surface is obtained on the pump disc face.
NOTE: Replacement pump discs have a lip left at the opposite side of the lapped face. The purpose of this is to hold the disc central in the housing during the lapping-in. It should be filed off before the pump is finally assembled. Care should be taken not to damage the lapped face.
Wash all components and passages thoroughly with petrol after lapping, to remove all traces of grinding paste. Check the pump disc springs for fatigue by assembling in the timing cover and placing the pump covers in position. The latter should be held 1/8" off the timing cover if the springs are correct. The pump spindle should be renewed if excessive wear has taken place on the teeth. Reassemble the oil pumps, replacing the cover gaskets. Before fitting each cover fill the pump chamber with clean oil. Having assembled the pumps, lay the timing cover flat and fill the oil ports using an oil can. Turn the pump spindle with a screwdriver in a clockwise direction and it can then be checked whether the pumps are operating correctly. Before replacing the timing cover on the engine, fill the filter chamber with clean oil and fit the filter element.
NOTE: With the engine running, the oil feed to the big end can be checked by partially unscrewing the feed plug in the timing cover between the oil pumps. The oil return can be checked by slackening the rocker pipe banjo bolt on the cylinder head and observing the oil flow.
