Tech. 3


Oil Cooler Mods to the Right Engine Case

Provided by Bob Scogin L.A.

Photo credits and thanks go to Bob Carbo for his help with this, without which it couldn't have been done.

(Left) Looking at the inside (engine side) of the cover. The piece that serves as the port  for oil returning to the filter cavity is visible in this photo. It's the shinier cylindrical shaped part that's positioned at about one o'clock on the cavity wall ,just to the left of the channel that feeds oil into the crankcase. It goes through the outside of the cover and penetrates the filter cavity and is welded to the cover on the outside end and the cavity wall on the other.
(Right) Looking into the cover with the filter removed. You can see the oil hole that feeds (oil leaving cavity) the engine, and the filter bolt hole. To the right of these, in the wall of the cavity, you'll see 2 holes,one at about 2 o'clock and one at about 4 o'clock. The hole at 2 o'clock is the end of the welded in piece. The one at 4 o'clock is the original hole. It should be noted that this hole has to be plugged for this modification towork as that is the only way to divert the oil out and into the cooler.If the hole isn't plugged the oil will simply take the path of least resistance which is the original passages.

(Left) The front of the cover showing the ports and filter cavity opening from a 3/4 perspective.
(Right) Looking at the front of the cover.You will recognize the tach drive hole near the gasket surface of the cover. To the left of it you'll see the 2 welded in ports which are drilled and tapped for 1/4"NPT.
The lower port is the outlet and is welded on over a hole drilled into the passage between the pump and filter cavity (see XS News 24). The top port is the return into the cavity from the cooler and is integral with the piece that penetrates the cavity.

Extract from XS News number 24 

Last issue there was a piece by Tony Hall on the lubrication system of XS650, which briefly mentioned oil coolers. This is something a lot of members have asked about and, as Promised here is the drum. But before getting into the specifics of fitting one to an XS, a bit of background is in order.

Oil, like the motor it's in, is designed to work best within a certain temperature range. As oil flows around a motor, it not only lubricates the moving parts, but also cools the motor by absorbing heat caused by friction and combustion. It does this in the same way as the air that passes over the outside of the motor. As air/water/oil flows over a hot metal surface, some of the heat is imported to it and it continues on it's way. As the metal continues to generate heat there is more air/water/oil to take it away. In theory, the motor remains at the correct working temperate.

But what if it doesn't? What if it runs a little too hot? Perhaps your bike has a sidecar, or has two people on it most of the time, or you live in a hot climate or ride in stop-go traffic a lot. There's not much that can be done to improve air cooling except to direct more air to where its needed. We've all seen VW cars with the top edge of the bonnet propped open to act like an air scoop, and this author once had a car with two radiators. Of course, neither of these options are open to the XS owner.

To provide cooling for the 650, one must use the oil. Here again though, our choices are limited. An XS holds 2,500-3,000cc of oil but only a fraction of that is in circulation. The rest lays in the oil reservoir, away from the hottest parts and supposedly cooling off somewhat before being sent on another trip around the motor to pick up more heat.

So why are our choices limited? Because the oil reservoir on a 650 lies in the bottom of the motor, that is, it's has a wet-sump. Most cars have wet-sumps as well, but almost all unbolt from the block. If there is the space, they can be modified or replaced to carry more oil. The idea being that the more oil there is, the longer it stays in the reservoir and the more it cools down before going back into circulation.

Very few cars, but many bikes (H-D, Triumph, etc) including some Yamahas, have a dry-sump. Only the oil in circulation is inside the motor. The rest is held in a separate oil tank, connected by pump. Obviously, space must be found for this tank and, on a bike, this can be a problem. Indeed, many use the frame as the oil tank. If space can be found, the size of the tank can be increased Again, this is not open to us.

Any four stroke engine with an oil pump (some Husqvanas don't have them) can be fitted with an oil cooler, and the forgoing is merely to explain why this is the only option for the XS. In a nutshell the 650's oil capacity is a bit on the small side, it can't be increased and it never leaves the motor.

So, what is an oil coolers? Its a radiator, the same as that found on any water-cooled motor, through which the oil supply passes. It's mounted on the bike, somewhere in the air stream with pipes connecting it to the lubrication system. Thus, the engine imparts it's heat to the oil and the oil imparts it to the air. How much so depends on the size of the radiator. Simple.

A couple of questions arise here. Are they really necessary? When you consider that most modern bikes have them as standard, and that most machines that can expect to be worked hard, truck, race cars, locomotives etc., do as well then it seems that an oil cooler wouldn't go astray on a 650. Are they hard to fit? On a bike with a dry-sump, no. After mounting the radiator, you simply connect it to the pipe that takes the hot oil back to the tank With the correct piping and on hand, this will take ten minutes at most. On a wet-sump engine, there's a bit more to it.

Because the, oil never leaves the motor, one must tap into an internal oil line. That means drilling holes in the motor and, obviously, there is no room for error. But wait a minute, the oil does leave the motor. What about the pipe that feeds the top end? Yes, oil coolers have been plumbed into this before and it would be very easy to do. Simply cut out a section a few inches long from the middle of the pipe, attach the hoses from the radiator, one to the top and the other to the bottom. Done. The problem is that only a very small quantity of oil passes through this pipe, due to the restriction in it and only that amount will be cooled. It's just not enough. What about drilling out the restrictor to the size of the pipe? Don't even dream about it. The oil supply is finite and therefore, increasing the supply to one area decreases it to another. In this case, the big-ends and main bearings. These are the most expensive parts the motor and must not be starved of oil!

OK, so now we've discovered that this is not a simple job, let's get to it. By the way, the method described here was learned during a conversation with Tony Hall. Onya Tony.

Firstly remove the right-hand engine cover and then strip everything from it. As you look at the inside of it, you'll see that the oil is drawn from the sump, through the round hole at the bottom, see photo 1, into a pipe. From here it turns 90 and goes to the oil pump (two crescent shaped holes see photo 1) where it is pressurised. It then goes along another pipe for an inch or so, and then turns 90 toward the small filter cavity. It's at this turn that we'll tap into the system. During manufacture, the case would have been cast as a blank unit and the oil lines, along with the holes for the mounting screws, kick-start shaft, tacho drive, etc, were bored later. Because you can't drill around corners, whenever a change of direction was required they drilled right through the housing, once in each direction so the two holes intersected, then simply plugged up the ends of the holes at the outside of the housing. See photo 2.

Of the two plugs, we need to remove the upper one, the one nearest the tacho-drive. this is done by scraping the resin, if any, from the hole with a sharp instrument to reveal the plug. Next we must remove it. Drill a hole, about half the size of the plug, through it and into the oil line. It's made of steel and is only 5 or 6mm thick. A hand-drill is fine for this but go easy with it. Also, notice that the hole is not perpendicular to the surface of the case. Be sure to drill in line with the hole. Of course, this is best done with the housing held in a vice, but be careful how it's held. You mustn't damage the gasket surface, or tighten the vice so tight that it cracks the housing.

Now, wind a broken-screw extractor (not a broken screw-extractor) into the hole you've drilled in the plug, so that it's in tight. Before going any further, enlist the help of an assistant, speaking of which, don't you wish that motorcyclists had assistants like magicians? It's their costumes that do it. Anyway, grab the nearest person and dream on.

With the screw-extractor still in place, remove the cover from the vice and reposition it so that the screw-extractor is held in the vice, with your assistant holding the cover, just to support it's weight. Now, get a block of wood, or soft mallet and gently tap the cover away from the vice, pulling out the plug. That's the easy part.

Looking down the oil line, you'll see the other line, about half an inch or so down, going off to the small filter. Not only do we want to take the feed from the line that we've just unplugged but we must also block off the line to the filter. If this isn't done, the feed will go to both cooler, and the filter. Only half the oil will then be cooled.

To accomplish both at the same time, the line that's been unplugged will have to be bored out and tapped to accept a hose fitting of some kind, and this fitting must go into the line past the intersection of the other one. How complex this is depends on your choice of fittings. The example shown in photo 3 has tapered BSP (British Standard Pipe) threads. Cutting them requires a BSP tap. The fittings are made of brass and look nice when polished, are reasonably cheap to buy, and take clamped-on rubber hose. Boring out the case in perfect alignment with the hole isn't that critical, in that, it's the taper of the threads (with thread tape) that forms the seal. Just screw the fitting in until it feels tight with the elbow facing the right way, and it's done.

The example shown in photo 4 has forged aluminium fittings. These are very expensive to buy, have a straight UNF thread, take braided stainless steel hose, and are anodized, usually blue or red They are also more difficult to fit.

In either case, boring out the oil line will need to be done with a drill-press (see photo 5). This is to ensure that the drill goes squarely down the oil Line. If a hand drill is used it could go askew, and the metal surrounding the hole is only so thick. If the drill were to break through this, you'd have yourself a paper weight or, turned over, a novel ash tray.

Put a drill the size of the existing hole into the drill-press. Slip the oil line to be bored over the drill and have your assistant hold it so. The case is now being held in midair, at a very strange angle. Now, position the work table so that the case can be clamped to it. This will take some fiddling and is quite time consuming, but to get the drill to go squarely down the hole, it must be done. With each adjustment of the work table, wind the chuck up and down to see if the drill is binding, making sure that the table's own clamp is tight each time. When it goes in and out freely, clamp the case to the table using two or three clamps, do a final test for binding, and the case is ready to be bored. A word of warning, near enough isn't good enough, this must be done correctly, or good-bye case.

As previously mentioned the hole is not square to the surface of the case and, therefore, a drill won't bite into the metal without wandering. You'll need to machine a surface into the case that is square to the hole. This is known as spot-facing and requires a spot-facing drill, obtainable at specialty tool stores. The spot-faced area is 16-17mm on a 10mm hole. At this point the table can be raised or lowered, without upsetting anything but must not be otherwise moved. Remove the test drill and chuck the spot-facer. Make sure all clamps are tight (including the drill presses own) and, using the drills slowest speed, spot-face the hole, only until there is a complete circular surface surrounding the hole, and no further. Remove the spot-facer and chuck the drill that will do the final bore. The size of this depends on the fittings to be used which you should have already purchased, Someone at the store will tell you which drill and tap to use. The fittings, of course, should have an internal diameter similar to the original hole. Without disturbing the table, bore the hole to a depth of 40mm. Remove the drill and chuck the tap to be used. Remove the drills belt drive, and while winding the chuck down, turn it back and forth by hand to cut the thread. This, instead of using a tap-handle, is done to ensure the thread is cut squarely with the hole. From the time the correct position of the table and case is found, they must not be disturbed until tapping is completed.

If using of the forged aluminum variety, the one that actually goes into the case doesn't exist. One must turn one's own from hexagonal bar. The one shown in photo 4 is made from aluminum and anodized blue. If using steel have it plated with gold-zinc. It could also be made of stainless steel and polished. Note that the step at the end of the thread bottoms on the spot-faced area of the case, causing the treads to bind, forming the seal. See diagram 1.

That pretty well covers getting the oil out of the motor. To get it back into the system you need to make a replacement cover for the small filter. The outer face of the original is too thin to tap. The type shown in photo 3 is of a conical shape that protrudes inch or so further out than the original. The fitting of the return line is tapped into the side of the new cover. The inner face is the same as the original so it doesn't foul on the filter inside.

The one in photo 4 is the exact same shape as the original but turned out of a solid bar, giving almost an inch of metal to tap into. This leaves no room for the filter, so it must be removed. What, run without an oil filter? This particular motor has had both filters replaced by an external car-type unit. See photo 6.

They are available from Peter Wust, Ellwngerstr, 87, D-73441 Bopfingen, Germany.

Ph 0011-49-73626881.

Either cover can be used with either type of fitting, it's a matter of which one you like the look of. Either way, the motor will end up an inch or so wider on the right side. If using the conical cover with the aluminum fitting don't forget to spot-face it as well. So, we've collected the oil as it comes out of the pump, rerouted it via the hoses and radiator, and put it back into the small filter cavity. What about the hoses and radiator? There are after-market oil coolers, Lockhart, Hayden, etc, around or you can adapt one off another bike. With most modem bikes having them finding one at the wrecker's shouldn't be too hard. Either way, it'll need to be attached to the bike. This can be done with clamps, or welded-on brackets which will have to be made. It comes down to whether your frame has recently been painted, or is to be done in the near future. The radiator should be mounted under the lower triple clamp, tilted slightly from the vertical. This has the effect of slowing down the air as it passes through, so it picks up more heat. Allow enough clearance for turning the steering to full lock. It should also be mounted upside down, that is, with the fittings on top. See photo 7.

If they are on the side or bottom, the oil will gravitate back to the sump whenever the motor is turned off. When it's again started, the oil must go quite a distance before reaching the small filter cavity, which was only a short way from the pump. The motor won't receive fresh oil for several extra seconds.

Mounting the radiator upside down solves this problem. The oil up to the highest point in the hoses will still run back to the sump but the radiator stays full. Unlike water, oil will push air along a pipe, even downhill So, when the motor starts the pump will push oil into the hose, which in turn pushes the air that's in there, which pushes the oil in the radiator along the return hose and into the motor. Thus, there will be a momentary pause, then a shot of fresh oil another momentary pause, then a continuous supply. This is far better then one long period with no oil at all.

As for actually doing it the order is as follows; Call around for prices on everything mentioned here, decide how much you can spend, then buy the appropriate radiator and fit it to the bike. Decide on, but don't buy, the fittings and hose. Have the outlet fitting made if necessary. Have the new filter cover made, but not drilled. Then take the bike to the shop to buy the fittings and hose. If the bike's not together, the motor, exhaust pipes and tacho drive should be in place. It's now a simple matter of trying different fittings that will connect the radiator with the motor, routing the hoses so that they don't touch anything and are free of sharp bends. Take the bike home, drill and tap the clutch and oil filter covers. As previously explained, drilling and tapping the clutch cover is critical, the filter cover is less so, as there is no hole to follow. Where exactly you locate the hole is a matter of personal taste. However, like the clutch cover, once the location is found and the piece is clamped in place, it must not be moved until the operation is done.

When it's all done and the cooler is mounted for the final time, fill it with oil then connect the hoses. One final word, just as oil can get too hot it can also get too cold. For this a cover for the radiator during water is a good Idea. These, are common on the radiators of heavy trucks. Take a look around next winter and you'll see some. The cover could be of embossed leather, or whatever takes your fancy. People who do this sort of thing can be found at bike shows. Don't forget to use plumber's tape on all threaded fittings. By the way, the fittings in photo 4 are also available to take clamp-on rubber hose. You can also buy hose with "false" forged ends. It looks the same, but clamps on and is not so expensive. If considering clamp on hoses remember, this is the bike's oil supply we're talking about. The XS doesn't have any kind of low-oil warning device. If a clamp came loose, and you didn't happen to notice the oil, its good bye motor. Check the clamps and hoses regularly. If you wanted to, you could plumb oil temperature and pressure gauges into the system.

Places to call are;

SPV Racing, Condell Park. Ph 02-97919899, or 1800-804482.

Pirtek. Ph 02-98387888.

Any car or bike high performance shop that stocks Earl's or Russell products.


20 August, 2017