Adventures In Oil Modification by Tony Donisi <>

This will chronicle the successful installation of the head oiling system described previously by both Landry & Schoeb. I want to thank them both for the invaluable information they supplied. I modified their basic application which I will describe below.

Parts Acquisition And Description

Noting the parts list on the previous two versions of the modifications, I first saw that there were a lot of NPT adapters. This was especially true on Schoeb's modification, which used the NPT's at the junction. After some research, and my own experience with automobiles, I modified a few things, which I hope improved the overall design. Some of the information below may be obvious to most readers, but was not obvious to me at first.

NPT Taps

The NPT (National Pipe Thread) male/female connection works as a seal because of a tapered thread design. The thread is tapered at an angle of 1° 47'. This angle causes the thread to sort of self seal by threading it in only part of the way, since the threads are constantly widening. When tapping the hole, as stated by Schoeb, be careful not to tap too deep. I don't think the point was emphasized enough. The tap is tapered, so tapping too deep will cause the hole to be too wide. If the hole is too wide, then the male connector will not seal at all. I first tried the tap on a piece of scrap aluminum - and I'm glad I did. From my experience with regular taps & dies, I just tapped to almost the end of the tap itself, not realizing that the tap was tapered. The hole came out too big, and the NPT male did not fit snugly in the hole as it should have. I found that I only needed 2 - 3 turns or so after breakthrough to complete the thread and provide a proper seal.

The NPT connector is useful for connecting to the engine block, as described in both previous modifications. However, for all the other connections there are better choices as outlined below.

A/N connections

The A/N (Army-Navy) style fittings have been used for years in automotive and aircraft applications. These connections provide a high pressure seal (Up to 3000 psi) by way of their specially machined mating surfaces. They come in a variety of sizes, usually designated by dash numbers. There are AN-3, AN-4, AN-6, etc. For this application, Aeroquip makes a series of AN-4 connections to the -4 braided steel teflon line, the same teflon line used by both Landry & Schoeb. No teflon tape is needed with these connectors. There is also an adapter from 10mm Banjo bolt to AN-4, along with various Tee's, elbows and the like. To get information on these connectors, and the hoses, there are plenty of automotive mail order houses which will send free catalogs. Two of them that I deal with are Summit in Ohio (216-630-0290), and Jeggs (800-345-4545).

I ordered a whole bunch of parts, because I am always tinkering anyway, but the ones I used are listed as follows. From the block, I used the Aeroquip NPT male to AN-4 Male adapter. This is the connection to the block at the main oil gallery. I ran a hose under and around to the top of the head, this hose I measured and test fit first, one end I used a 90° AN-4 to hose adapter, and at the other end I used a straight AN-4 to hose adapter. At the output of this I installed an AN-4 male "Tee". This allowed me to branch to both the cylinder heads. To the closest head port, the front, there was a short piece of hose with AN-4 straight connections on both sides. The opposite end of this hose with the AN-4 Straight was connected directly to an AN-4 to 10mm banjo bolt adapter. For the rear head, the same hoses and adapters were used, with the exception of a longer hose (of course) and instead of a straight AN-4 to hose adapter, I found that a 45° one worked better. Figure 1 shows the schematic of the hose routing.

Figure 1

Hose Routing

The AN-4 fittings not only look better, they are easily connected and disconnected without excessive torquing and teflon tape. They provide a great reusable seal. Just look under the hood of any serious race car.

Parts list


-4 Teflon Braided Steel Hose2
AN-4 To 10mm Banjo Bolt1
AN-4 to 1/8 NPT
AN-4 Straight to -4 Hose Connection
AN-4 45° to -4 Hose Connection
AN-4 90° to -4 Hose Connection
AN-4 "Tee" Connection


1 The AN-4 to 10mm Banjo bolt comes in Packages of 2 Each.

2 The 4' Length of braided hose is a conservative estimate. I actually bought 10', I will use the rest in other applications.

The connectors above are specially made to connect to the teflon hose. The ordinary AN-4 to -4 Hose is not suggested. Aeroquip makes a line of "TFE Fittings" which are recommended. The AN­4 "Tee" can be of any manufacturer, it is suggested that anti-seize compound be used on the connecting threads. The parts listed above are more expensive than the normal brass fittings, but well worth it.

Doing the job

Weekend 1; Hose Assembly; 1.5 Hours

I assembled all the hoses using test fits before I even started the job. Surprisingly, the hoses went together easily, I thought that it was too easy, that they were sure to leak -- but they didn't.

Weekend 2; Bottom Hose Connection; 3 hrs.

After assembling the hoses the previous week, I started the job. At this time, I did not disconnect the original head oil lines, I decided to do the modification in steps. The first step was to hook up the bottom feed and hose, drive around for a week and check for leaks. After it was verified by driving that there were no leaks, I would connect the new oil feed to the head. I want to stress that at all times during the modification, some head oiling was used, either the stock or the modified. I did not start the engine without oil to the heads!

Disconnecting the muffler system was easy, as well as the right engine cover. I've done both before on many occasions. Drilling the hole was a little difficult because of the cramped space, even with the bike jacked up. What I did was to stuff a lint free rag into the oil gallery before drilling to catch the metal filings which could find their way up into the engine. When I was finished drilling and tapping, I pulled out the rag, and cleaned everything extremely well. The NPT connection fit fine, I used teflon tape, and one of my machine shop friends told me that there is even a teflon tape in liquid form, which I did not use. I connected the hose from the bottom to the top only, and used an AN-4 plug to seal off the hole in the end that came up near the heads. Driving this around for a week, I notice no leaks, not even a dribble! Hooking up a pressure gauge to this connection, I read about 80-90 psi, when cold, at idle. This is the pressure that should come out of the main gallery.

Weekend 3; Top Hose Connection; 3 hrs.

The next week, with the success of the lower line, I decided to hook up the uppers. I hate removing the carburetors, so I tried it with just removing the radiator. This worked fine, however the rear head connection gave me a little trouble. I removed the old oil feed lines without cutting, but it was difficult, and they did get quite bent up. On both heads, I had to bend the banjo bolts slightly, as did Landry & Schoeb to make them fit easier. With the AN-4 fittings, connecting was a snap, and I plan to hook up a pressure gauge in the future.

The blocking of the original oil feed bolt went fine, the bolt was a 10mm X 1.25. At this time I started the engine and checked for leaks. There were none. I was amazed. Out of curiosity I checked the pressure at the original feed line to get a number for comparison. The pressure was about 35 - 40psi at cold idle, a full 50psi below the modified version. I've read previously that its the volume of the oil to the heads that matters, not the pressure. This may be true, but pressure and volume are intimately related, and increasing the pressure by 50 psi increases the volume of oil to the heads significantly.


I bought the bike in September 1995 with 13,000 miles on it. It now has only 23,000, since I did not get to ride much during this miserable winter. The modification was successful, and there were no leaks or snags. I've literally been through every inch of the V65 which probably helped a lot. The engine does not run much cooler, but it takes a lot longer to reach operating temperature. The gas mileage increased, by about 3.3 mpg. This is astounding by itself. The gas mileage number came from an average of 6 tankfulls before the mod, and 6 tankfulls after (A total of 1-1/2 months time). The engine did not run noticeably quieter, it was quiet to begin with. I have adjusted the valves at 20,000, and will adjust them again soon. I will relate the difference in the clearance and the cams. The only engine modifications from stock are a Dynojet jet kit, and a K&N filter, and of course, always synthetic oil. I took it down to the track just before the oil modifications, for fun, and I did 11.9 @ 110mph in the quarter mile. This was with "normal" non destructive riding, I shifted at 8500 - 9000 rpm, using the clutch smoothly, as I would on the street. I think I could have got another second if I power shifted and revved higher, but I didn't want to. There is no reason to beat on the bike to get another second in the quarter mile. I will report in the future if the quarter mile time improved any with the modification.

I don't see how anyone could fail to see the value of the oil modification. An engine that is running right, and lubricated correctly should not be able to gain over 3 mpg just by re-routing the oil lines. This is a drastic change.

Addendum: An Oil Pressure Gauge

On my 1984 Magna, I connected a 1.5" diameter mechanical oil pressure gauge, which worked fine. The way I connected it was to use a brass 1/8" NPT female "T" and connected that to where the original sending unit was. This was because I didn't want to disconnect the original oil pressure light. From this tee, I used an adapter to 1/8" compression fitting, with which I ran 1/8" copper tubing to a convenient point at the frame by the handlebars. Since copper does not flex easily, I had to run the nylon type 1/8" hose from the frame to the handlebar mounted gauge. I used a 1/8" compression to 1/8" compression adapter to connect the copper to the nylon tubing. I surrounded the nylon tubing with small diameter rubber hose just for added security and resistance to possible rubbing. I had this gauge connected for about 20,000 trouble free miles.

I plan to connect a gauge to the above oil modification setup. What I will do is put another AN-4 Tee connector in line (with a female to female connector) and then use Aeroquips' AN4 male to NPT female. (Don't ask me how I found out about this adapter, it wasn't easy). I will adapt the female NPT to 1/8" copper compression tubing. This I will run up to the space between in the frame by the front of the gas tank covered by those little plastic covers. I will relocate the original sending unit here, using an NPT female tee. I am mounting the original sending unit there because I think its ugly sticking out the side of the engine.