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XS650 Top End Oil Pressure Gauge

Discussion in 'The Garage' started by TwoManyXS1Bs, Mar 27, 2016.

  1. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    I've been wanting to monitor the top end oiling of my XS1B for a long time. So, I added an oil pressure gauge to monitor the oil pressures delivered through the front oil pipe to the top end.

    Back in 1974, I had plumbed an oil pressure gauge to the main oil gallery, front of the right side clutch cover, on my other XS1B. Almost had a heart attack when I saw the low pressures, 15-20 psi cold, almost nothing when hot.

    This time around I thought I'd do it differently and NOT molest any precious, rare original castings. So, I added a fitting to the top of the oil tube, out-of-sight under the fuel tank.

    For reference, here are some threads that cover oils and mods for oil cooling and pressure gauges:

    Grimmith and Lindsay G like this.
  2. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Modifying the front oil pipe for an oil pressure tap:

    With the front oil pipe removed, file a flat on the very top, removing the pointed top.
    Mark and centerpunch the center of this filed flatspot.


    Drill straight and square with a 5mm drillbit.
    Carefully tap the hole to M6 x 1.0.


    File off the top again, straight and square, leaving a small flat annular ring around the threads.
    There's enough copper in there for about 2-1/2 threads, 2.5mm (0.100").

  3. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Making and fitting the 1/8" compression fitting adapter:

    We'll modify a 1/8" compression union, as shown on the left.
    On the right is the modified union, with M6 x 1.0 threads.


    The union is chucked-up in the lathe, and one end is turned down to 6mm OD.
    Then a threading die is used to cut the M6 x 1.0 threads.


    This newly threaded end is parted-off, leaving about 2-1/2 threads, 2.5mm (0.100").


    The oil pipe threads and the modified union threads are thoroughly cleaned, then assembled with red Loctite.
    The fit needs to be snug, but not so much as to strip the brass and copper threads.

    Lindsay G likes this.
  4. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Finishing the front oil tube modification:

    After the Loctite cures, the front oil tube is ready for the 1/8" tubing


    Attach the 1/8" tubing to the compression fitting.
    Do not torque through the loctited threads. Apply torque to only the brass fitting's hex heads.


    Reinstall the front oil tube to the engine.
    Route the 1/8" tubing up, around, through the frame, to the desired location.

  5. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Modifying the 0-15 psi oil pressure gauge:

    Fitting the standard 1/8" NPT to 1/8" compression adapter to the back of the oil pressure gauge takes up to 1-1/2" of length.


    I wanted to shorten this, so modified the brass adapter to be a 1/8" compression fitting with 1/8" NPT threads.
    This reduced the installed length to 0.9".


    The wiring emerging from the back of the gauge is for the internal lighting.
    A white high-brightness LED is bonded inside the gauge shell.
    A 390 ohm resistor is soldered in-line to the power wire, and all sheathed with heat shrink tubing.


    A bracked is fashioned from 0.062" aluminum, to be clamped by the bottom handlebar clamp bolt, between the clamp and riser.
    Soft/compliant foam is bonded to the bracket, with cutouts to clear the gauge's backside screws. The cutouts for the screws will keep the gauge from rotating in the bracket. The modified 1/8" compression fitting also clamps the gauge to the mounting bracket.

  6. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    This video shows the cold and hot oil pressures I'm getting on my XS1B:

  7. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    Neat installation and interesting videos:thumbsup:
  8. Signal

    Signal XS650 Junkie Top Contributor

    Thanks 2M. Like the oil temp gauge as well.
  9. DogBunny

    DogBunny Motorcychologist Top Contributor

    With 2M's help, I have installed my own top end oil pressure gauge.

    Video is about 7 minutes long and includes a couple of other modifications.
    Thanks 2M !!!
    robinc and TwoManyXS1Bs like this.
  10. robinc

    robinc Member of the 'yellow meter gang' Top Contributor

    Nice job 2M. I had seen your previous install and got me to wondering if it could be plumbed into oil delivery tube some how. Well you've just answered that question and very nicely indeed. You're engineering abilities amaze me. Thank you for once again charting new ground to the benefit of all.
    TwoManyXS1Bs likes this.
  11. MaxPete

    MaxPete Lucille, Betty, Demi & Gretel: I ask, THEY decide. XS650.com Supporter Top Contributor

    2M - this is great work indeed. I do have a question though - did you separate the top of the oil feed tube from the cylindrical fitting which has the two outlet tubes coming off it? I'm talking about the photo with the oil tube top fitting sitting on the red towel...

    If you did separate those two parts - how did you do it?


    TwoManyXS1Bs likes this.
  12. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    I'd say that very low pressure, with hot oil, is a good thing. In fact if oil pressure was to increase greater than 1 or 2 psi, it would mean that the passageways, flowing oil to the cam lobes and rocker arms, are starting to plug up.
    TwoManyXS1Bs likes this.
  13. Hey MaxPete, I should let 2M answer, this but you don't need to sweat the feeder pipes off at all, 2M has shown that there is no need to, file a flat, centre punch, drill & tap.....
    Great idea 2M
    TwoManyXS1Bs likes this.
  14. DogBunny

    DogBunny Motorcychologist Top Contributor

    MaxPete -- if 2M doesn't mind, I'll answer for him. The red shop towel is wrapped around the vertical part of the oil feed tube so that the tube can be put in a vice, allowing drilling and tapping the hole for the fitting. In the pic, you can't see the vertical part, but it's there.

    retiredgentleman -- thanks for the words of assurance, but I still find zero needle movement at idle a little disturbing. In a phone call, 2M explained that the oil pressure indicated isn't exactly the real top end pressure -- I think that's what he said, that the real pressure is greater than indicated.
    Of course, the pressure at the pump is a lot more before the oil starts getting diverted throughout the engine.
    TwoManyXS1Bs likes this.
  15. retiredgentleman

    retiredgentleman XS650 Guru Top Contributor

    DogBunny.....................don't forget these engines use ball and roller bearings. All they need is the correct amount of oil flowing. Oil pressure is not important. In car/truck and lots of motorcycles that use journal bearings, with babbit inserts, oil pressure is very important, because the oil pressure is what keeps the shaft and the bearing from coming in contact with each other.
    If you see a bike with a factory installed oil pressure light, it means the engine has journal bearings. XS650 does not have an oil pressure alarm light, because none is needed.
  16. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Absolute coolness! Well done , DogBunny!
    Zero psi when hot??? Let the neurosis begin.

    Hey, Robinc. This "new ground" is seriously worth debating. By revealing top end oil pressures, are we introducing a viable diagnostic tool, or opening a can of worms? I've seen several burnt-out top-ends on this forum, likely attributable to lubrication failure, and long wondered if top-end oil pressure monitoring could be useful. We really don't have much data on the relationship between oil delivery rates and engine life expectancy, aside from the usual "little to no pressure" reports from main gallery pressure taps, and the 'splattering oil' test from an open valvecover.

    I have this sequence of 'top-end oil delivery' scenarios in my head:
    1- If there's any top end oil pressure, there's more at the main gallery.
    2- If just a little bit of oil reaches the top-end, perhaps misting from camchain fling-off, is that enuff to keep the top-end alive?
    3- It takes at least 1/3 psi at the mains just to push oil up the front oil pipe.
    3- If just a marginal 1/2 psi is at the top-end, that's probably enuff to keep it from burning up.
    4- I've experienced top-end clatter when top-end hot pressures get below about 2psi.
    5- The majority of top-end oil is squirted out small nozzles in the rockers, aimed at the pad/cam interface.
    6- XSJohn (rip) installed some auxiliary oil squirters in his intake valve covers, aimed at the valve tops, and reported reduced clattering.
    7- After installing a high-volume pump, my pressures went up about 30%, and got reduced clattering.
    8- What I'm also interested in is more flow to the top-end to enhance top-end cooling.
    9- Outside of conjecture, it would take additional thermal monitoring instrumentation to validate all that hypotheticalness.
    10- It kinda makes sense...
    Last edited: Nov 11, 2016
    robinc likes this.
  17. TwoManyXS1Bs

    TwoManyXS1Bs BBQ Hunter Top Contributor

    Hey, DB, yeah, I probably need to clarify that. Pushing fluids uphill requires pressure at the bottom. Taking pressure readings at various heights on a tall column of fluid will reveal reduced pressures the higher you go. Atmospheric pressure (14.7 psi) at the base of a column of water will push that water up about 32 feet. Oil, being less dense (at about 75%), will be pushed up to about 43 feet. That works out to about 35" of head per 1 psi, or about 18" per 1/2 psi, which is about the height difference between the oil pump and handlebar mounted gauge.

    So, if the handlebar mounted gauge shows 1psi, the mains are at least 1-1/2psi, and the top-end around 1-1/4 psi. If the gauge shows ZERO psi, who knows what it is down below. Since there *was* a reading while the engine and oil were cold, we know then that the pump is indeed working. What's left is to figure out if this is something to worry about, or just take a pill and go back to bed...
    Last edited: Nov 11, 2016
  18. 650Skull

    650Skull SSSSSSSSSlither Top Contributor

    When XSJohn, (Rip), done his oil pump mod, it was an answer to push the oil through his oil cooler and to feed the 2 oilers for the rear tappets. Also opened the restriction in the oil feed to the head for the extra oil from his oil pump mod. he did move the restrictor to above the oil cooler but in conversations with me he stated having the opened up restrictor before the oil cooler would give him the same result for his mods.

    I know XSjohn did flow measurements, to keep the oil flow around the engine as per standard and used the extra flow to compensate for the resistance through the cooler and extra oil for the rear tappets. Using the HP oil pump without opening the restriction in the oil feed to the head would be starving the top end of any gains from the HP pump.

    Maybe opening up the restriction to give more oil to the head will make a difference. As you know in racing form the standard XS650 oil pumps are sufficient. Ivan Hoey who races his rephrased big bore 750 in the period P4 class for 750 and open class up to 1300cc racing, (this guy is winning state championships against ex Wane Gardener bikes), he tried a HP oil pump but went back to the original pump it because he felt the HP one was costing him engine power.

    I suspect some of the oil starvation damage to the top end is due to poor maintenance, not checking the filters and/or not changing the oil regular
    retiredgentleman likes this.
  19. DogBunny

    DogBunny Motorcychologist Top Contributor

    Lots of interesting info coming out here on a subject that doesn't usually get much play on this Forum.
    I finally wrapped my head around what retiredgentleman has been saying. Low oil pressure is actually a good thing. When the oil is cold, it is thick and sluggish. There is a lot of friction between the oil and the walls of the oil passages. Friction equals resistance. The oil pump is turning, but the sluggish oil can't get out of its way fast enough, because it is not moving fast enough due to friction, and pressure (think back-pressure) builds up in the system that we see on the pressure gauge. In a word, high oil pressure equals low volume. The whole reason the pressure is high in a cold engine is because the sluggish oil can't move fast enough, i.e. the volume is low. This is counter-intuitive at first, but it now makes sense to me.
    If you believe this, than obviously the reverse is true: when hot, the oil thins, friction reduces, volume increases and pressure decreases.
    So, yeah, I am now not so worried that my hot idling oil pressure is zero. Just so long as I do see oil pressure when at higher RPMs, confirming that the pump really is working.
    retiredgentleman likes this.
  20. DogBunny

    DogBunny Motorcychologist Top Contributor

    If you believe what I just wrote above, then think about what 650Skull wrote about Ivan Hoey ditching his high-volume oil pump because he thought it was costing him engine power. How can this be? Well, the high-volume oil pump is trying to move oil faster than the oil passges can handle it. So, the oil pressure goes up, the pressure pushes on the oil pump, creating resistance in the pump, and the oil pump is actually acting as an engine brake.

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