Whats the plug for on the oil pump cover

[gryphon]

I'm looking at the oil pump cover for a '92 and later pump and there's a plug just to the left of the top righthand bolt hole. Is this for an alternative oil supply fitting or a pressure gauge or what.

[gryphon]

Well, at least I see I'm not the only one who doesn't know.

[Buddy WMC]

Gryphon,
I'll check my 93 parts and service manuals and see if I can find out for ya.

[Buddy WMC]

Gryphon,
My 93 parts manual exploded view shows the check ball, spring, O-Ring and cover screw on the inside top of the pump. On the outside of the pump, there is a drive shaft retaining ring, another spring, O-Ring and cover screw. Hope this helps ya.

[gryphon]

When looking directly at the outside of the pump cover there is a plug inside a threaded hole. The backside of the hole leads into the gear cavity. Can't find anything in the books that tells why that hole is there and why it's been plugged. It diesn't give direct access to anything. If it were a Shovel pump then it's in just about the right place for a pressure gauge or switch.

[gryphon]

This is really kind of crazey if you think about it. Right there in the middle of your oil pump is a threaded hole with a plug in it. It was obviously intended to be there and yet, with nearly 100 viewers here and 50 at another site, nobody really seems to know why it's there. Since it's above the gears it's on the pressure side so it can't be another oil feed. It would seem that it would almost have to be for a gauge or a sending unit. But if that's the case you would think that someone would know. I can't imagine that the guys who designed it said "Okay, and we'll put a threaded hole here and then plug it for no good reason at all". It's the same size thread as a sending unit or a pressure gauge. If it will work in that application I may use one on my new engine build rather than using my S&S pump because I can use it  for my Dakota Digital sending unit. Right now I'm using multiple fittings and a tee on my S&S motor but I don't like doing that.

[dave_9113]

Gryph,

That is the bypass valve.

On Evos, your oil pressure switch comes of the case at the location where your head oiler line would be on Shovels, but you know that. 

Now putting a sending unit there, I have no experience in doing that on Evo, so I can't comment with authority. 

dave 

[gryphon]

Nope, not the bypass valve. This is not on the top of the pump or on the main body at all. It is on the cover and the hole just goes straight through to the cavity just above the feed gears. I mean, this is jus a straight through hole. No valves or other parts to it. just a plain old threaded hole (with a plug in it) in the face of the cover.

[gryphon]

Here's a picture of the plug I'm talking about. The hole just goes straight thru to the cavity just above the feed gears on the pressure side.

[IBARider]

Well,  I guess if the plug wasn't there, you'd have a big mess! 

I've got the same cover on my desk here, off a '97.  I can only guess that they kept the gauge port from the shovel days.  Hell, I put a plug in there on my shovel and have the gauge on my lifter screen port.

[dave_9113]

Gryph,

See if this helps:  http://www.bikebandit.com/harley-davidson-motorcycle-flhtc-1993-oil-pump/o/m1145sch143288

Look at schematic and description of item #120. 

dave

[gryphon]

Dave,
   Item #120 is the bypass valve and it does have a plug in the side but it is not the one i'm describing. If you look at my photo you can see that I'm talking about the plug in the face of the cover NOT the body of the pump. As IBArider says, it may be a holdover from the earlier days when there was a pressure port on the pump cover. It was a crappy place for a gauge but worked well for a sending unit. I cannot think of anything else that hole could be used for. Otherwise there's no reason for it at all.

[dave_9113]

I'm stumped.  I agree with you.  Let us know how that sending unit works when you hook it up.   

dave

[psyco369]

looking at that diagram there is 2 -120's the bypass valve and the plug in the pic 

[gryphon]

Either way they're not the correct ones. I really wish someone knew for sure. If it's not an available pressure port then I'd like to install my S&S pump on my new build. If it is an available pressure port then I'd rather use the stock pump since I have a real use for one. The large 4" cylinders don't allow for much room on the stock pressure port on top of the cases. I can utilize the pressure at the screen port which I'm doing on my present motor but because of my exhaust I need to use multiple fittings and I don't like doing that with an engine that vibrates. Too easy to eventually crack a fitting and sealing them is a royal pain.

[fxr4mikey]

Gryph,

See if this helps:  http://www.bikebandit.com/harley-davidson-motorcycle-flhtc-1993-oil-pump/o/m1145sch143288

Look at schematic and description of item #120. 

dave

interesting..... on the 2000 fxr4 it's:

item 270 in the schematic:
it's name is: PLUG PIPE
it's part number is: 1650631-001


appears that on my bike, it does NOTHING   

[1997bagger]

I'm going by reading applications when I purchased a oil pump, some listed a chain oiler for shovelhead applications, possible same orfice with a plug in and not a restrictor of some sort?

[baldoldfxr]

The plug in question is slightly higher up the pump than the older type pump which does have  a spare 1/8 npt fitting which could be used for a pressure switch/gauge fitting alough not on an fxr/flt as the gearbox is too close to the pump,
also on the early one's there is a boss around the hole which means there is enough thread for whatever is screwed into it
can't see on the picture of the later pump how much thread you have in the cover, is it enough to safely screw anything other than the blanking plug into it ?, its not anything like the old chain oiler feed this is a small pipe sticking out at an angle & also a screw & locknut setup to control the oil flow.
gryphon I made up an 1/8 npt banjo bolt & have used a banjo piped out to a end fitting to mount the sender under the gearbox maybe something similer might suit you ?

[gryphon]

With the plug screwed in and tight there is at least as much thread left as has been used. So, being pipe thread I would have to say that there is easily enough thread to screw something into. The Shovel pumps had a raised boss there but the covers were also thinner and the boss was necessary in order to have enough thread. Even though the Shovel and EVO holes are in slightly different locations the both lead to the cavity above the feed gears.