Topic: oil pressure sender thread size?

[budman]

I was doing some digging and found this thread a couple of months ago.  I purchased a 10mm X 1.0T plug for the sender hole and it will not fit my 750K4 engine.  I can just barely get it started.  I have an old oil pressure gauge with 1/8" NPT threads, so I tried that just to see if the threads match and while it fits better than the 10mm X 1.0T plug it still won't go in but a few threads.  I guess my next step is a 1/8" BSTP plug.

[Deltarider]

it still won't go in but a few threads

Caution: they're not supposed to go in all the way!

[budman]

Caution: they're not supposed to go in all the way!

The sender goes in all the way.

[budman]

The 1/8" BSPT plug arrived while I was at home for lunch today.  I can say beyond a shadow of a doubt that the sender threads on my cases are 1/8" BSPT.  The plug threaded in smoothly and snugged up at the end.

McMaster-Carr part #4860K131

[dusterdude]

For those of you wanting to use a 1/8 npt switch,do this.look up plews-edelman on the web,they sell an adapter that adapts the jap thread to npt.works great

Sent from my LG-D850 using Tapatalk

[markreimer]

it still won't go in but a few threads

Caution: they're not supposed to go in all the way!

THIS!

My '74K had a sender in it when I bought it that was threaded in all the way. I replaced it with one from 4into1 and it didn't thread in all the way. Perhaps I was sent a sender with a different/incorrect thread pitch. Or maybe the one that was in there before was wrong, who knows. Either way they were definitely different.

I didn't realize sender units have a tapered fit, I over tightened my replacement and cracked the main oil galley. Just a heads up to those looking around for info on oil sender units - mind the torque spec!

[firebane]

The issue is that people don't understand what NPT actually stands for and they think it means National Pipe Thread where in fact it actually means National Pipe Thread Taper and the taper is designed to help seal the threads.

The taper isn't usually much but its enough.

[Deltarider]

mind the torque spec

Just do it by hand and when you feel resistance, do not think it has to go in all the way. All the oilswitches I've seen on CB's (not many to be honest) still showed their thread.

[754]

How much torque when it cracked.
You might be able to weld it., or dive a sleeve down the hole..

[markreimer]

How much torque when it cracked.
You might be able to weld it., or dive a sleeve down the hole..

Wish I could remember. I just finished doing a bottom-end swap using a donor motor over the weekend. I tried to have the case welded twice with it in the frame. The welder said he didn't think he could get good enough access to fix it, and was right. It failed immediately both times. But he was confident if I split the cases and brought him just that piece it would be no problem to repair.

I've never gone into the bottom end, so for me... pulling the motor and taking my fresh top end and putting it onto a donor bottom end was easier. Did the whole thing over a weekend and back on the road now.

My plan now is to try and repair that case, I mean why not, the bike has a running motor in it now, may as well attempt a bottem end repair and overhaul 

[754]

Might be easier to drive in a sleeve...pretty good access from the cap near the point cover, and the hole is maybe reamed..

[markreimer]

Wouldn't that block oil flow? I think I must be misunderstanding. Or are you suggesting only driving in a sleeve where the threaded section is?

If you want to see more details on what happened, what I tried and what I ended up doing, take a look here, don't wanna hijack this too much

http://forums.sohc4.net/index.php/topic,143281.100.html

[Deltarider]

Have a look at the pic below if you will. Note that you still see the thread of the pressure switch. That's perfectly normal for a tapered thread. It's not supposed to go all the way down. If you try to force it all the way in, you will ruin things. You can also see it in Fig. 99 on p.37 of the Honda Shop Manual CB500 - CB550. And for heaven's sake, leave the torque wrench in the toolbox and do it by hand.

[754]

The sleeve need only be 1 to 2mm wall thickness...the hole is like 14 mm or bigger.

[przjohn]

Why would you want to block the oil sensor hole? Is it because there is another spot, looks, wiring? It seems to me that having a gauge is great if you happen to be looking at it seconds before your motor blows, but an idiot light catches your attention. Scenario, a cracked oil tank leaks all over your rear tire and just before you get off the hiway onto a nice curvy road the oil light goes on. Kind of happened to me except on a 2 stroke Kawasaki H2. No light but when I got off the hiway the oil cap had loosened and oil was all over the right side of the tire when I stopped for gas. I think especially for bikes with a dry sump they are a safety and mechanical red light.

[markreimer]

He was suggesting a sleeve because I over tightened the tapered switch and cracked the main oil galley right where the switch threads in, causing oil to spew out like crazy while running. Blocking off the switch would save the bottom end of the motor. You could always plumb in a switch on the right-side galley plug or something.

[754]

You can run an adaptor out end of galley, to a hose to a handlebar mounted guage.

[Deltarider]

A hose? To a handlebar? A handlebar that can swing? You will not do such thing. Not for a gauge that is only usefull seconds before your motor blows as Przjohn rightly states.

[754]

What, you have never heard of a handlebar or headlight mount oil gauge..seriously ?
I did say hose which can be very flexible..not hard pipe or tube..
 The guage will generally give you advance notice, except in catastrophic failure.
The oil light will only come on AFTER you have lost almost all pressure..

[firebane]

If I was going to run a gauge on my bars for oil pressure I'd be going electrical not mechanical.

[przjohn]

Still, wether it an electrical, or a pressure activated gauge, my question is not answered. With either of these methods you still need to sense a port. Why block the port off is my question?

[Deltarider]

If I was going to run a gauge on my bars for oil pressure I'd be going electrical not mechanical.

The only oil pressure gauge that makes sense is a model as made by VDO, with a built in warning lamp. VDO used to have them where you could even program yourself at what pressure that light should come on. But even then: the only legal acceptable position IMO for such a gauge would be like in the pic, but you'll have the original looks of your bike spoiled as a consequence. On the other hand: you don't need a gauge at all. A sudden pressure drop en route is extremely rare on our bikes (personally I don't know anyone who experienced that). All I ever heard of were timely warnings by a flickering lamp @ idle. And if that occurs only with a very hot engine you can ignore it.