Plunger Oil Tank.

[metalflake11]

Hello all.

Does anybody know the thread size for the filler neck please?

Also is there a fork topnut or something that is the same?

There is a method behind my madness chaps!

[muskrat]

G'day mf11.
1,1/2" x 20tpi same as the primary inspection cap. 65-8500 or 65-3364
Cheers

[duTch]

 Yup, same as Musko-  just measured it but he beat me back....I'd guess that's Cycle thread  ...
  I'm using in my primary a beat- up what I think is aftermarket Triumph rocker inspection cap as per pic....was figuring to do some kind of breather in it,  but aaaah....

[metalflake11]

Hello Muskrat, cheers.

They sure are, but the threads near the top on both oil tanks (one on, one in the wash, literally) are worn out. As a consequence, they are stripping the threads on the caps as they are quite short. There's plenty of thread in the neck not being used, so I thought maybe a fork nut might do the job as the thread is a lot longer.

[metalflake11]

Thanks Dutch!

How deep is the thread on that rocker inspection cap please?

As in, are there more threads than the standard cap so it will go further into the chaincase/oil tank.

[duTch]

 Here's my same primary cap in the oil tank.

 I think fork legs are generally only about 1,3/8" tops  anyway (?) , but worth a try

 You posted while i was typing^^,  seems the threads about same length

[metalflake11]

Thanks again Dutch, hoped there would be a bit more threaded section than that!

I like it though, and might get one for my chaincase.

[Sluggo]

Just an FYI, I have a lot of triumphs and aftermarket rocker inspection caps like the one pictured are quite popular, but just be aware there is several SIZES as well as styles of them.  Preunit Triumph and Unit models IIRC are different sizes, not sure about the threads but I can measure if you like.
I have a collection of them from basket cases and projects that came thru the shop, Some of the purists dont like them at all, but I set them aside and like to use them on my own machines. But I can tell you for sure to check carefully as there is several variations in the thread sizes for openings.  500 twins are similar but slightly different than the preunit rocker boxs.
The alloy one pictured is my favorite style, and cleaned up they are quite attractive, and for extra bling you can index them and then drill small holes around the top for the Industro-steam punk look
(Match your blinged out steering damper knob similarly drilled)
There is some being reproduced today, some in steel and chrome, but not as cool in my book.

A couple other ideas since stock is not the issue here, On HDs there is some aftermarket-accy oil tank caps with a graduated taper that are oil resistant rubber and a LONG dipstick (ill leave out the puns) and situated on the top of the cap is a oil temp gauge which I admit, is rather clever and I have a few of these on my bikes (HD & otherwise).   

Other options I have seen is automotive engine block freeze plugs sometimes dislodge and some stores sell a rubber plug expansion with a bolt in the center, a few turns and it squeezes the rubber into a tight fit, Bodge, but will get you home, The other is for plumping and pipe end caps with a hose clamp, and I have seen both of these repurposed on motorcycles for missing rocker caps, oil tanks, primaries and the like. A few were permanent features and dressed up with skulls or other bling. (Some quite clever)

Necessity is the Mother of Invention. (Insert Zappa reference)

[metalflake11]

Thanks for the heads up there Sluggo.

Mine is just hanging on, but with no sealing washer on, so I get oil streaks down the tank.

I could get the shoulder turned down a bit on one of those pictured, so the threaded part reaches deeper into the neck where the threads are still good in the tank.

[duTch]

 Ta Sluggo- I was going to mention the different sizes but got lazy/attentionspanblewout, I think the pre-units were bigger than units and my '69 Daytona had smaller ones (no way to get a feeler gauge in adjustment was '?' fraction of a turn out from zero)....
 At a guess, I'd say mine is from a unit 650..... hmmm

[metalflake11]

These things are never as easy as they first appear are they?

[Sluggo]

Nitrile oil resistant O rings are the key, Triumph owners lose their caps with regularity, simply replacing the fibre sealing washer with a O ring is an effective solution to lost inspection caps.  I had a friend that his expensive chromed Vokes air cleaners would shake and fall off came up with a great idea as well.  He took fishing line and a swivel with a snap hook (Like a carabiner D ring) and tied a clear section of fishing line onto each and secured the air cleaners that way so if they shook loose he didnt lose them under a lorry tyre on the motorway..  I worked in aviation and many will drill holes in fasteners and safetywire with stainless as well.

[Sluggo]

 Ta Sluggo- I was going to mention the different sizes but got lazy/attentionspanblewout, I think the pre-units were bigger than units and my '69 Daytona had smaller ones (no way to get a feeler gauge in adjustment was '?' fraction of a turn out from zero)....
 At a guess, I'd say mine is from a unit 650..... hmmm

I suppose I could do a survey and do some measurements, I recently tidied up my cyl heads and rocker box in storage so they are all sorted, But we are getting off topic posting up Triumph bits on a BSA board eh?
(king of tangents and easily distrac...........Shiny things!)

But yes, on many its hard to get a feeler gauge in there. Some nice little custom gauges have appeared on ebay as well as really nice 1 piece adjuster tools,
 (Screw adjuster at the top and lever on the side makes finite adjustments a breeze)

I hoard the late Triumph oval cap rocker boxs as they are wonderful, there was some late 500 twins with a side plug on the Rocker box you can remove and stick in a gauge...  But I learned long ago to just do by feel
and calibrated fingers.  If you practice you can feel (Clack clack) the difference between .002, .004, .006 etc.
I also have a comparator from my Visual/Dimensional inspector days in manufacturing,,

Its a series of holes and bumps in different measurements.  You can literally run your fingers over and train yourself to measure by feel.  (Thats more than 4 thou! send it back!)  Here is a tip, (Shaping sheetmetal and bodywork as well) CLOSE YOUR eyes!  Run your fingers or hands back and forth, you will ALWAYS get a better sense of shapes and sizes with your eyes closed.  Its a proven brain tool.

[duTch]

 I measured up for ' O ' trying but finding one in the right diameter with a usable section was challenging,  so shelved it pending....
 After also losing my air filter- again, but found it before it too was run over- I did what Sluggo's mate did,  but used redundant bicycle brake/gear cable (stainless) doubled-up and threaded through a 'lectrical eye terminal bolted to my unused air-box/battery mount, and squished the other end through the house clamp- even used the little ally cable ferrules to stop it unraveling, works a treat....

 You type to fast Slug go.... we are getting of track into the rough- but I will just say 1/4 turn of 14" bsc/bsf is ~10 thou, I still use that to rough out my valve clearance (and with hex-head adjusters can easily do 1/6 x 2 turns )
 Back to oil tank over and out....

[Greybeard]

Bottom right of Sluggos first picture there is the type of cap that I have in both my primary case and oil tank.