Author Topic: Sealing primary chain case screws  (Read 653 times)

Offline a101960

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Sealing primary chain case screws
« on: 02.08. 2017 10:43 »
Sealing primary chain case screws. Anyone got any suggestions? I have tried fibre washers without success. Is there any kind of non setting thread sealant available that would do the job? The most troublesome are the one marked "A" and the two to the right of it. I am using ATF by the way. It is not gushing out, but there is an an anoying weep after standing a few days, and it drips slightly after a ride. As I say not a huge amount but enough to annoy me.

Online ellis

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Re: Sealing primary chain case screws
« Reply #1 on: 02.08. 2017 18:51 »
Try using small O rings on the screws. they certainly work for my 1960 GF.

ELLIS

Offline a101960

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Re: Sealing primary chain case screws
« Reply #2 on: 02.08. 2017 19:09 »
Quote
Try using small O rings on the screws. they certainly work for my 1960 GF.
Ellis, that has crossed my mind. What size should I be looking for, and just as important, where can they be bought from? All those that I have seen offered for sale seem to be in mixed sized packs.

Online ellis

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Re: Sealing primary chain case screws
« Reply #3 on: 02.08. 2017 22:14 »
Try a hydraulic factors. I think I used 9mm o/d x 5.5 I/d x 2mm thick. Hope this helps a101960. Or try EBay for a cheap o ring assorted kit for about £4.00.

ELLIS


Offline duTch

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Re: Sealing primary chain case screws
« Reply #4 on: 02.08. 2017 22:44 »

 II've tried 'O' rings  but not much success yet,  but persevering, think I tried 6mm x 2mm section (=10mmo/a).
 A half decent Bearing supplier should have them- they do where i now go.

 
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Offline Sluggo

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Re: Sealing primary chain case screws
« Reply #5 on: 02.08. 2017 22:47 »
I have never used an O ring on case screws like this, but its an interesting Idea I plan to file away and use perhaps.  But while many of my bikes have left their mark here and there, typically screws are not the source of the leak. 

I will submit that careful dressing of the gasket surfaces usually helps in spades...  Rupert Ratio in his guide to BSA unit singles does a GREAT job detailing how to get a BSA oil tight.  Worth a read.  However in stamped tin covers there is very little to do other than work the surfaces as flat as possible, but on alloy castings its very common to get the threaded holes distorted a bit.  I dont have a diagram or photo handy but to describe look at a flat alloy surface with the holes drilled and tapped.  After much time and torque and on-off again applications the metal around the hole or stud can pull out slightly. (Pucker) so then you have a not so flat surface anymore.

The fix is to slightly deburr and chamfer the holes. a 10 thou chamfer should do the trick. THEN carefully RE-TAP the threaded hole with a sharp and good quality tap to clean up the threads all the way to the bottom. (Use a starter or cutting tap to begin and bottoming tap to complete)  Blow out all the holes and check your bolts,studs or fasteners threads as well and if in doubt run a Die over the threads or in a pinch use a thread file.

To clean up a gasket surface a sheet of glass works well.  (A car side flat window works well as its tempered)  lay down the glass and tape some suitable wet/dry sandpaper to it.  Use light machine oil and carefully slide the alloy cover or case around back and forth working slowly. and checking frequently.  It will be obvious where the high and low spots are.... get the surfaces true and totally flat.  If experienced and really bad condition start with 220grit, but work up to 400 grit should be good,  but 600 for the anal types and totally OCD will have bragging rights at 800 grit as well as a near mirror finish.

I am a big fan of Hylomar as well, so, many theories on gaskets and sealing washers, o-rings and such, But thats another topic.  But I would submit your leaks are traveling down the screw threads but the actual cause is actually distorted gasket surfaces.  Water, Oils and lubricants have a funny habit at appearing in one location but the actual source is somewhere else.
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Offline KiwiGF

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Re: Sealing primary chain case screws
« Reply #6 on: 03.08. 2017 07:30 »
Sealing primary chain case screws. Anyone got any suggestions? I have tried fibre washers without success. Is there any kind of non setting thread sealant available that would do the job? The most troublesome are the one marked "A" and the two to the right of it. I am using ATF by the way. It is not gushing out, but there is an an anoying weep after standing a few days, and it drips slightly after a ride. As I say not a huge amount but enough to annoy me.


I've had trouble with the hole located near to your "A" that is not "blind" like the others, but goes all the way through the inner case. I'm not sure if this just my chain case and all other cases have all blind holes, I've fitted a longer screw to that one and put a nut and fibre washer on the protruding thread so it seals on the back of the case. I tried putting gasket sealant on the thread but that did not work.

Any others that leak I just take them out and wind a bit of twisted up ptfe plumbers tape around the shaft so it makes a sort of washer under the screw thread. Not as elegant as o rings but it works.
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1956 A10 Golden Flash (1st finished project)
1949 B31 rigid “400cc” (2nd finished project)
1968 B44 Victor Special (3rd project,in progress)
2001 GL1800 Goldwing, well, the wife likes it
2007 KTM 950 Adventure, cos it’s 100% nuts