ET: Engine (Twin) 2BA Countersunk Screws (406)

Bill Thomas

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I have felt some of the new Multi's, And they are very light,
The plates were not around in my day, The only thing is the lift was made for only one plate,
They have modified the lift lever, But I haven't tried one yet,
Don't need it with the standard clutch,
Trouble is my stuff is old and worn out, Must have been better when New ?.
 

BigEd

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Vic, These screws are Soo Tiny, They lock down via the outer plate to small metal tubes that are inside the springs,
I got a bag full many years ago, Somebody in West London Section,
I think they are B.A. ?. 9 Of them !,
The photo shows them next to a 5 P / 5 cents coin.
I got some black, 2BA, Countersunk hexagon head Allen screws this week. They were on eBay sold by "elmhousecollector".
Two lengths available, 1.25" and 1.5", so they need to be shortened before fitting, £5.00 for a pack of 10, including postage. I have some stainless ones fitted at present and got these for spares as this kind of thing seems to be increasingly hard to find.
 

Bill Thomas

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There was a good tip on the Forum ! , Where else ??? :D ,
Keep a pair of long screws to start to pull the springs together,
Then swop them out after a few threads.
 

b'knighted

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Keep three long studs to go between the springs and pull the plate down with a box spanner on the nuts. (Long 2BA screws with nuts are sold for mounting trailer sockets.) Once the plate is snug 3/4 long Allen screws can be easily screwed in before replacing the studs with the final Allen screws.
My countersunk Allen screws require a 3/32 Allen key but Stu Spalding recommended using raised countersunk screws which apparently use the next size up. I have never managed to find these for sale.
Having had to attack the Knight's clutch this week, I found the appropriate tools were not in the bike's tool kit. This led me to restock with ebay items 402241134899, 373190540552, 203145518010. This provides the three sizes of Allen key needed for clutch cover, primary chain case/timing chest and spring plate as well as long screws with nuts and a lifetimes supply of spare screws. All these ebay purchases arrived within two days.
 

b'knighted

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The 3/32 Allen key was flexing when each of the nine screws released with a crack. I doubt that they would have released if loctite had been used. The amount of slot available in a countersunk hole for use with a standard flat screwdriver would have been hard pressed to undo screws that tight without rounding out. Similarly had they been std slotted screws, loctited in because the flat screwdriver wouldn’t tighten them enough, I'd expect them to be permanent.
The factory didn’t find the need for spring washers, shakeproof washers or loctite. If I find that something won’t stay done up I may resort to spring washers or nylocks but not a chemical lock.

The knobs holding D panels are knurled, so tightened with fingers. I'll own up to cheating and tightening while wearing riding gloves but would new owners glue them in?
 

oexing

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So you believe in nylocs but have never tried Loctite 221 or 222 ? I have never seen nyloc screws so my advice on these countersunk screws would be 221 as this is no harder to undo than a nyloc in another place. So while you most likely won´t find Torx BA screws and countersunk Allen screws have a small hex keys only I´d rather have common slotted screws, more torque from these.

Vic
 

Bill Thomas

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Vic, The standard screw has always been a pain,
If you think the head is countersunk, There is no support for the slot at each end !,
So easy to round off, Plus we used to pin pop the plate into the screw slot,
So it wouldn't come loose, But we have all seen that one would !.
Cheers Bill.
 

vibrac

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There are big screwdrivers and small screwdrivers and one that's the right size and that's the one they used at the factory back in the 50's
If I can remember back to when I had a standard clutch I think I used alan head screws cut to length
 

MarBl

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I would like to support Vics recommendation for 221 and 222, but because I am lazy, I use the easier to apply Loctite 248 stick on all screws smaller than M5 instead. They say its medium strength but in comparison to the fluids, I found it to be closer to low-strength and rather easy to unscrew if necessary, much easier than with the fluid 243.
Of course that doesn't give you any guarantee, that a screw may not still eventually come loose, especially problematic ones like the aforementioned clutch screws. But it provides some extra safety. And of course you always need to clean the threads first.
There is also another, oftentimes overlooked advantage, which I only realized after using the stuff for some years. Loctite does an excellent sealing job, keeping moisture out of the threads, and I never found any corrosion on screws secured that way, especially not on otherwise problematic connections between different alloys.
 
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