Engine oil blow out

[limeyrob]

For reliability you don't want more than about 3"- 4" of unsupported copper pipe or any where its supporting anything.  Its the high frequency vibration that does for it.  If you can clip it back (put a rubber sleeve in the clip) that works too.

[Swarfcut]

 Craigy....If you have ordered a new feed pipe complete, better to leave it in one piece for now and ensure it is well supported, as suggested by Rob. Split small bore rubber tube lengthways as a cushion under P Clips or similar, you can always substitute a flexy
 if and when the quality part purchased eventually fail. The trick is to damp out vibration to the pipe as much as you can.

 Swarfy.

 

[Craigy]

…..and it really does vibrate - rattles your eyeballs 😳

I haven’t been able to work it out yet, it’s ok when it’s pulling but on constant revs/deceleration it really vibrates.

I’ve had a feel around different parts while I’m riding but can’t seem to trace it. I know the drive chain really shakes at certain revs during tick over, so I’ve played around with that and the primary chain but it didn’t seem to make and divergence to the initial vibration …..just another problem 🤔

[limeyrob]

Unless something is loose the serious vibration will be from the pistons and crank. Piston weights vary quite a bit between makers and I'm not persuaded that the "basic" balance set is the best.  I bought an A65 new and while it was smooth at low revs it vibrated a lot at high revs and being a over square engine it needed revs.  I later built it with high comp pistons that were significantly lighter and I was expecting problems.  It was much smoother so my conclusion was that BSA were not optimizing the balance.

[Swarfcut]

  One of the characteristics of this type of engine "The Vertical Twin" is that there is a sweet spot in the rev range where  initial vibes smooth out, before entering another more vicious phase. This smoother speed depends on the difference in mass of the moving parts.

  BSA employed a balance factor, expressed as a %  of the reciprocating mass, that is pistons, rings, rods etc. This was then converted into an actual chunk of metal (a service tool to clamp on the crank)  to mimic this weight and placed on the big end journals of the crankshaft  and the whole ensemble placed on knife edge rollers and allowed to come to rest. Material was then remove from the flywheel so that there was no heavy spot, often seen as drillings in the flywheel. There is a BSA Service Sheet detailing the procedure.

 Any change in the weight of these reciprocating components over time will affect the balance factor and hence the engine speed at which the motor is smoothest. Back in the day 50-60 MPH was where you wanted the smoothest ride, and that's what an engine in good order will give with the standard balance factor. Alternative published figures are available for different purposes, particularly racing. Pretty crude, these days dynamic balancing is the way it is done. Even back in the day it was far from perfect, identical machines differing in perceived smoothness. Then add general wear, piston rattle etc and there is your rough ride.

 My Plunger bike was a real shaker at normal road speeds, 'til I discovered it was a low geared sidecar bike in an earlier life. Standard gearing for a solo machine is  42 teeth on the rear sprocket, 19 teeth on the gearbox. Worth a look, revving its socks off at normal road speeds is not what you want!

  To state the obvious, frame to engine mountings and engine steady links need to be good and tight, the steadies running forwards from the rockerbox/cylinder head to a lug between the frame down tubes are often absent, as is a bracing bar across the underside of the fuel tank. Don't expect a smoothness found on modern machines, oldies just can't do that.

 Swarfy

[limeyrob]

Good call about the gearing. I've always found BSA twins can pull an extra tooth and it does smooth them out a bit, well it shifts the vibes at bit further up the speed range.

[Craigy]

Cheers guys, I’ll check out the mountings first. Also the strap on the underside of tank is ‘homemade’ could this be an issue by not having the desired effect?

[Craigy]

I had a quick look today at the mounting bolts, I think the gearbox ones have found a new home, so that might explain the vibration. Parts book say 67-4028 (5/16 Whit x7/8”). I’ve put a screwdriver in the hole and it didn’t seem very deep but I suppose with the frame that’s probably 1/2” taken up there

[limeyrob]

Give those a good clean out so the bolts can go all the way in.  If you don't already its worth getting some Whit taps and dies for cleaning up threads.  I have a cheap "garage" grade set of BSW and BSF and then 1/4, 5/16 and 3/8 Cycle.  Once you get the thread good and clean you can loctite the bolts in.

[muskrat]

G'day Craig.
I remember my plunger those holes were flogged out (loose bolts) so redid them 3/8". This was back in 1981. I should have used helicoils or better timeserts. No net back then.
As Rob says, run a tap up to clean the thread then use red loctite on new bolts (UNC will do).
Cheers

[Craigy]

UNC - really!! You might have just saved me a 3 week wait from Draganfly.

I was going to call in to see Murray at britbikes in Adelaide tomorrow to see if he has any lying around….if not I’ll hit Bunnings 😁

Whitworth taps might need to be ordered as can’t see anywhere local having a dusty box out the back

[limeyrob]

You don't need many Whit taps - 1/4 5/16 1/2  and only a few BSC.  E-bay has cheap "garage grade" tap and die sets - they are fine for thread cleaning.
Musky is right, it always pays to check the thread charts as UNC sometimes has the same pitch as Whit.  The nut on the camshaft is an unusual  CEI (not 26 TPI) but its almost identical to UNC. I ran a UNC die down the cam and the nut fitted perfectly.
If a thread in case is getting iffy you can get a tap and grind the end off square then cut the thread to the very bottom, then saw a bolt to just fit.  This will often get 3 or 4 more threads which is good enough for most jobs.

[Swarfcut]

 Just had a look at a couple of Plunger Gearbox casings.  The early type (pre'53 or thereabouts) has somewhat raised mountings and the rear face of the casing is smooth. A quick measure with a caliper gave 15mm for the depth on these blind holes.

 The later casing has webs extending forwards, which I think I can see in the above picture, and two vertical ribs on the rear face to match the position of the blind holes. So BSA obviously had a problem and beefed up the casting. This example has blind holes of 20mm.

 The snag with blind holes and supposedly standard bolts is the problem of muck and debris at the bottom of the hole....the fastening appears tight but in fact may not be exerting a clamping force. With a gearbox already in the frame an alternative is to use threaded bar to the bottom of the holes, then a nut and washer to the frame mounting lug. You can't fix studs to the box before the whole unit goes back into the frame, there is not enough clearance between the top of the box and the corresponding frame lug on the saddle tube.
   Goes without saying to clear blind holes to perfection.

 Whitworth threads, nice and coarse into soft alloy were the fastening of choice. These days UNC is the dead ringer for BSW, only 1/2"BSW differs from 1/2" UNC by one thread per inch, otherwise same TPI in the threads we use.

 New sets of chaincase 1/4 Whit you can bet are actually UNC. The difference being the thread angle of 55 degrees for BSW, 60 for UNC. Ideal, some would say for use in worn Whitworth threads.....

 Swarfy.

[muskrat]

G'day Craig.
If your going to Adelaide go to Classic Fasteners  https://www.classicfasteners.com.au/ They have a great selection of nuts & bolts in most thread forms and I think they stock Tracy Tools (UK) taps & dies. I buy my CEI thread stuff from there.
Cheers

[Craigy]

You guys are an absolute credit to this forum and your knowledge is first class.

Swarfy, great info cheers, I just wish I could retain half of what you write.

Musky, I’ll try Classic Fasteners, I’ve used them before, great little shop. It’s only half hour from me. Don’t know if you know of britbikes, I’ve never seen so many parts/bikes etc in one place. Murray is a great bloke but he’s retiring so I assume that’ll be the end of that.

Limeyrob, also great info when I need it cheers

Assuming UNC is a decent alternative thread, I’m guessing if I can get my hands on UNC grease-nipples, these can also be swapped out……all this info 😁