Author Topic: A7 Bobber Engine needle roller conversion  (Read 1047 times)

Offline Degsy

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A7 Bobber Engine needle roller conversion
« on: 16.04. 2021 16:47 »
When I spilt the engine to clean out the sludge trap I was surprised to find it had a needle roller conversion.  This bike was put together from parts back in 1980, I don’t know if it was a DIY conversion or professionally done, does anyone recognise the work?

There is what looks like a large weld under the oil pressure relief valve (see photo). I don’t know what that is all about, any suggestions?

I will replace the crank end oil seal, I’m hoping the rest of the conversion is ok.

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #1 on: 16.04. 2021 22:08 »
G'day Degsy.
Similar to an SRM set up. I haven't seen the three retainers on the inside of the bearing before. Mine is a light interference fit.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Online chaterlea25

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Re: A7 Bobber Engine needle roller conversion
« Reply #2 on: 17.04. 2021 01:50 »
Hi Degsy,
It looks like the "weld" around the outside is to provide an oilway from the pump side of the PRV down to the dowel hole, that is connected to the oil feed block that feeds the crank
The dowel seems to be missing?
On the SRM conversions the dowel is hollow and there's an O ring around it to seal the joint rather than put pressure on the gasket

The oil from the pump looks to feed in to the groove around the roller race then out to the PRV and around to the oil feed block ???

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: A7 Bobber Engine needle roller conversion
« Reply #3 on: 17.04. 2021 08:41 »
Is it possible a Devimead job? They used to do the end feed conversion before they moved away from BSA's.  They had good knowledge of the A10 and A65 motors. Had them do a couple of end feed jobs in the 80's on my A65 Windle BSA

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Re: A7 Bobber Engine needle roller conversion
« Reply #4 on: 17.04. 2021 10:47 »
 Like CJ I considered the weld to be the feed to the timing cover, but as they don't make drills that go round corners how is the oilway formed? A brass or copper tube in there somewhere?  The weld does not look like a true fusion weld, more like a lump of something sitting on the parent casting, Lumiweld or similar?

 Is it a trick of the light but those three retaining bolts for the race don't look the same, so maybe not a  true professional conversion. Most examples used an expensive timing side bearing which combined ball and roller elements, rather than a ball race on the drive side as here. All point more to a homespun solution than a true precision job.

 The man with some of the answers is  Forum member MrShifta, he has a bike which featured in Classic Bike all those years ago when end fed cranks first made the big time.

 I have seen bikes where the feed is external, via narrow bore tube and compression fittings. Ugly, functional but easy to check oil pressure and supply.

 Swarfy

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #5 on: 17.04. 2021 16:33 »
Thanks Guys

This bike was put together from parts back in 1980 so your comments about it being an early conversion would make sense. 

I have been trying to map out the various oil way routes by blowing compressed air through and seeing where it comes out and then drawing the route on graph paper like a wiring diagram.  The only diagram I know is from the BSA service notes and not easy to read (is there a better one?), plus I have the the bearing conversion which complicates things, but the geek in me wants to understand the lubrication system.  I will stick my diagram on here for your amusement when it is done.

Cheers

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #6 on: 17.04. 2021 19:22 »
 Search  the Entire Forum for "Baffled, Confused and Covered in Oil" a topic under the broad heading of Lubrication System.  All will be revealed, the less said the better.

    The basic system has led many a merry dance, produced world wide insomnia and mental anguish. Failure of the system has made many engine builders and parts suppliers rich.

 Then you add an end fed conversion....... baffled and confused, you will be, just like the rest of us.

 Swarfy.

Offline MrShifta

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Re: A7 Bobber Engine needle roller conversion
« Reply #7 on: 22.04. 2021 18:59 »
I can only say Swarfy that my conversion was very similar to this and did have retaining screws to hold the combined bearing in place. I completed it in 1983 and the details were published in Classic Bike in October 1984.  As far as I know mine was the first A10 to be done. The A65 's were being done by SRM sometime before then.

Later in 1984 SRM started to offer to convert A10's.

If this one is 1980 it must be a big coincidence but hey ho nothing is impossible.

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #8 on: 24.04. 2021 09:03 »
Hi guys

Yes the oil feed comes from the pressure relief valve through the external pipe under the “welding” and into the oil seal in the timing case and then into the crank quill.  The oil does pass through a dowel on its way to the crank feed (see photo) no O ring so as you say it relies on the gasket which is not ideal, I don’t know why the dowel has notches cut in it.

Interesting comments about the early days of needle roller conversions.  The bike was put together in 1980 but it looks like my engine must have had some major rebuilds and the conversion could be much later.
When I got it the engine was seized and the cylinder barrels had a big chunk out of the skirt (see photo) would throwing a rod be the only thing that would do this?  The crank case shows no signs of anything bad happening in the past although the crank does have a clear dent on the edge of the flywheel.

Someone had done a reasonable job of cleaning up the damaged skirt but  the bike had been sitting unused outside for a few years and the barrels were rusted (see photo) to the point that the one remaining rebore would not have cleaned up the rust pitting.  It looks like the barrel has a liner, am I right in thinking the cylinders did not have liners when they left the factory.  Anyway I was lucky and found a replacement cylinder locally that had been rebored but not used, so no need to try and use the old one.

Swarfcut  I have given up trying to draw a complete map of the oil system, there seems to be oilways and pin holes all over the engine, but at least I do have a better understanding of the lubrication system now and your advice to read the forum and learn from the grief and work of others is well taken.

Cheers

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #9 on: 24.04. 2021 14:19 »
 With the smaller throw of the A7 crank compared to the A10 there is a possible that the rod fouled the barrel skirt but not the crankcase. Or some fool just dropped the barrel and sadly knocked a chunk out. Also the crankcase and barrel may not have started life together, the engine was rebuilt with a damaged barrel and just left to rust. That skirt has been dressed and a hole drilled to stop a crack developing further. I'm assuming that was how you found it.

  A competent repair for that barrel would be a cast iron weld, in a similar situation I found a guy in Hinckley, Leicester whose business was repairing industrial cast iron gas and water valves, top class operation with bodies heated in a muffle furnace. My barrel was a toy compared, but it still cost. The repair may then take a rebore, or the barrel can be sleeved. It is certainly too good to scrap and useful to someone.  No liners were fitted to standard cast iron barrels.

 The dowel looks to be shaped to maintain its location as part of the oilway system and to stop it moving (rotating) to block the supply.

 Rod failure on an A10  is pretty spectacular....... Have a look at my example in "Great Mechanical Disasters"

  These engines seem to survive for years driven gently even with cranks full of sludge. Sold on in good faith the new owner opens up that throttle and that bargain becomes a millstone money pit. A complete strip of an unknown new purchase does no harm and at best is just the cost of the gaskets. At worst it enables a measured approach to any rectification required before major damage occurs.

 Swarfy.

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Re: A7 Bobber Engine needle roller conversion
« Reply #10 on: 24.04. 2021 20:50 »
Hi Degsy,
Check out where the dowel fits in the crankcase and outer cover to see if there are location's to keep the dowel in place, and would the oilways be blocked if the dowel was turned to some other orientation ?
Is the dowel a press fit in the inner timing case? If it was mine I would want to add O rings and a simple plain dowel

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #11 on: 29.04. 2021 11:17 »
Well my A7 engine teardown continues to throw up interesting surprises.

I noticed that the roller bearing hole has been machined out wide enough to take retaining tabs and in doing this it has broken through to the antidrain valve spring so oil might flow past the ball valve and out through the spring into the crank case past the ball bearing race (see photo). 

As Swarfy has pointed out to me this could cause a drop in oil pressure to the crank end feed and the big end bearings, I can see there is evidence of excessive wear in my big end bearings. I don’t think I can ignore this potential problem.
The needle roller bearing comes out by hand once the tabs are removed (see photos) and this gives a better view of what is going on with this conversion.  To me it looks like there is less restriction on oil flow than you would have with a bush so I do not want to be losing more oil pressure through the antidrain valve spring.

First I need to get the grub screw out, the spring and ball, then one option might be to try my Aluminium brazing rods and see if I can Braze over the hole and if it goes well I might be able to replace the spring and ball valve. 
Another option is to remove the spring and ball valve and put in a plug to cover the hole but making sure it does not go too deep and restrict oil flow.  Would mean no anti drain valve but I could live with checking and draining the sump routinely if it means I have a working lubrication system.

I think given the possible extra demands on my old oil pump I might need to splash out on a new SRM replacement.  The bike had been converted over to a cartridge oil filter and I am removing this and going back to a mono grade oil and frequent oil changes.  The removal of the pipe work and cartridge will I hope make a slight improvement in oilflow.

Any thoughts gratefully received.

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #12 on: 29.04. 2021 14:06 »
I know little about the roller-bearing/quill-feed conversions, but, to me, this looks weird. (I would say "bad" but, like I said, I'm no expert on the topic.) Aside from the slip-fit bearing, I don't see a purposeful way the bearing is lubricated. By accident? By leakage through the breached spring gallery? The leak past the edge of the screw is definitely going to reduce oil flow to the crank. The PO clearly had an unreasonable fear of sleeve bushes. I could imagine blowing off the quill feed and fitting an oversize sleeve bearing that recovers the spring gallery. Others will hopefully comment on whether or not my concept has merit.

Richard L
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Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #13 on: 29.04. 2021 14:38 »
Hi Richard

It is difficult to get a full picture from these photos, but if you look at the bearing Journal photo you will see a hole below the antidrain valve spring, this hole is the oilway that is fed directly from the oilpump the oil then runs through the groove and out the hole on the other side which feds to the back of the Pressure Relief Valve (PRV). 

Now the circlip that is soldered to the outside of the bearing butts up against the raised rim you can see in the bearing journal, this effectively seals off the back end of the bearing so it is fed by the oil running through the groove on its way to the PRV, it looks like they might have filled in some of the holes in the bearing outer body, perhaps in an attempt to restrict the amount of oil flowing into the bearing and then the crank case.

So I am not worried about how much oil the bearing is getting although it is possible too much of it is flowing through the bearing into the crank case.

My concern at the moment is the oil may be leaking through the anti drain spring and bypassing the bearing journal's raised rim and flowing into the crank case and this is oil that should be flowing round the groove in the journal and into the PRV and then lubricating everything downstream of that, most important is it goes through the quill end and feeds the big end bearings.   

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #14 on: 29.04. 2021 19:57 »
 If  the outer race of the bearing is  the same OD above and below the circlip, a tubular support sleeve is needed above the circlip ledge to fill the gap, support the race and blank off the side of the spring. Can't be that simple, but that's how it looks. All a bit of crossed fingers  design.   Faith, Hope and Loctite......certainly need some Bearing Fit to stick it together and fill the gaps to make sure pressured oil only goes where it should.

 Swarfy.

  Additional. Looking closely at the very first picture the three bearing clips offer some side support, but little in the way to prevent axial movement. There is also a distinct gap between the bearing and the case, illustrated by the view of the exposed spring as if an outer sleeve is missing or completely overlooked in the conversion. This sleeve would solve the problem with the  exposed spring and allow the 3 clips to clamp the circlip to the ledge,  positively locating the bearing. Full oil flow to the PRV cavity would also be restored.