Author Topic: A7 Bobber Engine needle roller conversion  (Read 1052 times)

Online RDfella

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Re: A7 Bobber Engine needle roller conversion
« Reply #15 on: 29.04. 2021 20:06 »
Sounds to me as if another crankcase half would be the best option.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online muskrat

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Re: A7 Bobber Engine needle roller conversion
« Reply #16 on: 29.04. 2021 22:31 »
G'day Gegsy.
I'd look at sleeving the case and using a different INA bearing. I'll look up mine tonight.
My setup closely resembles this https://cybermotorcycle.com/archives/bsa-a10/mybsaa10rollerconversion.htm
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online chaterlea25

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Re: A7 Bobber Engine needle roller conversion
« Reply #17 on: 29.04. 2021 23:29 »
Hi Degsy and All,
The needle / ball bearing does not need an oil feed from the pump, residual oil splashing around the engine provides sufficient lube
The intrusion into the anti drain spring is one of the main problems
A conversion to the A65 setup where a longer grubscrew (1/2in) would be used would not even block the oil leak
The loose fit of the bearing is a further serious issue
I had not realised that it had the combined bearing until now, was the ball bearing facing the timing pinion? and the outer half race clamped by the timing pinion
I think another set of cases would be a good place to start on a bid to sort out an engine for your bike

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #18 on: 30.04. 2021 14:33 »
Hi Folks
For such a small grub screw it was surprisingly difficult to shift, but I got it out along with the spring and ball (see photo)and I have decided to remove the antidrain valve and sort that problem later in some other way.  I found an Aluminium bolt with the same thread as the grub screw so I could turn that into a plug for the antidrain valve and blank the hole down the side of the crankcase Needle roller housing.

This however does not solve the problem of too much oil flowing from the channel in the bearing hosing and out through the needle roller bearing into the crankcase, thus causing a damaging drop in the oil pressure through the pressure relief valve and to the crankshaft bearings.

Swarfy – you suggest a sleeve and I have been wondering why there appears to be remnants of something like loctite on the outer edges of the bearing housing, you can see this in the photo here as green/yellow patches, I could not understand why this was visible because there is a gap between this side of the bearing and the crankcase so the loctite could not be sticking anything there, unless there was a sleeve in that gap previously and that was glued in.  I will check but I don’t recall seeing anything like a sleeve when I stripped the engine down.

Making a new sleeve is an option although beyond my technical abilities. 
I get your point about axial movement, at least there does not appear to be evidence of any movement (Yet!).

I need to get all the bits out on the bench and have a good think about possible solutions.

Cheers

Degsy

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #19 on: 30.04. 2021 14:55 »
Sorry missed some of your replies on the next page...

Wow! new crankcases and the additional machining required, things are getting serious.  I hope to find some reasonable bodge that can sort this setup in some way.

The ball bearing end was facing inward and facing the crankshaft (see photo).  Interesting to find when I googled this bearing it was available on Amazon! but once cleaned the bearing feels OK.

The guy who sold me this bike back in January did say he had an A10 engine,  I think I will contact him and see if I can guilt him into selling it.  Although I do want to use this engine since I have bought new pistons and rebored replacement cylinder barrels.

Cheers

Degsy

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #20 on: 30.04. 2021 16:28 »
Hi Musky

Interesting to read the needleroller conversion in your link, it says... 

"A groove 4 mm square is machined around the bearing to join these two holes. If this groove coincides with the BEARING oil groove, oil pressure to the big ends will be LOST!!! "

This is my problem, I also have the oilway groove but I believe my bearing oil groove does coincide with the oilway.  Tomorrow I will go back and double check the alignment, but if you look at the bearing it looks as if they have soldered up some of the bearing groove oil holes in an attempt to control the amount of oil that is leaking through the bearing.  Perhaps they thought it was a good thing to give the bearing more oil without realising that further downstream they were starving the big end bearings and my big end bearing shells are very badly worn.

Cheers

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #21 on: 30.04. 2021 18:16 »
Hi Degsy,
The more I see of this engine the more I believe it is a monumental Fu*k up  *sad2*
The thrust element of the combined bearing is not being used at all with the bearing fitted like that
Who ever started off this job picked the wrong bearing with its oil holes and circlip groove
If they fitted the bearing at the proper interference to the crankcase with the thrust bearing outwards ignored the circlip and blanked the oil holes , they would have had some chance of success

John
1961 Super Rocket
1963 RGS (ongoing)

Online RDfella

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Re: A7 Bobber Engine needle roller conversion
« Reply #22 on: 30.04. 2021 20:10 »
I agree with John. Boring the crankcase to accept a bronze bush would also mean ensuring oil is delivered where it needs to be - and then you've got the crankshaft to somehow revert to standard. There is no way I can see of 'bodging it up'. Frankly, you need another engine.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Svend

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Re: A7 Bobber Engine needle roller conversion
« Reply #23 on: 30.04. 2021 20:37 »
Hi
Just a question the drive side is it a ball baring, and no a roller baring? Then there will be no pressure on the ball race in the timing side ? And the way the nx35 is turned doesn’t matter. The crankshaft is fixed and the side trust form the oil pump is taken by the drive side ball baring.
It I just a gestation sorry for my poor English.
Best regards Svend  *????*

Online Minto

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Re: A7 Bobber Engine needle roller conversion
« Reply #24 on: 30.04. 2021 21:24 »
This thread has been fascinating, I'm so sorry that it appears to be beyond sorting.
52 A10 plunger
Aprilia RSVR

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #25 on: 01.05. 2021 10:35 »
This is all getting a bit depressing and I havn't shown you the state of the camshaft yet.

The circlip that is soldered in place buts up against a thin spacer that seems to position the bearing flush with the crankcase and I think the circlip would take any side loading so I don't know if that makes the way round of the bearing irrelevant, I will check to see if it can be swapped round with the ball bearing side on the timing side, although this is currently the least of my problems.

If you guys are thinking new engine then I am starting to think what have I got to loose trying to find a fix as it is, obviously I want to avoid a catastrophic failure at some point.  At the moment I am still going down the, how can I work with what I have got and fix this.

As Swarfy said early on, it is hard to believe someone would go to the trouble of doing a needle roller conversion and the bodge the job.  This bike is a strange mix of bodged work and sensible upgrades, like the belt driven Alton alternator conversion, it has had what looks like an early version of the alternator from the French company that does the Norton Commando electric start conversion.

Bye for now

Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #26 on: 01.05. 2021 11:53 »
I feel for you Degsy. In cases like this it's best to, as I believe you are, take careful stock of what you've got and carefully evaluate all the options. It struck me too that this engine is an odd mix of careful engineering (eg the recesses for the three retaining tabs) and downright carelessness. In my view - and here I speak without your engine on the bench in front of me - I believe trying to repair the present disaster by retaining the present bearing is a non-starter. That would involve some decent machining (which I understand from your earlier comments would have to be farmed out) with no guarantee the end product would work. Was the bore for the needle bearing even bored accurately in line with the drive side?
Then you have the ruined non-return spring hole to sort out. That could probably be TIG welded and re-machined. Presumably the crankcase could be bored out to take an insert. And given the number of disasters in this area I'd be looking to go back to a bronze bush. Which of course means taking the sleeve off the crank - and hoping there's no more disasters there.
So, if it were me, I'd start with the crank and check the timing side can be returned to standard. If lucky, that could mean just blocking the quill hole. Then I'd restore the crankcase to standard too, but I'm lucky insomuch as I have the machining facilities. For those who don't, another pair of crankcases is the best and probably cheapest option. A crankcase half would suffice (and timing sides should be more readily available than drive sides) but remember there'll be some machining required to match it to your existing half.
Sorry this may not be what you want to hear, but any attempt to bodge your way out of this can only lead to more problems and further expense.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Degsy

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Re: A7 Bobber Engine needle roller conversion
« Reply #27 on: 01.05. 2021 17:47 »
Hey
Thanks for the comments RDfella, I am not giving up on this engine’s current configuration, not yet, although I recognise your suggestion is the sensible option, but then in the past I have not always chosen the sensible option and I am still as you say, taking stock, also after this morning your suggestion has become a lot easier.

I needed some cheering up after the depressing direction my engine has taken in this thread and I am glad to say I am feeling more positive about my options now.

The guy who sold me the bike lives nearby and he had said he had an A10 engine, I contacted him yesterday and he said come round and help me dig it out of the shed and we will see what it is like.  I should say this guy is a real horder with loads of bikes and half done projects, none of the bikes are getting used and some are outside under tarps in the garden.  I spent this morning helping him dig out all his A7 and A10 parts from deep in his shed, we laid them out on the grass and we found the almost complete A10 engine and an alloy head I was interested in.

Typical for a compulsive horder, once he saw all the parts and frames laid out he decided he might want to rebuild the A10 and now did not want to sell me the engine or the alloy head (I just know he never will rebuild it).  But he is a good guy and let me take some parts and would only take half the money I offered, which would have been very cheap at that price.

See the photo below, I only wanted one crank and one oil pump as a spare but he didn’t want the others.  The really good news is I now have a spare pair of crankcases and two crankshafts so this means the retrofit option just got a lot easier.

Cheers

Degsy

Offline Swarfcut

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Re: A7 Bobber Engine needle roller conversion
« Reply #28 on: 02.05. 2021 12:43 »
  As presently set up, the circlip "soldered " to the outside of the roller bearing only has to locate against the machined ledge. All side thrust and float on the crank will be controlled by the non standard ball race now on the drive side.

 The three tabs look long enough to reach down to the circlip, holding it firmly against the ledge, and  also steady the race. A more supportive solution would be a sleeve to fill the gap and bear down on the circlip, all held in place by the three screwed tabs, with their legs shortened to suit. Not too difficult a fix, and well worth a try rather than dumping another abused crankcase. The sleeve may also block off any unwanted oil feed holes on the bearing outer, above the circlip and also reseal the opened up side of the ball valve oilway.  Discard the spring and ball valve and use an on /off tap and fail safe control from the oiltank instead.

Swarfy.

Offline Svend

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Re: A7 Bobber Engine needle roller conversion
« Reply #29 on: 02.05. 2021 13:48 »
Nej Degsy and Swarfcut.
I nearly agreed Swarfcut, you have a baring solution which is good engineering practice. Be aware not to squeeze the outermost part off the trust baring it is not suppose to be in press fit whit the crankcase that’s why ther is space. The yellow stuff is merely for trying to make it oil tight where you se the treads for the oil plug.
Degsy if you still are pursuing a change to standard crankcases, I would be willing to exchange cases  *smiley4*. If it is impossible for you to find, what you looking for I now where to find at set but don’t know the prices.
Venality hilsen Svend