Author Topic: A7 engine rebuild - several questions  (Read 2027 times)

Online JulianS

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Re: A7 engine rebuild - several questions
« Reply #15 on: 09.01. 2018 18:37 »
This is what BSA said about the position of the drilled rod;

Online berger

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Re: A7 engine rebuild - several questions
« Reply #16 on: 09.01. 2018 20:39 »
well  I must have got very confused.com ,its too much abuse. thanks for clearing that one up I will sleep well tonite

Online Triton Thrasher

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Re: A7 engine rebuild - several questions
« Reply #17 on: 09.01. 2018 20:48 »
At first glance, your dad ran the bike out of oil.

Online Rex

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Re: A7 engine rebuild - several questions
« Reply #18 on: 09.01. 2018 21:20 »
This is what BSA said about the position of the drilled rod;

Pretty much settles that....

Offline coater87

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Re: A7 engine rebuild - several questions
« Reply #19 on: 09.01. 2018 22:17 »
 I can maybe see this hole being of limited use on a brand new motor at high RPMs, when the clearances are still tight and the oil pump is still putting out the best it's design is capable of.

 We all have looked at the innards of these motors, and I personally believe that once a few miles have been put on and the oil is warmed up- you are not "squirting" oil out the far side rod. I think it would be a good sign if some was dribbling out of that hole.

 I could be wrong here, but I just cannot see the stated benefit of this actually working the way BSA set up the oiling system on an A series motor. *conf*

 Lee
Central Wisconsin in the U.S.

Online JulianS

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Re: A7 engine rebuild - several questions
« Reply #20 on: 09.01. 2018 22:36 »
The first A10 engines had identical rods, no drilling, accordingto the 1950 parts book. Move to the 1951/52 book the left rod has changed to a drilled one.

The R and R billet rods I tied and rejected some years back had 2 identical rods, no drilling, but the Thunder rods with which I replaced them came with a drilled left rod.

The early A65 lacked the hole but BSA reintroduced it after a few years, then if you look at the oil in frame A65 left rod you will see a hole each side of the rod.

So who knows?


Online RichardL

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Re: A7 engine rebuild - several questions
« Reply #21 on: 10.01. 2018 12:20 »
I think my rods are R and R via MAP. They came with no hole. As a believer in the theory that it's there to promote oil flow, I drilled one.

Richard L.
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Online Klaus

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Re: A7 engine rebuild - several questions
« Reply #22 on: 10.01. 2018 16:26 »
All my bikes I have fit with new conrods are not drilled.
No problems if its road or race use.
Plain bearings, dont use hight pressure.
My old lathe has also plain bearings  running without any pressure, only a dippring lift some oil into the catcher.

Ok, an engine is another case ;)

but dont hype this hole.


If you think, everything is under control, you are not fast enought.

Online RichardL

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Re: A7 engine rebuild - several questions
« Reply #23 on: 10.01. 2018 18:08 »
Klaus,

Curious, then, about your idea (humorous or serious) as to why  BSA engineers decided to add the hole.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Online Greybeard

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Re: A7 engine rebuild - several questions
« Reply #24 on: 10.01. 2018 19:23 »
Klaus,

Curious, then, about your idea (humorous or serious) as to why  BSA engineers decided to add the hole.

Richard L.
My guess, a knee jerk reaction after an engine failure during racing.

Offline duTch

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Re: A7 engine rebuild - several questions
« Reply #25 on: 10.01. 2018 23:27 »
 While rebuilding my Rockety-Flash (Rocketash?), I pondered the effect of the centrifugal action of the oil in the journals as the crank spins, but have never seen it mentioned anywhere...?

 And also maybe worth noting that the oil hole in the C-rod only aligns with the hole in the crank at 90º before& after TDC/BDC, so that's when there would be a quick squirt/s....haven't seen that mentioned either, but may be wrong on both counts ..... open slather ... *eek*



  nb -(did a typo in 'centrifugal' with a 'u' where the 'e' should be- as my old boss used to say, "it's not a stuff-up if I find it first" *smile*)-
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Offline Tomcat

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Re: A7 engine rebuild - several questions
« Reply #26 on: 11.01. 2018 08:06 »
Klaus,

Curious, then, about your idea (humorous or serious) as to why  BSA engineers decided to add the hole.

Richard L.


I read somewhere long ago that when the A10 engines were first built that the left cylinder kept on seizing up. Someone in R & D said "It would be easy to diagnose if there was a window in the engine". So that's what they did, fitted perspex to the LHS of the engine and found there was insufficient lubrication to the left cylinder. And the cure was an oil hole in the LH conrod to squirt oil onto the LH cylinder.
FYI the Left hand side is AKA the Kerbside, the Nearside, the Drive side and No 1 cylinder!  *fight*
'48 A7 '59 SR '74 850 Commando TDM900

Online RichardL

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Re: A7 engine rebuild - several questions
« Reply #27 on: 11.01. 2018 13:24 »

. And the cure was an oil hole in the LH conrod to squirt oil onto the LH cylinder.


Ah, but the hole is always pointed at the web. If anything, the oil would have to fling from the flywheel onto the cylinder wall. I'm not saying it doesn't, but I'm still on the "promote flow" bandwagon and can envision both functions. Can't imagine any spurting taking place, anyway. The hole in the rod is infrequently over the holes in the crank.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline Johnhayesuk

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Re: A7 engine rebuild - several questions
« Reply #28 on: 23.09. 2018 13:24 »
Hi guys my 1952 a7 leaks a loads of engine so here goes, I raised her up onto a makeshift table, anyone have pictures videos etc that can help me take the engine apart and rebuild with new gaskets etc anything, advice, where to purchase what not to do the bike is a real treasure that I love riding around the Malvern hills and down into wales but I’m sick of getting covered in oil and when I get back my floor is a mess too

Offline Berni

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Re: A7 engine rebuild - several questions
« Reply #29 on: 23.09. 2018 16:19 »
Hello Guys,
thanks a lot for all your information's. Now I'm meyself. The base engine is now fixed, all bearings are made, a restored cylinder with again .06 is build on, but a standard not a high compression on. Now I have again a question, can someone tell me the crankschaft degree to adjust the ignition? I want to do it with the degree disk. Someone told me 32°, but he was not sure.
Thanks again for your help.
 
Germany A7SS