Author Topic: A10 Engine Rebuild Checklist  (Read 1745 times)

Offline rowan.bradley

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Re: A10 Engine Rebuild Checklist
« Reply #15 on: 04.12. 2017 17:06 »
Remove the old ball and spring from inside crankcase. You should be able to see/measure the plain bore of the hole containing ball and spring.
Open the small diameter to match that.
Use the A65 spring and 1/4 ball.
I still don't understand this process. How deep do I need to drill the hole? Presumably this affects the spring tension so this needs to be right. Or if I drill right through, what does the bottom of the spring rest against?

Can someone please explain exactly where the oilway goes behind this oil pump hole? It seems to go directly into the crankcase, perpendicular to the oil pump jointing surface. The surface of the existing ball seems to be about 17mm below the oil pump jointing surface, so there will be no shoulder for the new spring to rest against unless I restrict the drilling to less than say 15mm, or unless the drilling is a larger diameter than the existing hole which contains the existing ball and spring. I have not removed the plug yet so I don't know what this diameter is - can someone tell me this? Is 15mm deep enough to give the right amount of space for the spring? After this I guess there is a drilling straight from the bottom of the hole into which fits the PRV, intersecting with the oil groove around the timing side bearing bush, and meeting the hole beneath the oil pump at right angles. Is this correct?

I don't what to start drilling until I know exactly what I'm doing...

Thanks - Rowan


Current bike: 1958 A10 Super Rocket (in bits), purchased in 1967.
Previous bikes: M21

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Re: A10 Engine Rebuild Checklist
« Reply #16 on: 04.12. 2017 19:14 »
Hi Rowan,
Sorry I should have measured and responded sooner *red*
Ok
The hole from the delivery of the pump is opened up to 5/16in.
The depth to where it meets the grub screw that's fitted form the inside of the crankcase
is 0.8in. the pointy bit of the grub screw reduces this measurement to approx 0.78 at the centre of the hole
I remember the last one I looked at had the point of the screw flattened off
The hole from the pump meets another at right angles that feeds the main bush
No need to seat the ball on the new pump, seating it reduces the spring pressure per sq mm.
Just make sure the gasket does not interfere with the ball where it seats on the pump

John
1961 Super Rocket
1963 RGS (ongoing)

Offline rowan.bradley

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Re: A10 Engine Rebuild Checklist
« Reply #17 on: 05.12. 2017 00:07 »
Hi Rowan,
Sorry I should have measured and responded sooner *red*
Ok
The hole from the delivery of the pump is opened up to 5/16in.
The depth to where it meets the grub screw that's fitted form the inside of the crankcase
is 0.8in. the pointy bit of the grub screw reduces this measurement to approx 0.78 at the centre of the hole
I remember the last one I looked at had the point of the screw flattened off
The hole from the pump meets another at right angles that feeds the main bush
No need to seat the ball on the new pump, seating it reduces the spring pressure per sq mm.
Just make sure the gasket does not interfere with the ball where it seats on the pump

John
Thanks for this info. So the spring rests on the end of the grub screw does it? I would not have thought that flattening the end of the screw would make any difference, because the spring must surely rest on the edge of the screw, not its middle?

Thanks - Rowan


Current bike: 1958 A10 Super Rocket (in bits), purchased in 1967.
Previous bikes: M21

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Re: A10 Engine Rebuild Checklist
« Reply #18 on: 05.12. 2017 20:09 »
Hi Rowan,
Quote
because the spring must surely rest on the edge of the screw, not its middle?

Yes,
Maybe when the previous engine was converted there was a shortage of the correct length screws??
Its harder to measure to the semi pointed end though???

John
1961 Super Rocket
1963 RGS (ongoing)

Offline rowan.bradley

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Re: A10 Engine Rebuild Checklist
« Reply #19 on: 07.12. 2017 11:26 »
If I understand this correctly, the spring must be much longer after the conversion than before, because the ball (i.e. the front of the spring) is about 16mm higher up, but the back of the spring, where it rests against the grub screw, is in the same place. Is the spring supplied by SRM (part number 68.0353) the correct length for this installation (it is about 25mm long uncompressed)?

Thanks - Rowan


Current bike: 1958 A10 Super Rocket (in bits), purchased in 1967.
Previous bikes: M21

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Re: A10 Engine Rebuild Checklist
« Reply #20 on: 07.12. 2017 11:43 »
Hi Rowan,
The SRM spring is the correct one,
Maybe your old spring has partially compressed?

John
1961 Super Rocket
1963 RGS (ongoing)