Sleeving oil pump bore

[56G80S]

Back again!

Spent - spending - so much cash on the engine and other parts for the rebuild I have now convinced myself that I should do something about the timing side crankcase half. I'm already going to be in for around £900 so another £xxx makes sense to safeguard that spend.

Steve at AMC ClassicSpares doesn't have one. There's rubbish on the 'Bay and wrong year (small timing side axle) and even so the price is high.

Multiple searches found this from oldandsmelly:

"As I mentioned earlier, a friend of mine had the oil pump bore sleeved as in:

http://www.jampot.com/article_read.asp?id=325

Hopefully, this link works. The actual boring and sleeving was beyond his and my skills so he entrusted it to a local machine shop. The bike now scavenges fine."

I think I will try and go down this route so downloaded onto the PC. Why do this?

Guaranteed mating accurately with the other half;
Proper job with new plunger and it'll see me out although I will be covering a lot of miles;
No risk of mediocre replacement and failure (!) or low volume with consequent damage to all those new parts;
While with engineer I can get the new timing side bush perfectly line bored rather than reamed.

The only thing is that I don't quite follow the article in terms of the stepped bore in the cases. Numpty I am but it appears to only cover the scavenge side. Hope someone will come along and explain to me so I can be clear (when I find someone to do it).


JohnnyB

[Mick D]

Hi

Unless I read it incorrectly, (or misunderstand you), the stepped mismatch was between the two crank cases and apparent as a step at the crank case / barrel mating face, this would result in the barrel not aligning with the travel of the piston. Fixed by clamping the timing case joint face to the mill and skimming the barrel mating face perpendicular.

Nowt to do with the oil pump.

Regards Mick

[56G80S]

Hi Mick

I understood the crankcases fine.

It's the oil pump plunger that has a step in it between the front part and the rearward part (toothed part and further back). The pump can only be removed from the rear. I wondered whether the sleeving process was to bore through at the larger diameter and then fit a sleeve which incorporated the necessary step. I further wondered about the alignment and if a "false" front plate (for where the rocker box feed is taken) could be made, drilled at the four mounting screw points then at the crosspoint for the mounting screws and thus provide a true centre to be used as an accurate locator/support for a boring tool rather than an existing worn bore.

Looking at the pictures in the article, it looks as if the borer has operated right through the entire length.

Perhaps (probably) I'm not understanding the pump. Is it only the rearward part that actually pumps? I thought both the rear and forward parts pumped.

JohnnyB

[Mick D]

Hi Johnny

I think the return side was re-bored and sleeved using the pressure side to assure alignment, no material was removed from the pressure side. The sleeve is only fitted to the return side.

Yes, the pump is a dual one, return to the rear, pressure forward.

I note the re-bore gets very close to break through on the bolt threads

Regards Mick

[56G80S]

Hi Mick,

Good point about the wall thickness, having said that, mine isn't as bad as described in the article, I'll take another look While eating lunch in the kitchen (as no-one else was in) the other day I saw a Wheeler Dealers episode and the installation of valve guide sleeves - they must be thin things!

Dick Casey's (RideNut) post on another thread does highlight that wear is usually on the rear, scavenge, part. I suppose that isn't really surprising as the oil goes a long way before getting back into the pressure end and crap will fall out of suspension before reaching the pump again? The mighty mesh filter!!!!

JohnnyB

[56G80S]

Update - after a long chat with Ken de Groome (and Les at Russell Motors though that was mainly to speak to Ken) the view was do a bit more exploration, a couple of practical tests and I'm a fusspot.

So I'll do as recommended, then fit the new drive side mains, timing side bush etc test assemble the bottom half and see how things go.

Mick D says I told you so!

Ken a lovely chap.

Johnny B

[1608]

with regard to the original post about sleeving the oil pump bore. I feel there is an unnecessary worry about oil pressure in the singe engines. With bearing type b/ends they would more than likely go on for ever with a misting type oil system, they don't need a lot of oil pressure. With twins and shell type b/ends they only need a good flow and not a lot of pressure. Oil pressure drops I know when the shells or b/ends are worn, but thats just down to overall wear. If there is a good flow on the return side then the feed side is probably ok too. After all, as a veteran mechanic once told me
oi pumps live in an oil bath and are the last things to wear beyond use.
Theres hoping I've stirred up a good debate...

[clive]

with regard to the original post about sleeving the oil pump bore. I feel there is an unnecessary worry about oil pressure in the singe engines. With bearing type b/ends they would more than likely go on for ever with a misting type oil system, they don't need a lot of oil pressure. With twins and shell type b/ends they only need a good flow and not a lot of pressure. Oil pressure drops I know when the shells or b/ends are worn, but thats just down to overall wear. If there is a good flow on the return side then the feed side is probably ok too. After all, as a veteran mechanic once told me
oi pumps live in an oil bath and are the last things to wear beyond use.
Theres hoping I've stirred up a good debate...

Some years ago a Surrey member did a charity ride with us, no oil circulation on his bike, a single, was established at the beginning of the run. He got about 150 miles before it seized but of course that may have been an overheating seizure rather than the big end! The oil supply provides some cooling as well as lubrication I think.

[56G80S]

Thanks for the re-assurance. The problem was really about lack of scavenging rather than feed.

Ken was keen on checking oilways clear and I'd already removed the blanking screws to do so........

but I am having trouble removing the key one at the bottom of the scavenge drilling. I'm a bit nervous of his solution - impact driver. I have one but rarely use it. I'm going to try heat first.

It'll have to wait until I collect the MG ZT-T Tourer CDTi I've to collect from Pangbourne. Going to be a long day Tuesday.

Johnny B

[56G80S]

I've now managed to remove the blanking screw from the bottom of the scavenge drilling, next to the sump plug.

Ken de Groome said that failing all else he'd used an impact driver. As I'd used both heating and freezing, that's what I did. Was very nervous about it but did the trick with no damage. What a patience he had listening me drone on.

Lo and behold, the thing was clear. A length of welding rod went nicely through.

Johnny B