Different size on crankcase pushrod holes

Persa · Post by **Persa** » Sun Jan 20, 2008 3:03 pm

Hello

When I bought my present restoration project a year ago I also got another engine for future project. This engine is supposed to be a 1958 AJS model 30 CS, which the engine number confirms (58 30CS 07205). The funny thing is when I looked at the crankcase halves the other day, I noticed that the size of the pushrod holes were different in the two halves, the left one (driving side) having bigger holes than the right. Is this as it should be or do the halves come from two different engines?

If they do come from different engines, will they still work together? There's a number stamped on the timing side when the cover is removed, 016872. Does this number tell you anything?
Thanks for you help!

Regards

Persa · Post by **Persa** » Wed Jan 23, 2008 9:14 pm

Hi again!

If I'm being tiring I apologize but does anyone know the answer to the question above? If two halves that fit together belong together, meaning it's impossible to combine a 500-crankcase with a 600-crankcase? Thanks!

Tolly · Post by **Tolly** » Wed Jan 23, 2008 9:48 pm

Biscuit may be able to answer this as he has more knowledge than most. Sorry for putting you up for this Alan but I have never had my G11 barrels off!

Biscuit · Post by **Biscuit** » Thu Jan 24, 2008 12:00 am

All the pushrod holes on the '56 G11 are the same size.

The 500/600 crankcases for 1958 have the same part number.

Will odd halves work together? I believe they will, others disagree. I have worked on a couple of singles that, judging by the misalignment of the dynamo seating, were obviously not a pair.

It has often been said that the cases were machined together, a glance through the AJS and Matchless archives of pictures from the factory show single cases at least being machined individually.

Tolly - I didn't lay my hands on a twin until 1998, I don't have more knowledge, just better access to it, and dare I say this - an apparent ability to search for information better than most.

Don Madden · Post by **Don Madden** » Thu Jan 24, 2008 6:13 pm

Since no one seems to have seen this problem before & we can't inspect the cases, measure the holes in each case & also compare with the matching ones in the base gaskets. That will give us some reference, as calling one set of holes larger than the other is rather vague.

Cheers, Don.

jim501 · Post by **jim501** » Thu Jan 24, 2008 6:38 pm

quote:
Hello

When I bought my present restoration project a year ago I also got another engine for future project. This engine is supposed to be a 1958 AJS model 30 CS, which the engine number confirms (58 30CS 07205). The funny thing is when I looked at the crankcase halves the other day, I noticed that the size of the pushrod holes were different in the two halves, the left one (driving side) having bigger holes than the right. Is this as it should be or do the halves come from two different engines?

If they do come from different engines, will they still work together? There's a number stamped on the timing side when the cover is removed, 016872. Does this number tell you anything?
Thanks for you help!

Regards

No straight answer to this one. Looks as though you have two odd cases... BUT ... I haven't seen it but Biscuit has a photo showing AMC cases being machined seperately. Perhaps, with sufficiently accurate holding fixtures, AMC were able to do this and assemble cases at random. Biscuit has also personally mixed and matched cases with no ill effects, on singles.
I was at BSA up till they closed. BSA machined the locating spigot and dowel holes on seperate cases and then assembled them together around a boring bar to line bore the main bearings. The top face/barrel joint and sump plate face were similarly machined with the two cases assembled together. Those two half cases then remained together through the rest of the assembly process. Given the accuracy of the holding fixture, it should be possible to machine individual cases and assemble them at random but that's the problem. You don't KNOW the bearings are in line. With BSA's system, you did. Without the measuring equiment to check you're guessing. Sorry to be of little help but I'm of the opinion that things that have to live together, crankcase halves, con rods and caps, etc, get machined together and stay together. What about the camshaft bearings ? Are they going to be in line with odd cases ?

cheers
jim

Biscuit · Post by **Biscuit** » Thu Jan 24, 2008 7:28 pm

Look here:- http://www.mc-albion.dk/AMC/General/AMC ... ent_setup_(Machine_Tool_Review.pdf
They need to be studied closely as the photo's are rather poor. There are two examples of crankcase halves being machined, to finished size, on Herbert capstans, one I don't recognise and the other a twin timing side.Edited by - Biscuit on 24 Jan 2008 7:30:15 PMEdited by - Biscuit on 24 Jan 2008 7:31:37 PM

Can't get the link to work, go here http://archives.jampot.dk/ click on General and scroll down to AMC factory equipment.Edited by - Biscuit on 24 Jan 2008 7:34:18 PM

Persa · Post by **Persa** » Thu Jan 24, 2008 8:42 pm

Thank you all for your answers and help! I will now (or at least before I assemble the engine) try to figure out if they belong together and/or if they will match anyway;)

Regards

GSAX1 · Post by **GSAX1** » Thu Jan 24, 2008 8:52 pm

Has anyone noticed that the filter tunnel doesn't match up completely with the other case? Even with "matching" cases that had been together since they left the factory. Suggests to me that machining was done separately. Also the conspicuous absence of "matching numbers" on each half that almost every other motorcycle engine cases have.

Michael

arkwright · Post by **arkwright** » Thu Jan 24, 2008 9:34 pm

Alan, the crankcase to centre web spigots and the crankcase main bearing surfaces were machined on the Herberts but the crankcase mouths and crankcase to barrel surfaces were not.