600 ccm barrels on a 500 ccm engine?

Lassenc · Post by **Lassenc** » Thu Jan 18, 2007 6:22 pm

Is this possible? I know the jugs won't go in directly, but if the block is bored out, are there any other issues?

Or is it possible for me to use a G12 bottom end, with a 500/600 ccm crank?

The original Model 30 block I had is a '56 but is busted, so it is scrap, really.

And then I have the Model 20 which is '54

'54 or '56 did they really do that much in those years that would overrule the '54?

Plus!

I have a crankspline/sprocket question!

As you see, the first picture had a fixed sprocket.

http://stalkerzone.dk/upload/DSC00003ajs.JPG

http://stalkerzone.dk/upload/IMG_0115ajs.jpg

On the second you can see these, which look more like the correct ones and came with the basket case.

Are they both original? Is this crank even a 500/600 ccm dynamo crank?

I would like to know before I go any further!

With kind regards, Lasse

PS:

Yes, I have thought of getting a complete 600ccm engine, but who has one? CONTACT ME THEN!

lassenc@gmail.com

matman · Post by **matman** » Thu Jan 18, 2007 10:33 pm

Hi Lasse,

mmmh, lot of questions...

First of all, I think all the crankcases of the 550, 600 and 650 engines are almost identical. The 500 and the 600 have identical stroke of 72,8 mm, they only differ in the bore size (66 vs. 72 mm). That could lead to problems with the distances between the studs, but perhaps one of the REAL experts will answer this.

The 650 engine shared the 72 mm bore with the 600, but its crankshaft gave 79,3 mm of stroke.

What I know definitely is that it is possible to cross a 600 crankcase with a 650 crankshaft - my bike operates that way. You just have to lift the barrels with a special spacer, thickness about 3,3 millimetres, to equal the difference of 6,5 millimetres of stroke.

The only problem I see for your conversion is the bigger bore of the 600 cc barrels. It will still be okay to machine the crankcase for taking the larger diameter barrels, but when it comes to differing distances between the studs, the whole thing won´t work. (As far as I know, there have also been changes in the diameter of the studs themselves - from 1/4 to 5/16? - or was it from 5/16 to 3/8?)

To your other question: the first of your pictured sprockets came with the AMC gearbox in 1957. The shock absorber then was integrated into the clutch, and the construction on the crank´s end - as seen on your 2nd picture - was no longer needed. This earlier construction was necessary in combination with the Burman-type gearbox. The coil-spring-charged sprocket could slip under extreme load and equalise torque peaks. The Burman-clutch itself wasn´t damped. This construction should fit your `54 bike better than the latter one (but depends on the gearbox installed).

I am sure that now many of the cracks (e.g. Lawrence) will teach us the truth about twins...

As I meet Paul Hanenberg next week, I could ask him whether he has some reasonable "engine projects" for you. Okay?

Kind regards, Jan

Lassenc · Post by **Lassenc** » Fri Jan 19, 2007 6:38 am

Sounds good, I have tested that the distances of the studs, and the barrels do fit over them.

Will I be able to use the spring type shock absorber with the pictured crank?

Don Madden · Post by **Don Madden** » Sat Jan 20, 2007 2:44 am

No. Cheers, Don.

Lassenc · Post by **Lassenc** » Sat Jan 20, 2007 8:28 am

I have found that I have the later clutch with the rubber shock absorbers.

That clutch, with a B52 box, and the fixed sprocket then?

Lassenc · Post by **Lassenc** » Sat Jan 20, 2007 8:30 am

And the pressed steel primary, if it makes a difference

Don Madden · Post by **Don Madden** » Sun Jan 21, 2007 2:22 am

I have never fitted the AMC clutch onto a Burman gearbox & can't say if there is any problem.

I have replaced the Burman gearbox/clutch in a 1956 with an AMC gearbox with its' clutch by extending the slots in the rear plates for more adjustment.

Cheers, Don.

Lassenc · Post by **Lassenc** » Sun Jan 21, 2007 11:23 am

Didn't the AMC Clutch come in '57 and the AMC box in '58?

Duncan · Post by **Duncan** » Sun Jan 21, 2007 9:36 pm

Both fitted as a pair starting in 1957.

Apparently a three eights spacer is all you need to fit an AMC clutch to a Burman box.

See: http://217.157.196.176:8181/ajs/Technic ... Jampot.pdf

Edited by - Duncan on 21 Jan 2007 9:39:29 PM

matman · Post by **matman** » Sun Jan 21, 2007 10:51 pm

Hi Lasse,

I have thought about the problem you described in your actual thread. As the latter 1957-on crankshaft is shorter than the earlier type (with the shock absorber on its end), it should under no circumstances touch the outer half of your (tin) chaincase.

Maybe this problem results of having mounted the engine sprocket the wrong way round?!? The "collar" of the engine sprocket should to my opinion point to the outside, the sprocket itself running close to the engine resp. the inner half of the chaincase.
On one of your pictures it is shown in a way it should NOT be installed. In the narrow tin chaincase this could lead to contact between sprocket/chain and chaincase; the small dome or "bump" on the tin chaincase only houses the shock absorber(with about 4 or 5 cm of diameter), but isn´t large enough to encircle the sprocket, too.

So, with an AMC clutch on your Burman box, a correctly mounted engine sprocket and a tin chaincase, the "drivetrain" of your bike will stay a bastard, but will probably work. And, listen to my words, bastards definitely CAN work!!!

And, with a construction like that, you could save your bike´s authentical 1954-appearance.

Good luck, matman