‘56 AJS model 30 600 twin

Schwany · Jan 31, 2022

Same Matchless/AJS front brake and hub as well as rear brake and hub came on the '67 P11. Only difference is the hubs are skimmed so they have no fins on the '67 P11. I put many miles on the P11 and never busted the backing plate on the front brake. It wasn't under any particularly unusual amount of tension for a brake stay when the front hub and stay are shimmed correctly. I did not ride the bike off road though. Maybe that is why I never had any problems with it.

The chrome on the brake stay looked like heck for 45 years and I replaced it with a stainless piece Eurotrash Jambalaya sells last year.

The little 7" SLS front brake is not very strong riding much over 30mph. It will slow the bike down and eventually stop it, but not quickly. When I was 22 years of age, I thought it was enough brake. Now not so much anymore. I did everything I could think of and made it better, but eventually replaced the front end and brake. If you plan to ride at much of a pace, brake earlier than you would on your Commando. Up to you of course. Merely a friendly suggestion.

Forgot to mention: If you have to replace the bearings in the rear hub you are in for a real treat. Particularly if you enjoy frustration and really horrible designs.

ILLF8ED · Jan 31, 2022

Not sure this is the official way to get penetrant to the bottom of the pistons inside cylinders. Will see how it works. I poured the last 4 oz of Kroil through the drain hole. More of the penetrant coming mid week from Amazon.

baz · Jan 31, 2022

ILLF8ED said:
Not sure this is the official way to get penetrant to the bottom of the pistons inside cylinders. Will see how it works. I poured the last 4 oz of Kroil through the drain hole. More of the penetrant coming mid week from Amazon.
View attachment 84662

When I got my BSA b50 engine the piston was seized solid
I had to split the case's so I just had the barrel/piston/crank to work on
I made a plate to bolt on the top of barrel and placed a packer on the piston
And tightening down the 4 studs and lots of heat and penetrating oil I managed to force it out
And I saved the barrel ,it had to be bored 40thou to take the damage out
Heat is your best friend here
Good luck with it

ILLF8ED · Jan 31, 2022

baz said:
When I got my BSA b50 engine the piston was seized solid
I had to split the case's so I just had the barrel/piston/crank to work on
I made a plate to bolt on the top of barrel and placed a packer on the piston
And tightening down the 4 studs and lots of heat and penetrating oil I managed to force it out
And I saved the barrel ,it had to be bored 40thou to take the damage out
Heat is your best friend here
Good luck with it

It’s a twin. The cases cannot come apart while the cylinders are attached.

baz · Jan 31, 2022

ILLF8ED said:
It’s a twin. The cases cannot come apart while the cylinders are attached.

Yes I know that
I was giving an example of how hard it can be
I once bought a pre unit triumph that had sat outside with no head
The pistons were seized but heat/penetrating oil a wooden drift and a bfh did the trick

ILLF8ED · Jan 31, 2022

I’m not good with acronyms, but I can guess “bfh”
Im working slowly on it. Shining a light through the drain hole…not much corrosion visible. I think pour another 8 oz can of penetrant in there once it arrives. Pretty sure it’s only piston rings rusted to the bores.
I broke the handle on my dead blow hammer, so need another.
Obviously this machine sat out in the weather. Between the gearbox and engine was a black widow spider the size of a penny. Also old paper wasp nests everywhere.

Triton Thrasher · Feb 1, 2022

johnm said:
Funny enough the AJS twins have separate barrels so you actually might be able to split the cases. Can't be certain but you might be able to.

I suppose a careful study of the manual and diagrams would show where all the crankcase fasteners are.

I do know they are more complicated than other twins, with a plate between the case halves, holding a centre crankshaft bearing.

ILLF8ED · Feb 1, 2022

johnm said:
Funny enough the AJS twins have separate barrels so you actually might be able to split the cases. Can't be certain but you might be able to.

Only if the crankshaft is also split. The cylinders are not coming off and the pistons connected to the crankshaft are inside.

mdt-son · Feb 1, 2022

Schwany said:
Same Matchless/AJS front brake and hub as well as rear brake and hub came on the '67 P11. Only difference is the hubs are skimmed so they have no fins on the '67 P11.

Not quite. The front hub was fitted up to 1962 (and strangely, on the 1963 G12CSR) and was the predecessor of the "interim hub" AMC developed for 1963. Although an evolution rather than a revolution, the latter differed in all parts (e.g., by using ball bearings rather than tapered bearings). Apart from 1963 roadsters and G80CS (- G12CSR), it was fitted on the G80CS and the P11 between 1964 and 1969. Obviously, AMC did not trust the new design for use on their 1963 desert racing sleds!
As for the 1956 rear hub, it was fitted between 1955-57 only. 1958-63 there were no less than 4 new rear hub designs, brake drums and associated parts, not including brake and hub on the G3C trials bike. 1964-1969 G80CS and P11 used the 1963 type hub and brake drum as fitted on that year's G80CS. The only commonality of parts between the 1956 G11 and the P11 are the rear brake shoes and the rear hub bearing assembly.

- Knut

johnm · Feb 2, 2022

ILLF8ED said:
Only if the crankshaft is also split. The cylinders are not coming off and the pistons connected to the crankshaft are inside.

Off course. Didn't think very hard on that did I.

Getting old

baz · Feb 2, 2022

How far down the bore are the pistons?

Schwany · Feb 2, 2022

mdt-son said:
The only commonality of parts between the 1956 G11 and the P11 are the rear brake shoes and the rear hub bearing assembly.

- Knut

Thanks for the correction.

My point was about what I feel is the horrible design of the rear hub bearing assembly. I should have said the hubs appear similar to what is on the P11. The hubs appear to use straight pull spokes and probably the same dimple and drill pattern on the rims. I'm not looking it up though. That is your job.

I had a heck of a time replacing the bearings in the P11 rear hub. I don't think I am alone in that. I may be the only one that would admit it on this site though. My reputation on the interweb is not that vital to my survival. I have no plans to ever replace bearings in that hub again, but it must get easier the second time around.

I think the OP probably hasn't used the correct combination and order of cuss words to get those barrels off. I have ideas about how to do it, but ideas are not wanted. Only solutions from those that have freed up stuck pistons on his model bike.

ILLF8ED · Feb 2, 2022

baz said:
How far down the bore are the pistons?

19mm from the top ring mark on the cylinder to the top edge of the piston.

baz · Feb 2, 2022

How far down the bore are the pistons

ILLF8ED said:
19mm from the top ring mark on the cylinder to the top edge of the piston.

Hmmm at least it's not at tdc so if you have to apply force the crank will rotate

ILLF8ED · Feb 2, 2022

A little progress today. Used the BernzoOmatic torch with propane and oxygen to get more heat and managed to get the front four Cylinder studs out that were frozen. To free up the cylinders I don’t think this little torch is big enough.

ILLF8ED · Feb 24, 2022

There is no oil seal on the drive side between crank shaft and engine case. What keeps oil out of the primary on an AJS model 30?

N0rt0nelectr@ · Feb 28, 2022

Maybe you could soak the entire engine in Diesel. Remove the engine and put the whole lump into a container big enough to hold the whole thing.
I would think one that you could cover and let sit for days or weeks might be best.
Had a friend with a HD Servicar that the rear drums were stuck on. He did that and it took some time but he got it apart with no damage I think he used a 15gal grease drum but in his case it was left open.

ILLF8ED · Mar 12, 2022

N0rt0nelectr@ said:
Maybe you could soak the entire engine in Diesel. Remove the engine and put the whole lump into a container big enough to hold the whole thing.
I would think one that you could cover and let sit for days or weeks might be best.
Had a friend with a HD Servicar that the rear drums were stuck on. He did that and it took some time but he got it apart with no damage I think he used a 15gal grease drum but in his case it was left open.

This is last resort…I ordered a 20 gallon polyethylene bucket and lid from Amazon today. It will probably take 5 to 10 gallons of diesel oil to submerge the entire engine. How long to soak it…maybe a year.

Thanks

mdt-son · Mar 12, 2022

ILLF8ED said:
There is no oil seal on the drive side between crank shaft and engine case. What keeps oil out of the primary on an AJS model 30?

A scrolled spacer which forces oil back into the crancase, p/n 014295. You will find it in the section ENGINE SPROCKETS.
A similar scrolled spacer was fitted to some two-strokes in the 50s and 60s (contemporary two-stokes may still have such a design).

If the scrolled spacer is missing, please note the 1957 version p/n 023163 will not fit as the crankshaft drive side and primary drive changed for this year.
AMC Classic Spares or Russell Motors may be able to supply the spacer. It's not carried by AMOC Spares.

- Knut

ILLF8ED · Mar 12, 2022

mdt-son said:
A scrolled spacer which forces oil back into the crancase, p/n 014295. You will find it in the section ENGINE SPROCKETS.
A similar scrolled spacer was fitted to some two-strokes in the 50s and 60s (contemporary two-stokes may still have such a design).

If the scrolled spacer is missing, please note the 1957 version p/n 023163 will not fit as the crankshaft drive side and primary drive changed for this year.
AMC Classic Spares or Russell Motors may be able to supply the spacer. It's not carried by AMOC Spares.

- Knut

Thanks I do have the scrolled spacer. Just need to find a way to get the engine apart.