Before getting stuck into the engine rebuild, a couple of things should be looked at
Each casing (left and right) have a number stamped into them at the factory. Basically there was a bloke who sat next to a pile of casings. He was so experienced, at what he was looking at, that he could tell which casings would fit exactly. He would pick them from a pile, test fit them and then stamp them as a pair.
At least having the same number stamped in each half gives a bit of confidence on the refit that they would be the originals from the factory.
If you are looking to buy a pair of cases, an engine, or even a complete bike it’s worth checking the stamps.
I’ve had bikes and engines that do not have matching numbers (maybe three or even four) and have found them to fit together just as well as matching stamped ones. Matching ones give you that sense of security. Non matching numbers may give you a bit more bargaining on the price - just like non matching engine and frame numbers.
Here’s the new inlet and exhaust camshafts.
There are options on using sportier cams with high compression pistons and all that super speedy stuff (the original cams left a bit of power out of the engine as the engine bearings weren’t really up to the incredibly massive power of the mighty 744cc T140V Bonny - like almost 50BHP - cor )
If you want a faster bike go buy a new one. I’m happy with just getting it running nicely and pootling around.
The cams need to be checked athat they are running nicely in the bronze bushes. So give 'em an oiling and threadle them into the bushes and put both halves of the engine cases together.
Once the two halves are pushed together thread a few of the casing bolts in and nip them up. You can see the cam lobes down through the tappet/followers hole. This is where the followers move the push rods up and down to cause the rockers to push on the valves to open and close.
Put your fingers under the cams and check that there isn’t any movement up or down by the cams in the bushes.
Feel for movement of the cams in the bushes. They will have a good bit of float (that is movement along the cam’s axis in and out of the hole) until the cam pinions are attached to pull them tight, but nothing showing that they are ‘slopping’ about up or down, left or right in the bush.
These are fine. I would have been surprised in the relatively low mileage engine if there were any. I’ve only had wear in very high mileage engines.
So, that’s ok then…
Just for interest, here’s a new set of cam bushes from the stash. They are sintered bronze - a sort of alloy mixture containing oil - that can actually self heal.
The old ones, if required, can be fairly easily taken out by using a bearing push/puller. But the new ones will need to be sized to ensure a correct fitment to the cam shafts.
It’s a fairly easy operation to size them correctly if you have the bits to do it. This is them.
A reamer to cut to the blind ended bushes to the correct internal diameter, a guide to ensure the reamer stays true to the open bush, and a correctly sized ball bearing to push through the open bush to size it.
These kits are quite hard to find, they aren’t that expensive and should last a lifetime if kept oiled and greased up.
If you need to borrow a set, give me a shout…welcome, over