Tuesday, October 7, 2008

Problems with changing to a later side points camshaft

While the cam end float was being checked there were a few points that are worth taking note of. The side points shaft I have stands proud of the outer bush/inner casing by over 1/4 inch. I had noticed there was a problem when the bike was running and I removed the side case to check if the lower drain hole to sump was clear as bike was leaking from the gearshaft. The shaft had actually worn a hole in the outer case which was visible as a hairline crack on the outside. At that time I smeared gasket cement on the wear point and re-assembled the outer cover before starting the bike. The gasket cement was not removed so there was, for whatever corrective reason, adequate clearance then. I checked all of this again this time and it is still clear so I'll leave well alone. As you can see only the crankcase halves were vapour blast and the difference is obvious compared to the side casings. Time to get out the brass wire brush again.
Note: On looking at the top left picture and how the shaft sits proud of the case you can also see that because there is no timing cam fitted into the end of the shaft because it is still using the distributor there is a straight through hole to the crankcase through the shaft. I thought that the outer timing bush with its rotational breather valve gave you crankcase breathing to balance pressure. I toyed with the idea of loctiting a blanking screw into the recessed end but while looking at it (see second picture camshaft bush and endfloat section) I noticed there is already a straight through hole drilled through the crankcase wall, below and to the right of the bush, which is also always open. There is a raised cast divet on the inner side so this appears not to be an afterthought by someone, but I am going to see if I can view some other casings before I make a decision on this one.
Another part ready for final assembly, just waiting for a bearing from the US (kindly sent by a helpful individual called Paul-the manufacturer would not send direct) which will allow me to get a step nearer assembling the crankcase halves.
PS> Have looked at other distributor type casings on the internet and they all have the hole drilled through the crankcase. I think I will blank off the camshaft and I might even machine 1/4in off it if I can get it done at the same time as machining the bearing for the timing side.