New timing side bush

[Invicta]

I have ordered new timing side axle and oil pump plunger from the club spares scheme and have obtained a new timing side bush, but it does not have the half hole slot for the dowel which locates it in the crank case. If I remove the dowel from the crank case fit the bush and then try to drill it using the half hole in the crank case as a location, the drill will wander off into the softer alloy of the crank case rather than drill into the harder phospher bronze bush. Should this dowel location slot have been milled in the bush when it was made, or are they all made without it? I can cut and file this slot by hand, but then how do you keep it lined up with the dowel hole when re fitting it? I shall be putting the crank case in the oven and the bush in the freezer but even then I don't expect that I will be able to twist it round if it does not line up. For those of you who have replaced this bush , how did you overcome this problem.

[clive]

The bush is made without the slot. As you say the slot needs to line up so that the space in the bush lines up with the oil pump. This is the critical shape or the pump will mill out its own space in the bush. Its unlikely every dowel hole is in exactly the same place hence no cut in the new bush. I would suggest you ignore the current hole (which may be enlarged from drilling out the old dowel?) Fit the bush in the right place and then drill a new hole. It will need a steady pillar drill and i suggest as short a drill bit sticking out as you can get away with. Others may differ in their approach.

[Invicta]

Thank you for the advice Clive. I appreciate just how critical the positioning of the hole for the oil pump plunger is and there does not seem to be any room for error. The original dowel is still in the crank case as I knocked the old bush inwards from the timing side so as not to disturb it. The dowel is positioned exactly 90 degrees from the oil slot at the top of the bush. Looking at the dowel hole in the old bush it appears to have been milled rather than drilled. I agree that if a new hole is to be drilled then a pillar drill and a securely held bush with a short drill is vital.

[SPRIDDLER]

Can you not use the old one as a pattern for the new one and drill/file/mill the hole before fitting the bush? If the bush doesn't end up in exactly the right position I'd reheat the c/case, drift it out and try again.

[56G80S]

I used the approach that Sprid. mentions but used needle files to make the groove in the new bush. I find that sometimes power tools move too quickly for me and end up making a mess! I was completely unable to remove the old dowel and left it in place. Fortunately I managed to get the new bush in place so that all lined up, oil plunger tunnel and dowel. I did use a very sparingly Loctite as well.

At least a couple of thousand miles on, all good.

Johnny B

[Invicta]

Thank you for all your advice gents. I did as Spriddler suggested and used the old bush to get the position for the half hole slot in the new bush. having marked it out I used my pillar drill and vice to hold the bush while I drilled a series of very shallow holes in a line and then finished it off with a round needle file. I think I have got it in the right position to within a few degrees. We shall see how acurate I was when I fit the new bush. I will be taking the crank cases etc. up to Ken de Groom to line ream the bush and fit the new timing side axle.

[56G80S]

Ken de Groome line reamed mine, it was a relief to know it was done by someone who knew what they were doing!

Johnny B

[willowbedone]

Ken de groom rebuilt my g80 crank fitted the bush and rebuilt the crankcases That was a while ago it's a proper job by a talented man Well worth the trip and he does not over charge