The centre stand and crankcase mounting repair

The centre stand on this bike was wobbly which I had attributed this to the fact that the mounting bolts were loose. In fact I found that these were damaged and wouldn't screw up any tighter. The bolts themselves are 30mm M10 bolts with a 5mm M12 shoulder. The shoulder fits into the centre stand and the M10 section fits through lugs moulded into the bottom of the crankcase. Each bolt has two washers and is retained by an M10 nut.

I found the threads were damaged so I recut them using an M10 1.0 tap and die.

I cleaned up and examined the stand and crankcase lugs and found that both were damaged. (Wouldn't it be nice if I took something on this bike apart and found it was in good condition!) The LHS in particular was badly worn and the holes were distorted. One side of the stand was worn very thin.

LHS crankcase lug-hole worn oval

LHS stand lug- hole distorted and worn close to the side of the stand- I think I got this one just in time.

RHS crankcase lug

RHS centre stand lug- enlarged but still almost circular and there is a lot of metal remaining all round.

The stand is steel and so could be welded. I decided to fix this with repair washers fitted inside the metal and to the outside of the stand. I couldn't fit anything on the inside as this would obstruct the fit with the crankcase. On the RHS I  enlarged the bolt hole to 18mm with drill and reamer. At this size its a good fit for an M10 washer so I fitted two into the thickness in the metal and fixed them with spot welds on both sides.

Hole drilled and reamed to 18mm

This fits two stainless steel 10mm washers perfectly

Washers secured on both sides with weld.

On the LHS the hole was already, so distorted and the edges worn so thin that I didn't want to drill or ream here. In fact owing to the wear there wasn't really anything to drill into and the hole was already too large for my repair washer! I used a 10mm drill as a line marker, passing it through both lugs to position a 10mm washer on the outside of the RHS mount. I did this by eye, holding the drill such that the washers were at the same height and the drill passed horizontally between the two legs of the stand.  I could then clamp  the washer in position and secure it with weld. However the wear was so bad that the washer didn't cover all the damage. I filled in  below and behind the washer with extra weld to replace the missing metal.

All that was necessary now was to drill and ream the holes on both sides to accept the 12mm bolt shoulder. I had used stainless steel A2 washers for the infill. These are very hard and probably harder than actually required. This meant I had a difficult job to drill and ream them to 12mm but after many drill sharpenings I eventually succeeded. 

Centre stand lug, reamed out to 12mm and welds ground down.

Welded washers now accept the 12mm shoulder

I ground the weld down in both sides of the stand before degreasing and painting in blue Hammerite; this isn't quite a colour match but I wanted a durable finish.

Inside surface ground smooth

Painted in Hammerite.

The Motor Lugs

The motor lugs were distorted and would need lining. I ordered some 1/2" (12.75mm) brass tube specified as 10m id. This is thinner in the  wall than I would like, but its a bit of a compromise as I don't want to remove too much metal from the lugs themselves.  I enlarged the M10 holes (probably rather larger already!) using a drill bit passed through the narrowest first to line drill both holes.

Once the hole was enlarged close to 12.75mm I was able to pass an adjustable reamer through and line ream them both to accept the tubing as a tight fit.

In the meantime I cut two inserts from the tubing. The lugs are not actually the same thickness and I needed inserts of different lengths so I cut one 13.4mm and one 14.8mm. I cut these on the lathe partly to ensure the ends were square but also to chamfer the leading side for insertion. I suspect cutting them with a hacksaw would be perfectly adequate.

I pressed both linings into the lugs with hand pressure and secured them with Loctite bearing fit.
The linings had closed up a little in the insertion so I cleaned them with an M10 drill and checked that the bolts would fit.

The repaired stand could then be attached and jobs done.

Refitted to frame.