Wednesday, October 22, 2008

Repair of internal C15 clutch lever

The worn section was filed away square and a similar piece of 3mm square prepared to fill the opening. This was left larger in length and cut away after brazing so I wasn't trying to fit a piece the size of a tablet. After brazing the excess was trimmed and filed away and as I had left the majority of the hole there, it just needed to be redrilled. I was lucky enough to find a pre-drilled trailer pin which I then cut the required slot in. I fitted 3 hacksaw blades side by side into the saw and cut the slot in one go. I gave 1mm clearance at the bottom to allow for a rocking movement to assist the arch the lever will travel through. The pin has been left deliberately long as I intend to wait until the shaft and clutch are in place before cutting to length and drilling for the pushrod and 5/32 ball bearing. Took a few hours in all but better than waiting weeks trying to find a replacement.
Finally had the gearbox dry assembled so I could measure up for the ball bearing holder. With the pieces in place I decided on the best length overall which ended up as 14mm overall. So the shaft was cut to that length. It looked too short but when I measured the 5/32 bearing it came it at just under 4mm so I would only need a hole depth of 3mm as I wanted the ball bearing to stand proud. Drilled the 4mm hole carefully after pilot drilling and checked the depth a few times with the ball bearing. When I was happy it stood proud 1mm I punched two divets to entrap the ball bearing. It can spin as it is supposed to but the divets stop it falling out. Handy if the clutch cable ever breaks. The repair looks good and the main bearing for the timing side is complete and in the post so I can start on that and maybe get to final assembly. Lot longer job than I ever imagined.

Monday, October 20, 2008

Internal Clutch lever repair

When stripped the internal clutch lever was shown to not only be seriously worn but had a piece missing from it as well. You can see in the picture how the lack of the cap and the bearing caused the clutch push rod to wear its way into the lever body. The only thing that stopped it going right through was the hardened steel pin (also worn) that fits through the hole. I tried several places to get a replacement and they are not easily available so a repair job is in order. I will file the wear area back square and then braze in a new piece and re-drill the hole. I will post the result in the next day or so.

Wednesday, October 15, 2008

Camshaft end float(2)

Assembled casings with bushes in place and had 1 thou endfloat which was OK. Had time on my hands so decided to strip and re-assemble with cam followers in place to check. Cleaned up the feet of the followers with an oilstone and then assembled them in place, with the oil holes facing backwards, and replaced the camshaft and the outer cover. Using a screw in the end of the camshaft and an electric drill I then ran the camshaft at low revs holding the followers down with light finger pressure to see how it all ran together. Seemed fine. That is until I took another look. When disassembled the top lip of the inner timing bush had been lightly tapped by the cam follower foot leaving a mark. This showed that they floated slightly and also that the 1-2 thou clearance I had given the bush when fitting was going to cause problems as it provided a snag. I had a think about this and it answered a question I had. The bruising of the bush seen from the inner crankcase had, I thought, been caused by the bush wandering out and meeting the flywheel. It was the other way it went out into the path of the cam follower foot, which explains my bent pushrod and marked piston. When the foot was caught on the top of the lip it could not fall with the cam and therefore the valve was held open as the piston rose to meet it. The bush needed no attention on the inner crankcase as not necessary, but what I did do was scrape the bush on the follower side, with the flat edge of a stanley blade, to remove all of the excess. The bush and the surrounding casing are now level and there is nowhere for the foot to snag agian. I reassemble all and tried again with the drill and light pressure on the followers and all is fine. There is 2 to 3 thou end float on the shaft but not enough to worry about pushing the outer bush inwards to take up, as it was already loctited in postion. I would think a 50W oil would soften any gaps in this area.
I have ordered the remainder of the gearbox bushes and that will be my next area of attention while I wait for the maching on the timing bush. Will post soon.

Saturday, October 11, 2008

Bearing Replacement

Bearing finally arrived and is now being shipped to machine shop to convert old bush type to needle roller. Will post pics of finished bearing before fitting when I get back from the machine shop.

Tuesday, October 7, 2008

Distributor pin

Both these photos show no sign of the pin you have going through the distributor wall. Hope this clarifies how it is just held in place by the clamp and the shaft by the bush and a grub screw.

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.

Outer timing bush

The outer camshaft bush was also cleaned with acetone and fitted with loctite using an old camshaft as a mandrel. The location pin was centred and the bush tapped home to seat. The breathing valve lined up but I can look at that more closely later. To measure the end float of the cam the two cases have to be assembled. On first fitting there was no end float and a bit of binding. I thought I might have to tap the inner bush back into the case to less than the 2thou it was set at. I decided first it might be a better idea to make allowance for the gasket which would be used when finally assembled. Pieces of card and a few casing screws were used for this exercise.

I put a casing screw into the end of the shaft and used this to pull and push the shaft to test the end float. Usually you would have to tap the outer bush inwards to take up any float. I was fortunate that with the case screws tightened and the card in place there was just discernable end float with no binding.

I am happy with set up so the loctite can be left to set. A bit of time at this point to file the breather/bush profile to match would be beneficial but any swarf has to cleaned thoroughly away.

Cam shaft bush fitment and end float

While trying to replace the inner camshaft bush it came to light that the engine had been altered by the fitting of a later type camshaft. I have not seen any difference from the normal C15 Star cam profile so I do not think it was to facilitate a different cam profile. The problem is, is that neither of the stock bushes available do the job any more due to a difference in cam shaft diameter and size of the hole in the crank. A one off bespoke bush has to be turned in a suitable material. I had a good look at the one I removed on dismantling and found that although not the prettiest bush in the world, it was within acceptable tolerance. This bush had drifted in service as was evident by bruising where the crank had hit the edge of the bush as it drifted into its path. This was all cleaned up with a smooth file and the bush and case were cleaned thoroughly with acetone before using an old camshaft to tap it back into place. Loctite was applied liberally before this, that was the reason for cleaning with acetone, so it could get a purchase. I made sure that the outer side of the bush sat proud of the aluminium case by 2thou (approx) and that the oilway lined up.

top right picture
Looking at the camshaft there was no bad wear on the profiles or the shafts so could be re-used. Light dressing with an oilstone took a small wear burr off of the end of the smaller inner shaft and avoided the shaft dragging through the bush on re-assembly.
I wanted to set the end float of the shaft before the loctite had a chance to start setting so the next step was the outer camshaft bush. I had already measured this and found it also to be within acceptable tolerance. The guide I used for this was, with one end of the shaft in its bush ( secure the bush first lightly in a vice) there was only 1/32in play up and own when measured with a steel rule. Any more and I would have scrapped them both. Remember though that there has to be some clearance as a bush works by it's component parts being separated by a film of oil.

Engine Mount

Nothing worse than an engine sliding around the bench while you are trying to work on it so I made the following frame using a few scraps of floorboard. More by luck than design, in trying to keep the centre of gravity through the middle line of the base, where the uprights are mounted means the engine lies over on its side nicely for the jobs that require this. We'll see how we get on later when the crank halves are assembled.

The reason for the angle of tilt was to keep the timing bush oilway at the base of the bush vertical. This was then used to check the non return valve which is on the opposite (inside) side. The valve was removed and cleaned thoroghly and a new 1/4 ball bearing and spring reseated before assembly. The oilway was then filled with thin oil and left to see if it remained in the valve and not leaking out past the seated ball bearing seal. The valve worked so the retaining grub screw was loctited into place.

The observant might notice that some bushes/bearings should have been fitted into the heated case before the valve was assembled. However, wear means that with the exception of the sleave gear bearing in the gearbox all other bushes were a tight hand fit, with a tap at the end to seat, and all have to be loctited into place on re-assembly. This means the only heat required is at the gearbox end to fit the bearing and as this will be fairly localised it should not effect the non-return valve. I would like to have made a set of slightly oversize bushes throughout but have no access to a lathe and need to keep the engineering favours to a minimum as I need to convert the timing side bush later, and get the small end bush reamed while still attached to the crank.

Monday, October 6, 2008

Oil pump preparation

Decided to have another look at the oil pump in closer detail as had time to spare. Last time I looked at it when dismantling I found what was the source of my bearing failure as there was a small globule of silicone sealant that had been picked up by the pump and lodged alongside the bearing in the non-return valve at the top of the pick up pipe. This "ball" had obviously been circulating with the oil as it had been worn smoothly cylindrical and was roughly 1/16 in diameter.

This time I removed the pick up pipe by driving out the retaining pin in the body of the pump. Inside this there is a 7/16 ball bearing, the bearing on inspection was in a very worn state with rust and pitting. I had another pump which when dismantled had a perfect bearing so I used that as a replacement. I re-seated the ball in the pick up tube with a soft drift and a sharp tap with a small hammer, and then cleaned everything before re-assembly. I assembled the pick up tube to the body of the pump, making sure the bearing was on the right side of the pin - the underneath - and then reassembled the two sets of gears within the pump. It took two attempts before, on tightening the screws, that the pump ran smoothly under fingure pressure in both directions.

As I had time on my hands, and curiosity, I next filled a small film cartridge pot with thin oil and rottating the pump spindle by hand found it pumped up the oil very easily. Then out of more curiosity I wanted to see if the non-return valve worked so I left sitting uprght with a piece of card underneath to watch for drops. 12 hours later the oil wells on the top were still leve with oil and no marks on the card to indicate drips. This was a very thin oil so after 2 hours work I'm happy that the oil pump at least will work well.

Friday, October 3, 2008


The nitrogen air tanks fitted nicely along the top of the angular oil tank made by the last owner, and because it is narrow at that point it doesn't cause problems riding. The loose wiring is a retaing strap for the oil tank cover. Tank is not original and looks to me like a Yamaha DT175 tank but I dont think it detracts from the look of the bike. I'll get back to the engine rebuild when I can control the pictures a bit better.

Frame without engine

Here is the pic of the frame with the engine removed. Not very standard at this stage but upgraded it slightly to complement the excellent work done by the last owner. The first was the addition of an ignition switch and a rewire and harness for the electrics. The second was the addition of second hand Ohlin shocks which have raised the back end nicely. The engine was removed before they were fitted so I have yet to try them out.

The painful way to rebuild your cherished C15 engine

Will start by opening blog and will continue as news become available. As a start here is the frame minus the engine. A few internal problems caused me to remove the engine for a rebuild and I thought that others might benefit from the process