Tuesday, January 27, 2009

Inner Timing Case - oil pump/sump - timing gears - gearbox

(pics in no particular order)

The oil pump to timing shaft has to be tapped in from the distributor port above. Assemble the bush with the oilway facing down onto the shaft and lower the two down making sure that the worm gear does not snag on the teeth of the timimg gear. With a hollow pipe tap this into place until tight, then from below tap lightly up from below until you get a clearance of 1-2 thou that allows it to turn freely. Rotate crank to make sure all is in order. Insert grub screW with a drop of studlock and tighten into place.

The oil pump with new gasket was next to be fitted. The overhaul of the pump has been covered earlier in this blog. There is a knack to getting the oil pump in place due to the lift pipe. The rear of the LHS is tapered norrower and its a case of getting the rear LHS of the pump neat to the LHS of the mounting boss and "rolling" the pump into place. Try this a few times before you try it with the gasket (no gasket goo). Make sure you also turn the crank so the shaft turns and you can locate the slot/pin of the pump and shaft into place. Clean both surfaces when you are happy, lightly grease the gasket and fit. Tighten, but not overtight, the mounting screws ensuring you have the serrated washers to stop it vibrating loose.

Before fitting the sump I spent a bit of time cleaning the 2 metal plates (one with mesh filter) and making sure that the plates were flat. The mesh sits upwards, opposite to what you would assume. Make sure the holes for both pickups fit over the pipes. You may have to do a bit of bending of the mesh. I fitted a magnet into the sump before assembly again making sure it fouled none of the components.

I used gasket goo on all sides of the assembly - except the last where it meets the crankcase - and I used a light grease on this. I intend dis assembling this now and again to clean and check what the magnet has picked up and want it part easily and be reused.

The next stage is the insertion of the two cam followers and the timing cam gear. These were previously cleaned and checked and the high spots taken off with a rub of an oil stone. The oil hole in the body of the follower should face to the rear of the engine on both of them. Push them up from below and hold up at the top of their travel until you can insert the cam gear into the inner cam bush. Before pushing home fully line up your timing marks. There should be a visible dot on both gears and one is on the crown of a tooth the other in a valley. When in line push gear home and allow the follwers to drop onto the cams. A secondary check to make sure the timing is correct is to rotate the crank until the cams lift both followers an equal amount at the same time. The timing mark on the larger gear should be in a vertical line below the centre of the two followers and if you hold a steel rule in that line the timing mark on the lower gear should also be at the top and in the same line. If there is a problem you may have to look for other timing marks that were added later.
I've just noticed that I did not post something previously with regard to the assembly of the gearbox and as this took up 3/4 of the time of the rebuild I'll treat it seperatly in a later post.

Friday, January 23, 2009

Bottom end start point

Bearing outer finally arrived so I was able to commence the bottom end rebuild. A dry fit (well it wasn't, I f*cked up in haste and went for assembly) revealed negative crank endfloat as the bearing outer lip was in contact with the side of the crank and the thrust washer was slightly off centre. The thrust washer is held in place by the bearing inner sleave and as this had not been tightened home I was able to re position it.

I took 5thou off the face of the bearing using the side of a gind disc in a disc griner and a micrometer (in hindsight I should have allowed about 2 more) re-fitted the outer race in the crankcase using the oven and tried again.

I cleaned off all the bearings and the surfaces using pre-wipe and put Hylomar on the crankcase faces. The sump plug was given a final tighten an pop marked with a punch to keep it in place. The shaft on the drive side never locked onto the inner bearing at any time so I decided to loctite this. Mistake.

The cases were always fiddly to get flush and in line and by the time I was in place the loctite had set with the bearing 5mm out of place. I spent hours making a puller to pull the shaft through the bearing. Just as well the Hylomar doesn't set.

All in place and bolts tightened. I used the engine mounting bolt to nip up that area because if you dont you wont have uniform pressure all around the casing.

The reason I said I should possibly have gone for a few more thou is because the assembly turns but you would need to put on the drive gear on the shaft to turn it because it is not totally free. ( no prizes for perpetutal motion).

I am going to chance that when the drive gear/rotor and the timing gear/oil pump worm screw are all tightened along the shaft it will pull the whole crank/bearing into place. There are no gaskets used yet so if I'm not happy when thats done I'll take it apart and take the few thou off.

I have not assembled an engine for 30 years and cannot remember what the acceptable tolerance for the turning of the flywheel should be. Will it bed in when run, or cause problems. If you have experience of this please comment.

Big Tip: The reason for the alternator cable being in place already is because to get through the to grommets you need a 90 degree turn. Put it in first. I defy anyone to be able to do that with a 6 core cable when the cases are assembled. I used 6 core because my Boyer ignition will not allow me to take a feed for lights from it's circuit so I am doubling up the cables to see if I can take a feed from source. I spoke to Boyer and they said this shoul be feasible. We'll see later.

Best of Luck.

Edit: Left it alone for a while and had a rethink. When I looked at it again, as I was turning crank the needle roller rolled itself out of the shell and I found it ran freer.

This is more like alignment than endfloat so looked carefully at the cases and could see a noticeable misalignment at the joint where the base gasket would sit. I slackened off all the bolts/ nuts and put the needle roller back in place. I then put on the barrell and head and tightened them to level the joint and then re tightened the crankcase nuts/bolts. Perfect. The crank now runs in the bearings as it should and after putting on the oil pump worm and timing gear I tightened that side. Waiting for the driver side oil seal so I can tighten up that side and should be ready then to continue.

Wednesday, January 14, 2009

Conversion to single oil bath primary/crank areas

Hi, not a lot done over the Christmas holidays due to a bearing machining disaster. New bearing on way when I can at last start the full rebuild. In the meantime I have shown here a few pics of a conversion I have done on the drive side crankcase, to share oil source with engine and also to improve engine breathing.

The two ports drilled (below drive side bearing) are such that their lower level is in line with the top side of the screw boss which can just be seen under the lower stator fixing in bottom pic. This is so that the two holes act as a weir keeping the oil level consistent with the previous method which had its level drain in the top of the outer casing boss in the same position. (Dont forget to fill with oil on assembly though).

I am counting on the oil/air mist being blown about in the lower crankcase to feed this area with fresh oil in running. I have, to assist this, replicated the oil drain from the ledge on the inner of the casing on the drive side. On the timing side this ledge/oil feed supplys the inner timing cam cam bush so there is an oil source there. This hopefully will drip feed into the primary case area just up over the main drive sprocket. I will post how I get on later, but all ports have been threaded so that the operation is reversible without splitting the crankcases.
Edit: To finish primary crankcase breathing
Rather than port any air fluctuation out through the chain oiler (which I want to block permanently) I have vented the oil filler/clutch adjuster cap. Pics can be seen above. There is a raised ridge within that can be drilled to hold a baffle. Two further holes vent the air. I used a 10c coin as the baffle as it has a serrated edge and fits perfectly.
It also has 2008 Eire on the coin and a harp.= when and where the rebuild was started.

Wednesday, November 19, 2008

Replacement of splined shaft gearchange

Gearchange shafts are hard to come by but I spotted a replacement shaft sold by Draganfly in UK. Good value so ordered one and prepared shaft. I measured the shaftlength before I cut off the piece to be replaced (57mm). When it was cut I noticed that it was slightly off-centre as you can see in top pic. I measured a few disecting lines across it and then centre punched the centre of the shaft to be replaced. To retain some strength in the boss that holds the shaft I decided to only drill in 3/4 of the way. The supplied shaft was an inch overlength so you can decide wherever you want to drill to. I drilled a small pilot hole after setting up the piece in pillar drill and then drilled in with a 12.5mm drill bit to the appropropriate depth. Once drilled I checked the depth again and then measured the shaft length I needed, cutting off the excess. It was just a case of then using the vice to push the two pieces together to give me the finished shaft. I am going to have one trial fit with cases just to make sure but then just braze the join and a new gearchange for 1/4 of what a good one would cost.
Just as well I tried it assembled with cases. If you notice the larger cutaway for the tightening bolt in the new shaft, this meant that for there to be adequate spline length available outside of the case for the gearlever to catch the inner splines the shaft had to lengthened by 2mm more. This was easy with a tap of a hammer, but it would have been a messy job if already brazed. Happy enough with shaft now, span it in a drill slowly to check alignment along its length and will braze it together now.

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.