SQ4 - changing the oil

 It's high time Square Four had an oil and filter change, so with the oil return line repair complete on the Huntmaster the Square Four is back on the bench after a 10-minute run to warm the engine oil up. 

As usual it's an absolute pig to get the oil tank out but it's very easy to drain the tank and the sump - I have a new sump plate (well, it was new 10 years ago) with a drain bolt and magnet in the middle of it. I had something like 300 ml of oil out of the sump - I'm not sure whether that's unusual or not. 

I was surprised to find the sump strainer damaged - I think I'll get a new one from Draganfly. 

With the oil tank out I can degrease the area around the top of the box where the filler is - it's always quite mucky around here because it's very difficult to top the box up without getting grease everywhere.

The oil tank is also a very tight fit - it's always a struggle to get it out. I'm wondering if it's fouling the frame tube, perhaps stuck between the frame tube and the gearbox plates.

I had the tank in the parts washer for 15 minutes washing the outside and the inside and was pleased to find very little sludge and no debris in the tank at all. There's obviously been some further washing of the engine through the detergent oil that I'm currently using as the cases appear very clean and the goo in the bottom of the tank and on the sump of drain plug is just like the dark grey substance you would get from the crankshaft sludge traps.

You can see one of the cams in this picture - the wear ridge is quite clear. I have a new camshaft ready to go in when I decide that I'm bored enough to rebuild the engine!

I filled in my maintenance spreadsheet but for the record the mileage is 4089 miles.

FH - bottom end complete

A little bit later than expected I am back in the workshop. My generator decided to burn out it's alternator winding, and took the battery charger with it which meant buying a new generator, building a trolley for it (it doesn't fit where the old one was) and building a trolley for the welders - because their spot is now taken up by the generator...

Having got most of that out of the way, I can strip the cases again to fit the replacement connector rod nuts, BSA part number 37-1691. These are genuine new old stock from Vale-Onslow. Looking at the picture below, from left to right we have the modified Draganfly nut, an unmodified nut, and on the right the new lower profile nut:

This, by the way, is the mark left by the Draganfly nuts before I modified them:

Here are the Draganfly big end bolt washers. These are laser cut stainless and whilst some suggested they were rather small, they are much the same size as the bearing surface of the nut so I am leaving them in place.

Stupidly, I forgot to picture the new nuts in place on the big end caps. Mrs H phoned to see where I had got to (I'll just be 10 minutes dear!), and that's always a distraction. Suffice to say that they were torqued up to 22 lbf. ft in accordance with the BSA data sheet and I oiled up the various bearings before closing the cases. I made sure to remove all traces of Threebond and was very sparing with it when reassembling.

The case bolts are all stainless, from Acme as usual and they fit beautifully. I made this chart from the diagram in the Draganfly catalogue to show me where the different bolts go:

Lovely and easy putting them in; I used my frame spreader to make it a bit easier.

Now that the bottom end is in, we've got a number of workfaces to tackle:

• the barrel and pistons
• the primary case
• the timing gear

We can look at any of these really but before we do there are some components around the engine that will become less accessible as we progress. The first of these is the engine breather shown here in the form in which it arrived:

This isn't how Ariel designed it. It's supposed to bend around and appear behind the FERC, above the gearbox sprocket somewhere.

Another item is the magneto. It's fitted here temporarily with the long bottom nut, which is on the job list for zinc plating. With the primary case loosely bolted in place you can see that it's quite restricted in there:

Something that surprised me, and thanks to Daniel Rix on the FH Facebook page for this, is that you cannot get the brake bell crank on with the primary case in place. That's a pain, because I want to get on with the mechanical build and I hadn't planned on doing any plating just yet... and the bell crank needs plating.

The other thing I must remember is to fit the oil lines before I fit the primary cases! Access will be a trifle difficult if I forget, so let's not get ahead of ourselves and we will get on with sorting out some of the details.

FH - more shims & trimming nuts

 Following Thursday’s abortive first attempt, I pulled the cases apart again for a look at the big end nuts and to fit another shim to the drive side main bearing.

Roger Gwynn, all round guru, Ariel Hero and founder of Draganfly Motorcycles (without whom us Arielisti would be lost at sea) told me on the AOMCC Forum that the big end nut/crankcase clearance is close in these engines but you don't need to remove much material to avoid a clash. Roger recommended grinding some material from the cases.

What I've done today is make a 1 mm chamfer on the offending edges of the two timing side nuts, so now I know what clearance I need to provide. If I can provide that clearance without modifying components I will be a happy bunny.

Club member Mick suggested that the fact that no bolt thread protruded beyond the nut wasn’t satisfactory, since the locking part of the nut was probably bearing on a reduced (tapered) part of the thread:

I've ordered a new set of nuts, still self locking but to a slightly shallower pattern (still big end nuts, not something nasty) and I'll use these with larger but thinner washers I think. That will guarantee the self locking bit of the nut is on the full diameter of the bolt thread. I’ll probably have to make the washers myself on the lathe.

Meanwhile, adding a 0.1 mm shim to the 0.25 mm shim already there has given me 0.07 mm end float, or about 0.0027”.

That will do nicely.

FH - Assembling the bottom end

 With the crankshaft together and the few internal components of the crankcase assembled, it's time to put them together. First step is to thinly coat the mating faces with Threebond 1215:

With the cases bolted together, we can measure the end float again. This time we have 0.18 mm - last time we had 0.34 mm, and I added one 0.25 mm shim under the bearing. Something has changed, or I have made an error because 0.34 - 0.25 = 0.09, not 0.19...

That's 0.0075" - we are aiming at 0.005". I'll see what shims I have in stock.

The next challenge comes when we check crankshaft rotation - it doesn't. There are two clashes one on the rear of the case, one on the front; the rear is a scrape that allows the crankshaft to move, but the clash at the front is more serious and prevents movement altogether. You can see the witness marks in the picture - this is probably the big end nuts fouling the crankcase:

That's coming apart again.

FH - Finishing the crankshaft

In our last post, we determined that the big end clearances were good. At the same time, I checked the new gudgeon pins in the small ends and found those to be good too, so with the sludge trap cleaned and assembled some time ago we can commit to closing up the big ends with the proper big end nuts. These are £3 each, and can only be used once.

We torque them up to 22 lbf.ft, or about 29 Nm using the Draper 3/8" torque wrench.

I took the chance to clean the crankshaft down again with some brake & clutch cleaner and dropped it into the drive side crankcase half which I had laid out over the hole in my bench:

Here's another view, showing the new 356 camshaft as fitted to BSA A10 Road Rockets and early Super Rockets.

Tomorrow, I'll use some Threebond 1215 to seal the crankcase halves. Meanwhile, I need to sort out the bolts to hold the cases together. I have this lovely box of studs from Acme Stainless:

This sketch, from Draganfly's 'List 15' (a very useful document) shows where the studs go:

FH - Engine bottom end

 While the painted parts are away, I've got the engine on the bench. Way back when, I established the state of the bores, mains and big ends and what I want to do now is to trial fit the new large bearing crank into the original cases.

A little while in the kitchen at home saw the main bearings fitted:

It's then no more than an hour's work to assemble the crankshaft and the timing gear; the good news is that the timing gear bushes already in this case are in very good condition with very little play. Shame I already bought a new set.

It was clear that the crankshaft was a bit tight. The setup with the DTI reveals no end float and the crankshaft was mildly stiff to turn, but then it does have a large plain bush at one end:

Investigation revealed that the drive side bearing wasn't fitted fully home against the crankshaft web. With that fixed, we have 0.34 mm end float:

That's about 0.013"; we want a maximum of 0.005", according to BSA Service Sheet 208 - Waller is silent on the subject. Since 0.005" is 0.13 mm, we need to shim 0.21 mm; I've bought 0.25 mm shims which should give us 0.09 mm end float, or 0.003".

More later when bits arrive.

W/NG - Assembling the bottom end - again...

So, a bit of spare time arrives and I have the camshaft, the cam bush, a 3/4" reamer and a gasket set. Let the bottom end rebuild commence!

First, it's back to the Rothenburger to remove and replace the bush, which I can do in one heat cycle. I'm careful to avoid the new bearing. I knock the new bush into the hot cases, driving the old bush out as I do it - a simple operation when you have enough heat.

Whilst that is cooling, let's look at the camshaft. The principle reason for replacing the camshaft is because the inner journal is badly worn. I reached out to the AOMCC Facebook community and came up with this camshaft, which is actually the profile used for the sidevalve machines. You can see it has a much longer duration than the Ariel F cam normally fitted (the one on the right), but it has the same base circle diameter. This means I will get more fuel in and and exhaust out again, and make more power but I won't have to change the followers or the pushrods.

Another problem solved by the AOMCC is the knackered half time pinion, the one at the front of the picture. A member kindly sent me the one behind, which looks unused.

Coming back to the crankcase camshaft bearings which I fitted earlier. When you buy a bush it is usually undersize, and this was no exception. It needed reaming to size, whilst aligned with the bearing in the timing chest - so I used the timing chest bearing as a guide whilst reaming the crankcase end bearing. In this next picture I have the timing chest bolted in place and a 3/4" round bar passed through both bearings to demonstrate their alignment - the bar turns smoothly and freely.

This next picture shows a block of wood I use to support the crankcase whilst working on it. The cam follower pin, crankcase nose etc. fits in the hole.

Before I assembled the engine, I fitted the camshaft so that I could prove the bearings. The camshaft turned smoothly and with no wobble, so I proceeded to dismantle it all again and to assemble the crankshaft into the cases, and to bolt the cases together.

I replaced the assembled cases in the frame and assembled the engine plates. Now that I had the crankcase held securely, I refitted the oil purifier with some Loctite 243, as suggested by Chris Williams at Alpha Bearings. A lot of folks really struggle to get these out and they often come out in pieces; I have had this one out before (and cleaned it before), so it was quite easy, but I was surprised to find it had quite a bit of sludge in it. Chris's point was that they might be difficult to get out, but if they come out when the engine is running the crankcases will be scrap.

Once that was back in, I took the opportunity to use the oil can to pump some oil into the end of the crankshaft, and eventually I saw it emerge around the big end proving that the oil ways were aligned.

Now, I could fit the new half time pinion & camshaft and set the valve timing.

I had a look at the cam followers and selected the best two. The inlet one is quite worn and I should really replace it.

Before I put the timing cover in place I need to fit the magdyno. Before I did that, I cleaned up the slip ring which was a bit mucky.

Here's a new felt seal for the magneto drive:

Next, I fitted the timing gear case with it's small gasket, and added the large gasket with Threebond 1215:

I fitted the timing gear cover and rotated the engine several times to ensure the new gears were quiet and free, adding the camshaft magneto sprocket and the magneto chain, nominally tensioned at this point. I'll finalise that when the barrel is on and I can set the timing.

Since we are nearing the end of activity from this side of the bike, I'll refit the mudguard bracket to the engine plate. The original bolt fitted here looked like it had had an M8 nut forced over a BSC thread, and both were scrap. This is a new stainless 5/16" bolt & nut.

With that done, I can fit the oil tank, hook up the oil lines and fit the oil pump.

Next, I need to clean and paint the barrel, fit the barrel & piston and set the ignition timing. Then I will close up the magneto drive having set the chain tension; I'll then inspect the clutch before I finish building the head. I know that I have to make a valve guide drift and paint the head, and possibly give the valve seats some attention - I'll do that while I wait for the clutch tab washers, nut and any other components I find damaged.

W/NG - Assembling the bottom end

I said the next step was to sort out the camshaft, and it was. The reason for that was that I wanted to replace the camshaft bush in the timing side crankcase before the crankcase halves went together and I have done that, because I have found the camshaft and I know what diameter the journal is - I'm confident that the bush can go in as-is, and not need reaming.

So without further ado I can clean the bearing journals and use the Rothenburger MAPP torch to warm up the cases and drop the bearings in, with their spacer and circlip on the drive side.

The crankshaft has been away at Alpha Bearings in Dudley, the UK's premier supplier of big ends for classic motorcycles who have replaced the big end and realigned the crankshaft at what would have been a very good price (and with a one-week turnaround) had the small end eye not turned out to be oval. I was aware that it was very worn and for some reason had no oil hole. The crank came back from Alpha true to less than 0.001" and looking excellent:

The small end eye now has it's lubrication slot. I had a small worry when I thought the mainshaft was not correctly pressed in - though Alpha's had not touched the shafts:

I spoke to Alpha and several people in the club about this suspecting that I knew the answer - it is a taper fit. Alpha explained that if this gap were absent, you could not be sure the taper was pulled up correctly - so that's another one for the memory bank. The AOMCC audience all concurred, so I am happy again.

So next, we are into shimming the crankshaft for the prescribed 0.008-0.012" endfloat. This is the set up I used - the DTI is actually attached to a magnetic stand on the vice anvil, and the heavy crankcase assembly is just sitting on the bench. Not ideal, but I found that if I move the crankshaft against the case using a twisting motion with a screwdriver (flywheel to inner case wall), that cases will not move at all.

In this way, I found that I had a total of 1.4 mm endfloat with no shims. That's about 0.055".

That's a start, but we need the correct endfloat with the rod in the centre of the crankcases. To do that, I used a bore gauge to establish a position where the rod to crankcase measurement was equal on both sides and measured the end float from this position.

I have some 0.3 mm (0.012") and some 0.5 mm (0.020") shims, of 26 mm ID. Time for some calculations:

That leaves me with 0.22 mm end float, or 0.0086". Perfect.

I bolted up the crankcase halves sealing the joint with Threebond 1215 and assembled the cases into the frame, fixing the front engine plates loosely onto the crankcases and then dropping the lot into the frame, retaining it with the single 1/2" stud at the bottom of the down tube. 

When you start on the rear engine plates, you do the drive side first, with two studs into the engine and hold the plate to the frame on the gearbox top stud, then pass the footrest bar in. If you don't do it this way you will never get the spacer in.

When that is done you can put the rest of the bolts and studs in with the timing side plate and the magneto platform. If you look closely you will see the bash plate fitted, though you cannot finally bolt this in place if you have not put the sump plate on.

You can see why the magneto platform needs those extra studs and bolts to stop it flapping about.

I made an earth wire for the magneto:

With it all tightened up, I did some trials with the timing case. Turning the engine over with the camshaft, rockers and half time pinion in place sounded awful, so I had to investigate.

That pinion is knackered. I also realised that the camshaft bush that measured up OK was actually oval - I should have looked for that before. It was OK in one direction but when I looked at 90° to the original measurement I could see it was quite worn.

The next step is to pull the engine out again, replace the camshaft bush and reassemble with a new half time pinion.