Monday, 26 November 2018

More timing gear

In a recent post, we looked at stripping the gear in the inner timing cover. This time, we are going to complete the strip in that area in preparation to splitting the crankcases.

As you will remember, I'd removed the dynamo sprocket after a bit of a struggle and went on to make a gudgeon pin puller so that I could lock the crankshaft, prior to removing the rest of the timing gear.

I locked the crank with a bit of 5/8" bar through the little end eyes, protecting the crankcase mouth with some strips of 3/8" MDF, then I knocked back the tab washers on the oil pump & camshaft nuts.

Both these nuts appear to have a 25/32" hexagon, close to 20mm - I used a 20 mm six sided socket. Fortunately neither nut was particularly tight and they came off with no drama.

The camshaft pinion is provided with two 1/4" BSC tapped holes, so its easy to pull the pinion off:

With the cam pinion out of the way, I could wind off the oil pump drive and remove the oil pump. It's a mazak pump - we'll think about replacing that at some point, but it probably won't be in the first phase of this rebuild. I also took the opportunity to remove the oil pressure relief valve while the cases were still in the engine stand - it's all present and correct, but its full of gunge.

The oil pump drive is damaged - it's old damage, not by me fortunately. We'll have to get it clean to see if it is usable:

I was concerned about pulling the crankshaft pinion off - or rather, I was concerned about spending more time making another puller. In the event, it moved with the slightest encouragement from a pair of screwdrivers.

So that's it for the moment - I just have to clean the parts up, inspect and store them before moving on to the crankcase and crankshaft.

I'll just have a sort through all this sludge...

Saturday, 24 November 2018

Cake Run

Overcast and chilly but dry, and recovering from a couple of days with the grandchildren, today came another opportunity to give the SQ4 another test run after the summer oil leaks and HT problems which were eventually traced to be the cause of a persistent and long term misfire. Although the cold weather might be masking a hot weather running problem, the bike is running better than it ever has.

Preparing for the trip, I noticed the oil level was lower than expected, though a few minutes idling had it a little closer to normal. I topped it up, and resolved to look at it again when I got back.

A 27 mile around North Norfolk had me grinning from ear to ear as usual, though I thought the handling was a little uncertain; the brakes appear to be bedding in, the chain needs adjusting and the lower chain guard is clanking as usual.

Back in the workshop (after collecting the pear & ginger cake from the excellent Picnic Fayre in Cley), I set about adjusting the chain and rear brake. Since I was adjusting the chain, I removed the wheel to take off the chainguard - more on that in another post. I moved the chain back half a turn and lubricated it; I adjusted the brake up 3/8 of a turn and put an 1/8 of a turn on the front as well. The primary chain looked OK, and the oil level was good. I checked and nipped up all the spokes on the rear wheel.

Turning my attention to the engine, I had a good look around underneath. There was quite a leak coming from somewhere judging by the clean oil 'trails', possibly:

  • the engine breather, which had a drip on the outlet pipe
  • the sump plate or plug
  • the front offside main bearing
  • the oil filter
  • the oil feed to the engine or to the top end
  • a combination of several things

Essentially, there were too many possibilities to narrow it down. I tightened the oil feeds, the sump plate and plug, the crankshaft bearing cover and the timing cover but essentially none of them needed attention.

The front main bearing cover has a peculiar copper/asbestos gasket which looks more like an exhaust ring gasket and I suspect is wrongly installed. It's not the gasket I would have chosen for that application.

More later.

Thursday, 22 November 2018

Gudgeon Pin Extractor

Gudgeon or wrist pins retain the piston to the connecting rod with varying degrees of clearance, transition or interference fit according to the predicted running temperature of the engine, and are retained by a circlip at each end in addition to any fit. This means that removal of the circlips will sometimes allow the pin to slide out, but more often than not you'll need to warm the piston such that it will release its grip on the pin. Obviously, belting the end of a tight pin will do your connecting rods no favours at all, so anything other than light tapping is a no-no.

A much better approach is to use a gudgeon pin extractor. These usually consist of a threaded rod passing through the pin, some means of holding the pin, a tube large enough to allow the pin to come out and a large washer to spread the load.

I made this extractor to deal with the FH gudgeon pins, which were quite tight. It is made of a bit of 1" tube, with a closed end turned from aluminium; that's M6 threaded rod in the middle. The tube is long enough to accommodate a 3" gudgeon pin.

A turned steel plug fits neatly into the gudgeon pin aperture in the piston and is reduced to just fit inside the pin such that it doesn't slop about. It's threaded M6 internally and is retained with a nut for the moment.

Here it is, set up and ready to extract the first pin:

Here's the extractor set up on the piston. The end of the tube is shaped to fit the piston, spreading the load over the piston wall:

A blast of heat on the piston crown and some steady winding are all that is necessary to draw the pin out of the piston, without placing any side load on the connecting rod. When you have done winding, the pin is neatly enclosed in the extractor:

Job done.

Thursday, 8 November 2018

Inner Timing Cover

In the last instalment, we removed the outer timing cover to gain access to the dynamo drive, the ATD and the oil pump. We removed the dynamo drive chain but then stopped with this old, lightweight Japanese puller distorting itself while attempting to remove the large dynamo pulley on the idler pinion.

Over a week later, with three trips away for work I can tell you that the old puller never managed it and I had to make a new one. The new one, backed by a piece of 1" x 3/16" angle, is considerably stiffer though it loses out by having a coarse thread - the centre thread on a puller should be a fine, hard thread. Anyhow, it worked well enough and the dynamo pulley is now off.

Here we are - I told you it was off. Nothing untoward here apart from damage around the ATD which suggests it has been whirling around and rubbing the timing case:

The next step was to remove the inner case, which is held in place with four screws. A quick dose of the traditional remedy - leather hammer and impact driver, though not necessarily in that order, had it free in a jiffy. A mysterious 'tink' followed and this little chap appeared in the drip tray:

I wonder what it is?

Now we can see the crankcase, which looks fine & dandy. The idler will have to go back in to release the crankshaft & cam shaft nuts.

Here's the crankcase side of the inner timing cover. You can see the damage the loose ATD has caused in the top right of the picture.

And close up:

The magneto shaft, whilst it will turn the points, is very wobbly. This is more than a bearing problem - I think the shaft is broken.

Here's the timing cover in the parts washer, almost clean.

It was about now that I discovered you are not supposed to put paraffin (kerosene) in these little parts washers...

Wednesday, 31 October 2018

Timing chest

These are the weapons we'll use to attack the timing cover. The original screws are all intact and most of them are in pretty good shape. I'd ground my largest impact driver bit to fit in the screwhead recesses without causing damage:

Half an hour later. Beats me why people insist in putting gasket sealer in screw holes.

A general view. No obvious horrors so far:

This is the early Mazak pump. Take a close look at the upper mounting bolt - there appears to be some little gremlin sitting on to of the pump. I wonder what that is?

The dynamo drive:

I thought this chain was supposed to be endless?

Before I start cleaning this up, let's have a look at the magneto & the auto advance unit. In this video, I have not attempted to remove the auto advance from the magneto. That movement is all in the AA unit and the magneto spindle:

Oh dear...

Removing the barrel

Next stop, remove the cylinder block. Nuts are stuck fast, so we need a dose of Plus-Gas:

This is the 3/8" flange barrel used by Ariel throughout Huntmaster production, and by BSA until the 1/2" barrel flange appeared for the 1955 A10 Road Rocket. Poking around waiting for the Plus-Gas to do its job, take a look down the pushrod tunnels:

That's a leaf, possibly hawthorn... How did that get in there?

Nuts undone, we need to break the red Hermetite sealing the base gasket. this won't take much force and I'm not overly worried about the pistons anyway, so we'll do it like this. Two bolts in head bolt holes, either side of one piston; a suitable bar between them (if this had been remotely reluctant to move I would have made a stiff bar out of a bit of angle or something) and a lump of wood on top of a piston.

A quick tweak on the crankshaft has the block pop up - but it's not all plain sailing. The timing side piston sticks at the bottom of the bore, in the rusty unworn section and takes a bit of persistence to remove it. When it comes off, we find these rather worn cam followers:

A look at the flywheel reveals this is the earlier, smaller, built up crank used until 1958 - perhaps not surprising in that this engine is marked 'LF' and is clearly a 1955 design. The crank has no radial bolts in the flywheel like the later 'large bearing' cranks.

Ariel adopted the large bearing crank in 1958, when BSA rationalised it across all A10 models; the large bearing crank initially appeared in the 1955 Road Rocket.

Here are a couple of general views. The engine has been fairly damp inside for a while:

We'll have a closer look at the camshaft later. I've seen worse.

However... have a look at this video - it's as though someone forgot to put the shells in!

Monday, 29 October 2018

Measuring the bores

Before we get into the rest of the strip down, lets have a preliminary look at the bores. From up here they look really clean - there are no ridges at the top of the stroke:

There's a bit of a clonk when you turn the engine over.

Right now I am hoping that is in the timing chest, maybe a loose dynamo chain. Offside piston crown has been scratched by some exuberant decoker in the past:

Nearside piston crown is much the same:

Onto the bores - I measured them each in two positions, at the top and at mid stroke with a comparator and a Moore & Wright 2" - 3" micrometer. Both measurements were in the fore & aft direction which should be worse than the transverse direction:

Here are the results of my preliminary measurement:
  • Offside cylinder, top of piston stroke, fore & aft: 2.818"
  • Nearside cylinder, top of piston stroke, fore & aft: 2.815"
  • Offside cylinder, middle of piston stroke, fore & aft: 2.826"
  • Nearside cylinder, middle of piston stroke, fore & aft: 2.822"
Nominal standard bore is 2.755", so these are a worn 60 thou overbore. We'll measure the bottom of the stroke when we get the cylinder block off - we can measure the pistons as well and decide what we are going to do. Sixty thou is the maximum oversize so essentially if these are too far gone we will be resleeving this barrel... These Ariel barrels are not the same shape as the much more common BSA A10 barrels on which this engine design is based, and we are unlikely to find a better one.

I'm told these dished pistons are not available either, so we will be looking at flat topped pistons and an increase in compression ratio...

Saturday, 27 October 2018

Starting the Engine Strip

Inspection starts with a look at the rocker box. Both covers are present, one has it's captive nut, one is missing...

Here's an ugly looking stud and some cornflakes gaskets for general amusement!

All is well at the inlet. The cover stud is seized to the nut and has come out with it:

Removing the exhaust side stud with two 5/16" BSC nuts locked together:

Removing the inspection cover studs, we find one elegant Ariel stud with BSC threads at both ends, one 1/4" for the nut and one 5/16" for the rocker box. The other one, which has no nut is bent and is 5/16" both ends, one BSW, one BSC. Obviously a replacement but a shame, because the thread in the rocker box has been recut BSW. I'll be making a special on the lathe.

A stripped stud retaining (or not) the rocker box at the rear. Steve Carter, an AOMCC member who rides thousands of miles each year on his Huntmasters, uses a bolt here to avoid the worry of losing that nut down the pushrod tunnel:

General view of the head mating surface. All the springs look good at first glance:

Here's the underside of the rocker box:

More cylinder head general views:

Quick shot of the underside of the head. Looks OK, bolts were very tight but came out with some effort:

Bores and pistons. After I took this shot I gave them a quick clean up - the bores are unmarked and have no ridges; pistons have no undersize showing.

These are the dished pistons. Simon Gardiner (AOMCC) tells me that dished are the 6.5:1 standard pistons; if they had been flat-topped, they would be the the export/sports 7.25:1 pistons.