MK11 square re-build do`s and don`ts!

[bob cottam]

Hi All. Having received my newly line bored cases back from the engineers (big hats off to Hamlins!)I am preparing to start building the bottom end on my `58 square four. I have built several motors of various types before, so no novice, but this is my first square, and i am trying to ensure that i do not fall into any traps i.e. "make sure you do X before you bolt up Y otherwise you will have to strip the whole thing down again" I`m looking for pearls of wisdom here, tips for the 1st timer.
Normal re-build rules will of course apply -scrupulous cleanliness from oil tank forward, sensible mods (oilways superclean,club rods/Morgo/ return filter etc. I have read and digested Bruce Longmans directions on fitting the new rods-clearence issues around flywheels/bobweights, but i note there may be concerns over barrel spigot/conrod clearence with the new rods??
I will be using the IMD pistons with the new rods- i would welcome any observations also on flywheel balancing to suit-or will these components give a better result than standard anyway?
All info and tips gratefully accepted!, Cheers, Bob Cottam.

[roger.fellows]

Hi Bob, have you considered how readily any bypass oil will get from the Morgo to the crankcase without hanging around for too long in the timing chest? Extra breathing is almost certainly a good option - I'm sure others with more expertise will be along to advise. There's quite a bit on this forum about trying to keep oil in, but you'll have to dig around a bit. The balance factor is supposed to be zero, but you may need to drill flywheels and add Mallory metal in order to achieve that. That's above my pay grade. I expect you'll have thought about matching up pistons/rods to compensate for weight differences. Can't speak to con-rod/ barrel clearances. The engine I put together forty years ago prior to any of this sort of discussion ran very smoothly for 10,000 plus miles before getting to be very oily. That smoothness was not my fault. I suspect it's inherent, specially compared with singles and probably twins. Simes will recommend a dry fit - seems like a very good idea. My late father's error in assembly is one of the reasons the bike I inherited from him is in bits - he used a Huntmaster engine sprocket instead of a Square Four one. The engine did a lot of work converting primary case alloy and oil into old-fashioned aluminium primer - and we did a huge amount of work persuading it to fire up. Have fun!!

[berniejones]

Small world - I also had mine done by Hamlins!
A few things I know now that I didn't before:

I also had the crankshaft mains reground and, during the process, they cleaned up the cheeks of the journal a bit. The result of this - maybe compounded by a difference in the depth of the new crankshaft bush - was that there was a positive end-float of about 20 thou when the cases were bolted up.
Unfortunately, Ariel supplied shims only to increase crankshaft end-float and not to reduce it. After trying a number of options I ended up accepting the float hoping that as all the gears on the shafts are square-cut that there's no significant axial load. Time will tell!

I had to get new oil lines for the feed to the head from Drags - whoever built them was a bit slap-happy with the solder as the T piece on the top section was completely blocked which I only discovered after first start and waiting unsuccessfully for oil to appear around the rocker shafts. Worth checking if you've renewed these!

I also fitted a Morgo pump and had some concerns about whether it was performing correctly due to the fact that the return stream never settled down to a 'sputter' as you would expect when the bottom of the scavenge pipe is slurping at the surface of the oil in the sump.

After measuring the flow and return rates I was satisfied that the ratios were about right (1:3) but after stopping the engine was still getting around a pint of oil from the sump. I've concluded that the output rate is probably dumping quite a bit through the OPRV resulting in a build up in the timing case. Certainly there was a lot of oil being thrown out through the breather which I've now run back to the vent pipe on the oil tank - will have to see if that works as only just started the run-in.

Finally, I think that I would also consider changing the oil feed/return arrangement to the case by tapping the oilways and then using BSP connectors. The flat plate so beloved of BSA is the main cause of oil drips from my A65 and I suspect the Ariel may do the same.

--Bernie

[bob cottam]

Thanks for the replies! I have a magazine article somewhere which touches on the very subject of oil return to sump from timing case with the Morgo-the guy-Graham Horne, was a seasoned builder of fours and recommended drilling extra drain holes to improve drainage of the "relieved" oil back to sump.
Looking at my cases, there is already an extra hole ,drilled at the factory, but not quite all the way through, (see pics), it seems to correspond to the bulge in the alloy in the rear main bearing housing (2nd pic), and seems to be a redundant feature?? I am tempted to drill right through here. Does anybody know what Ariel intended for this blind hole ? chain tensioner pivot? ?

[bob cottam]

sorry- above pics in reverse order , "pic 2" is top one!!!

[Simon.Gardiner]

...(big hats off to Hamlins!)....

And they remember the guy who drove all the way down from Preston with the Square 4 crankcases!
(Preston-Bridgwater and back in a day? I can't help wondering if you picked the engineering company by the one that gave you the longest drive!!)

SG

[harry.thompson]

Back to your original question, I did the same as you 3 years back. The engine worked fine so I aimed at as little as possible other than the real intent of cleaning oil ways (aka sludge traps in the cranks). You can not ignore the three things you also mentioned: Morgo pump, new rods and return filter. The first two are really beyond question if you love your bike.

Three other things:
1. In hindsight there is a oilbar feed system devised I think by Bruce Longman for the cam and pistons. I thought it too much at the time but now I ask myself why not when I see the geyser that is the oil return from the Morgo
2. Detailed measurements of everything. Sure you will do all the journals etc. I would even suggest that we should all be getting the cases 3D modelled for future pattern parts. 3D scanning and printing is much more accessible these days. I didn't but I will next time.
3. Peter Kemp advised me to sit and dress the castings to remove all the little burs and smooth out all the radii. Its tedious and thankless work but it makes sense.

No amount of cleaning will be enough and when you change your oil first time after the rebuild, do not loose heart!

[chris.shearwood]

All info and tips gratefully accepted!, Cheers, Bob Cottam.

Hi Bob,
I would suggest spending the extra money to buy lipped bearings for the drive ends of the crankshafts. These bearings were unavailable for a while but I think Draganfly has them again. The lip prevents the outer race from interfering with the crankshaft if the outer race becomes loose in the crankcase. I think this was the reason they were originally specified.
It might be your regular practice but if not, on assembly you might try fitting all the pistons into the barrel and then attaching the conrods to the pistons instead of lowering the barrel onto all four pistons at the same time. This method gives much less risk of breaking a ring and I find it much easier generally.
Regards, Chris

[bob cottam]

Thanks for the replies-appreciated! Yes i also went for the lipped bearings- managed to find British made RHP`s at a good price so went for them.I like the idea of fitting the pistons into the bores first, and then pins as the barrels are lowered.I did this on a v-twin i recently built,worked a treat, virtually eliminated risk of broken rings, much less stressful!! Incidentally, i did drive all the way to Hamlins- but did an overnight stop and visited the very interesting Haynes motor museum at Sparkford -good day out and great restaurant! Well you have to don`t you.....Bob C

[bob cottam]

Sorry if this question is duplicated-my last attempt has disappeared into the ether somewhere and could pop up at any moment!! but here goes:
Looking at the two photos of my crankcases posted above,does anyone know what the blind hole drilled in the timing chest (with biro pointing at it ) was intended for- it seems like a redundant feature, at least on the MK2? What did Ariel intend here? Other pic shows associated bulge in alloy as seen from inside crankcase where drilling is situated. I am toying with the idea of drilling through to provide extra drainage for excess Morgo oil to drain......Bob