Hi Ian, if I remember right, you mentioned-on this forum-that you owned an Ariel Sq 4 at some point, I wonder if I could pick your brains a bit 
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I have a '58 Sq4 and my manuals only cover Ariels upto '51 (alloy cylinder head and barrel). Besides the difference of the earlier two ported (4G)/later four ported head (Mkll)are the internals the same? Do the set up specs i.e timing etc of the '51 hold good for the MKll models as well? I sure would appreciate any info at all, that you have on this subject. Are there any manuals that you would reccomend for the MKll model.
Thanks and regards,
Hank
Hi Hank..I can't help much I'm afraid..As I had a Mk 2 and not any of the earlier types I don't know about comparative settings..What I can tell you, contary to what you might hear, is that in my experience the Mk 2 did not suffer from the rear cylinder problems of some of the earlier models. The back two cylinders do run hotter than the front two and over time will wear at a faster rate but I never had any problem with them....Clean oil is important for the square four as it has relatively small oilways internally, so consider fitting an external filter and change the oil regularly.
In warmer weather a 50 weight oil is recommended.
Mine was a 56 model and still had the smaller oiltank so I fitted an oil cooler under the front of the petrol tank (off a Jap bike) and I think that is a worthwhile mod as well.
Check that the cylider block is fitted the right way round..they can be 'reversed'. Between the front two cylinders is an air gap and the casting slopes up under the head to direct air to that area...
You will probably find you get some mechanical noise from the straight cut crankshaft coupling gears on the 'over run'..it's noticeable, but normal, so don't worry about that. They have fibre 'silencing rings' rivetted to them to help reduce this.
If the throttle gets 'sticky' and the cable is OK check the lubrication of the SU carb..they need topping up with a light oil every so often. I found the SU basically trouble free and very easy to set up..If you use it in the wet weather make sure you have a rubber cover over the distributor to avoid problems.
I loved the originality of design, power characteristics, sound and smoothness of the square four and of the hundreds of bikes I have owned it is one I genuinely regret not hanging on to..I'm quite envious!...Ian
email (option): ian@wright52.plus.com
Hi Ron/Ian,
Thank you both so much 
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Ron- for taking the time & trouble to scout out the books for me and providing the links as well.
Ian-those are some great tips and invaluable as well as they come from an ex-owner and it's a relief to hear about the rear cylinder over heating thingy.
As usual this is a blue chip site where you can get most things on bikes under the sun!
Regards,
Hank