Ariel square 4 maintenance

[MARK.WALSH]

Hi All
its over 10 years since I restored my MK1 square 4, and apart from when some idiot knocked me off the bike in 2015 causing both damage to me and the bike, the machine has been used regularly and has now over 8000 miles on the clock.
Overall, the bike is always easy to start on just a couple of kicks, although out of all the vintage bikes I own it is the most likely to go 'off the boil' from a tuning perspective and can sometimes turn a pleasant ride into a disappointing one. (although its never broken down and left me stranded!)
From a maintenance perspective, and as an aide memoire, I zero the odometer every 200 - 250 miles to grease the rear suspension and add approximately 1 pint of oil to the oil tank. Other oil/grease points are done at larger intervals and this seems to keep things in order and working well.
My question is, how often would you recommend changing the engine oil? The manual says 1500 miles but this seems far too long, I would think under 1000miles to be safe and prevent sludge. (I also run a filter on the oil return)
Also is there a recommended interval for checking tappet clearances?? Mine were about .12 inlet and .15+ when I checked them recently - but in fairness I probably hadn't checked them for over 4k miles, and it didn't seem to clatter that much (maybe I'm going deaf in my old age!)
Finally, with 8k plus on the mileage, when should I be thinking of doing a full overhaul?. I assume the bike must be close to 1/2 life now for needing the oilways cleaning out amongst other major bearing checks etc. Any advice from long term owners / users would be appreciated.
All the best
Mark

[Roger Gwynn]

On the one hand when using modern oils and filters the oil change interval can be extended and save the planet and you pocket. On the other hand it is a good ides to change the oil at regular intervals, irrespective of the mileage. Annual is usually quoted but if in regular use every month or so I would suggest that you could leave it longer. I tend to check my bikes over each winter and attend to most of the items on a list compiled during the year

[Roger Gwynn]

With regular oil changes and modern filters your sludge traps should not sludge up, they will of course but will take a long time. I must admit to never having kept a SQ4 on the road for long enough! There are people out there who have...

[paul.jameson]

With an oil filter in the return line I have gone over 20,000 miles without checking the sludge traps. I know of people who have done much more than that but I don't know their frequency of oil changes, how clean the engine was inside when it was rebuilt, etc.