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Oh dear! Your plastic tank may be suffering from osmosis. The dreaded firbreglass bug that bedevils many ‘plastic’ boat hulls.
Some tips here:50:1 is correct for the Supa 5, but the older ones 33:1 is more the mark.
800 miles is not far. Might be wise to ease it in longer with a tad more oil for good measure.
I remember when I bought a Yam. DT175 in the seventies. Ran sweet from new, but pushed it a little after 5 or 600 miles and it partially seized. Pulled over and let it cool for ten minutes and it started up fine. Never had problems again. Maybe just need a little patience.
Depending on whether your Mikuni air/fuel screw adjusts the air, or the fuel at tickover, it will show you either have too much fuel at tickover, or too much air. If the latter, you have an air leak somewhere.
My familarity with Mikunis lapsed after I sold my last CX500 MANY Moons ago! So I will bow out to greater knowledge.
Might want to check that you have not lost a tooth on the first gear pinion. Had that on a Villiers once. Knocking increased as speed increased. Snick into a higher gear and all quiet.
Two people with the same problem?
Dry plug – fuel starvation. Check filters in the fuel tap; carb inlet.
Check float needle operation and float position. Check all jets for obstructions. Check for no air leaks between carb and crankase.Can’t help with the Bristol issue. Shropshire Hills.
I know a lot of people blame wear on carburettors, but who else has a genuinely well working original carburettor with 50,0000 miles on it?
I take it you meant 50,000 and not 500,000 !
Please Sir – me. Yes, there’s always one.
Honda 400/4, 55,000miles no issues.
Three Honda CX 500’s, all did over 100,000 miles each, no issues.
BMW R80/7, 211,000 miles, periodically replaced the rubber diaphragms on the Bing’s (3 times in all).
Moto Guzzi V50III, 308,000 miles, replaced the needles once. Dellorto.
(Plenty of other issues, but was my favourite bike to ride).However, the Amal carbs on the BSA’s used to wear their slides and well under 50,000 miles. Don’t the C15 had done 40,000 when part ex’d, and the A10 – whilst a nice engine – was often with the head off. Single carb on the A10.
Do singles have something to do with it? Shouldn’t do, as all the high mileage bikes above had one carb per pot.
I can’t add anything to this discourse, but thank the OP for an interesting read. I have a small book by Rob Carrick & John Wood entitled ‘Villiers Singles Improvements Handbook’ and the technicalities of tuning two strokes is a very complex subject. Pretty irrelevant to MZ discussion, but a great little book. The only tuning I ever did to my first bike, a Francis Barnett Plover, was put put petroil in the tank! Later had a 9E in a DOT trials, but did nothing to that engine.
I would plump for the centre of the gudgeon pin, but the key element is surely the proximity to the cylinder head and the gap remaining between the two which will ultimately determine the compression ratio. But perhaps that is an answer to an unasked question?!
Unrelated directly, but we have had issues with household LED bulbs where they have been used as replacements to standard incandescent.
They have a tendency to flash occasionally when switched off. The rate varies from room to room. One room 34 seconds, another about 80 secs. Just a sudden flash. Contacted Western Power (distributors) and after the engineer checked all was as it should be with the line installation, said that it could be caused by a tiny feedback through the Earthing system that charged the internal capacitor of the individual bulb which then discharged in one flash. Not the sort of thing you want in a bedroom!
So, sensitive indeed, and in a different application.
If it’s not worn and need replacing – leave it in there. At least it won’t fall out and cost you time searching the floor.
