Wristpin

Checking is relatively simple but if they need adjusting it gets more complicated as reduced clearances are increased by grinding metal from the end of the valve stems . The worst case of a loose valve seat probably requires the rear body work to be removed to give decent access.

The needle can become worn - more often damaged by over tightening , but that should be visually obvious. If all else fails it may be worth checking the valve clearances or even a loose valve seat - usually the inlet.

That vid applies to a much older cast iron block engine. I repeat, all you need is an electronic coil (Magnetron) . Undo two hex head screws to release the coil, clip the wires tight under the flywheel with out removing it. Fit the new coil and set the air gap between it and the flywheel and connect the original wire from the kill terminal on the throttle plate to the new coil and it’s job done. Just make sure that no fault with the ignition switch is going to send 12 volts down the kill wire.

If your universal filter is designed for an application with a fuel pump there is a possibility that it is not letting enough fuel through from a gravity tank. If going genuine Briggs you need the red 298090S and not the white one which is for pumped applications.

I don’t follow the “ can’t convert to electronic bit” I think that you may have read something referring to a much , , much older engine than yours. All you need to do is fit a Magnetron coil - £20 for a pattern one. No need to remove the flywheel, just leave the points and condenser where they are so that they hold the breaker plunger in place to keep the oil in !

That image is typical of a coil that’s recieved a dose of volts via the kill wire. Sounds as though the ignition switch is breaking up internally . . Toprove the point you can connect a lighting bulb or multimeter to the kill wire . Then turn the key to the start position many times ( I think that the book says 50!) and watch the bulb or meter. I would get a new switch - being careful to get on that is an exact match . The ignition switch page of this may be of assistance https://www.dropbox.com/s/3c4cw5ruve7bb9d/WH Quick Reference0001.pdf?dl=0 https://www.dropbox.com/s/p8ntrlau5gk8uyl/Wheelhorse ignition switches0001.pdf?dl=0

Should we be seeing an image or two? Most Ospreys and 21s are showing their age. Rather than welding cracks and patching it’s better to spend some time making some repair sections , particularly to support the front wheels and spread the loading back across some good metal. If the rot is in the vicinity of the blade boss mounting, that’s a bit more serious as there needs to be enough strength to keep the belt in tension.

Pull the oil dip stick and give it a sniff. If it smells of petrol its possible that the carb is flooding and raising the oil level in the sump. Another quick test is to remove the yellow ?? kill wire from the throttle pate which will totally isolate the engine from the influence of the safety switches etc and will determine whether it is an engine problem or a systems issue but be aware that the engine will not stop on the key with that wire disconnected.

Not only was the machine trying to drive the knackered gearbox but of course the blade disc is always connected to the engine so a 21 or Osprey needs to be in good order for trouble free starting. Another problem that afflicted 21s was that the throw of the standard throttle control was not quite enough to move the carb lever to both full choke and stop. One or the other but not both, especially when there was a bit of wear in the linkage. As far as your purchase goes, how was the machine described? If for "spares or repairs" it is definitely "buyer beware". If described as "used" the implication should be "may be worn but at least working" .If the ad mentions a drive problem - again you are in trouble. New transmissions, or even repair parts, have not been available for many years, so you are at the mercy of sellers' honesty. Some years ago I wanted a 15" petrol Flymo to meet a customer's particular requirement and purchase one that was described as "just serviced" . It plainly hadn't been and I supplied both ebay and the seller with several images to show that it hadn't been . Ebay did nothing and the seller eventually offered a full refund providing that I payed all the return carriage costs and then put me on a "blocked buyer" list.

There were some in a sort of goldy yellow metallic. As those Mountfield were actually Murrays it’s possible that In a given year Mountfield under ordered / oversold and had to top up their stocks with what ever the US factory had available. I remember someone from MTD saying that their factories stopped making mowers in June and switched production to snow clearing and cultivation equipment ready for the autumn before switching back to mowers for the following year before Christmas.

The wear between the piston and pin will certainly be noisy but shouldn’t prevent it running. My pet hobby horse for vintage two strokes is old oil for old engines. That is don’t make up the mixture with s modern synthetic oil , use a vintage two stroke such as those marketed by Millers or Morris Lubricants which are basically a non detergent SAE 30 or 40 and have plenty of body to help with main bearing sealing etc.. I’m guessing that the mixing ratio for your engine will be 16:1.

Rather than honing the bore which implies stones and the removal of metal , I’d clean it up with a flap wheel. The Cords piston ring people used to sell various sizes of what appeared to be standard 80 and 120 grit flap wheels on extended spindles to reach down the bore and I’ve subsequently used standard diy wheels with an extension shaft that I think came with some wood boring bits. Clean the bore as best you can and offer up the rings to it and see what gaps you have. If you need new rings you may find that Tarpen economised by using the same sizes as another mass produced engine manufacturer but if push comes to shove there are a couple of firms that will make rings to order - but at a price! As you are probably aware, with a two stroke you not only need compression in the accepted sense but also sufficient sealing to transfer the mixture from the crank case via the transfer ports. That takes us to crankcase sealing including , if applicable, the joint between two halves, the main bearing seals and the joint between the case and cylinder barrel. Two strokes are equally sensitive to crankcase integrity as they are to cylinder compression.

A good dollop of red oxide then!

I remember the earlier machines as being a flat colour and the later ones as being a metallic paint. Presumably the rest of the machine is available for a colour match. Find an easily removable unfaded part - such as the seat bracket to any decent auto paint supplier.

This may help https://www.dropbox.com/sh/1vbmib95du0vesn/AADXsfyv-W_7d4mpxWvifJSua?dl=0

If you look back through older posts , I have, time to time posted scans of pages from various Hayter piublications. Assuming that the worm drive box has not destroyed itself through lack of lubrication it is mainly a matter of eliminating / compensating for wear to get a “ good clutch” - one that both drives well and disengages cleanly.

This may help https://www.dropbox.com/s/pvg63wyrievumwn/Lawnflite 504 deck0001.pdf?dl=0 Three suspension links with R clips and one cable connecting the blade brake to an anchor point on the transaxle.

https://www.planttalk.co.uk/threads/need-to-leave-the-job-in-a-hurry.430/

I would follow Nigel’s advice and sharpen the blades. The later 30” deck on the 604 had a bar blade but also a fan to create enough air flow to fill the bag. On your machine it is the wings on the 8 blades that create the air flow . Unless you are just going to cut and drop, I would keep them.

Two machines recently sent in for “service” !

Found this https://www.amazon.co.uk/Buckbock-16100-ZF2-V01-Carburetor-16100-ZF6-V01-16100-ZF6-V00/dp/B07KQ6X9J1/ref=sr_1_7?ie=UTF8&qid=1549663344&sr=8-7&keywords=huayi+carburetor

Just realised that you have a Honda copy and not the real thing so the link may be of limited use. Pattern carbs are so cheap on the evilbay that a new one may be the simplest way to go.

Not the easiest site to navigate but you will probably find what you need here. http://www.honda-engines-eu.com/en/welcome.html

An interesting plaque with the archaic word "relict" - for widow. If anyone has an interest in the history of adjustable spanners , there's a man named Ron Geesin who has a collection of over 3000 and has written a book on the subject. The Adjustable Spanner, History and origins.ISBN 978 1 78500 035 5

As you say the change to a pumped system may be indicative of an issue but the addition of the pump may have been with other "hidden" alterations such as changes to the water passages within the block casting. A bit of time studying manuals and parts books may give a clue to any running changes.