Hello all, it's been a while. I have good news on the mower! As spring is beginning to arrive I have once again been able to get outside and do work on the machine.

Pulley from FB Marketplace was fitted just before winter last year, and I'm glad to say it has done the job really well. Self drive now working brilliantly.

Throttle problem is also now remedied (although carburettor needs another quick clean as still hunting a little bit, but I do have now some proper carb spray and cleaning gear). The throttle problem progressed further before it got better, upon starting the mower it would rev out of control and sounded as if it was about to go into orbit! After much faff I ended up tinkering and resetting the governor, as it seems either it had slipped out of alignment or the previous owner had mucked about with it. Throttle is now lovely and controllable and the engine runs at a good steady speed.

Microswitch for the electric start was replaced as had started to fail, and I also ended up replacing the battery connector too on the mower's wiring harness as it was perishing away and didn't fit all too well into the battery itself.

Hopefully I can finally sell the thing now and move onto something a little easier (Briggs 35 Classic, anyone?)

Thank you again for all of your help!

Facebook Marketplace is a brilliant place to start.

I finally have a fix! Sadly not guaranteed for anyone else to work, but feel as if I should share the outcome.

Ended up ordering a 60mm diameter V-belt pulley with an 18mm bore and fitting it onto a sleeve that was a good fit over the PTO shaft. Tightened the pulley onto the sleeve with the 2 grub screws and was nice and secure. However, pulley massively too big, belt was really tight once fitted and self drive constantly working. Intended to machine it down but getting access to a lathe has proved difficult.

Put up a post on Facebook Marketplace asking if anyone had one for the Briggs Quantum XTL 50 engine, one bloke did, offered to send me it for nothing! I gladly accepted and it is on its way as we speak.

I will however post a full set of dimensions on here once it arrives for anyone in future wanting to machine one themselves or make / send off their own CAD model to be machined. I imagine it's a pretty unique problem but I might as well provide the information I wasn't able to from the internet.

I believe I also discovered the reason why the pulley had worn through and dropped off in the first place. There was a missing rubber engine mount that fits between the plastic deck mount and the engine on the pulley side of the mower, causing the mower to be tilted down to the right (when viewed from the front). As a result the pulley was contacting the height adjustment rod. After a replacement rubber mount was made the engine sits level, and there is plenty of room for a pulley to fit in there without interference now. Still baffles me as to how it had worn through though.

Will be back to let you know the overall success of the mower once pulley is fitted and final checks done. Throttle seemed to be better last time I started it up after some fiddling and bending the metal tab upwards a bit.

Thanks Mick, that is a really helpful drawing, was useful to have when trying to remove the broken shaft earlier. I didn't realise until you posted this that it was a single piece, as by the photos and description I gave, I thought the shaft still on the PTO had an 'end cap' on it so to speak, I didn't realise it was open ended and it was the PTO shaft I could see sticking through it, hence why I thought it was a 2 piece affair that used both holes in the PTO shaft.

Managed to get what was left of the pulley off of the PTO shaft, took a bit of hammering with a punch but the roll pin and remaining shaft came off. You can see in the first photo just how (paper) thin the end of the shaft had become.

Currently in the process of designing and prototyping a pulley, shall let you know how that goes. If my fix works I shall make sure it is very well documented on the internet!

The connecting rod as in the height adjustment rod?

Did the pulley originally slide over that piece that's still pinned in place and then get pinned by the hole that's behind it on the actual PTO shaft.

Current awaiting some more Allen keys to get the blade off (damn Atco making it a size I don't have!) and then I can take the engine off to take some measurements for designing.

I've realised that it seems to be a bit of a mower that's not necessarily designed to be taken apart, I've encountered a seemingly random mixture of metric and imperial nuts (in the same location too!) upon disassembly, and an Allen key for the blade too? Anyway, I shan't be beaten!

Work has been sparse and unfortunately probably will continue to be due to incoming bad weather (and bad news!) this week.

There is no pulley on the PTO shaft as I began to suspect. Just this weird shaft thing that's still pinned in place. The height adjustment lever also looks like it's bent / not fitted correctly as currently there's no way a pulley could've ever been on there without scraping on it (well, actually, that's precisely what the paint shows it's been doing. What I mean is that's obviously not the correct setup).

Looking at a YouTube video which I managed to find of the PTO shaft / self drive mechanism I can see what the pulley should look like. Unfortunately the internet does not seem to hold such part. I'm aware it's a redundant mower with very few parts available.

I may (unless you have any better ideas or sources of these pulleys) try to set the image on screen to scale and get the dimensions for the pulley from it, and try to 3D print a prototype part. Then if it fits I'll see what sort of cost it would be to get a metal one machined.

Going to try to keep costs as low as possible, but still make a reliable repair, as this is a "repair for profit" mower!

The back pulley on the roller side is fine, rotating when the roller does and is all free moving, so that's a small bonus, I guess.

There is currently no drive belt so I'm currently trying to access the mechanism / PTO shaft to make sure it is all in order before ordering a new belt and also find out how I would go about installing it.

I think I'll have another go at setting it tomorrow then now I know that it's not a throttle as such. Doubt it'll make any difference but I'll try move the throttle cable to the other side as well and see if I get any improvements.

You don't by any chance know how to get to the drive belt pulley on the engine do you (do you have any photos of what it should look like?) I've taken off the plastic cover but all that reveals is the rod that alters the height of the wheels. Was thinking of taking the engine off to get a better look?

Problems this time with an Atco Admiral 16SE, powered by a Briggs and Stratton Quantum XTL 50 Engine. I'm struggling to find any documentation / manuals for both the engine and the document online, even YouTube doesn't yield much.

Upon starting the mower, the throttle / speed is adjustable for the first 5 or so seconds, but then the engine runs at a speed which is no longer controllable by the throttle handle. At this point the throttle lever does nothing and the speed of the engine is the same whether the throttle handle is set at the tortoise or the rabbit. I've tried bending the metal tab that the spring sits into (as is shown on YouTube) but this doesn't sort the problem, either the "fixed" engine speed after running for a few seconds is slow(er) or fast(er) and it still cannot be controlled by the throttle control on the handlebars.

I can (and you can see by the video) that the throttle control moves the little metal tang back and forth which the spring sits into, and then this spring goes through the hole in the governor arm. There seems to be very little tension on the spring when the metal tang is bent to set the engine at a sensible speed (when the "fixed" speed is reached after a few seconds of running) so I don't know how it ever would've controlled the speed in the first place.

The photos and the video show the setup exactly as the mower arrived (apart from me bending the metal tang to try and get it to run correctly!) so I'm wondering if some parts are missing? The spring doesn't seem to "grip" onto the edge of the hole in the tang so it just slides about when the throttle is moved, perhaps this is why no adjustments to the speed can be made? I don't know how this could be modified if this is the case.

I should say the carburettor has been  fully cleaned and serviced and the engine is not surging / revving up and down, I just can't sort the speed of the thing!

Hopefully somebody has some good knowledge of this engine and can provide some insight as to how to sort it out - because for once, the internet can't!

Throttle linkage video here: https://youtu.be/da2zuhNAxxs

Cheers, yes, it has been a very enjoyable process. Looking forward to repairing some other lawnmowers this summer.

New plug turned black after approx. 45mins of mowing. Not overly concerned as long as it will continue to spark! However I will try to back off the main running screw next time I come to mow and see if that makes a difference.

Like a sewing machine it now runs!

New gaskets arrived and fitted for the exhaust, carburettor and cylinder head.

Oil changed for SAE-30, was deciding between this and 10W-30, but research showed that SAE-30 was better for old engines so this is what my Suffolk got. When I had drained the old oil out there was frighteningly little (I hadn't bothered to check the dipstick previouslt as the owner had said it was all checked and ready to go). I think the lack of oil could've been restricting the engine causing due to the friction and causing a lack of power, part of the reason why the exhaust sounded really heavy and noisy. The general noise of the engine (exclusing the exhaust) is also now much, much quieter and smoother, probably because there's less banging and clanging now the correct amount of oil is in!

Spark plug changed for a new NGK B2-LM (which is what was in originally but it looked knackered). Not too sure of the black plug issue yet, I'll check and report back after a couple of mows, but with the points / ignition sorted and the engine running so much better and much more consistently I am sure this is an issue of the past. Start-up is now achieved within 2 pulls, mostly just 1, and without choke, so I'm really pleased with this too.

Exhaust gasket changed and seals excellently between the exhaust outlet stub and the muffler / silencer, can't feel any exhaust "wind" from around the joint, so this is brilliant. Exhaust now sounds smooth, doesn't pop, doesn't "putt", doesn't sound rough - it's absolutely brilliant. The entire machine sounds happier, healthier, smoother, quieter, and stronger.

However, once all these replacements had been carried out, I ran into a problem. A terrible scraping and rattling noise coming from the clutch, even when the engine was idling and the clutch shouldn't have been engaged. Great, I thought, I've fixed one noise and now another's started.

So, I unbolted the engine and slid it back, to find one of the clutch shoes stuck open. I could just about shift it back closed, but I couldn't get it to move as freely as the other shoe. Presumably this show was not getting enough grip on the clutch drum to spin it over properly and instead it lost and gained grip repeatedly, causing the horrific noise.

I soaked the gap where the clutch slid onto the pivot pin on the clutch casting itself in WD-40, and wiggled the shoe back and forth as best I could. Eventually it began to free up. So I then began removing the circlip and the spring, and sliding off the clutch shoe. Lots of rust on the pivot pin and inside the mounting hole of the clutch shoe itself. Sprayed it all out thoroughly with cleaner and WD-40, little dab of oil on the pivot pin, and reassembled it all. Degreased it all with some spray and cleaned all residue of oil and grease out. I repeated these steps for the other clutch shoe as well - thought I might as well since I was in there rather than it become a problem in the future. Again, lots of rust on the pin, so I was glad to be able to see to it.

Started it up, works absolutely brilliantly, no bad noise whatsoever. I can let it idle and bring the throttle up, clutch grabs, and the blades spin and the drive can be engaged. I've noticed now as well that when the drive is engaged, the engine no longer slows / bogs down, which was a problem I had had previously - again I imagine the lack of oil and lubrication was the cause of this issue!

It's the sewing machine you said it would be and all the videos on YouTube show it to be. Total cost to purchase and for parts / tools comes to around £60. I am well chuffed and beaming as I write this report up.

Thanks ever so much Mick for all your help, advice and patience - you're an absolute star! 🌟

You know I think you might be right. I knew I needed an exhaust gasket from the various manuals I've looked at, but on inspection of the mower this morning, there isn't actually one there, it's just the exhaust stub going straight into the muffler / silencer.

This might just be the cause! Even if it wasn't the points causing the noise I'm happy they've been checked and the start-up ignition is better.

Think we could be (more than) half way to sorting this out!

Noticed on removing the cowling that the governor spring that goes to the governor arm was in the hole closest to the governor flap - most of the photos I've seen have it in the middle hole so I relocated this when all the work was done.

Removed the pull start mechanism and removed the flywheel by prying behind it with a crowbar, and threading the flywheel nut flush with the end of the crankshaft, giving it a sharp whack with a hammer and off the flywheel popped. No damage done!

Got the quite black-looking points all cleaned up, bought a feeler gauge from Screwfix (https://www.screwfix.com/p/hilka-pro-craft-12700132-32-blade-feeler-gauge/4406r) for just £4.29 and set the points to 0.018" / 18 thou. The measurement was set into the plastic insert in the flywheel (which I later realised that I could've removed instead of taking the entire flywheel off, but I often like to take them off for better access and to clean it all out, so it wasn't really an issue, didn't take me long at all). Reset the spark plug to 0.020" / 20 thou too whilst I was at it, although I shall be changing for a new one (which again I will re-gap of necessary).

Reassembled and did a very quick test fire. Seemed to be running decent and started much better than it ever has done before. Not too sure on the smoothness / exhaust noise issue yet though as I didn't have time to do an extended run.

Awaiting all the new gaskets and plug, so I'll fit these and adjust the carburettor too I'll update you on how that all goes when I get chance.

Thanks very much for the tips Mick. I'll whip off the engine cowling and make sure everything is moving freely. I'll send some photos as well so you can see if everything looks to be set ok (and is original!)

I think I'll have a go at whipping off the flywheel and cleaning the points with some contact cleaner I've got. How would I go about setting them (how would I know if they need to be set?) Toolstation / Screwfix have feeler gauges very cheaply so I can buy one if necessary.

Also, how do I set the throttle cable adjustment? I can turn the nut that will pull the governor arm closer to the operator or push it away, where should this be set?

Thanks for your help

Hi everyone,

Picked up a Qualcast Suffolk Punch 30 a couple of weeks ago off Facebook Marketplace. Can't find any builders plates or info anywhere on the mower, apart from the grass box having a green sticker that says "Qualcast Suffolk Punch 30" on it. I assume this is the grass box it had from new but I've attached photos in case this isn't correct and it needs identifying. However, the petrol tank is on the handlebars, with the Zenith carburettor.

When I went to pick the mower up the owner showed me it starting up etc, and it ran really nicely. However, it was running as fast as you'd ever want to run it with the throttle lever on the handlebars barely cracked open, and there was no way to get it to idle.

So, having stripped, cleaned, and adjusted the carburettor to the manual's instructions (3/4 turn out from fully seated for main running speed screw and 1 turn out from fully seated for the idle speed screw) it will now idle, however, full speed now sounds inconsistent and not smooth at all. It's not revving up and down / surging, but the tone of the engine and the exhaust just sounds, well, awful to me.

The exhaust sounds quite loud and makes 'putt' noises sometimes, feeling the exhaust, the blast of the exhaust gasses against my hand is consistent, but the engine doesn't sound smooth at full speed. It just doesn't sound happy, consistent or how an engine should sound to me. It sounds rough.

I know these engines run beautifully when all tuned up as per dozens of YouTube videos but mine won't seem to be consistent at full speed (a sensible 'full speed', not revving the engine as far as it will go, may I add).


Some things I would like some answers to are (in addition of course to any suggestions and advice you have to get the mower running better):

1) How should the throttle tensioner be set?

2) There is a small arm with a screw and spring that touches the carburettor and then swings away when the throttle is opened. This hasn't been mentioned in any manuals I've read or any videos online. How should this be adjusted?

3) The spark plug on the mower turns very black and carbon-y after a short period of running (was clean before today and a half-hour of running has it looking like a piece of coal!) I understand this is due to the mower running rich, but how do I adjust this (without the mower revving too high?)


I'm ordering new gaskets for the cylinder head, carburettor and exhaust and I'll be changing the oil and spark plug as well. I doubt this will help much as they're not damaged, just very old, and like the rear roller drive belt, look to have been on there for donkeys years!


There's my plea for help, and thanks in advance for all your help. Let's get this beautiful old machine working right again!