Don't suppose you have a video of posted somewhere, like I said it's a job to say what it is without hearing it.

You seem to have covered most of the problem areas.  I guess the next step would be to check the valves, maybe give them a grind in and reset the gaps. Also make sure a valve seat isn't moving about when it's running.

Hi amatureleccy, and welcome to TGMF.

I have scrapped so many of these over the years, now wishing I had kept them.  Do you have any mower shops local to you, they might just have a scrap machine with this engine on for a few quid, or they might just be glad to get rid of it.  No guarantee the carb will be good though.

Regarding your original question, I haven't tried putting a primer version on one myself, they tend to be more of the fixed speed setups rather than having a throttle.

Hi Jimmy, and welcome to TGMF.

From your description it's rather difficult to diagnose. These engines are notorious for diaphragm issues, and sometimes even after changing the diaphragm and gasket the issues persist.

Does it belch black smoke?
Does the engine bog down and run rough when moving the machine backwards and forwards?

If yes to either of those questions you could try fitting two gaskets on top of the diaphragm instead of one.  In fact if you still have the old gasket and it is in good condition you could put that on top of the new one.

Thanks for the info.  Did you change both belts, or just  one of them?  Also I would suspect that the Variator pulley between the two belts is not doing it's job properly which is quite common on these machines.

Inside the Variator pulley there is a couple of tin rings which have little tabs on them to cover the plastic ramps which push the pulley halves together and keep the belts tight.  These little tabs tend to break off. Quite often when the spinning the Variator by hand with the belts removed these broken tabs fall out.

Variator pulley Part number 411001 (I will warn you though, they are not cheap).

All this is assuming you've changed both belts, and that the gearbox is good and clutch inside it isn't slipping.

Mally, welcome to TGMF.  Sorry for late reply, you probably have made a decision by now.

These machines are quite cheaply made like a lot of modern machines, the one's I have seen have been ok though to be honest. Had a few with gearbox issues, but not sure if that was caused by the customer not setting it up from new, or if they were just faulty.

If you went ahead and bought it, I would make sure the drive cable is kept adjusted and lubricated to extend the life of the drive system.

Yep, I see the vid now.  Well all I can say is it's still got a fuel issue. So anything's possible.  My bet is still a carb issue.

I have an example of a machine where the customer sent in a machine he'd tried to fix, new carb fitted and it wouldn't run.  This video shows his old carb which I cleaned and refitted. Gave him his new carb back in a bag. 


https://www.youtube.com/shorts/pAwoG9C88No

Forgot to say, I can't view the video of the mower unfortunately, it just says this,

"Dynamic Link Not Found
Short URL (https://photos.app.goo.gl/zLUyKN5RkH) not found

If you are the developer of this app, ensure that your Dynamic Links domain is correctly configured and that the path component of this URL is valid."

I can safely say it's not the governor, it would just rev its self to death if set incorrectly, or hardly rev at all if set the other way.

The fact that it's surging means the governor is working. 

Quote from: Paul B on May 19, 2024, 09:22:38 AMThat's really helpful., thanks. That makes a lot of sense. I should have sought advice before buying the Suffolk punch. I will have to work on getting the ground to the right quality to be able to use it properly.

That would certainly help. Just getting the grass down nice a short should also help.  You need to cut more often with this type of machine just to keep it at a a decent height.

Quote from: Paul B on May 19, 2024, 09:22:38 AMThe guy I bought it from did say he later found a plastic front fairing for the mower, I will of course collect that. However, do you thing that would improve it?
Many thanks again.

Do you mean the Grass box? If so it will probably make matters worse as it will add some weight to the front. Instead of over the driven roller.  I'm sure you'll be fine once the lawn is levelled a bit though. 

Ok, so the rear roller is still turning but slipping on the grass?  Either the machine is bottoming out over the bumps, or the grass is just far too long for this machine. 

Cylinder mowers really don't like long grass and undulating surfaces, they tend to just fold it down instead of cutting it. They did make a long grass kit which basically removed the front middle rollers and just left the two small outer ones in place, but even then if the grass is too long it will struggle.

We would normally recommend a four wheeled rotary mower for this scenario. Even some rear roller rotary's struggle on bumpy surfaces.

It's definitely starving of fuel then, or it has a air leak between carb and engine.

Is the fuel fresh, I mean freshly purchased? It goes off so quickly these days.  I would still check the flow from the tank, making sure the cap isn't causing a vacuum and stopping the fuel.

And also make sure all the gaskets are correct and fitted the right way around as this can cause problems.

Hi Taz, and welcome to TGMF.

Sounds like it still has a carburettor issue. In a lot of cases where the engine hunts / surges it's the idle circuit of the carb that causes it. The little jet in the top of the carb in your case. 

Where did the replacement carb come from, was it a OEM one, or a generic one from Amazon or ebay etc?

I ask because although some sites state they are compatible with certain models, and to a point this is true as far as the fit is concerned, that doesn't mean it has the correct size jets inside for the size of the engine.

Normally when a customer has changed the carb and brings it to me for repair because it still won't run correctly I ask them for the old carb and work on that. At least you know it's right for the engine.

Check the fuel flow from the tank, pull the pipe off the carb end and check. And while you have the pipe off, make sure the fuel cap is letting air in, so the fuel can flow out. Tighten / loosen cap and check flow from the end of the pipe.

I'm going to guess a little on this one, because I'm not sure of the age and model series you have.  I reckon if you remove the four allen screws from the side cover, you'll find the adjusting arm on the front roller frame has slipped down behind the plastic adjuster plate. 

While in there you should be able to see why it's not driving, probably pink gear behind the pulley has failed.

Some images would be handy if possible.

Hi Paul, and welcome to TGMF.

No worries on the first post thing, this intro board isn't compulsory but here should you wish to say hi. 

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