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Collection, Preservation and Display of Old Lawn Mowers

Dennis premier mk1

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Martin B

Dear colleagues,

I have a Dennis Premier MK1 that I am trying to get back into useful service. It is a 36” but I don’t know how old. Looking at some of the  entries on this forum, I think it might have one of Dennis’s own build engines, has “Dennis” in the output casting.

The issue I am hoping you can help with is this: the cylinder head is held on by 6 studs, three have short and three would have deep nuts on them. Unfortunately the deep nut and stud that the Petrol tank mounts on has been sheared off just below the cylinder head. A “bodge” bracket to  mount the tank to has been made to fit on the other two deep nuts that hold the cowl in place. It  works just looks nasty.

If I can drill out or otherwise extract the remains of the stud, can I get a replacement? Anyone know the thread size of these studs and the stud length?

Can I safely run the mower without that part of the cylinder head being bolted down ?

Thanks in anticipation 

Martin

Forums

Mowing Wurzel Thu, 01/05/2025

Good Day Martin,

Most of the threads on the Premier MK1 are either UNF or UNC.    

UNF being  a  finer thread

 with higher TPI than the UNC

I would have thought there would be a classic  automotive make, like BMC where studs were the same thread's.    Anyway, I attach an extract from the Premier Mk1 Parts Book.

Please send a photo of the Silver VIN plate on the frame side.

The first DENNIS Premier MK1's  were Sold in August  1961, after several years of testing and improvements, with an old Z series serial sequence.    

Dennis in around August 1963  moved the production from Guildford to  Stanhay  of Ashford in Kent,  (a company still going) With  PA,PB or PC prefix serial numbering

Then by in the early 1970's  the Hestair Group, who bought  Dennis Bros. out, sold off the Mower concern to a separate business' called  GODSTONE HOLDINGS,  this was managed by John Dennis,  so still a true Dennis Mower  Company, and still maintaining quality machines, based again in Surrey.  

A lot of  completely untrue stuff has been unfairly written on this chapter in Dennis's story.   Dennis "GODSTONE" being the last to use the "E" type 597cc engine, which they were still using in 1975.......... a few years later, overseas built  engines, cheaper in price and quality being offered, (n my opinion.)  

 

 

So on the cylinder head; these engines are low compression,  and the cylinder head is of  cast iron and weights more than you think when going to pick it  up........  but please ensure all studs are tightened up before running.

We look forward to seeing some photos......

Martin B Sat, 10/05/2025

Many thanks for the replies and guidance. 
I cannot get the stud out so it will have to stay as is for the time being. It looks like it has been sheared for quite a time, visible stud is rusty. I have revised the tank bracket to fit under the cowl, looks much better.
Having given the carb a good fettle and changed the oils and fuel, she is breathing once again and sounds fantastic, even though there is a little rattling from the prop shaft and various drive chains. The sheared stud does not seem to be a problem.

As for the grass box, i have had to reinforce the split and missing parts of the lip, re painted it looks great and is very sturdy.

She is ready for her first proper run, which she will get in a few days.

Will put some more 

pictures up soon.


Thanks for your support

Martin  

Martin B Sat, 10/05/2025

Guys,

Many thanks for the replies and guidance.

I cannot get the stud out so it will have to stay as is for now. It looks as if it has been broken for some time as the visible part was rusty prior to my drilling it. 
I have revised the tank bracket to fit under the cowl, it looks so much better. 
I have reinforced and rebuilt the lip to the grass box that was badly damaged and that is serviceable again.

I have cleaned and given the carb a good fettle, changed the oils and given her some fresh fuel, and after some tweaking she runs again and sounds fantastic. There are some rattles from the prop shaft and various drive chains, but otherwise all seems good. The lack of the sixth cylinder head bolt doesn’t seem to be a problem.

So just needs a test run now, which I will do in a day or so

Here is the only pic I have at present. Will take some more and post soon

Thanks again for your support

sorry about that the duplication, didn’t think the first version uploaded and I can’t see a way to delete an entry 😂
Martin

 

Martin B Mon, 12/05/2025

Thanks for the help so far.

Beginning to think I should try harder to get my broken stud replaced, but fear that to do so I may need to strip down the engine, which would likely involve a head off and perhaps more sheared studs.

Before I contemplate that I would appreciate your help on identifying what engine it is I have so I can be looking for replacement studs and head gasket etc. it looks like the parts image as supplied by Shed 14.

I attach an image of the mower plate and a  couple of general ones.

Can I also ask about the magneto? Does this look as if it is on the correct flange to you? The lugs on the impulse starter are only partially engaged on the drive and there is a lot of play and a gap behind that drive allowing that cupped washer to float leaving the bearing exposed, just doesn’t seem right.

Any thoughts would be appreciated, thanks again for your support 


Martin