It started moving !
Hi all. I bought this mower last year and had it serviced, I pointed out to the service ctr that is wasn't self propelled and I thought it should be. He informed me that it must of been disabled at some point in the past and it couldn't be rectified. But today I went to pull it out of the garage and it locked up, I figured it was a stone stuck somewhere jamming the main roller, but then noticed the blades move. I started her up, and opened the throttle and off it went down the yard with me running after. I caught it before and damage was done, shut it down and it's now gone back to me needing to push to mow. Something clicked in and back out. Can anyone shed any light on this please ?
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What you have is a Mk7 Punch.
What you have is a Mk7 Punch. It has (or should have) a similar dog clutch to the Colt to engage the rear roller drive (the knob sticking out of the rear left of the chain case). Loss of drive may be no more than a sheared Mills pin through the roller spindle and the sudden regaining of the drive could just be a section of the pin temporarily engaging and then shifting out of engagement again. Easily cured with a new mills pin or a home made substitute. A more serious cause could be failure of the welds between the roller shaft and the roller drum - letting go and then grabbing again. If that is the case it needs to be sorted sooner rather than later or it will enlarge the hole in the roller drum end plates making finding the centre and welding more difficult.
https://www.dropbox.com/s/a01eo07xu0js7lj/Suffolk%20Mk7%20Punch0001.pdf…
Hi again, just been and
Hi again, just been and looked this morning and can see what you mean. Guy at the service ctr should of known about that pull out 'cog'... Anyway I took the plate off the side and this fell out. I can't see right off the bat where it's come from, needless to say the clutch no longer functions 
The cog lifts out, and is still sprung though..
It looks like the pin from
It looks like the pin from the roller drive (just like Wristpin said), if you remove the green knob from the rear roller, you should see where it goes. The picture of the pin you posted seems to show a rollpin, it should be a mills pin. A mills pin is a solid pin that is made slightly thicker in the middle of its length by flutes or knurling.
If the guy who serviced your machine, couldn't identify and fix such a simple problem, could I tactfully suggest that you never go near his place again.
All is revealed!
All is revealed!
As Hortimech says, it doesn't say much for your repairers that they could not identify or fix the problem .
If it is a roll or spring pin it is only held in place by being slightly oversize and the chances are that the compressive forces of the drive being engaged are closing it up, loosing its grip and allowing it to fall out. The correct Mills pins have flutes that are slightly oversize and are deformed when the pin is installed making them a nice snug fit.
If you are unable to obtain a mills pin a possible substitute is a Spirol pin - similar to a roll pin but rolled up "Swiss roll wise" : more substantial and exerting more sideways grip.
It would be quite easy to make your own Mills pin using a bit of mild steel rod of the right diameter and then "distressing" an area in the centre with a hammer and cold chisel or even just "glueing" it in with a drop of Loctite.
If the drive pin that you
If the drive pin that you found has fallen out of the hole in the drive shaft you may need to inspect the hole for wear that has allowed the pin to become a slack fit and fall out. When you can see what you are dealing with then a plan can be made regarding the way forward.
Thanks very much for all your
Thanks very much for all your helpful comments. I'll maybe have time to start tinkering tomorrow and will post back when I'm getting somewhere. The pin thats fallen out is solid, not hollow and does have some marks on one side, looks like its been hit repeatedly by a heavy hammer. Anyway, I'll sign owf and chat again soon, thanks for the PDF 
PS. And Wristpin, no, I wont be returning there 
I see that Central Spares
I see that Central Spares have a Mills pin in their catalogue part number 26178 equating to an old Suffolk number of F016L08810; which while not equating to the part number originally listed for the MK 7 Punch (L4978, later F016L04978 ) may be suitable.
If you want a practical test for the state of the hole in the shaft try offering the undamaged shank of a 1/4 " twist drill which should be a reasonable snug sliding fit but I suggest that in practical terms any compensation should be confined to the pin .
Back in the day when Colts and Punches of that era were everyday visitors to our workshop I can't remember loose Mills pins being a problem; a few well positioned diagonal cuts with a cold chisel would raise enough metal to restore a light drive fit. Supporting the end of the roller shaft on something solid is good practice so that the reaction of tapping in the pin is not taken by the roller bearings or bushes.
Welcome to the OLC forum.
Welcome to the OLC forum.
Follow the link to a copy of the operating manual for your mower and many of your questions should be answered.
http://www.oldlawnmowerclub.co.uk/sites/default/files/opmanual/Suffolk%…
Most certainly it should have drive to the rear roller as you found when it tried to escape. A photo of the left side of the machine would confirm it but I suspect that you are having a problem with the clutch that is located on the roller drive shaft. The clutch is a simple dog type clutch that is spring loaded to engage the drive and pulled out and turned to lock it out of drive.
Keep us posted and we shall help where we can