Lawn mower help urgently required please!

[Slime]

Hi all
I frequently use a Yamaha YLM342 but the chain keeps popping off as it's very loose.
Does anyone know how to tension the drive chain ............................. or is there a tensioner missing?
I can find absolutely nothing on the internet.
I hope the photo of my floppy drive chain makes sense of what I'm talking about.

Many thanks,
Slime

Oh, the plastic cover broke off a few years ago.
You can see a tiny bit left around the screw that held it in place.

 

[Burnerman]

Unfortunately you won't get spares for this one......
I can't see any sign of a tensioner system but there must have been some method - they usually have a white nylon slipper. Maybe there has been something connected to that lower bolt hole.
Do check that either of the rollers aren't adjustable to pull the chain tight that way though?
John

 

[lostinthelight]

I can only think of two ways of extending this one's life.
A bolt/stud in the bottom hole with a cog or bearing on it to straighten the run of the upper chain, or try and remove both cogs after removing their retaining circlips and then remove some links to shorten the chain.. As John says ,spares are non existent unless you can pick up an old one. The last one I had I someone came a long way and gave me 65quid for spares.

 

[Stivino]

I wonder if the tensioner was incorporated in the missing cover? As there seems to be only one screw holding the cover on, the three holes might have been to accept moulded locators in the cover.
ebay
you tube

 

[Burnerman]

It looks like an endless chain, I doubt if there’s enough slack to knock a link out and a new chain could sort it, but I guess the sprockets will be hooked too.
I do look after one of these but haven’t seen it for years and it’s miles away!
John

 

[lostinthelight]

There doesn't look too much wear on the sprockets.
Chain repair/shortening:

Adjusting Roller Chain Lengths With Offset Links

What is a roller chain offset link and how is it used to lengthen chain assemblies? We have the answers.

www.bearingcentre.net