Mower belt problem

[Ron19]

Can anyone help please? I need to fit a belt to the side of the grass collector on my Westwood mower. Not the one from mower to collector, but the one on the collector itself. A 36 inch belt is too big, I can fit it to the pulleys and then slip it over the tensioner but then the top pulley just turns and the belt does not control the lower one.
With a 35 inch belt I can not get it over the two pulleys at all. Nothing in the picture looks as if it could be adjusted.
Thanks

 

[mechanic mark]

westwood mower parts - Google Search

Try looking at website above

 

[Ron19]

westwood mower parts - Google Search

Try looking at website above

Thanks very much thats a great resource for a Westwood machine.
My problem is more basic, I have a belt the same size as the one which broke but have no idea how to get it on. The next size up is too large to make the driving pulley turn the next one, it just spins around.

 

[mechanic mark]

WESTWOOD 2 BELT SET POWERED GRASS COLLECTOR T1200 1984 - 2000 we1464 & 1414 | eBay

POWERED GRASS COLLECTOR. GENUINE PIX BELTS TWO BELT KIT FOR WESTWOOD POWERED GRASS COLLECTOR Westwood S1100, S1300, S1600, T1200, T1250, T1600, T1800 & D1200. 2000 Series, 1010 & 1012 LASER L80, L95, L110 & L120 1 x PTO BELT 1 x INTERNAL BRUSH BELT THESE ARE HIGH QUALITY BELTS THAT WILL...

www.ebay.com

OEM Belts for your collector.

 

[mechanic mark]

BELT ROUTING DIAGRAM FOR WESTWOOD GRASS COLLECTOR - Google Search

 

[bertsmobile1]

If it is the correct belt and it is not tight then the belt run is wrong
Have a look on the underside of the cover as it will often have a trace of the belt on on it from debris being flung off the belt
It can really only go on 2 ways and you should need to move the tension arm the limit of it's travel against the spring in order to get the belt on

 

[StarTech]

Okay this should be what you need as the pulley in the middle appears to be a flat idler.