SWM Jumbo

[mattylad]

I have dragged my bog standard Jumbo from the depths and have a clean slate to play with.

It is totally stock and runs the case reeds.

The footrests do not have a return spring and I cannot see how one is fitted.

It is also fitted with SWM (Betor) 35mm forks, it is my understanding that the first bikes had 38mm. Were they changed at the factory during the last days?

Overall the bike is in excellent condition so I assume they are standard factory fitment.

What other modifications would you recommend?

gearing, carb (26mm perhaps), exhaust system, ignition timing.

Thanks for your help

[martinm]

Hi Matt

The springs on Jumbo footrests are usually mounted on bolts behind the back edge of the rest. However, one of the best mods is to take them off and replace with a set of modern wide footrests....whether you change the postion of the rests is up to you. There is a trend for lowering and setting them further back, with my Jumbo it felt 100% better just having the wide rests in the same position as standard.

Forks were 35mm on the early models, and 38mm later. Best mod for your 35mm's is to find a set of Marzochhi yokes from an early SWM (Fantic 200, Armstrong, etc can be used although stem size is different.) This is a straight swap for the Betor yokes and places the handlebars a lot further forwards improving the steering.

Reeds were fitted on the first models and removed on the later versions. They reckoned that the motors with reeds were very firey and removing them improved grip and made it easier to ride. You will need a blanking plate and a carb rejet if you want to try it, I can also send you the jetting specs.

Cheers

Martin

[monoped]

Matt, I think you will find that the 38mm forks were fitted on the very last production bikes circa 1983/4. The footrest design was al little unconventional, but they did have springs fitted as standard.