Hi all,

Looking for the fork oil quantity for a '83 Jumbo with 38mm Betor forks.

Thanks,,

Your best bet is to message Martin at www.motoswm.com  he will be able to help with anything SWM

Start with 200cc per leg, recommended is around 220.  Which weight to use is personal preference but maybe SAE10 where you are due to it being a bit hotter than here

 

The recommended quantity in manuals is usually the maximum which can give a stiffer action, you can generally use less than recommended. If you start at 200 you can add a bit at a time if you find them too soft

Thanks I'll try your recommendations.

Am I right in thinking the vents on the caps should let air out on compression and suck in when released?

I've never really understood the purpose of those vents or how they're supposed to work.  All I've ever had from them on most bikes with Betor forks is a squirt of oil in the face when the forks compress.

 

I've always closed them off with a blob of araldite, so can't help you with this one.

The vents on one of the fork tubes on my bike has venting issues,  a very audible one when the forks are working. Even after a robust soak and clean its made no difference. Its either the araldite route or.. speaking to the Magical's man in Spain before Christmas, I was led to believe some new ones may soon be available as replacements with a valve you can fiddle with.....

Both caps on mine were letting air in and out which is different to my Bultaco. I pulled them apart and cleaned. It seemed someone had tightened nuts down onto spring forcing small sealing washer to not seal. I backed the nut off leaving room for spring to work and let sealing washer open and close. Works great now, only vents on full compression and let's air in on the up stroke. Think this is how it should work........