RM 2003 125. Rider has just gone up from 85cc and is light (approx 125 lb). I think the bike has had a stiffer rear spring fitted and I cannot set the race sag without the spring being too loose, so I assume it is too stiff for his weight, but how can I tell what spring rate it is, as it is not marked in any way. It is red.
I guess in theory to put a known weight on the spring and measure it's deflection is one way, but can this be relied upon in practice? I just need to know what it is, so I can work out what lighter rate one to get.
Also as a second Q, is there a danger of going too light on the rear spring?. IE If I get an appropraite spring for his small size, which allows me to set the correct race sag, is there a danger of it deflecting too much under the bike/rider weight when landing off jumps?
I guess in theory to put a known weight on the spring and measure it's deflection is one way, but can this be relied upon in practice? I just need to know what it is, so I can work out what lighter rate one to get.
Also as a second Q, is there a danger of going too light on the rear spring?. IE If I get an appropraite spring for his small size, which allows me to set the correct race sag, is there a danger of it deflecting too much under the bike/rider weight when landing off jumps?