Yamaha TRX850 Enthusiasts Forum

After digging through a pile of notes I had on researching options for std TRX. Forks I found these on modifying the std .5kg/mm springs by chopping off a couple of coils. Apparently if you can cut upto 4 coils from the std springs but any more the spring will get spring bound and bottom out.. This will bring the rate upto 8.5kg/mm so I figured I have some spare std springs in a box and another pair of std Trx forks lying around so let's see what result I get.. No loss if it doesn't happen as per my notes as they are only sitting gathering dust. The spare forks I've stuck on the bike have std springs in them also and the ones i just removed had emulators (plus choice of .8 and .9 springs) so I can gauge the result between the three.. Got a call that my modded R1 forks with gold valves comp and rebound and resprung are waiting to be picked up but it will be the end of the month till the billet trees are ready. This gives me something to play with for a few days before the motor is in for a rebuild... This may be a cheap alternative than forking out for new springs if you weigh around 80 to 90 kg

This is a great mod for uprating fork springs and one I've used on a few of my bikes.This type of mod used to known as a "demon tweek" alas the name was hijacked by a business for it's company name.
The closely wound springs are the lowest rate,so I take these ones out and replace with a poly pipe spacer tube to establish the new correct spring preload. The advantage of poly is that it's easy to work when forming the helical seating for the cut spring.

John Bradleys superb books "The Racing Motorcycle- A technical guide for constructors" Vols 1and 2 give the mathematical equations for calculating spring rates from the spring wire gauge,length and so on. Formula also given for shortening springs. Without doubt the best motorcycle engineering books ever published.

Good luck with it Brian.


Mark.

Thanks for the finishing touches on the explanation to this theory Mark..

80 to 90Kg's....no one if that fat

Yeah, I know what you are sayin rod .... I'm hovering at 62

89kg and counting me, gotta feed the bear.

Time to feast on them salmon hey Mince... well the spring mod ain't gunna happen now as when I pulled them out it seems both pair of springs are .7 linear.. So surprise surprise obviously the 0z models come out with .7springs linear springs not a progressive . So prob fine for on the road for you fly weight 67kg type.

MEEEEEEEEE

If you have your R6 shock rebuilt/revalved you prob find the rear spring would suit your weight maybe a touch hard but with the .9 spring on it.. Got a price of around $220 at MPE for a rebuild/revalve to suit...