Suspension Nightmare

[BamBamTheAprilia]

Hi having some real issues with my Rex , been riding her at Three Sisters in Wigan ( for those who don't know it, it's a large Go kart track 1.5 kmhttp://www.three-sisters.co.uk/circuit.asp ) I'm lapping at around 1min 6secs and the suspension really is struggling to cope . Hit a bump the it shakes it head and slides similar with the rear , basically it's tying itself up in knots!! I'm 6'4" and around 100kg ( 16 stone in old money ) . I think the issue is that the bike is undersprung and underdamped ( I could be wrong ), if my memory serves me right the springs are set for a 70kg rider . So over to the experts, I guess Cobba will know? Thanks in advance !

[cobbadiggabuddyblooo]

Rebuild the front and rear suspension to suit your weight is the only way around it...
Rebuild and respring your rear shock and springs in the front to start.

[BamBamTheAprilia]

yeah I guessed as much but just nice to have it confirmed . I think I'm going to need to develop deep pockets as I would like more adjustability all round . I think an expensive visit to Maxtons is called for

[Overlord Neil]

BamBam, I've got a near complete R6 front end I was going to swap out on my TRX, if you'd be interested? It off the EB5 (1998-2003) so its conventional forks that look very similar to the original TRX jobbies.

Front forks excellent condition, no pitting or damage (Used)
Allballs seal kit (new)
9.5 KTech springs (new) (I'm 95Kgs and 6'2" so weight should be about right for you)
KTech bush kit (new)
10w fork oil (new)
R6 Front fender in Black (Used)
TRX headstock, will need machining/boring from 41mm (TRX STD) to 43mm (R6) theres plenty of meat there so shouldn't be a problem if you know a friendly machineshop. (used)
R6 front axle (Used)

Will need an R6 front wheel and spacers to complete, having a brutal clear out so looking for £150 the lot plus postage.

[BamBamTheAprilia]

Thanks Neil , just considering my options at present and trying to draw on others experience of how they have improved their rex . I all I can say is Tuesday's ride round Three Sisters was akin to being on a bucking Bronco , chuffin scary !!!

BamBam, I've got a near complete R6 front end I was going to swap out on my TRX, if you'd be interested? It off the EB5 (1998-2003) so its conventional forks that look very similar to the original TRX jobbies.

Front forks excellent condition, no pitting or damage (Used)
Allballs seal kit (new)
9.5 KTech springs (new) (I'm 95Kgs and 6'2" so weight should be about right for you)
KTech bush kit (new)
10w fork oil (new)
R6 Front fender in Black (Used)
TRX headstock, will need machining/boring from 41mm (TRX STD) to 43mm (R6) theres plenty of meat there so shouldn't be a problem if you know a friendly machineshop. (used)
R6 front axle (Used)

Will need an R6 front wheel and spacers to complete, having a brutal clear out so looking for £150 the lot plus postage.

[BamBamTheAprilia]

I just thought I would include some information I have from Maxton Suspension over in Frodsham ( just up the road from me ).
YAMAHA TRX850

FRONT

The front forks on the early TRX850 are a conventional fork. The damping
internals are an old design called a Damper Rod system. The Damper
Rod system does not have any shim stacks; it uses different size holes to
control the flow of oil. The larger the hole, the more flow and the less
damping you have. The smaller the hole the more damping you have.
On this old design the forks do not have any compression damping, only
rebound damping. The standard Yamaha forks do not have much
damping and the fork springs are too soft for most people. This means
that the forks dive under braking and bottom out, then spring back when
let go of the brake.

We supply harder springs for the forks to stop the dive under braking. This
costs £85.00 + V.A.T, the springs are chosen to suit your rider weight.
Unfortunately the original damping system can not be revalved; we throw
the standard internals away and start again with our own damping
system. The damping system we fit inside the forks is a modern 20mm
cartridge system. The cartridge damping system has shims and shim
stacks for rebound and compression damping, the Maxton cartridges are
built to order, so we valve and spring them to suit your bike, what you use
the bike for and your rider weight. The Maxton 20mm cartridges cost
£380.00 + V.A.T.

We also supply an adjustable version of the 20mm cartridge; this has
rebound damping and preload adjustment, this costs £480.00 + V.A.T.

To install either type of cartridge with new forks seals costs an extra
£145.00 + V.A.T.

REAR

The rear of the bike feels hard and has a tendency to kick you out of the
seat on bumpy roads, this is because the spring fitted to the shock
absorber is on the hard side. You'll find if you carry a pillion the bike
handles better. We respring the unit and fit a softer spring measured to suit
your rider weight and to suit what you use the bike for, the cost of this is
£95.00 + V.A.T. We also supply a replacement unit for this bike which is an
Alloy bodied high pressure gas unit and is fully adjustable via a shim stack
system, the unit is built to order so is sprung and valved to suit your rider
weight and what you use the bike for. The NR4 unit costs £435.00 + V.A.T, but
we also make a 4 way adjustable RT10 unit that is mainly for racing or track
days and is £605.00 plus V.A.T.

[Rod.s]

It's been discussed many time before, some like to up tech the bike by fitting modern forks/shock, others like to keep the standard look and fit emulators and rebuild the 15+ year old rear shock.

I'm also 6'4" and 100kg..ish.. and have gone with the rebuilt, emulators, springs and importantly fork oil to suit my weight for the front end. The rear shock is also rebuilt and fitted with a spring to suit my weight. When I follow a standard TRX through the twisties I can see their bike misbehaving while I'm sitting pretty. Also prior to Cobba's 1000HP up grade his bike was no faster than mine in the corners, admittedly he had better brakes which helps.

http://www.trx850.com/phpBB_forum/viewt ... ech#p59461

I still advise anyone who is having issues to…
Rebuild the suspension to suit your weigh and use modern tech, use emulators etc
Ignitech ignition
rebuild the standard carbs with new kits
better brake pads or up grade the callipers/master cylinder
professional engine tune, valves etc.

and enjoy

[cobbadiggabuddyblooo]

Too true, I always enjoyed riding Rods TRX ( there my old emulator forks fitted ) as it just sat where it should through the corners and is very compliant.

With the std CV carbies running sweet meant while my FCR's struggled to find a balance exiting corners under 5000rpm I could never really get him out of my mirrors until we came to a good straight section.
The FCR's really need work on the ignition mapping to get them a lot more responsive under 5000rpm..

[jjmoto]

It's a bit of a trek from the wirral but mct in Stowmarket down here in sunny Suffolk will rebuild your shock & forks then set the bike up suit your weight & riding style. Can't remember the price but they rebuilt the shock on my previous TRX for about £120.

[cobbadiggabuddyblooo]

That sounds about right (around the $200-250 Australian and a little more if you need to re spring )