Yamaha TRX850 Enthusiasts Forum

No here is the challenge with the R6 rear wheel in the std TRX swingarm.
When the R6 axle with sliders arrives I'll look a the option of modifying the std swing arm to a 28mm axle, otherwise I'll have to make another axle sleeve from 28mm diameter to 20mm
1....
To get the wheel central I need to remove 8mm from the outer edge of the hub which houses the dust seal.
( I have 9mm to play with till the bearing)
This will allow me to put a top hat spacer in on this side and and I need 3mm to get the wheel centred and the other 5mm removed will give the same 5mm swing arm clearance from the hub as the std trx rim.


2....
Next task is remove 6mm from where the sprocket bolts on like I did with the 750 5.5" rim sprocket carrier.
The offset on the hub is the same and I'll need to make sure when the studs are put back in place I have a 5mm more clearance.


3....
Now I need to work out a caliper set up and as you can see in the photo, the R6 disc runs 20mm closer to the centre of the rim than the TRX and YZF750 wheels.
My 220mm caliper set up from the black bike won't work as the caliper will clip the spokes due to the disc placement 20mm closer to the hub centre.
You can see in the photo the disc is inline with the rim and tyre.

Dammm... R6 axle sliders fit perfectly in place of the std TRX axle sliders but the R6 axle is 30-40mm too short...
So contingency plan
I’ve got ahold of some 28mmOD / 20mmID stainless tube and I’ll cut that to length and make an axle sleeve.
I’ve been looking at single piston Calipers with a passive brake pad on the inner side as there isn’t the spoke clearance to run an active inner piston on the caliper. ( approx 30mm is a minimum spoke clearance ) I’ll look at making an alloy under slung bracket and torque arm like std.
This may take a month or so to gather parts and make templates and in the mean time, I’ll complete the front wheel and fit that over the next couple of weeks.

Front wheel fit up was completed today and big thanks once again to Rod for the 2-3 hrs slaving over the lathe to make up the spacers and axle sleeve.
I have ordered new tyres and will fit up the front rim early next week. Stuck to the Dunlop’s and trying out a set of Q3+
I ‘ll give you some feedback on the suspension changes next week too.

First ride tomorrow on the new suspension set up.
Thundercat forks with retrofitted cartridges comp/ rebound and progressive springs 0.65 to 0.9.
Fork brace
06 R6 rear shock with revised shim stack ( stiffer start/ softer mid/ ) and more rebound damping plus revised ride height with 5mm shorter dog bones.
Still running the Std rims and 120/60 160/60 Pirelli Angels
I’ve set this one up for the road so a little more plush than the black trx for the track.
I’ll jot some notes in later tomorrow

BASE SETTINGS FRONT SUSPENSION
0.65-0.9 progressive spring
Q3+ 120/70 R6 rim 32psi cold

Rider sag.... 38mm
preload....... 3 lines
Rebound..... 8 out
Comp......... 9 out

BASE SETTING REAR SUSPENSION
0.98 spring
Angel GT 160/60 trx 5” rim 37psi


Rider sag....
preload....... 4
Rebound..... 11 out
Lo comp...... 11 out
Hi comp..... 11 out

..................................................................................
Good feedback and damping for street and medium pace under power.
Heavy brake , hard pace could do with more preload/rebound/comp on front.

cobbadiggabuddyblooo wrote:First ride tomorrow on the new suspension set up.
Thundercat forks with retrofitted cartridges comp/ rebound and progressive springs 0.65 to 0.9.
Fork brace
06 R6 rear shock with revised shim stack ( stiffer start/ softer mid/ ) and more rebound damping plus revised ride height with 5mm shorter dog bones.
Still running the Std rims and 120/60 160/60 Pirelli Angels
I’ve set this one up for the road so a little more plush than the black trx for the track.
I’ll jot some notes in later tomorrow

Let me get this straight, we are talking here about the white one, right? The bike that you would keep completely stock original?

Yes, well Robert after taking it for a ride .... mmmm the suspension short comings really shined through and well it started the ball rolling didn’t it....
The plans are to keep it looking cosmetically stock now and why the RSU Thundercat forks and std dash with GPS speedo fitted into it.
It will take a trained eye to notice the suttle differences like 5 spoke instead of 3, forks and revised rear shock.
Love the TDMR’s and a little more responsive than the FCR’s.
I’ll replace the current YEC 6 speed motor with the motor I rebuilt out of the black trx as I’ve revised the cam timing on the motor and reduced overlap to give it a little more dynamic compression and lower / midrange torque and better suited for the road.
The close ratio box is a pain in the arse on the road running from 2nd to 5th where I’d be 2-3rd gear on the std trx 5 speed.

Yeah but it's a 6 speed

A close ratio 6 speed...
But it’s worth in once you get in the mountains just a bit of a pain in suburbia.

Note to self
2.3/2.3

Lift in/ex TDC

cobbadiggabuddyblooo wrote:Note to self
2.3/2.3

2.3/2.3=1

Today I got stuck into the motors and spent 2 hrs pulling both top ends off my motors.
Seems the 6 speed 870 motor has Cosworth pistons fitted.
So I’ve emailed them with the job number stamped into the piston to get some specs on them.
They weigh only 6 grams heavier than the Arias Pistons but I can easily get them to the same weight by removing some material from the pin.
I’ll place the ceramic coated top end , 878 Arias piston, head and cams onto the 6 speed bottom end.
Both motors are fitted with Carrillo rods so looking forward to finishing off things tomorrow.
I’ll put the Cosworth pistons and cams onto the 5 speed for the street but swap the Slipper clutch to the 6 speed motor.
Just waiting on an email from Cosworth on some piston specs.
I need to get this completed before Thursday as I’ll take the keys for the new house and that will be my focus for a while.

Managed to pick up the R6 rear wheel that I had re engineered to fit into the trx swing arm.
Much like the yzf 750 wheel I had modified many yrs ago, 6 mm was removed from where the sprocket bolts on for alignment.
28/20mm axle sleeve and new caliper and mount made with wheel spacers and sits perfect.
Now I need to find the time to remove it from the spare swing arm and onto the bike....
I thought next time I come up yo the new house, I’ll take a video of the run up the mountain.
It’s a short sprint of only a couple of minutes but a fun one....

This sounds like a good mod.
Could you post up the dimensions of the parts you have had made.
I'll warm up the angle grinder.

Here is a great explanation on resonance and will give you a visual perspective on how exhaust tuning and pulse works to give you gains.
This also relates to tuning of your airbox and timing the resonance to the valve overlap.
When you see how the flames interact with music remember frequency is a number of revolutions just like a motor.
You will see at certain frequencies the gains in the flames so you have the length correct so that gain happens within your combustion chamber, more heat = more power.
Enjoy....
https://www.youtube.com/watch?v=dihQuwrf9yQ