What did you do today? Cobba's rebuild

[coxylaad]

have you got a summary somewhere or a handy calculator

At some point I plan on building myself a set of headers, it would be nice to put some science behind it.

[dandywarhol]

have you got a summary somewhere or a handy calculator

At some point I plan on building myself a set of headers, it would be nice to put some science behind it.

On that page -
http://www.maxracesoftware.com/

[cobbadiggabuddyblooo]

Handy link with Yamaha multipin connectors

http://kojaycat.co.uk/epages/950000457. ... y_Unsealed

[cobbadiggabuddyblooo]

http://www.dymagsdirect.com/sb5-superbi ... nformation

[cobbadiggabuddyblooo]

Handy link on the equation to working out inlet and exhaust pipe lengths.

https://www.engr.colostate.edu/~allan/f ... page7.html

[coxylaad]

I've saved that to my favourites.

One day I will design and build an exhaust using some science.

[cobbadiggabuddyblooo]

Handy info when you scroll back on previous chapters too.

[coxylaad]

Information on Ohlins rear spring rates.. Ohlins shock springs are generally a 57mm spring diameter
Fitted and sprung to weight, mine is a 01092-34/100 L0613

01092 refers to the unladen spring length
01092 is an Ohlins specific coding for a 170mm spring length

-34/100 is the spring rate
-34 is an Ohlins specific coding /100 is 100Nm (10.19 kg/m usually noted as a 1.2 kg/mm)

L0613 is the production batch number

Spring deflection is around the 80mm on my spring.
Preloading the spring is proportionate to this value.
if 17mm pre load is added to the spring this will reduce my travel to around 63-65mm which is the stroke of the shock. (shock should bottom as the spring binds)
So if say 22mm pre load is added, it impacts on the actual shock travel because the spring will bind before the shock compresses to the full stroke and reduces your rear wheel travel.
If you have an incorrect spring fitted, you may get your rider sag set ok with the spring fitted to your bike but your free sag numbers will be out due to either your shock bottoming out (too stiff spring before bind) or your spring binding before shock bottoms out. (too soft a spring)


You can see from the photo of the original spring fitted when I purchased the shock was too light being a
01092-21/75 498
Same spring length by the first part of the coding but an Ohlins 21 which is a 0.75kg/mm
The 498 is the production batch.

How do you find this spring rate for track riding cobba?

I am going to investigate what my rear spring rate is, I believe its a stiff spring but I also have 170mm dogbones on the bike which will increase the rising rate. but then to counter that my swing arm is about 20mm longer. I want to make sure everything is spot on before my track day on 23rd.

[cobbadiggabuddyblooo]

Go to a suspension specialist because you have to many variables .
Your using the std relay arm so shouldn't need too much tweeking.
They will look at how the overall bikes wet weight, swing arm length and angle from dog bone choice , the sprocket choice, power output and of course your own body weight because they all will impact on the set up of your shock.

[coxylaad]

There's no one near where I live unfortunately.

Other than a slightly longer swing arm there is not much difference between your bike and mine. Is the over swing arm the standard length?

all my linkages are stock, shock length is stock, dog bones are 170mm.

what is the stock spring rate on the TRX?

[cobbadiggabuddyblooo]

Spring rate is dictated by the bikes and your weight.
Yes Over swing arm is the same length as the TRX.

[coxylaad]

yep, totally agree, and I have chopped a hell of a lot of weight off the back.

do you know what the stock shock spring rate is? I cant find that info anywhere.

on a side note isnt it cool with modern technology that we can have a conversation with you sat in australia and me in the uk

[cobbadiggabuddyblooo]

Stock Spring rate is a 0.9. but TRX WET WEIGHT IS 209 KG.. (70kg rider )

Yes agree that technology now days has opened the world to itself and its constantly evolving.
Just need to look at the electronics on your new beast compared to the original host TRX it's fitted into.

[cobbadiggabuddyblooo]

https://www.cycleworld.com/2015/08/11/a ... leaded-gas

Great read on the chemical reaction taking place to stop detonation...

Finishing the last of the prep to put in the spare motor that came out of a Japanese/grey import TRX.
All valve clearances are within spec and the shim values on inlets are 192’s or 190’s which tells me either it’s a later model Japanese import or a 95/96 model with low k’s that hasn’t had any deformation of the inlet valves yet.

Fair build up of carbon on the pistons but I can clearly see the hone markings on the bore with no glazing. I chose to dismantle the MLS head gasket that was on this motor and remove the centre shim and clean off the sealant from the 2 outer sheets of the gasket.
I then recoated the 2 outer sheets and chose to leave out the centre shim and put the head back on the motor so should up compression a tad close to 11:1.
Plus in theory MLS gaskets can often be re-used so only one way to test this theory...

So fingers xx I’ll find time to fit the motor next week.

[Racer-unk]

so Cobba, you gonna reverse engineer the exhaust cam timing for piston position to be at 120 Degree for the given pipe intended to be used......
So currently you will be building the engine I need......