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#1 PICARD

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Posted 08 December 2018 - 05:13 pm

Don't know if I'm missing something here, but, I've dismantled the front forks for seals and a clean up, and there appears to be a short spring in the lower leg that is not included on the exploded diagram on wemoto etc parts lists?? 03 900 btw. Can be seen here on the piston assembly. What's going on??

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#2 Apache

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Posted 08 December 2018 - 09:09 pm

Can't help you with that Picard but I'm on with some stuff on 4TX's and so far 3 items (minor cosmetic stuff) have been omitted from the Yamaha assembly listings. I assume they come with whatever they're attached to as a single item. Might be so with that piston assembly / spring ...

#3 dablik

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Posted 08 December 2018 - 09:15 pm

Your right Pete, it's omitted on the parts list ? but think i would be leaving it in matey, odd eh.


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#4 ramo

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Posted 08 December 2018 - 09:48 pm

Chinese copies, they all have em  ;)



#5 ramo

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Posted 08 December 2018 - 09:55 pm

Its i the workshop manual Pete, is it called the rebound spring or summat?

 

I changed my fork oil yesterday  :good:



#6 Hombre

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Posted 08 December 2018 - 10:24 pm

Snap!

 

My 2004 9er

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#7 dablik

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Posted 09 December 2018 - 12:06 pm

Its i the workshop manual Pete, is it called the rebound spring or summat?

 

I changed my fork oil yesterday  :good:

 

He's right Pete, just pulled my manual out form where it was hiding and it show's the spring clearly as part of the damper rod ie no individual parts number furrit :good:

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Edited by dablik, 09 December 2018 - 12:23 pm.

Bigred mk1 R1 Calipers- Braided lines- Givi wing rack-Crash bungs- Hi vis bullets-PR2's- and a hoot to ride.

Quad 900 Silver Laser duo tech pipes-Scott oiler-Engine crash bars- Radiator mounted see me ring LED's-Datatool system 3 alarm -Centre stand- Extender fender-Renthal bars-Handle bar risers-Mirror extenders-BMW GS Handgaurds-Acumen uprated horn & Nautilus-Stainless steel Radiator guard-Givi wing rack-OEM screen-Yammy touring screen-MRA Vario-MRA Double bubble cut down for fast as fk riding-Tiger screen-Tank protector-Stomp grip panels-Optimate lead   Gone to Heaven  :sorry: 

 

1991 MK1 in need of some TLC watch this space   :) Sorted and on the Road Mick  :P  :P it's the bike that Jack built  ;) Gone to Heaven  :wub: 

 


#8 PICARD

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Posted 09 December 2018 - 12:26 pm

Thanks chaps....should have looked in the manual myself ..doh. Will Defo be going back in. Had a slightly weeping seal, coincidently the same side as a torn gaitor, which was the intended original job...oh well, needed at mot time anyway. Thanks all.
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#9 dandywarhol

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Posted 10 December 2018 - 09:42 am

It is essential - it's there to stop the forks crashing against the lower leg on full extension.

 

I think it's also the "clicking" noise occasionally experienced and folks blame the main spring for being weak


Edited by dandywarhol, 10 December 2018 - 09:45 am.

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#10 PICARD

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Posted 10 December 2018 - 02:20 pm

Thanks dandy. I've measured the main springs and there's hardly any loss of length. Thought about upgrade but I'll never out ride the standard set up! No way was I ever going to leave any part out, just couldn't explain why it was missing from suppliers drawings. Sorted now...Thanks again.
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#11 Matlock

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Posted 11 December 2018 - 10:25 am

I'm rebuilding my XTZ750's front forks at the moment and with the exception of the adjusting rod, they look very similar to the TDM900's internals. The Tenere was launched in '89, the last TDM was built in 2013, I think. So no significant front fork development in 24 years on Yamaha twins.  :dunno:


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#12 dandywarhol

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Posted 11 December 2018 - 12:17 pm

I'm rebuilding my XTZ750's front forks at the moment and with the exception of the adjusting rod, they look very similar to the TDM900's internals. The Tenere was launched in '89, the last TDM was built in 2013, I think. So no significant front fork development in 24 years on Yamaha twins.  :dunno:

 

With the exception of the Mk1 TDM which used a proper cartridge stack damping system.  :huh:


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#13 the969

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Posted 14 August 2019 - 02:03 pm

Those prog springs...... were they standard?  Looking at the spec on the JBX site maybe not? 

 

Not a massive fan of progs, but it would be great to find out if they were in fact used on any or all of the TDMs.  I know mine haven't been touched so it would be useful to find out what's supposed to be in there before dismantling the bastards.



#14 TKH

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Posted 14 August 2019 - 03:46 pm

I've found this a few time with my TDM where parts are sold as an assembly and you can't normally buy parts of that assembly. Another example is the rear brake caliper. You can buy aftermarket refurb kits.



#15 fixitsan

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Posted 14 August 2019 - 05:23 pm

Those prog springs...... were they standard?  Looking at the spec on the JBX site maybe not? 

 

Not a massive fan of progs, but it would be great to find out if they were in fact used on any or all of the TDMs.  I know mine haven't been touched so it would be useful to find out what's supposed to be in there before dismantling the bastards.

 

 

They're dual rate, which some people call progressive. They're definitely not single rate/linear springs

 

Hyperpro 'progressive' springs are also dual rate, not progressive. EG https://www.ebay.co....pwAAOSwt0pc59j0

 

The Ohlins upgrade springs are linear/single rate (not progressive and not dual rate)  EG https://www.ebay.co....HIAAOSwVHdaoohq

 

A true progressive spring has a constantly changing coil pitch, between tight turns at one end to the most open coils at the other.

 

This might help - https://cdn.webshopa...-by-wilbers.jpg


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#16 the969

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Posted 14 August 2019 - 05:43 pm

 

 

They're dual rate, which some people call progressive. They're definitely not single rate/linear springs

 

Hyperpro 'progressive' springs are also dual rate, not progressive. EG https://www.ebay.co....pwAAOSwt0pc59j0

 

The Ohlins upgrade springs are linear/single rate (not progressive and not dual rate)  EG https://www.ebay.co....HIAAOSwVHdaoohq

 

A true progressive spring has a constantly changing coil pitch, between tight turns at one end to the most open coils at the other.

 

This might help - https://cdn.webshopa...-by-wilbers.jpg

 

 

Yeah cheers I get all that, I've had progs and linear, and I've changed from former to latter on several bikes. Just wondering if Im going to  have to do it again.

 

Interesting thing about progs / dual rate is that back in the day manufacturers bunged em in one way round and many now go in the other direction, ie more resistance at the bottom rather than the top of the stroke.

 

I just prefer knowing what I'm going to get 24/7.  Might try and pick up correctly rated linears (for 175 lbs in my case)  for the 4TX, anyone else done it?



#17 fixitsan

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Posted 14 August 2019 - 05:55 pm

 

 

Yeah cheers I get all that, I've had progs and linear, and I've changed from former to latter on several bikes. Just wondering if Im going to  have to do it again.

 

Interesting thing about progs / dual rate is that back in the day manufacturers bunged em in one way round and many now go in the other direction, ie more resistance at the bottom rather than the top of the stroke.

 

I just prefer knowing what I'm going to get 24/7.  Might try and pick up correctly rated linears (for 175 lbs in my case)  for the 4TX, anyone else done it?

 

 

Yes the tighter coils (softest part) seem to be preferred at the top. I've chewed this over a bit and believe that with the tighter coils at the top there is less oil being displaced by the spring itself, as the forks compress and more of the spring is submerged in the oil. (which in turn affects the air gap at the top)

 

I wouldn't have thought it mattered too much but then again we set the oil level to a relatively high degree of accuracy, so maybe some truth in it after all


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#18 the969

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Posted 14 August 2019 - 10:13 pm

 

 

Yes the tighter coils (softest part) seem to be preferred at the top. I've chewed this over a bit and believe that with the tighter coils at the top there is less oil being displaced by the spring itself, as the forks compress and more of the spring is submerged in the oil. (which in turn affects the air gap at the top)

 

I wouldn't have thought it mattered too much but then again we set the oil level to a relatively high degree of accuracy, so maybe some truth in it after all

 

 

exactly. Interestingly Hyperpro have always said that their non linear springs should be installed the other way round to the TDM's OE ones - including the ones they supply for the TDM itself.  Which are pretty much identical.

 

The real question is, what are the practical ramifications of reversing the OE springs?

 

 Whereas braking is normally progressive, hitting a crater or a rock in the road is not. Therefore the most violent forces are immediately absorbed at the bottom of the spring. Therefore it makes sense to have the most resistance at that end. Could that be it?

 

Its easy to forget that if something is under sprung (softer) the ride is harder.....   


Edited by the969, 14 August 2019 - 10:14 pm.


#19 fixitsan

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Posted 14 August 2019 - 10:24 pm

 

 

exactly. Interestingly Hyperpro have always said that their non linear springs should be installed the other way round to the TDM's OE ones - including the ones they supply for the TDM itself.  Which are pretty much identical.

 

The real question is, what are the practical ramifications of reversing the OE springs?

 

 Whereas braking is normally progressive, hitting a crater or a rock in the road is not. Therefore the most violent forces are immediately absorbed at the bottom of the spring. Therefore it makes sense to have the most resistance at that end. Could that be it?

 

Its easy to forget that if something is under sprung (softer) the ride is harder.....   

 

Now there's a conundrum, one which makes me wish I had kerbed this evening's vodka consumption sooner.....although knowing me I will dream about it now !


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#20 the969

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Posted 15 August 2019 - 08:59 am

Well, Ive heard people claim that it doesn't matter which way round you install them, ie as you would a linear. But that's the point - because they aren't linear,  and since the forces being applied (by the rooad or the brakes) are not equal at both ends of the spring, it must make a difference. Otherwise, why bother telling people which way round they should be installed? 

 

I wonder if choice of position is to do with those different forces or whether fixitsan's air gap theory (#17) is correct.  interesting to find out what the reasoning really is, anyone here actually know?

 

Local workshop had an SV 650 in the other day,  both forks had progs the opposite way round....    cancelling each other out = linear!  

 

 

 

 




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