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Author Topic: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp  (Read 24540 times)

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #110 on: Mar 20, 2018, 17:21:20 »
Just send me a drawing and your address and Iíll try to sort it out for you.

I'll take you up on that!  I'll need to measure things up and design it first so it may take a while before I get there.  Cheers!

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #111 on: Mar 20, 2018, 17:21:56 »
I use Elring Dirko HT (red), with great success. Especially as it's a lot cheaper overhere and it comes off very easily with just a bit of Acetone. And a little bit goes a very long way, i.e. a tube will last you several engine cases.

Awesome, thanks.

Offline datadavid

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #112 on: Apr 01, 2018, 14:23:40 »
This is nice!


Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #114 on: Apr 05, 2018, 14:23:28 »
Been pretty quiet recently - been working on the custom for Lars.  Now it is finally complete though!  It came out pretty good for a 4month, 60 hour total (spare time after work) project.  Really happy it is complete and can now get back to this.  Lars was stoked too, which made the whole project sweet and well worthwhile.

Offline Alex jb

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #115 on: Apr 06, 2018, 10:30:38 »
Like new!
Nice job.


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Offline der_nanno

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #116 on: Apr 07, 2018, 04:12:45 »
Sweet lil' bike!
Real freedom starts with the freedom of thought.

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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #117 on: Apr 07, 2018, 09:10:07 »
Thanks!

Now that the engine project is pretty much on track, or at least, things have been ordered and it is just a matter of doing the work, there is now time to focus on the chassis - wheels, frame, suspension etc.

The SR has notoriously poorly performing forks, so I have been focusing a bit on that first because it feels like that will be the most challenging.  I have done a lot of reading and have been trying to weed out the good information from the bad and trying to decide what mods to do and for what cost/benefit ratio.  Because eventually, if I come up with something good, it could be a nice product for all to have access to.

I have read a lot about the Race Tech cartridge emulators and they seem like the hot ticket for old RWU damper rod forks.  But they are pretty pricey and I am not sure many people would be that willing to go so deep into their forks.  I have also read through the Minton mods for forks for the XS650 and they seem like a good place to start - relatively small changes for good and cost effective results.  I think I will try and find some looser fork seals to reduce sticktion, experiment with fork oil weight and volume, and also preload - which would require either spacers or some special fork caps with preload adjusters.  For anyone interested, here is the Minton mods: http://www.650central.com/tech/mintonmods.htm

And here is good stuff about damper rod forks and the cartridge kits: http://www.racetech.com/page/title/Emulators-How%20They%20Work and here:

And I have listed the things that are adjustable on the fork.

Adjustable inputs:

Oil level
Oil viscosity
Preload on springs
Spring rate - single rate, double rate, progressive.  Also spring length vs spacer length.
Valve emulators - on top of damper rods, requiring destruction of the damper rods (in essence removing their original function)
Add air valves - for air fork function

The air fork function is what I am least familiar with.  I have a full-suss mountain bike with air shocks front and rear and adjust that every now and then, but still don't know why that method is chosen over others, or the advantages and disadvantages.  If someone can elaborate on this, I am all ears, but at this point, because it is least familiar to me, it is less likely something I will do.

Offline Sav0r

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #118 on: Apr 07, 2018, 10:54:09 »
What size emulators would it need? They have to fit inside the springs and are usually the same OD as the top of the dampers rod.

I ask because there are other options than the RaceTechs, they don't have it patented or something. But you can't beat cartidges, the fundamentally improve the damping function.
« Last Edit: Apr 07, 2018, 10:56:40 by Sav0r »
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Offline zap2504

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #119 on: Apr 07, 2018, 19:06:42 »
I know the Ricor Intiminators (different internal cartridge emulator) are real popular with V-Strom owners but I think the smallest version is still 39mm. Cogent Dynamics also has the Drop in Damper Cartridge (DDC) and fork springs but I don't know what sizes they have. If you want to retain the OEM 32mm fork tubes, there's not much more that can be done than a stronger spring (maybe custom or from a CB360/400) a fork brace (you already have that) and different weight oil. Front end swaps are doable, but would look funny if you did not use a spoked front wheel (unless you swapped both front and rear wheels), but using a front end with a disk brake adds a better braking dimension.