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Author Topic: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp  (Read 25051 times)

Offline The Jimbonaut

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #140 on: Aug 06, 2018, 13:49:18 »
That looks great. Think I read somewhere that this effect is called drillium which is itself a cool word. Is there any issues with water getting in and affecting the shoes/drum?


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Offline MiniatureNinja

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #141 on: Aug 06, 2018, 17:50:46 »
That looks great. Think I read somewhere that this effect is called drillium which is itself a cool word. Is there any issues with water getting in and affecting the shoes/drum?


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i've only ever seen "drillium" used in the bicycle world - but I mean really... we just attach spinning explosion powered heat generators to our two wheeled death machines
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Offline Sav0r

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #142 on: Aug 06, 2018, 18:44:14 »
Weakening holes is what we always referred to them as in the race car world.

Nice work though, it looks good.
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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #143 on: Aug 10, 2018, 10:07:07 »
Weakening holes is what we always referred to them as in the race car world.

Nice work though, it looks good.

Haha Yes!  I have heard that too.  Gets pretty dicey if you start drilling up structural sheet metal in a car.  People can sometimes miss the fact that the sheet metal itself does a lot for the structural integrity and not just the main structural elements.

I think in this case there will not be too many extreme forces on the parts.  The only boss that could be under stress is the brake lever wire perch - but I will be replacing this with an alternative system anyways.

In response to @The Jimbonaut about water...  If this was going to be a daily rider I actually wouldn't do this.  It was quite a lot of work for very little weight loss and 'looks' and it will let more water and dust in, yes.  However, because this is pretty much a purpose built machine, I won't be riding it often and will only be out in the sunshine  ;) ;D

Also drillium, lol.

Offline Sav0r

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #144 on: Aug 10, 2018, 12:44:14 »
You certainly have to pick and chose which places you weaken.

I've been meaning to model up the brake plate for my RD and then make some configuration for lightening it via CNC. The major benefit there is that I can pick and chose what gets removed and do so in fairly inorganic ways. Hopefully that would result in a lighter piece than just drilling holes but with less weakening. That's the idea anyways, and it's pretty far down on the list of things to do, I may never get to it.

In regards to the water issue, I doubt it's much of an issue. Drum brakes just aren't all that sensitive in my experience. My vintage Formuala Vee is drum brakes on all four corners and the braking character really doesn't change from wet to dry. Now when the axle seals leak it's a totally different story.
Sav0r the adventure.

Visit www.chrislivengood.net to get more information on my RD350 dubbed Mia Wallace as well as my other projects and snafus.

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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #145 on: Aug 11, 2018, 02:50:46 »
I have slowly chipped away at building up the wheels this week, or I should say truing.  I had built the rear wheel last week (but had not trued it) but then I decided to try and build the front wheel and film it.  What a nightmare.  It's really hard to instruct a complex process!  I ended up starting from scratch 3 times and the build itself took about 4 hours hahaha.  Then truing took at least an hour per wheel.  But it is just a time consuming process.  Very rewarding though!  I ended up getting both wheels to within 1mm lateral freeplay and 1-1.5mm axial (manual limits are 2mm).

Also, check out my makeshift truing stands!  This actually worked out really well because you don't need to measure or think about hub-rim offset, rather you can just measure from the edge of the rim to the forks/swing-arm and adjust it so it is centered. 

I'll get a shop to mount the rubber and balance the tyres  :)

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #146 on: Aug 22, 2018, 18:15:46 »
Managed to open up one of the old fork legs tonight.  I have done this a few times now and have sworn and grazed knuckles enough that I have found a couple tricks that make the process a bit easier - especially if you don't have an extra set of hands and especially if that damn thing is rusted solid(ish). 

Anyway, there is enough depth in the fork cap to drill and tap a hole about 15mm deep, so I do that first.  Then I hit the cap a little (downwards) to break it loose.  Then I ratchet down a socket on top of that and pry out the metal ring that holds it on place with a micro screwdriver.  I hate this damn ring, it is a nightmare to get out.  I am already looking at circlip alternatives for my own solution.  Then once the ring is removed, you can very carefully release the ratchet - with safety glasses on and no-one else (or thing) to harm in sight.  Sometimes it will just pop up, other times (like in this case) it will not - because of the rust build up.  This is where the threaded hole comes into play - you can screw in a bolt and bash upwards to get it out.  Pang!  Be careful  ;D

Now I can start experimenting with spring length, spacers, adjusters, emulators etc (all as discussed previously) without disturbing any of my other running SR's or dismantling this project's rolling chassis.

Offline der_nanno

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #147 on: Aug 23, 2018, 03:55:43 »
Oh that looks familliar. I thought about using a safety clip instead of the wire in the past. (early XS750ies and Yamaha TR1s use the same setup)
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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #148 on: Aug 23, 2018, 12:43:36 »
Forgot to mention that I had already soaked the fork caps in penetrating oil for a few days and had applied heat to them with the heat gun a couple of cycles as well - this definitely helps.

Yeah der_nanno, total pain to work with.  I actually just ordered some stainless circlips in the correct dimensions.  My only hesitation is that the ring is hardened steel - which is extremely tough.  The circlips might be a bit soft for the job?  Maybe not, I'll try it out.  They may well be just fine - it is just a small line contact to hold it all together I don't think there is enough room for the circlip to deform, rather it will get sandwiched in a good way between the cap and the forks undercut. 

Offline der_nanno

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #149 on: Aug 24, 2018, 05:26:11 »
If anything, it might wear out the ridge, because the edges of a snap-ring are really sharp. Rounding them off with a file might be the right way to avoid this.
Real freedom starts with the freedom of thought.

My Blog:
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My Mule TR1.1 build here on DTT:
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My XS Triple Sidecar build here on DTT:
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