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Author Topic: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp  (Read 45763 times)

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #400 on: Sep 05, 2019, 15:46:01 »
Lopping off the electric start bosses would be a pain because they have gasket sealing faces - which would mean a custom gasket.  Doable yes, but I already designed and had this sweet plug made  8)

Offline Sonreir

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #401 on: Sep 05, 2019, 16:43:48 »
Nice one.
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Offline Sav0r

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #402 on: Sep 05, 2019, 18:23:28 »
Looks great!

I probably would have stitched up like Frankenstein's monster anyways. Your fix is much cleaner.
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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #403 on: Sep 06, 2019, 07:05:23 »
And to answer the question about electric vs kick start parts weight...  Closer to the beginning of the thread I did a straight comparison of all the components and did not count in the battery, but did include the heavy metal kick start arm from the SR500.  And still, a huge weight savings - see image below.

I actually plan to use the base part of the SR500 kick starter and design my own arm to be machined up in 6061-T6.  This will of course be much lighter but I am almost forced to do this anyway because of the clearance required by the rear sets, despite the fact that I upgraded to folding ones!  I have heard the RD400 kick start lever has good clearance/sticks out further?  But then again, that would be heavy, forged steel anyway.

Offline doc_rot

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #404 on: Sep 06, 2019, 16:23:02 »
Not sure how it is on the SR, but when I thought about removing the starter clutch from my kz750 I noticed there is an oil journal where the starter clutch rides on the crank. I'm not sure but it may be necessary to have a spacer to replace the starter clutch so that oil pressure is retained.

Offline crazypj

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #405 on: Sep 08, 2019, 16:36:36 »
In all probability it's to prevent the bronze bearing on starter reduction seizing up?
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Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #406 on: Sep 09, 2019, 09:35:09 »
Not sure how it is on the SR, but when I thought about removing the starter clutch from my kz750 I noticed there is an oil journal where the starter clutch rides on the crank. I'm not sure but it may be necessary to have a spacer to replace the starter clutch so that oil pressure is retained.

That is correct.  That is why I had the drive gear machined down to just it's hub - to maintain any other important functions is might have - like oil flow control.  Below you can see what is was and what it became - final image shows the outsourced machine work which included grinding it down properly on a lathe. 

Offline teazer

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #407 on: Sep 09, 2019, 12:16:30 »
CB77 Honda used a similar arrangement with a hole in the crank to lubricate the bush.  CL cranks don't use a starter so they don't have that oil hole, but cannot always source a CL crank or crank end, so I used to use a carb needle to block the hole.  Cut it short, and "rivet" it into place.  Never had one come loose.

You could probably fill it with low temp solder or brass too.

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #408 on: Sep 10, 2019, 13:12:14 »
After rebuilding the engine and having spent so much time and money on it, I thought it wouldn't hurt to develop a billet magnetic sump plug.  One, because the stock one is tiny and the cast alloy is like butter, and two because well a magnetic sump plug is good!

I bought a countersunk neodymium magnet that works with an M4 screw and designed around that.  The printed prototype works really well and I will do one further iteration before ordering it in aluminium.

Offline JadusMotorcycleParts

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Re: Ton up SR250 - a cafe racer by the numbers: 100mph, 100kg, 30hp
« Reply #409 on: Sep 10, 2019, 13:15:16 »
CB77 Honda used a similar arrangement with a hole in the crank to lubricate the bush.  CL cranks don't use a starter so they don't have that oil hole, but cannot always source a CL crank or crank end, so I used to use a carb needle to block the hole.  Cut it short, and "rivet" it into place.  Never had one come loose.

You could probably fill it with low temp solder or brass too.

That's a great idea Teazer.  However I was concerned in this case that that oil galley in the crankshaft might feed other important things on the clutch side of the crank case assembly.  Oh well, no harm done either way I'm pretty sure.  In this form, it will just do it's thing the same way it did in stock form.