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Author Topic: Yamaha SR250 - A clean standard build  (Read 136010 times)

Offline JadusMotorcycleParts

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Re: Yamaha SR250 - A clean standard
« Reply #10 on: Jun 22, 2015, 08:12:33 »
Back to the drawing board for the brace.  Its one thing to see a sketch of it, then its another thing to print it out in 3D and 'feel' its size and proportions.  And this one was waaay to big and chunky I thought!

Offline JadusMotorcycleParts

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Re: Yamaha SR250 - A clean standard
« Reply #11 on: Jun 22, 2015, 08:20:28 »
Another attempt at the fork brace - this time much thinner and more in proportion.  Plus another attempt at some above yoke clip-ons.  This time in more of a riser bar style.  I like these a lot more.

Offline JadusMotorcycleParts

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Yamaha SR250 Exhaust header
« Reply #12 on: Jun 23, 2015, 04:08:31 »
Designed and printed (in pieces) an exhaust headers.  I like the style of header with sharper lines and tighter curves rather than the vincent style swooping bends.  So I tried to match the angles of the frame/engine so it looked right.  Has anyone ever used an exhaust header calculator?  I tried a few but ended up liking this one the best:  http://www.mezporting.com/exhaust_length.html

I also bought and tried reading Philip H. Smiths 'Scientific Design of Exhaust and Intake Systems' but it was just too heavy for me.  Most of the principles I understood but I got caught up in all the thousands of possible variables.

Offline JadusMotorcycleParts

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Yamaha SR250 battery tray
« Reply #13 on: Jun 23, 2015, 04:15:51 »
Seeing how the design fits everything in.  Not too sure about the ignition location...

Offline JadusMotorcycleParts

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Yamaha SR250 custom seat
« Reply #14 on: Jun 23, 2015, 04:28:20 »
Thought it was about time I figured out what I will do about the seat - for me the key to success for the SR250.  The real make or break.  No better way than to sketch up some ideas and print them out and test them!  Only had time to test the fit for the base of the seat and the mechanical attachment mechanism.  I decided I don't like the new trend of 'lush' plaid, pleated or diamond pattern seats...  I will go for something cleaner - a bit like Roland Sands seat designs for the modern Triumph Bonnevilles maybe  ;D 8)

Offline Shawzie

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Re: Yamaha SR250 - A clean standard build
« Reply #15 on: Jun 23, 2015, 04:46:59 »
Good start.  I've been working on an sr250 for quite some time also. I've really wanted to do a 16 front wheel conversion. Maybe even put on a 2ls front brake from a 400. I hope to see you do it!

Offline JadusMotorcycleParts

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Re: Yamaha SR250 - A clean standard build
« Reply #16 on: Jun 23, 2015, 05:06:38 »
Cheers!  How far along are you with your build?  Do you have a build thread?  Yeah, I will keep you posted on the 16" front wheel thing.  A better brake would be awesome actually.  Pretty pricy though I think?

I was wondering if it is possible to just improve the current brake by giving it a little mechanical or hydraulic help...  Like have you seen hydraulic clutch conversions?  Couldn't the same principle be applied to a drum brake?  So you get a better/stronger action from the lever?  Or even one of these things:  http://www.kickstartershop.de/en/Mechanical-clutch-booster

Offline stroker crazy

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Re: Yamaha SR250 - A clean standard build
« Reply #17 on: Jun 23, 2015, 09:03:38 »
The black bars look waaaaay better than the first attempt.

Very useful exhaust calculations can be found at http://www.dotheton.com/forum/index.php?topic=39814.60
Scroll down to Reply#67

Crazy
“Ride like the Wind” W.H.

Offline cosworth

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Re: Yamaha SR250 - A clean standard build
« Reply #18 on: Jun 23, 2015, 10:36:26 »
Have a look at my build in my sig. I'm a big fan of the SR250. If I had 6 in my yard I could build them all different and have a blast doing it. Tracker, brat, bobber, cafe, scrambler, and board tracker.

A very versatile base.
1981 SR250 café hot rod (sold)
1976 XS360 collector plates
1980 XS400 (on the bench)
1981 XS400 (in pieces)
2017 Husqvarna 701 enduro
Livin' the dream in western Canuckistan

Offline JadusMotorcycleParts

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Re: Yamaha SR250 - A clean standard build
« Reply #19 on: Jun 23, 2015, 13:45:47 »
Thanks for the links guys.  I really like your build cosworth! Nice job.  8)