1981 Yamaha SR250 Cafe Racer

I'm not running a rear fender, no ..

I'm already planning my next bike .. it has to have pillion pegs (my girlfriend says so) .. I want an original XS650, which I would restore in original colours/trim and put ace bars and shortened cables on, a nice set of pipes .. and leave at that .. they're so nice!
 
lunar_c said:
I'm not running a rear fender, no ..

I'm already planning my next bike .. it has to have pillion pegs (my girlfriend says so) .. I want an original XS650, which I would restore in original colours/trim and put ace bars and shortened cables on, a nice set of pipes .. and leave at that .. they're so nice!
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I'm building the same thing...but with an RD400. Having a 2-up bike is nice.

--Chris
 
Are you going to try and lower the rear end somehow? I've been looking for some 10" shocks to lower the fender down to hug the tire more but all I can find are non-adjustable shocks for a monoshock dirt bike. It'd only cost me $70 or so for brand new shiny shocks but I'm concerned about the non-adjustablility.
 
looks good the elec box is just awesome... very nice!
cheap and easy way to lower the rear is just pull the shock apart and cut out a coil... not sure if you are planning on doing that but it works
 
JRK5892 said:
looks good the elec box is just awesome... very nice!
cheap and easy way to lower the rear is just pull the shock apart and cut out a coil... not sure if you are planning on doing that but it works
Click to expand...


Didn't even know they could be taken apart! That may be the best option then since I could clean up and/or paint them at the same time.
 
Can't wait to see the finished bike, will be starting mine when the xmas rush is over. More time than money so i love the way your doing everything.
 
On the SR 250, the front end is too high. You need to jack up the rear to level everything out, or slip the front forks through (a lot.. probably affecting geometry) so I'm putting in longer shocks.

I would not cut coils, it's illegal to do on cars (for good reason, in a macpherson strut type suspension it'll make the spring lose it's captivity and risk falling out if unloaded) and unless you have a threaded shock base where you can wind the base up to keep the spring captive, it'll fall out if shortened.

Even so .. this changes the spring rate, and as you'll have to wind the base up to keep the spring captive (affecting the springs pre load) you'll screw up the match between the shocks spring rate and damping rate .. not a good idea if you intend to ride the bike hard and want the best out of it.

Look at what's available aftermarket from Hagon or Ikon or any other bike suspension manufacturer. Any shock will fit .. as long as it has an eye of 12mm.

If you want to drop the rear .. or jack it up, measure from your axle to to highest point above it, and work out with a square where you want the centre line of the bike to sit .. for me visually it was necessary to get the bottom of my tank square to the horizontal, and the front end was high so I slipped my forks through.

Then work out how much the rear has to come down to sit where you want, and deduct (or add) that measurement from the length of your shocks.

Now search through whats available aftermarket (or go to a wrecker and look around at other bikes but most dual shock rear bikes from the 70's will be 12" or 29.5cm long eye to eye (from the middle of the bolt holes) with a 12mm eye) and see what will do what you want it to .. and think about slipping your forks through a bit as well to sharpen up your turn in.
 
Hi ,
I got some more done the underseat electrics. I painted the components box and finished the battery tray. Inside the box where the bolts used to mount the rectifier underneath are, I used longer bolts and an extra nut toll mount a piece of flat aluminium bar to bolt my circuit breaker and relays to.

n704951495_1577358_4128.jpg


The battery tray is now braced to the frame from the front, held at the back by the components tray which is rubber mounted (bolts through fuel line) in four places. It's very, very strong.

n704951495_1577359_4476.jpg


The fuse panel will be accessible through the top of the components box but still sealed as it has a clear plastic cover.

n704951495_1577360_4868.jpg
 
That's a good looking box for the electrics. You definitely put a lot of time and thought into the design and think it's going to pay off handsomely.
 
Thanks a lot .. I can't believe someone registered just to say they liked my bike! :)
I am going to do a big post on the wiring and making the new wiring loom (which I am doing with the help of my friend Chris who is an engineer, he designed the loom so the charging, starting, lighting, instrument and indicator/brake lights are seperately fused in their own individual circuits as most old bikes don't run fuses on anything, just a main fuse .. if you blow it you have no idea what's wrong) that I hope will become a sticky and help other people with their wiring in future.

A big thanks to Chris!
 
This is going to be one sweet ride. I love it when someone pays attention to detail like you have. This build is an inspiration and I hope mine will turn out half this nice. Way to go. Please keep updating the progress as you have been.
 
lunar_c said:
Thanks a lot .. I can't believe someone registered just to say they liked my bike! :)
Click to expand...

Make that two!

This thread is a real inspiration to anybody wanting to do a cheap build, to make a fine job of it nonetheless. You clearly know your stuff already, but it would have the added bonus for people like me of teaching us a lot about mechanicals and electrics at the same time. I came across this thread looking at builds of SR250s. I too am a (long-term) student and so do my biking on the cheap, and when combined with a long-term passion for riding necessaity teaches you that you can get a lot out of a little or old bike. I've been lusting after a cheap old SR250 to do a job like this on for a while - perhaps when my MA thesis is done I'll reward myself and begin such a project. I got into SRs because an SR185 was my only transport for 18 months. Unlike the prior smaller bikes, I got into riding properly through that - ie getting out far away from home. Then it became my partner's bike, sat for a good while, and recently was resurrected to serve again as cheap transport for a broke family member! Great bikes! This is my bike now ('78 SR500) http://bikepics.com/members/mattb_sr500/78sr500/

When I get the SR250 I want to register it...then cut the frame (which would be hard to register afterward), use a bunch of Royal Enfield parts (cheap! Chrome tank, exhaust, black fender etc etc), and make a kind of generic vintage bike, bit like a big BSA Bantam. Here's a similar example (an SR400 http://www.daytona.co.jp/mc/single/DTX/dtx_SR.html see "99 K Flame Hard Tail (by SHEVRON)"). Having had the engine open, what sort of bigger size do you suspect you cylinder cuold be bored to?

Look forward to seeing more of you project - as I say, a real inspiration!
Matt
 
did not know you guys where studnets... i am finishing up my MBA in the spring... NEVER going back to school again!
 
Yep, I'm completing a BS.c of Medical Nursing (General) at Curtin University and I'm currently in my 2nd year. Another year and a half to go .. I really hope I can finish this bike up by February when uni starts again so I can ride in, rather than drive. Public transport is rubbish out where I live and parking at uni is a nightmare! As an added bonus, you don't need to buy a permit to park a motorcycle ;)

I hope to specialise in pediatric medicine later down the line as I enjoy the challenge and rewards of working with children (though it is difficult) so I hope they will think I'm cool rocking up on the bike and it'll help break the ice!

Tonight I repainted the components box (changed the layout a bit .. the CDI unit is mounted underneath along with the rectifier now, because I'll be putting an ignition key barrel where it used to sit in the sheet metal gusset joining the down tube and spine just below the front of the tank where the CDI used to hide) and got started on the switchgear. I stripped them down and I'll be repainting them and making new stickers for them. I also replaced the missing horn button with a momentary switch I bought from Jaycar electronics. I added another one too .. it will be used to activate the nitrous myself and Chris are planning on experimenting with later, using the bike as a test bed for our idea's.

It should be interesting to see what the bike will feel like with a 5-10hp shot (a wet system with a fuel jet also) I have left an extra spot in my electrical components box for an addition relay and circuit in my fuse panel to control the solenoids, which I will mount where the rectifier used to be, behind the engine on a polished aluminium plate. A small 1lb co2 fire extinguisher bottle with the appropriate valve and pressure release will most likely be used, which I will strip and polish and mount on the frame rail beside the hump at the back of the bike.

It will only be used on the track obviously. And yes I'm serious .. it's an unlikely candidate for nitrous but it's all a bit of fun and a learning tool.

Can't wait to get started on that ..
 
man i am not sure if your cyl heads could handle the boost... i know when i have dropped a 5-15 shot on prev bikes we have had to enforce all the welds on the heads of both rockets (2 CBR 600 and 1 GSXR 1000) and on the HD we put the shot on without going to SE jugs blew 2 head gaskets... that was very occasional use... may want to look into that... would be SICK man but not sure the motor could take it. you ever run NOS?
 
I thought everything looked okay for a 28 year old motor when I put it together (checking and double checking tolerances) but you raise a very good point..
 
ooh ya forgot to add these where not push button nos... it was full throttle nos triggers, you had turn it on though, no bottle warmers, So small did not need em
 
Make a kevlar seat, you dont want that monster to blow your levis off when the head lets go. A 250 on happy gas sounds fun. If the rest of the build is anything to go by you'll find a way to make it work.
 
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