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Author Topic: 1981 Yamaha SR250 Cafe Racer  (Read 177953 times)

Offline lunar_c

  • Posts: 122
1981 Yamaha SR250 Cafe Racer
« on: Sep 22, 2008, 13:48:17 »
Hi guys and girls,
This is my bike, a 1981 Yamaha SR250. It was basically given to me, and when I dragged it home, it was a pretty sorry sight ..



Initially I didn't have any grand plans for the bike, I intended just to clean it up and use it to get my license as I've always ridden offroad since I was a kid, but have never had my road license.

Then, as I got into cleaning it up I was inspired by some of the amazing work Deus Ex Machina (www.deus.com.au) in the eastern states (I live in Western Australia) do with the humble Yamaha SR and decided since I have always loved 60's race bikes such as the Manx Norton's and British cafe racers, that I'd turn it into a cafe racer.
I played around with the stance of the bike by slipping the forks through the stanchions 2 inches, raising the rear shocks, lowering the bars and removed the seat in order to measure it up and fabricate a cafe seat, I also repainted the tank and shaved the badges (what a mission that was, that tank has so much filler in it, it was junk, but my "budget" dictated I save it!) and the bike began to look like this ..



And here's a couple of photo's of the tank before and after painting, I shaved the badges also hence all the filler ..



After about a zillion coats of high build primer it finally started to look straight ..



I had a friend who is a spray painter paint the tank for me (but still using rattle cans) and I think we made a pretty good purse out of a sows ear..



I then decided to clean up the rear end of the bike, so I gutted the middle section by removing the side panels, airbox, battery box, inner guard and tool box (for want of a better description, you could probably only fit a 10mm spanner and some loose change in there) deciding to relocate the battery, run a pod filter on the carburettor, and hide the electrics. At this point I stripped the bike ..



I then decided to go solo, and remove the loops that mount the pillion pegs, sidestand and muffler from the rear downtubes. I also removed any superfluous mounting tabs and brackets for a cleaner look, and welded plates over the holes where the loops were.

Here's the frame before modifications ..



And after a lengthy session with the grinder (actually 3, two of the ones I borrowed from the workshop died on me before I bought a good one!) and wire wheeling the paint off ..



And after all the grinding, cutting and welding here it is with a coat of paint and the rubbers back on. As you can see I still need to fabricate a clamp/bolt on muffler mount and sidestand, but I am waiting until the bike is a rolling chassis again ..







If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline lunar_c

  • Posts: 122
More..
« Reply #1 on: Sep 22, 2008, 13:50:10 »
I used gloss black RustKill epoxy enamel which gives a very tough finish, but creates an immense ammount of overspray which unlike most paints, is extremely sticky! Wear a mask and long sleeve clothing and do it in an open area or a booth if you can! Here's a pic of the frame with the tank on ..



Once the frame was done I started on the myriad of other things that needed detailing and painting. Every nut and bolt has been wire wheeled and polished, after all it only takes is time and patience so why not do it to the best standard you can, right? ..



The forks are a little pitted at the top where they slide through the triple clamps, but they are fine in the travel area, so they will simply get new fork seals and oil. After wire wheeling ..



The engine mounts, all removeable brackets and sprockets were all stripped down and painted ..



As with the frame and everything else, the swingarm was taken to bare metal before being painted to ensure a good finish ..



And finally here it is painted ..



The triple clamps turned out especially nicely after painting and polishing the bolts, and there's two spare tapped holes for when I get around to ditching the speedometer housing and running a nicer gauge and making an alloy panel for the idiot lights ..



Speaking of the speedometer, I am keeping it for now (as this bike is being built on a very small budget over time) so I decided to shave off the raised white lettering for the idiot lights and then masked it and sprayed it using K&H bumper and trim paint, which has a slightly speckled finish and is weather resistant. I polished the chrome trim piece and reassembled it after painting it's mounting bracket with the same epoxy enamel I used on the frame.



The headlight got the same treatment ..



With regard to the wiring, it was mostly pretty good so I simply labelled everything, layed it out on the bench, cleaned it thoroughly ..  



Unwrapped it checking for any faults, and replaced any corroded or crumbly connectors and plugs ..


 
Then rewrapped it in a quality black electrical tape, here it is ready to go back on the bike ..



The last things to do styling wise, are the fabrication of the seat and hump, and the front fender, which I've cut to the right dimensions, it still needs shaping and blending though ..



The engine is a SOHC, 2 valve 239cc single, running 8.9:1 compression. It's listed as producing 20hp from the factory. I'm fabricating a new exhaust that matches the diameter of the exhaust port (the standard one flares down sharply inside the cosmetic outer pipe) with a BSA gold star style silencer. I am also running a pod filter on the 34mm Mikuni carb and it will be rejetted to suit, but as it's pretty healthy that will be it for now. If I decide to continue on with the bike, I will rebuild the motor, raise the compression and so on later on.

Here is the engine as it is now ..

If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline SilentStrike

  • Posts: 50
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #2 on: Sep 22, 2008, 14:06:15 »
That  is a really nice project, keep them pics comming, good luck and have fun.
Island of Enchantment

Offline jay_kent

  • Posts: 1297
  • 1979 cb650
    • Cafe build blog
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #3 on: Sep 22, 2008, 17:18:31 »
wicked build,

I just finished getting one done for my wife. It was an ebay buy for $160, sat in the barn for 2 years. The manual says the top speed is 83 km/hr but I had it up to 115 and I'm 220lbs. Poor thing was screaming. It was a surprise for her, and if she didn't like it i was going to cafe it.

DTT build thread - here
More pics at my Cafe build blog - Here

"And yeah David...you're pretty much bugshit nuts just like the rest of us." ~Swagger

Offline lunar_c

  • Posts: 122
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #4 on: Sep 23, 2008, 03:21:30 »
Thanks guys!
They're a pretty unassuming bike, but the SR400 and SR500 in particular lend themselves very nicely toward the cafe treatment. Definitely take a look at www.deus.com.au they have a couple of cafe racer and manx inspired designs based on the SR400 that are simply brilliant! Personally I love the look of drum brakes (I grew up reading my grandfathers old motorcycle books!) so I like the SR250 for that reason.. I'd like to switch the front end out for something with a bigger TLS drum later, which would of course invite me to give it some more power to match ;)

The manual I downloaded online says 89mph.. or 146km/h in the metric money. With a tail wind perhaps .. So far I've ditched about 12kg of stuff from the bike, so I am hoping it'll be pretty nippy for an old 250 with the lower weight and engine breathing modifications.
« Last Edit: Sep 23, 2008, 08:46:07 by lunar_c »
If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline lunar_c

  • Posts: 122
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #5 on: Sep 23, 2008, 08:38:09 »
I got a little work done on the bike today. I cleaned and polished the drums, gear shift lever and brake lever, started on the carb and did a few other little jobs.

Here's a pic of the drums and levers ..

If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline Ease

  • DTT SUPPORTER
  • *
  • Posts: 2181
  • 83 XJ650RK, 77 TS-250
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #6 on: Sep 23, 2008, 15:44:04 »
You're doin a great job on that bike!

Lookin forward to what you come up with for a seat.

Offline lunar_c

  • Posts: 122
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #7 on: Sep 24, 2008, 15:12:44 »
Thanks for all the encouragement, guys! It makes my day.
Got the front end together today!

Head stem bearings in with Castrol HTB grease ..



Here's the frame on the floor of the garage with the front end installed and head stem tensioned. The swingarm is sitting next to the bike because I've lost one of the cup washers that hold the sleeve inside the swingarm pivot and have to order one tomorrow.. otherwise it'd be on there.. D'oh!



Tomorrow I will go and get the few replacement nuts and bolts I need to finish the frame assembly and order a few things. I'm also replacing all of the phillips head screws on the engine with hex head set screws. Then it's onto detailing the wheels so I can make it a roller ..   
If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline lunar_c

  • Posts: 122
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #8 on: Sep 25, 2008, 06:47:20 »
Hey!
I got heaps done today and I'm totally digging the look of the bike now, I have renewed enthusiasm and I'm eager to finish it!

Last night I sprayed the underside of the tank with black chip guard paint to protect it, I mocked up the bars today, and also put the brake pedal and foot pegs on

I also fashioned a small clip to hold the tank on it's rear mount out of some scrap metal, and filed down a bolt to match as it was MIA when I got the bike ..



This is an exciting picture for me! I am a university student (read: broke) so I decided to play around with the stock bars (usually lame results apply) but when I inverted them and cut 20mm off of the ends, they looked quite nice. I will heat them up and sharpen the angle at which they come in towards the tank to narrow them a little, but they can stay for now! It'll look sweet with rear sets but it feels reasonable now .. they could use to be about an inch or two further back, as I have size 14 feet.. I will fabricate some rear sets soon enough .. probably using some from a GSXR or similar bike, and making aluminium brackets to mount them from the standard peg mounts further back.



I also put on the headlight .. his face is back on!



I hope you all like it!
Cheers,
Ben

« Last Edit: Sep 25, 2008, 07:14:16 by lunar_c »
If you can't explain something to your grandmother, you don't understand it - Albert Einstein

Offline Canuck Plumber

  • Posts: 505
  • Badges? We don't need no stinking badges!
    • Long road ahead.
Re: 1981 Yamaha SR250 Cafe Racer
« Reply #9 on: Sep 26, 2008, 02:12:42 »
Great work on the detail.
God, grant me the serenity to accept the parts I cannot find; the courage to ride the bikes I build; and the wisdom to know when I've spent too much..