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Author Topic: 1980 SR250 Build, get Excited  (Read 4686 times)

Offline monkeyinfantry

  • Posts: 13
1980 SR250 Build, get Excited
« on: Oct 28, 2016, 00:40:18 »
Hey everyone, and welcome to my 1980 SR250 build. I picked the bike up on a whim on the good olí Craigslist one day. I saw the post for it near me, $250 and it was going to be scrapped for metal if no one was going to come pick up in a week.  I saw the pictures of the bike and they said ďSave me!Ē so I grabbed my trailer and straps. I figured it was a good price for a frame with a clear title, has the engine, and fully rolling.  The seller has the sister bike of mine; he was given my bike for free as a parts bike when he bought his.  Iím no stranger to projects or fabrication so it seemed like a fun little build to take on.

Here she is the day I brought her back:


Tear down and assessment: she looked pretty rough, but not the worst thing Iíve ever seen





Stripped the swingarm with some aircraft stripper and primed, it was the rustiest/largest part




Disassembled the rear wheel, polished up the spokes which surprisingly took a lot of effort to get nice and shiny again





Took the engine out of the frame, disassembled the top end. Piston is in good condition, had some soot on it that was cleaned off, she was running very rich. The rings were stuck on so I busted out the heat gun to pop them off. The cylinder had the tiniest amount of rust where the piston rings were in contact with the cylinder, but after cleaning it up It looks like I may be able to get away with just a hone job, Ill assess this more when I get new rings and such. Regardless, I think Iíll reuse the piston as it still looks mint even in the ring slots, just need some new rings, pivot pin, and circlips.










I bought a cafť seat from China off Amazon, I didnít like how it was going to sit on the frame, so I chopped it to make the subframe straight. I don't plan on going full cafe style, I'll probably end up with some sort of drag bar or ultra low road bar.










My bike didnít come with any keys, there wasnít even an ignition switch on the bike. So I decided to bust out my lock picking skills to open the tank. After about 2 collective hours of tinkering with it, the entire tumbler popped out of the hole! I put a large screwdriver into the hole and twisted, and she popped open. Itís rusty, but not the worst Iíve ever seen. I bought a new gas cap from China off Amazon and it looks like it should work perfectly.





I was sitting on the frame and realized how flexible the frame was so I decided to add some reinforcement gussets, they may be a bit overkill but they look cool ;) Iím also going to touch up some of the stock welds, they look pretty lackluster.



Next was tackling how the gas tank mounts in the rear. I was going to just make use of the rear mount that was already on the tank, but it interfered with the seat so much that it did not look good at all. So my plan is to chop off part of the old tab and use it to make a tab that goes straight down to the frame instead of the odd arch, so I could get the seat as close to the tank as possible. I cut the tab in half and thatís when I realized that welding on a gas tank may not be the best idea!
So this is where Iím sitting currently, Iím doing research on how to properly clean a gas tank to prep it for welding, but honestly Iím getting mixed answers all around. Some people are saying just buy a new tank and making it sound like we are dealing with an atom bomb, and other people are saying just use water and dish soap multiple times and youíre good, like it is no big deal. I do have a few gas tanks Iíve been looking at, but I think Iíd prefer to use the one I have. I wonít be welding on the tank itself, but it's on the part of the old tab which is damn near close to a seam of the tank. Anyone have tips for doing this and not blowing up my garage and face?



In the meantime, Iíll be working on reinforcing the frame more and Iím going to start disassembling valves. Do any of you SR250 peeps out there have a good method of removing the valve rocker pivot pins? They say thread an M8 (I think) into them and they should slide right out. First off I canít find a bolt that threads into these, are they fine threaded?? And of course, they donít just slide right out, the bike has never been opened before by the looks of everything. Any helpful tips?





Sorry about the varying quality of the pictures, I got a new phone mid build and they improved significantly. There could be many more pictures, but I think this is enough for now. I hope you enjoy my build!


Offline interceptor

  • Posts: 865
Re: 1980 SR250 Build, get Excited
« Reply #1 on: Oct 28, 2016, 07:28:04 »
Looking good  :)
Opinions are like farts... they stink and no one wants to hear it except yourself.

Offline magazine

  • Posts: 47
Re: 1980 SR250 Build, get Excited
« Reply #2 on: Oct 28, 2016, 12:13:35 »
Wow!  You really dove right in!  I like it so far.  Good luck with the build.  I have a similar seat from eBay.  The pan and color are identical  looking. 

Online VonYinzer

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Re: 1980 SR250 Build, get Excited
« Reply #3 on: Oct 28, 2016, 12:39:36 »
Nice work so far. One question...

Are those gussets welded in the center of the frame tubing? If so, move them to the outside or inside. Much stronger that way.

I'm no engineer, so I'll leave the technical crap to someone smarter than me. There are a ton of great write ups online explaining the reasons for this.
Like a river that don't know where it's flowin'
I took a wrong turn and just kept goin'

Offline sbruton

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Re: 1980 SR250 Build, get Excited
« Reply #4 on: Oct 28, 2016, 13:24:31 »
I'm in.  Great work! 

When you re-laced the rear wheel did you keep the 16" hoop or opt for something larger?

Offline monkeyinfantry

  • Posts: 13
Re: 1980 SR250 Build, get Excited
« Reply #5 on: Oct 28, 2016, 14:19:17 »
Thanks for the nice comments  :D

VonYinzer, I do indeed have the gusset in the center and now that you mention it, I don't recall ever seeing a gusset directly in the middle  :o... This is why you tac everything first  ;)

sbruton, I completely disassembled the bike and relaced the stock rear wheel to make it roll again so I could do suspension mockup and such. Whether or not I'm keeping the stock sizes, I'm not sure. I saw a build where the guy swapped out the spoke style wheels for XS400 aluminum non-spoked wheels, and it peaked my interests. I'm just not sure if I want to put the money plus the extra effort of fitting new wheels and new brake setup onto the bike, and a few other issues... but they looks soooo good.... heres the link if you're interested: http://david.scarbro.com/category/yamaha-sr250/page/2/

He actually bolted the entire front end from an XS400 onto it, which does simplify things a bit. hmmmm.... more thinking and fabrication to come  8)

Offline JadusMotorcycleParts

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Re: 1980 SR250 Build, get Excited
« Reply #6 on: Oct 30, 2016, 05:06:54 »
Man you really got stuck right in! Looks awesome!

To extract the rocker shafts just screw in a long M6 bolt (standard pitch) and try and pull it out with pliers. If that doesnt work, make up a plate that sits over the cam cover opening that has a 6.5mm hole in it. Then thread your M6 bolt through a nut, then through the clearance hole in the plate, then into the rocker shaft. Now you can use that nut resting on the plate to slowly screw/pull out the shaft.  Thats how i managed anyway.

I wish Australian and European laws were more lax on frame mods like you are doing, means you can be a lot more flexible with seat choice and frame design. I designed a seat specifically for the not messing up the stock frame, but of coarse, that meant some compromises!

One more thing, if you wanna go to an 18" rear for a more cafe look, we got stainless spoke conversion kits for that :)


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Offline monkeyinfantry

  • Posts: 13
Re: 1980 SR250 Build, get Excited
« Reply #7 on: Nov 07, 2016, 14:18:18 »
Got a few more for ya  ;)

Decided to move the gusset and replace it with a tube, just a cosmetic choice, it should have been structurally sound either way.



Other side





And to add on to my gas tank problems, I found this little (not so little) guy while stripping the paint off my tank some more.


I've researched welding up this tank and frankly welding on an already used tank is sketchy to me and I'm not willing to risk blowing myself up, maybe I'll attempt it at a later time when I get ballsier ;D I've also looked up some brand new gas tanks and the nice ones range from $400 - $600 which is ludicrous, only cheap ones you'll find are either from China (no thanks) or are tiny peanut tanks that would not go well with the bike at all. 

At this point I think I am going to give making my own tank a go. I've been watching Ron Covell DVDs and gathering as much information as possible on how to form my own tank and it honestly doesn't seem that difficult as long as you aren't going for a really curvy pattern which will require a special tool like an English wheel. I will be going for more of a boxy cafe style tank which should alleviate some of the skill/tooling required to hand form curved panels.

My first step will be attempting to make a "buck" or wood skeleton of the tank design, which will be used to mock the panels up for the left/right side and top. I'll be using MDF for this.
I will then make templates for the panels using construction paper/chipboard, and lay them on the buck to ensure the pieces will meet correctly.
After I'll proceed to cut the panels from steel sheets and attempt to form them to fit the buck and tack it together. Attempt is the key word  ;)

Once I have the buck and panels finished Ill make the neck tunnel, and finish with adding the mounts for the frame, and the gas cap bung.

If anyone is interested in starting to learn the process you should check out Ron's DVDs, they're not expensive and they're pretty helpful. Here's a link to his YT video about creating a motorcycle tank:
These are select clips taken from his full DVD, I watched it and ended up wanting more instruction/tips.

And always remember... Anything can be achieved with a welder and grinder  ;) and sometimes a hammer

Offline advCo

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Re: 1980 SR250 Build, get Excited
« Reply #8 on: Nov 07, 2016, 14:29:05 »
Bronze brazing rod...rinse the tank a few times with simple green, flush with water and braze that up for $10.
"He broke the mirrors off his Cadillac, 'cause he doesn't like it looking like he looks back."

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Offline monkeyinfantry

  • Posts: 13
Re: 1980 SR250 Build, get Excited
« Reply #9 on: Nov 07, 2016, 15:16:01 »
Bronze brazing rod...rinse the tank a few times with simple green, flush with water and braze that up for $10.
Any reason you suggest brazing it specifically? Just curious, I have a tig

And that seems like a pretty nonchalant way of cleaning the tank, i dont want to make a big ass pipe bomb. Like I mentioned before, one side seems to freak out over cleaning & welding tanks, and the other side looks at it as no big deal.

This is whats sketchy to me, i cant get consistent answers on this topic, and its clearly dangerous if not done correctly. Mehhhhh

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