1980 SR250 Build, get Excited

monkeyinfantry

New Member
Hey everyone, and welcome to my 1980 SR250 build. I picked the bike up on a whim on the good ol’ 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 “Save me!” 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. I’m 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 I’ve 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 I’ll 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 café seat from China off Amazon, I didn’t 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 didn’t come with any keys, there wasn’t 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. It’s rusty, but not the worst I’ve 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 ;) I’m 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 that’s when I realized that welding on a gas tank may not be the best idea!
So this is where I’m sitting currently, I’m doing research on how to properly clean a gas tank to prep it for welding, but honestly I’m 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 you’re good, like it is no big deal. I do have a few gas tanks I’ve been looking at, but I think I’d prefer to use the one I have. I won’t 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, I’ll be working on reinforcing the frame more and I’m 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 can’t find a bolt that threads into these, are they fine threaded?? And of course, they don’t 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!
 
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.
 
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.
 
I'm in. Great work!

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


Sent from my iPhone using DO THE TON
 
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: https://www.youtube.com/watch?v=UmQ_V5ihmZY
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
 
Bronze brazing rod...rinse the tank a few times with simple green, flush with water and braze that up for $10.
 
advCo said:
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

Sent from my SM-G935P using DO THE TON mobile app
 
Brazing when done properly does not melt the parent metal and therefore reduces the likelihood that you will burn more holes through the weak spots in the tank. You can TIG braze it. I recently brazed up a tank that had been sitting for 30 years with fuel in it.

I'm sure there is something that will chemically neutralize the gasoline, I can't speak for that. I threw the tank in a vat of vinegar to remove the rust, then washed it out with simple green and hot water about 5-6 times until I was convinced it was clean. Brazed on it for close to an hour (the tank was in terrible shape) and no explosions. But just because I did it doesn't mean you should, lol. If you're worried about it even after cleaning the tank thoroughly then don't mess with it.

Alternatively you can bring it to a radiator shop and have them hot tank it and seal it up, if you can find a place that will do it.
 
My SR250 had similar tank problems. I JB welded it up and painted it for the moment but have been looking at new tanks for a while now. I have found a few, and am considering some on Ebay out of China. Here is one in particular that I think could work. This one in particular does not have dimensions listed.
http://www.ebay.com/itm/Motorcycle-Vintage-Fuel-Gas-Tank-Honda-CB100-K3-Cafe-Racer-New-Plain-No-Color-/272221018355?hash=item3f61a318f3:g:5fIAAOSwubRXGwzJ&vxp=mtr

Here is another that has a little more café style to it with a huge tunnel.
http://www.ebay.com/itm/2-4-Gallon-Cafe-Racer-Gas-Fuel-Tank-Universal-Custom-Tank-for-Honda-Yamaha-BMW/232082007070?_trksid=p2047675.c100623.m-1&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D39823%26meid%3D30e1ede16f9b480ca0e36c6b19b796f2%26pid%3D100623%26rk%3D1%26rkt%3D6%26sd%3D272221018355
 

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magazine said:
My SR250 had similar tank problems. I JB welded it up and painted it for the moment but have been looking at new tanks for a while now. I have found a few, and am considering some on Ebay out of China. Here is one in particular that I think could work. This one in particular does not have dimensions listed.
(pic)

Here is another that has a little more café style to it with a huge tunnel.
(pic)

Yeah I've been looking at alternative tanks too, and that second one you linked looked promising, I just haven't got around to measuring the mounting points or anything, and I'm still not sure what direction I want to go in. I bought some MDF but still not sure if I'm going to dive into making my own tank.
 
monkeyinfantry said:
Got a few more for ya ;)


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.

You don't need to worry about blowing yourself up if you are welding or brazing a tank, just clean it and let it air for a day or two and you're good to go.......Have welded tanks before with no issue or worry, the only people that have had problems are the morons that do it with gas still lingering in the tank.
Your best and fastest option is to braze like AdvCo has stated, especially where your hole is......that formed area will have less of a chance of warping from heat. Once its brazed or welded, seal the tank from the inside with products like POR15.
 
with correct precautions you can safely weld on a tank that still smells of gasoline
all, needs be done is for combustion of any fumes to be made a certain impossability
and an absolute fool proof,cheap, method is a few chunks of dry ice tossed insided
keep the cap on and just the petcock removed as the dry ice boils into a gas co2 is what will be talking up space and with the small outlet the you can easilly see when the flow stops and its time for another lil chunk or 2 brazing those holes is done with a very close form fitting sheet metal overlay ,sized well beyond the hole to hopefully encounter thicker metal
do not put dry ice in a sealed container that will make a bomb with no fire ..
 
Almost been a month since I last posted, no I didn't blow myself up :p I've been busy with college and went up to my cottage for the holidays. I've also been mainly focusing on my buggy project cause I'd like to get it done for next season. I'll put the build in my sig for anyone who is interested, personally I'm a member of many forums because all sorts of fabrication interests me. I know some forums are iffy about linking to other forums, but hopefully it's ok considering it isn't another motorcycle forum.

As for the bike, no more pictures yet, I drew up some more braces for where the main seat tubes meet the frame's backbone. I just need to mark them up on some metal, cut'em out, and tac. After that I'll start to re-fabricate the top shock mounts so she can stand on her own feet.

I still haven't decided what I'm going to do with my gas tank, leaning more and more towards attempting to braze it up and hopefully I dont go kaboom. Found out dry ice is harder to attain than just walking into a chain store, might look into a purge setup for my TIG. I'll probably give it the simple green and hot water treatment a few times and do a flash burn with all openings unplugged to make sure the fumes are fully out, then hopefully when I braze it I dont turn into living Swiss cheese. More to come.
 
monkeyinfantry said:
Almost been a month since I last posted, no I didn't blow myself up :p I've been busy with college and went up to my cottage for the holidays. I've also been mainly focusing on my buggy project cause I'd like to get it done for next season. I'll put the build in my sig for anyone who is interested, personally I'm a member of many forums because all sorts of fabrication interests me. I know some forums are iffy about linking to other forums, but hopefully it's ok considering it isn't another motorcycle forum.

As for the bike, no more pictures yet, I drew up some more braces for where the main seat tubes meet the frame's backbone. I just need to mark them up on some metal, cut'em out, and tac. After that I'll start to re-fabricate the top shock mounts so she can stand on her own feet.

I still haven't decided what I'm going to do with my gas tank, leaning more and more towards attempting to braze it up and hopefully I dont go kaboom. Found out dry ice is harder to attain than just walking into a chain store, might look into a purge setup for my TIG. I'll probably give it the simple green and hot water treatment a few times and do a flash burn with all openings unplugged to make sure the fumes are fully out, then hopefully when I braze it I dont turn into living Swiss cheese. More to come.
flash burn there is one safe way to do that ,you got fumes coming out a hole fed by some flow behind it
put screen over the hole not chicken wire but pretty fine screen
flame cannot travel back thru screen srsly its a fact,its the similar principle to a gas lantern with silk globe, its an old tank welders trick
used to be easy to get dry ice ,safeway or the liqueer store
you can also get these little co2 deals that you put a cartridge in... it pierces and from what i understand releases it kinda slow
the guys that pull out the old gas station tanks use em ,puncturte cartrige and toss it in the tank for a mild time release effect
exhaust can be use as purge as well
 
I used a product that is designed for removing calcium, lime and rust (quite similar to CLR, which is commonly available in Canada). I was only using the liquid to remove rust from the tank, but when I poured it out and rinsed the tank, there was no hint of gasoline vapours. I then heated the side of the tank to cherry red while I pushed out some dents. Since that went well, I also welded some sheetmetal over the pinholes near the petcock. It's not a nice tank to begin with, so I'm not worried about how it looks. It didn't blow up and I have all of my fingers. YMMV.
 
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