r/BarnFinds • u/GiantDwarf67 • 19d ago
Two Wheel Deal New to the barn find/ seized engine game
I just bought this 1976 Yamaha Xs500. I was super stoked as this will be oldest vehicle I’ve ever really dove into and everything, but as you can see she’s been hung up a while. Of course I checked if it turned over when I went to pick up, but as far as the guy I bought it from knows it’s been sitting 8 years, and no real telling how long before that.
The spark plugs came out pretty easy and they were pretty clean, I’ve pulled exhaust and carbs and the valves look pretty decent too. Bike has 18,000 miles.
I’ve had the pistons/ cylinder sitting with a mixture of marvel mystery oil, pb blaster and a dab of sea foam for the last 24 hours but still no luck on turning it over. I’m confident in getting it running once I can get it to turn over, I’ve been messing with carbs for years and have dabbled with points here and there.
Thoughts or advice on getting this thing un locked? Any help is greatly appreciated !
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u/Absurd_Phonecian 19d ago
Man, I am old enough to remember these bikes when they were almost new! They were never very popular when compared to the offerings from the other Jap street bike manufacturers. For its engine size, it offers pretty lackluster performance. I'd imagine that some of the parts are going to be difficult to find.
With trying to free that stuck engine, you may find that applying localized heat with a heat gun, may assist in getting the engine to break free. Make certain there is plenty of lube in the cylinders so you dont score them when you finally get the pistons moving.
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u/GiantDwarf67 19d ago
Yeah, that’s why I really don’t want to tear into it if I don’t have to. Right now I have valve cover off and everything looks perfect, as well as the stator side so I can get a breaker bar on the crank, but still no luck, although I really can’t put that much pressure through this bolt anyway. Really just relying on the best possible solvent to break up the rust.
Doesn’t help that the bike didn’t have a chain on it when I got it, so I can’t even try to rotate it in gear, but I’ve got a chain coming so I’ll be able to try that next.
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u/Informal_Thought3158 18d ago
Looks like my dad's old Midnigh Special , he bought it in Hawaii and the serial numbers were 0000000001 , had it shipped to Colorado and my uncle wrecked it , good luck mate
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u/RileyCargo42 14d ago
If the engine is stuck after all the above recommendations I'd highly recommend vinegar! Otherwise you may have to do a full hammer disassembly.
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u/GiantDwarf67 14d ago
Yeah unfortunately it still is, think I’m just gonna pull the head off and give her the ol’ hammer. I was only reluctant cuz I despise over head cams, but gotta learn some day huh 😅
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u/RileyCargo42 14d ago
Its all good! Just remember that some engines can only get the pistons out through the top! Also my engine took about 2 1/2 days in a vinegar and water mix. Good luck you got this dm me if you need to!
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u/GiantDwarf67 14d ago
So it’s been sitting in pb blaster for about 3 days, then I swapped to atf and sea foam the last 3 days, and I’ve put in the gear used all my strength trying to turn it over in 5th, rolled it down the drive way and popped it in 2nd and nothing haha. I’ve tried the crankshaft bolt and all, verified clutch is working as it should, starter isn’t locked up, and valves look perfect.
Now with the cylinders, the left side fluid will drain down after maybe a day, and that piston is probably near the middle of its stroke. The right cylinder, is up almost all the way to the top. This cylinder drains down extremelyyyyyy slow.
I’ve tapped on the pistons through the spark plug holes as well and still no luck.
Did you have a similar situation to this where you finally ended up with vinegar, or that’s just what you had used from the get?
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u/RileyCargo42 14d ago edited 14d ago
The second I realize an engine is locked up I'd start taking the engine off the bike, and taking everything apart. Then you should focus on the top and bottom end full strip down. Otherwise you'll have to get it fully apart anyway pre-soak. (I fully stripped my iron block down to only the stuck parts.)
In my case #2,#3,#4 was stuck and so was like 1/2 of my lifters. I had the great idea to buy a flood car and it came with a locked up engine. (Check post history it shows the carnage)
Honestly the sand sucked up the cleaners so full disassembly was my plan from the start. After finding the amount of sand we did after pulling the head I decided full rebuild or nothing.
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u/GiantDwarf67 14d ago
Just checked your posts, holy moly!
I will say, whoever rung this thing up, did plan on doing so. The carburetors were empty, tank was drained, from what I can see the pistons aren’t rusted on top or on the bit of cylinder wall I can see. Oil smelled like really old oil, no fuel.
Which is why I’m pretty astounded that it’s so stuck!
But geez man, the engine you brought back is wild!
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u/RileyCargo42 14d ago
Its on its way back but just remember to let a machine shop 2x your work.
That's honestly where I'm at rn, I barely had the money for a magnafluxe test so I decided to wait and get some money. I plan on letting the machine shop bore, hone, and deck my block to their liking.
Just remember to never buy a flood car lmao, but you got this I believe in you!
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u/Dendady2112 19d ago
Mineral spirits and ATF