silverstreak Posted July 20, 2012 Share Posted July 20, 2012 hey guys i gotta 1977 yamaha DOHC 500 twin motorcycle and its in mint condition! has about 5000 miles. the tank has a nasty dint and i dont know if you can pop that out or something but the motor is stuck solid. ive tried everything, diesel was just a joke, sea foam didnt do anything, ive even tried CLR but nothing, brake fluid trans fluid did nothing aswell. its a good bike but it was sitting in a shop for 30 years. ive heard steam works because the metal will expand and break away from whatever is making it stick. if you guys have any suggestions please let me know! thanks! Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 20, 2012 Moderator Share Posted July 20, 2012 Does depend on which bit has siezed. If its a big end or the crank its a different issue. Link to comment Share on other sites More sharing options...
slice Posted July 20, 2012 Share Posted July 20, 2012 As Cynic says you have to find out whats stuck before you can repair it, if it's a piston then it's a complete tear down same for crank shaft (big end) just start taking stuff off until you can move it there's no other real way to find out I'm afraid. Link to comment Share on other sites More sharing options...
silverstreak Posted July 21, 2012 Author Share Posted July 21, 2012 i think its the piston, i dont wanna tear it apart i just wanna get it unseized Link to comment Share on other sites More sharing options...
dt 250 Posted July 21, 2012 Share Posted July 21, 2012 Take out the spark plugs and fill the cylinders with marvel mysterey oil and just let it sit for about a week or so for sure it'll free it up probly the piston rings are corroded in the cylinder but take off the magneto flywheel and use the biggest breaker bar you have to try and turn the engine while in neutral Link to comment Share on other sites More sharing options...
davetcollection Posted July 21, 2012 Share Posted July 21, 2012 Take out the spark plugs and fill the cylinders with marvel mysterey oil and just let it sit for about a week or so for sure it'll free it up probly the piston rings are corroded in the cylinder but take off the magneto flywheel and use the biggest breaker bar you have to try and turn the engine while in neutral You might want to take the carb(s) and bodies and exhausts off and spray oil below the piston(s) as well if you can to try and free the bottom of the cylinder. Like mentioned keep putting oil in very day for a week and leave standing, it may free up then. If not you're gunna have to strip it down to get the con rods off the crank to take the top end off. Good luck Link to comment Share on other sites More sharing options...
Moderator Cynic Posted July 21, 2012 Moderator Share Posted July 21, 2012 Oh, i tbought you were rebuilding it. If its been sat in a shop for 30years tbh you may as well tear it down. The seals will have stuck there will be compnents that have been without oil for 30 years. Sometimes little strokers can get away with it for a bit but all that valve gear will be bone dry. If you strip the motor and build it back up you will prob only need seals and gaskets. Start it otherwise and it may destroy its self. Link to comment Share on other sites More sharing options...
Moderator drewpy Posted July 21, 2012 Moderator Share Posted July 21, 2012 thought the bike was mint condition? dented tank and seized engine doesn't sound like mint to me soaking the engine pistons would be the only way to go, diesel's the cheapest option Link to comment Share on other sites More sharing options...
silverstreak Posted July 22, 2012 Author Share Posted July 22, 2012 thanks guys, the bike is mint, when my grandpa bought it in 1979 the bike fell over in the back of the truck and dented the tank in on the wheel well of the truck. my grandpa took it down the road a mile then put it in the shop in 1979 with a tarp over it. i guess the moistier on the concrete floor seized her solid. we tried all the unseizeing crap you can buy at our local automotive store but it hasnt done anything. ive heard before that steam will work to break the piston away from whatever is holding it. also, what is this mystery oil? ive heard of it but idk where you can get it or what. ive also heard of heating up some diesel and pouring it down the piston and let the metal expand. Link to comment Share on other sites More sharing options...
NEV Posted July 22, 2012 Share Posted July 22, 2012 If its seized with rust try Coca-Cola, its a trick we used to use on heat/rusted stuff in the boilers on the power stations, something to do with the phosphoric acid in it, see my project thread concerning seized up swing arm bushes. Link to comment Share on other sites More sharing options...
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