resleeving cylinder
#1
01-25-2006, 09:56 PM
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#2
01-25-2006, 10:00 PM
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#3
01-25-2006, 11:27 PM
resleeving cylinder
It also matters if its locked from being ran too lean or if it locked up from rust. If the motor sat without a sparkplug it could have rust seized. In that case you could hone it and replace the rings, maybe.
Also, If you have to pound the piston out make sure you use a pice of wood or something to keep from busting the piston. Make sure the crank is not at top dead center or bottom dead center. You want to make sure the crank has some place to go when you start to force the piston down. Only hit it as hard as you need to. Penetrating oil may or may not help if its seized up bad.
You won't be able to tell how much work is needed until the piston is out. Once its removed you can see if the cylinder is in bad shape.
One thing a lot of people forget is that a motor may have failed because of an ongoing problem. If this motor was seized a few times already and was always honed out, it may have been due for a next over piston a long time ago. A 30 year old motor could have had many owners and many abusers. If the cylinder ends up being too warn for the same sized piston/rings, it may never break-in correctly and seize up or lose compression within hours of being rebuild. You have to think about how much time and money you want to put into the bike. If you use ebay you can get lucky and find the right sized piston/rings combo for around 40 bucks. You also have to have the cylinder bored out at a machine shop for between $100-$150. If the rest of the bike is in good shape, you would have a pretty nice bike for around $200. Make sure its a YZ before you order any parts. A YZ would have no 2 stroke oil pump/tank or any lights. As crazy as it sounds, Yamaha's own maintenace steps for 70s/80s YZs call for new rings every "2th race" and new pistons every 5th. I'm sure your not racing the bike but it shows just how much care needs to be taken on the motors when pushed hard. I'm sure the bike has seen the redline more than a few times. I have worked on a few mid 70s Yamaha dirt bikes, I also have a few shop manuals if you need some any specs. PM me if you need any more info/help.
Also, If you have to pound the piston out make sure you use a pice of wood or something to keep from busting the piston. Make sure the crank is not at top dead center or bottom dead center. You want to make sure the crank has some place to go when you start to force the piston down. Only hit it as hard as you need to. Penetrating oil may or may not help if its seized up bad.
You won't be able to tell how much work is needed until the piston is out. Once its removed you can see if the cylinder is in bad shape.
One thing a lot of people forget is that a motor may have failed because of an ongoing problem. If this motor was seized a few times already and was always honed out, it may have been due for a next over piston a long time ago. A 30 year old motor could have had many owners and many abusers. If the cylinder ends up being too warn for the same sized piston/rings, it may never break-in correctly and seize up or lose compression within hours of being rebuild. You have to think about how much time and money you want to put into the bike. If you use ebay you can get lucky and find the right sized piston/rings combo for around 40 bucks. You also have to have the cylinder bored out at a machine shop for between $100-$150. If the rest of the bike is in good shape, you would have a pretty nice bike for around $200. Make sure its a YZ before you order any parts. A YZ would have no 2 stroke oil pump/tank or any lights. As crazy as it sounds, Yamaha's own maintenace steps for 70s/80s YZs call for new rings every "2th race" and new pistons every 5th. I'm sure your not racing the bike but it shows just how much care needs to be taken on the motors when pushed hard. I'm sure the bike has seen the redline more than a few times. I have worked on a few mid 70s Yamaha dirt bikes, I also have a few shop manuals if you need some any specs. PM me if you need any more info/help.
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