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Remove Nut on Primary Drive

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Use a thin walled socket and impact, like mentioned above a regular socket would work if necessary.

Dont use one of those motion pro gear jammers on helical gears, however for straight gears they are the best $10 Ive spent.

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Best advice I can give  get the proper tools for the job otherwise it will end up in a really bad mess. 

 

This is something I learned a long time ago and  is advice that I’m giving to my kids as well. 

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If the piston is stuck, how would an impact wrench spin the crank? Take the clutch off. Remove the nut. Done. If you can get the cylinder off, do that and hold the rod with a glove.

Jamming the gears with anything metallic is a bad idea that can cause chipped teeth.

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8 minutes ago, grayracer513 said:

If the piston is stuck, how would an impact wrench spin the crank? Take the clutch off. Remove the nut. Done. If you can get the cylinder off, do that and hold the rod with a glove.

Jamming the gears with anything metallic is a bad idea that can cause chipped teeth.

It is at bottom dead center from pounding it with a wooden block and hammer.  I figured that moving the crank would at least get me upward piston movement.  I was going to use an impact wrench but will use a breaker bar instead.

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Ok, old boys, old tricks. Find a Thin (cheap) Thin wall socket, Deep or shallow ( using an extension.)  If still won't fit, then the clutch needs to come off. But I think it will. Then leaving the clutch basket on, put a penny between the two gears, Drive and clutch gears.  Penney is copper, and won't screw up the mesh. If you can get a thin wall socket on it. Put it in Third gear or higher, lock the rear brake by hand and begin putting force on the nut. You've seized the Piston in the cyl, so that will help keeping the crank from rotating. This should help. As for the cylinder, after you get the nut off, using a propane torch, heat up the cylinder and  around the area the piston lies, and this should allow you to remove the cylinder.  You have a costly mess on your hands, but with careful attention you will overcome. 

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33 minutes ago, englishr said:

Ok, old boys, old tricks. Find a Thin (cheap) Thin wall socket, Deep or shallow ( using an extension.)  If still won't fit, then the clutch needs to come off. But I think it will. Then leaving the clutch basket on, put a penny between the two gears, Drive and clutch gears.  Penney is copper, and won't screw up the mesh. If you can get a thin wall socket on it. Put it in Third gear or higher, lock the rear brake by hand and begin putting force on the nut. You've seized the Piston in the cyl, so that will help keeping the crank from rotating. This should help. As for the cylinder, after you get the nut off, using a propane torch, heat up the cylinder and  around the area the piston lies, and this should allow you to remove the cylinder.  You have a costly mess on your hands, but with careful attention you will overcome. 

Always grab a spare socket set at the check out line (impulse buy) that can be ground-turned, or whatever mods necessary.

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 Since you have been successful in moving the piston to the BDC position,then try removing the four sleeve nuts that hold the cylinder to the cases.If only the piston is seized then you should be able to turn the nut on the crank easily and lift the cylinder and piston assy away from the cases.

  This should expose the sides of the piston (inline with the pin) in the cylinder sleeve cut aways. Remove the clips and piston pin and the cylinder complete with the piston should come away from the motor.

  Then it is a simple matter,just take the assy to a machine shop and they can safely press out the piston.  

 

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Try a regular not impact thin wall deep socket that is 12 point with your air impact gun.

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Just put the bike in high gear and step on the pedal that runs that giant disk brake on the back wheel and grandma should be able to take off any nuts you need to remove with the junk tools she keeps at her place. FFS

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Shop rags in the gears do a fine job, just make sure it is doubled/tripled over. Thinwall normal sockets should be robust enough to remove the nut. Use a long breaker bar and I think you'll be fine. I've removed hundreds of these.  The motion pro clutch/countershaft/magneto tool is not necessary but is super nice to have. Being a Yamaha of that vintage, it is regular thread, so counterclockwise will remove it. 

Put some automatic transmission fluid in the engine and let to soak. If you managed to move it, it isn't completely stuck. However, if you're serious about this, then plan on a full rebuild including crankshaft/rod/piston/etc. Plus every seal and bearing in the engine. Use the good stuff, no cheap knock offs and it will run for a long time. If you can find fresh OEM it is probably the best, they last at least as long as the originals. I had a CT1 that I put 55,000 miles on: wore out two cranks, lots of bearings, and rebored my way through two cylinders. Those 175s were great, we had several. Too bad 200cc bikes are out of favor, high end ones are the perfect woods bike. 

 

The remark about the disc brake was helpful, although these were drum, both ends. 

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Most sockets have a slight taper to assist initial engagement to the nut. That crank nut is a bit narrow/thin, I would grind the taper off the (use a 6 point) socket to get maximum socket engagement on the nut, will minimize the chance of rounding off the nut flats.

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1 hour ago, BigDaddy22 said:

Most sockets have a slight taper to assist initial engagement to the nut. That crank nut is a bit narrow/thin, I would grind the taper off the (use a 6 point) socket to get maximum socket engagement on the nut, will minimize the chance of rounding off the nut flats.

I do that all the time.  Half the sockets in my tool box have that area ground off.

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8 hours ago, motoxvet said:

I do that all the time.  Half the sockets in my tool box have that area ground off.

Actually, I would've ground down the outside of that socket in the photos until it fit.

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For the curious, and I didn't know this, pennies made after 1982 are made of 97.5% ZINC and 2.5% copper.  Maybe the cause if Bron had a problem with some kind of breakage ?!?!

Yep...gotta use the older pennies OR ELSE.
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