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Stuck sparkplugs

Blair84

CB750 New member
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Hello,

I've always loved these bikes and finally found a 1975 cb750 I'm working to get running by summer. I will probably be looking on here a fair bit the next few months trying to figure this thing out. The bike looks amazing and had been garage stored since the mid 80s.

My first problem is the engine is seized. I thought I'd remove the plugs and put some penetrating fluids in to help break it free.

I was able to remove the outer 2 plugs. They were 5/8s and came right out. The inner 2 plugs are 18mm and stuck so I'm assuming they were also stuck 30 years ago or the plugs would all match.

Any tips on getting these out? I've put a lot of force on them but held back as I don't want to snap them off.

Thanks
 
If youve got a deflecting beam torque wrench or similar...it can give you a clue to how much force you are applying to break them free...the 18mm plugs you refer to is socket size??not thread size i assume so just a 12/14mm thread....
 
if an intake or exhaust is open you could spray some penetrating spray in the cylinders. Also spray some around the stuck plugs....probably wont work but cant hurt. If you cant get them loose you may just pull the head, beings its stuck your going to have to tear down and rebuild anyway. With the head off a machine shop can can them out one way or another.
 
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