Is JB Weld good enough to repair a chipped/cracked cylinder head?

no it wont work anyone that knows anything about cars should not have given you some of these answers you can not repair a cracked head with anything you cant weld it or use jb weld it is trash you need a new head the only thing this one is good for is a paper weight you can pick one up at a junkyard cheap take it to a machine shop and have it reworked it will be best to do both sides not just one

Do you mean a crack in the cast iron cylinder liner? First off, if it's hairline how do you propose to get the epoxy into a crack that tiny? The second thing is, how do you know it's cracked? Unless you are using a bore scope, it means you have the head pulled and if you're that far, go ahead and pull the cylinder block and replace the liner of get a used block. Now if you mean an external crack, if your bike has cylinder liners it's probably no big deal since the block itself doesn't contain any compression and the downward pressure of the head holds the liners in place. That is, unless you have one of those BMWs with the nickesil cylinders or some other small engine without liners.

I wouldn't recommend it for that application. JB Weld is great, but your cylinder head is really not the place for it.

If you have the head off, and the engine taken apart, you are better off replacing the head with a rebuild or new, or if it's not too bad, have it professionally repaired.

The labor time it takes to get in there is WAY more trouble than the expense of the replaced/rebuilt head.

No combustion pressure 25,000 psi and temps as high as 14,000 degrees trying to hold water back with epoxy filler "J&B Weld" the stuff is amazing but not for this job. Either weld repair the area and re machine the head surface or replace the cyl head.

Like any other epoxy-type compound, the bonding surface has to be clean and stable. If you get all, and I mean all the foreign matter out of the crack and get the JB into the crack, the JB will hold for "awhile". Most of the stories about JB are short term fixes, not long term. I highly recommend having the head replaced or having the current head welded. It will probably be cheaper to replace.

Have it welded with aluminum weld,than take it to a machine shop and have the head resurfaced.

Don't use JB Weld

That would be like useing bubble gum

Have it weld repaired at a machine shop, the JB Weld wont, hold up to high temp or pressure.

You obviously already have the head off. I would recommend taking it to a machine shop and having them build up that area and machine it back down. ...or replace it. You could also find a like head at a junk yard and overhaul it yourself. ...but to answer your question..

Yes it can. Before you use the JB Weld make sure you clean and degrease the areas very well and then roughen the surfaces to be "welded" before application.

If the metal eroded so will the jb weld

it wont work, have it welded properly or buy a new head. dont risk the money to have to do it again. you have to have a seal good enough to seal out the combustion chamber pressure and those can get up there