Alternatives for repairing crack in head?

Got another little problem, and I'm probing for some different solutions...

Got a bike with a small crack in the head that leaks persistantly (of course!).

J -head.
On the outside it is visible from the base of the cam end cap insert, travels down underneath and travels along the back of the head toward the engine about 1 1/2 inch.

From the inside, it appears to be right through, and travel down from the cam cap plug base, down the inside wall, then along the bottom surface of the head about 1 1/2 inch.

Figure I'll probly just have to take his head off and have it welded, but apparrently that is too much $$$.

Drill and JB-Weld maybe...

Any suggestions?

JB Weld just might work, provided the head temperature doesn't reach much over 500 degs. I've successfully used it in a cracked crankcase, where it stood up well. That stuff is tough, indeed. Of course, the crankcase would not approach the temperature of a head.

You might consider brazing, if you feel comfortable doing it yourself. Sil Fos makes various alloy brazing/solders for different types metal brazing. I've used it in copper and ferrous applications. It wicks pretty well.

Good luck.

JB weld wont work, there's a product out there call Bellzona that the military uses but I wouldnt bet on it. Buy another head and gut yours and use parts in it.try
www.bikeboneyard.com/
they got a 74 Z1 900 head for $125, probably wont work on yours but they got loads of used parts

a friend of mine tried doing his own port work and almost punched thru the oil gallery on the exhaust side of no 2 cylinder he made 2 passes and it let go oil blowing straight out the exhaust it looked like he had blown the motor, we pulled the head off and i cleaned up the area real good with carb cleaner roughed it up good in fact i took a dremel and cut horizontal grooves into the surronding area .i then filled it with jb weld smoothed it out and then let it sit for a while in the open air to harden up, after about 5 hours we bolted it back on then let it sit overnight to cure.and around 8 in the morning we fired it up crossed our fingers no leak perfect he finished out the weekend racing, and last time i checked he was still using the same head.by the way this was on a turbo cartire bike that puts out huge heat and lots of pressure this was over 6 years ago and he's still using it so that says something good for jb weld i'd say.

BTW, I cracked a tooth and went to my dentist today. After he gave me a few options, I asked if JB Weld would work. He said it would but is the wrong color.......crown $950, ba filling (big ass) $140, JB Weld $3.....

Don't know how ell the crack would repair without drill stopping the ends of the crack. Sometimes adding heat to a cracked piece of material can cause the crack to migrate.
Your best bet would be a good used head, with a fresh valve job.

TeK9iNe wrote:

Got another little problem, and I'm probing for some different solutions...

Got a bike with a small crack in the head that leaks persistantly (of course!).

J -head.
On the outside it is visible from the base of the cam end cap insert, travels down underneath and travels along the back of the head toward the engine about 1 1/2 inch.

From the inside, it appears to be right through, and travel down from the cam cap plug base, down the inside wall, then along the bottom surface of the head about 1 1/2 inch.

Figure I'll probly just have to take his head off and have it welded, but apparrently that is too much $$$.

Drill and JB-Weld maybe...

Any suggestions?

It should't cost all that much to have it welded on the outside and then finish it off with a carbide yourself.

If you find the end of the crack and drill a tiny hole there, the cracking should not continue any further.

JB will work. Don't use the quick set stuff. Use the old stuff. It's good for a couple hundred degrees greater temperatures.

I would take a tiny carbide and channel the outside of the crack about .050" deep first before epoxy is applied. Rough it up good and clean it good.


I've repaired ports that were cut so deep in the roof they burned through the bottom of the tappet bore where the spring seat sits. Suzuki GS1000 ports don't have a lot of meat there

If your gonna get it welded make sure to give it to somebody who knows enough to try and isolate the heat wicked off - there have been a lot of valve jobs necessary after the fact on Kawasaki heads due to the seats shifting... there not in there too deep or tight in some cases.

It happened to me...

Well then, I guess we'll give the JB Weld a go.

Very good info...

Thanks all!

How did it turn out?

If you use an Epoxy, don't use JB Weld it is Iron filledu Use "Metalset" by Smoothon. That is what we used on aircraft. It is Aluminum and Titanium filled and it withstands higher temps than JB.

tb.smodev.com/tb/uploads/METALSET_A4.pdf

otakar wrote:

If you use an Epoxy, don't use JB Weld it is Iron filledu Use "Metalset" by Smoothon. That is what we used on aircraft. It is Aluminum and Titanium filled and it withstands higher temps than JB.

tb.smodev.com/tb/uploads/METALSET_A4.pdf

The MetalSet states in thier info the heat distortion can occur at 180 F.

JB Weld is good for constant temps of 500 F without distortion, and bursts up to 600 F for not longer than 10 minutes. It also has a higher torsional strength.

I got a bunch of it hanging around here, so quick and cheap is gonna win here

Thanks.