Cylinder head

Mikaw wrote: Beyond the old school swing arm pointer type sold at sears 100 years ago that I only trusted to torque lawnmower heads.

A bending beam torque wrench is arguably the best option for garage mechanics. They never go out of calibration and can take a lot of abuse. I broke a pin internal to one of my Precision Instruments dial torque wrench when the nut was sticking and then suddenly released (with a crack noise.) It cost me $75 to have it fixed and calibrated. Now I use the beam torque wrench for head nuts, unless they turn nice and smooth.

Maybe we should get back on topic. I went through the whole thread and didn't see anywhere that the originator specified what bolt in the head broke. He said "a bolt" then started talking about carbs. What bolt broke? Can't be a head bolt because it would have broken off in the block? I originally thought he was talking about a cam cap bolt which we all know commonly pulls the threads out of the head.

I guess when the kids are left alone we start to get into the cookie jar.

When steel is placed under stress such as tension it yields elastically. If it's a bolt under tension it will begin to elongate. Up until it reaches its maximum yield strength it will return to its original size when the stress is removed, hence the term elastic. Beyond its maximum yield strength steel will begin to deform. This is called the plastic zone. Finally, when the steel reaches its ultimate strength it will fail, releasing all of the energy stored in it. Mild steel in tension will neck down in the failure area to about half its original size before snapping. In torsion it can actually twist more than 360 degrees before failing. High strength bolts are more brittle than mild steel. They have a greater yield strength but much less of a plastic zone.

It was a cam cap bolt. Sorry i have been off for a bit. I did get a helicoil in and it torqued back up. I did not think it should snap like that either but rather strip the hole out of aluminum. But it did.

New head came so i will be putting that on today.
Besides dont break a bolt.
Any body have things i should be watching for?

Look for cracks, especially in the combustion chamber between the sparkplug and valves.

Back together. I believe it runs super. First bike I've built from boxes. Saved it from a care racer build.
Try to load some pics and a short video later.

Good Lord I must be getting way, way old. Zoomzoompop you got the head at 0831 hrs. this morning and at 1512 hrs. this afternoon you already have it running. Unbelievable.

Rick H.

Yup
But it has a little bit of white smoke? For the year of the bike is this normal? Last bike i owned was back in 1998 and that was was just to beat on.

I haven't followed the thread closely so apologies if the answer lies in here somewhere. Was the head rebuilt? Just wondering the condition of the valve seats, guides and seals. Did you do a compression test?

None of the above. Bought one of ebay. I will prolly do a whole engine rebuild over the winter. Just getting it rideable for the remainder of the riding season.