Saving a 1980 750 twin.

Hysteresis. A properly sized valve would probably create a more consistent fuel level. A bigger valve might let in bigger pulses of fuel. Fuel valves can work linearly, but I think they also can work in a pulsing mode. Exact same thing happens in electronic circuits. The pulsation can be eliminated through damping. Using a smaller valve would be analogous to damping.

Obviously, you have to have it big enough to flow for your maximum needs.

Fuel level in the gas tank is directly proportional to the fuel pressure at the valve. I would expect your symptoms would get worse as the fuel in the tank starts to run low. Also, a slightly more restrictive petcock factors in as well.

Glad you got it figured out.

So much for my quick top end swap.... no wonder it seemed low on power. The right piston pin was seized in the piston and took a puller to remove. Not sure how it started; further inspection required. the small end of the rod is trashed. Luckily i can remove the rods through the oil pan. but since I have to go this deep I'm wondering if i should pull the motor and go through the whole engine? that's a bunch more work i'd rather not do. There didn't seem to be any big chunks in the oil pan, just a little dirt that fell down when i removed the jugs. I just can't seem to get an easy one on the projects lately....

as bad as that is,at least you caught it before it got any worse.

leon

I am coming in late to this topic. The bike looks super!! Lots of great and innovative work you have done. I am in the finishing stages of my '78 Twin. Sat in a back yard for 12 years with a locked up motor. Thankfully running now but until I heard that first "pop" I was nervous. Love your build thread.

Looks great. nice paint

After inspecting the sludge in the oil filter/oil gallery I decided to go all in on the engine rebuild. Got some cool mods in mind as well. stay tuned.

I suppose I should be sad that your engine is toast, but truthfully, I'm glad we will get to see some more of your creativity at work.

Finally got the easy win I was looking for. New EBC single disk setup. Shaved 4 pounds off rotational mass and an additional 2.5 unsprung with the removal of the extra caliper. I bought a 12mm brembo MC to match. The fitment is super tight. less than 1mm on spoke/caliper and disk/fork leg. I'm digging the new look. Very interested to see how it feels.

Small update, but one of particular interest to kz750 twin owners.

I was cross referencing part numbers and realized the z1/kz1000 share the same head studs as the KZ750 twin. This means you can use APE's heavy duty head studs and nuts which are intended for the z1/KZ1000. I have bought a set and can now confirm, however, you do end up with 4 extra studs and nuts you don't need. These bikes are notorious for head gasket leaks, increased compression will likely make this worse, hopefully this will help address that.

it begins

Break a stud?
Steve

Just cleaning out old thread lock