TOPIC:

I just finished rebuilbing the topend on my 82' KZ750r. When I started it up, i had great compression and it felt super strong. The problem was the smoke, a lot of smoke! I ran it for maybe 5 minutes total, and by then it had burned or sprayed out all the oil. What went wrong?

can you walk us through what you did during the rebuild and how you assembled it,is it blowing oil out exhuast or crankcase vent or both?

Are you saying it used ALL the oil in the sump in 5 minutes?

Wow, I thought my zed was a heavy drinker!! Respect.

When I got the bike the case was full of gas. Which I decided was from the rings being collapsed. During the rebuild I took the whole motor apart, cleaned everything and put it back together. I replaced the rings (stock), replaced the head gasket, new valve shims for clearance. After I timed it and started it up within 5 minutes all the oil had sprayed out the exhaust.

Xtr3m3 wrote:

When I got the bike the case was full of gas. Which I decided was from the rings being collapsed. During the rebuild I took the whole motor apart, cleaned everything and put it back together. I replaced the rings (stock), replaced the head gasket, new valve shims for clearance. After I timed it and started it up within 5 minutes all the oil had sprayed out the exhaust.

did you measure the cylinders before you installed the new rings? but then again if the rings were that far far out of wack it should be be pushing a lot of oil out the crankcase vent from blow by.if the vent was plugged it should be blowing it out everywhere only other thing would be the worlds loosest valve guides to totally drain a motor that fast,but then again if your guides are that loose i would think your valves would be all over the place and wouldnt be seating not to mention that much oil should be fouling your plugs to the point where the motor wouldnt run!im confused,need more info! NURSE!

This is a twin, right?

By collapsed rings do you mean carboned into the grooves on the pistons?

One cylinder is sucking oil and spewing it out the exhaust.

Check compression with gage. Probably low on one side.

Suspect head gasket allowing oil to be sucked from cam chain tunnel.

Suspect ring gaps aligned on one piston.

Suspect forgot rings on one piston.

Suspect blew a hole in the top of one piston.

Duck wrote:

This is a twin, right?

By collapsed rings do you mean carboned into the grooves on the pistons?

One cylinder is sucking oil and spewing it out the exhaust.

Check compression with gage. Probably low on one side.

Suspect head gasket allowing oil to be sucked from cam chain tunnel.

Suspect ring gaps aligned on one piston.

Suspect forgot rings on one piston.

Suspect blew a hole in the top of one piston.

The motor is an in-line 4. By colllapsed I mean there was no gap left to them. I loosened th pipes from the motor and it looked like it was coming from all cylinders, but when I pulled the plugs 1 & 2 had oil in them. How could the head gasket allow oil to be sucked from cam chain tunnel? All pistons had rings and all ring gaps were offset when I installed them. How can I check that that is still the case?

id say to run a leakdown test,but if its leaking that bad im guessing you should go ahead and pull the head off and do an autopsy before anymore damage is done;)

No matter how well we think we put something back together when oil gets pumped out that fast, we did something wrong. You're going to have to open it back up to find the issue. I didn't notice if you said you honed or bored it when doing the rebuild?

Xtr3m3 wrote:

Duck wrote:

some stuff, see parent

The motor is an in-line 4. By collapsed I mean there was no gap left to them. I loosened th pipes from the motor and it looked like it was coming from all cylinders, but when I pulled the plugs 1 & 2 had oil in them. How could the head gasket allow oil to be sucked from cam chain tunnel? All pistons had rings and all ring gaps were offset when I installed them. How can I check that that is still the case?

OK. That's a new term to me. Looked it up. The reason the end gap goes away is that the rings got hot enough to lose their temper and are no longer springy.

Did you measure the ring lands to make sure they were in spec and still square? Did you measure the bores to make sure they were still round and not to big? Hone because bores were surely glazed? If it got hot enough to spoil the ring temper then it could have cooked your valve guide seals but I can't imagine that much oil getting through the guides.

Oil poors out of the head into the cam chain tunnel. The stream hits about where the head gasket is on the opposite side. If there is a hole here it will alternately pressurize the crankcase and suck oil out of the stream. You wouldn't see on outer cylinders.

Are there any valve oil seals or O-Rings somewhere that could cause this problem? It appears that the oil is coming from the head and not the case.