78 KZ650 Mission Cover Crack??

I recently bought a 78 KZ650 with just over 8K miles. The story I got was that 5 weeks ago the owner parked it in the garage and it was working flawlessly. No mechanical or electrical problems and no leaks. His friend winterized it for him and when he went to get it running to sell it he put some gas and oil in it and realized it was leaking oil so he didn't want to bother with fixing it so he sold it "as is".

I took it home and started digging into it hoping to find what was causing the leak and this is what i found (see attached pictures). If what the told me was correct, i can't figure out what would have caused this. I'm hoping that simply replacing the mission cover will solve the problem and the bike will run again.

Can someone please shed some light on what could have caused this and what i may be dealing with as far as repairs?

as a side note, the carburetors are leaking a lot of gas. Suggestions on that would be appreciated as well.

Thank you!

First rule when buying a bike is that the previous owner (almost) always lies.
It looks like there is a hole in the case just below the clutch push rod. I'm sure someone who has a 650 will be along in a while with sound advice.

Definitely a hole in the case. The big question is - what caused it? Below is a pic of how it should look. The curved metal chain guard was off for the picture. It is held on with 3 screws. Notice in my pic the screw hole just below the clutch pushrod; but in your pic that has been broken off. I wonder if the chain broke and jammed between the guard and countersprocket and broke the case? Ed

Regarding the carb leak; if it is leaking fuel through the overflow tubes on the bottom of the carbs consider the following -

Fuel coming out of the overflow hose (the little hose on the bottom of the carb) is the common symptom of the 3 possible problems described below. Remember - NO SMOKING or other activities that could ignite the fuel while working on carbs!

The float valve is not sealing. This may be (and probably is) just a matter of some minor dirt in the float valve and is very simple to remedy and can be done with the carbs still on the bike. Turn off fuel; drain carb by loosening big brass screw near bottom; and remove the 4 little screws on the bottom of the carb bowl. This will enable you to remove the carb bowl. You will then see the float. If you carefully remove the float you will see a stubby little needle that mates with a brass orifice; together, these two pieces are the float valve. Assuming there is no obvious damage to the needle or seat, use a Q-tip and some carb cleaner to clean the seat of the orifice and the needle. Be careful not to bend the tang that is attached to the float. This tang is the piece that the bottom of the float valve needle rests upon, and it determines the fuel level in the bowl, so bending it will change the fuel level. With the float valve cleaned it should no longer leak. To prevent a re-occurrence a quality inline fuel filter should be installed between the fuel tank and carbs. If there was damage the needle and seat should be replaced as a set; they are available.

The brass overflow tube inside the carb bowl is damaged. When you remove the carb bowl you will see a brass tube attached inside and rising toward the top of the bowl. This is the overflow tube and it leads directly to the overflow nipple on the bottom of the carb. Normally, the fuel level within the bowl rises somewhat close to the top of this tube. If the tube becomes cracked or separates from the bottom of the carb bowl fuel will flow through it and out through the overflow hose. Checking the condition of the tube is very easy after you have removed the carb bowl from the carb. Simply hold the bowl level and fill it up near the top of the tube with water of alcohol and see if it leaks. A slight crack in the brass overflow tube can be difficult to find. You can connect a rubber tube to the overflow nipple, fill the bowl with water, put finger over the open end of the brass overflow tube and blow in the rubber end and look for bubbles. If it does the best remedy is to replace it although some folks have found creative ways to repair them.

The fuel level is set too high. This condition occurs when someone has bent the float tang as mentioned above. This condition can be checked using what is referred to as the "clear tube test." The test involves attaching one end of a clear piece of flexible tubing to the carb drain hole and holding the other end of the tube above the bowl/carb joint. When the fuel is turned on it should rise in the tube to a level 2.5 - 4.5 mm below the bowl/carb joint. If the fuel rises higher than that level it may run into the cylinders or over the upper end of the brass overflow inside the carb bowl (mentioned above) in which case it will run out the overflow hose. This condition is corrected by removing the float and gently bending the tang to raise the float valve needle position. Doing this may take several tries before achieving the desired fuel level.

Correcting each of these three conditions involves removing the carb bowl. This task can be made easier if a short screwdriver bit is used, and depending on which carb you are fixing a mirror may help you locate the screws on the bottom of the carb bowl. Also, it is not a bad idea to have a new carb bowl gasket available in case the old gasket is damaged while removing the carb bowl. Ed

650ed wrote: ... I wonder if the chain broke and jammed between the guard and countersprocket and broke the case? Ed...

I think Ed is right on the money, can't see what else could cause that kind of damage.

Good part is that the damage seems to be confined to the mission cover and the cases seem to be okay - replacing the cover should fix the problem. Btw, if you're replacing the cover it won't hurt to replace the cover oil seals with new ones while you're in there anyway.