More petcock and carb trouble

Finally made time to work on the bike (78 kz650 b2) this weekend and I'm still having difficulty with the petcock and now carbs. I've ordered a rebuild kit and it's still giving me problems.

1st: When I start the bike with the choke on, it shoots up to ~4-6 rpms till I put the choke back down, which then causes the bike to die. It I try to throttle it at all, it dies as well. Additionally, a substantial amount of white smoke shot out from the exhaust while this happened. All four of the hoses below the carbs have gas in them as well...

2nd: The nylon spacer in the petcock has a tiny hole designed on the side facing toward the front of the bike (see awesome hand-drawn diagram attached). I noticed it was spurting (not leaking, but shooting) gasoline out of this hole.

I've been so busy with school/midterms/work, the bike had to sit for a few weeks - which may have added to the problems. The carbs are the only thing on the bike I'm completely unfamiliar with, so repairs are proving to be challenging - anyone have any resources for learning how to work on carbs?

Thanks again,

Zach

Welcome Zach.

I know of the hole you speak of in your diagram, and I have never seen gas spray out of one before.
I'm suspecting something's not sealing right, or the vacuum line is not hooked up right.

How have you connected the petcock to the carbs?

Check the carb section here, and at forums.kz650.info/ too, a site for 650.

Many, my self included, have rebuilt petcocks only to still have problems with them.
I ended up buying a new replacement for a Suzuki from Z1enterprises.
Others have since found a better GPz one I believe.

First – you need to replace or rebuild the petcock or you will continue to have problems. All the parts needed for a rebuild are still available. Ask if you need help funding them.

The 4 hoses that hang off the bottom of the carbs are overflow hoses. They should be routed between the rear of the engine and the swingarm and should terminate a few inches from the ground and should be open at that end so fuel can escape if an overflow condition exists. If any fuel drips from any of them you have a carb problem with the carb to which that overflow hose is attached – in addition to the petcock problem. The carb overflow problem must not be ignored because in addition to possibly causing a fire it may result in fuel also overflowing through the carb throat into the cylinder and down into the crankcase which will corrupt the oil and can cause internal engine problems.

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. See diagram below for details.

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