1980 KZ650 F1 carb issues, I think

Hi all. Proud new owner of a 1980 KZ650 F1 here. Ive had it for about a month and have put ~1500 miles on it. There are some issues that I think are carb related and I was hoping to get some help here, or at least confirmation of my suspicions. My symptoms are that
1) I have idle at 2000 rpm, which is already high, and it still tends to stall out at that. It used to be only during warm up, and now it' just happening when i've already started riding. Also, it used to be that I could keep it running idle at 2000 when warming up if I had the choke on (would die otherwise), but now that does not work either.
2) When I'm in first and am starting from a stop, the first bit of throttle I give feels like it's not doing anything, only after an initial weak pause of maybe a second does it start moving.
3) It leaks from the carb overflow tubes. Not sure if on all of them.

From reading up on it, it seems like my pilot jet might be stuck/gummed up, but I'm not certain about that. I have no idea how much the jets are screwed in
I am planning on cleaning my carbs, should that be sufficient? Do I need to take the whole thing apart or is it sufficient to just clean part of it.
I understand that in cleaning carbs, I don't really need the whole carb repair kit, but that some items should be replaced. Is this just o-rings? If so, what o-rings do I need?

Thanks,
Armen

Welcome aboard. Does your bike have the stock air box and air filter in place? Ed

Ah, yeah, I should have mentioned this of course. It's all stock. stock carbs, and it has an airbox and filter.

Sorry to say this but before you beat your head against a wall, you will need to remove the carbs and disassemble them for a complete cleaning.
That means knowing what you are doing and not just wash them out... but actually clear out every single port, vent, orifice, jet and hole, plus set the fuel level correctly....all of which is the downfall of 90% of folks who think they cleaned their carbs... they just don't do it any where right.
Most likely you will not need to buy any jets or carb kits if you research this!! There are numerous threads here on Kzrider about cleaning your carbs the right way!!

For a start, study this:
www.kzrider.com/articles/technical-tips/123-carb-cleaning-101
and this:
www.kzrider.com/articles/technical-tips/124-carb-cleaning-102

I've never needed to replace anything in my KZ650 carbs except the carb bowl gaskets.

You have already identified one problem with the carbs - the fuel overflow. That is abnormal and must be corrected before you fiddle with anything else. It could be causing the stalling, etc., and whether it is or isn't related to that issue it still needs to be corrected.

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 or 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

missionkz, 650ed, thanks both for the suggestions, I will read up and go through the list that 650ed wrote up. Otherwise, I'll start on a teardown of the carb, as per missionkz. As for knowing what I'm doing - of course I don't. I will read up though, and trust that that is enough.

You will after you read up on this.... also, it is nearly impossible to clean these carbs without some very narrow wire.

www.kzrider.com/forum/2-engine/598397-ru...-dies-at-idle#674990