TOPIC:

Well, I was trying to ride the rest of the season before getting back to the garage. Today I went out on a 20 mile ride on country roads. Things were great. Then about 10 miles of highway at 60-65, pulling about 4600-5000 RPMs. Parked the bike for about 2 hours to caffeinated my head. Started her back up - rich fuel smell. At the first red light could tell power at the throttle was down, engine sounded different. Pulled over and shut down. #2 pipe was touchable/cool. About 4 weeks ago I noticed this issue and the remedy was a new set of plugs, and she was running great. Been riding between 80-120 miles a week, mostly low speed under 50, gas mileage in the high 30's (38.9 last fill). Overall bike WAS running well with plenty of power...

As many of your know I worked this bike back to street worthy going back to November and have become very familiar with my KZ and riding her every chance I get.

Ok, so here's my to do list:

• clear tube test (completed within range)
• carb sync
• valve clearance check

I was leaving this out until rain days or colder weather when I can't ride, however I want this problem to go away. My best guess is the valve shim is way off, sucking gas and not closing correctly causing excessive burn. I pulled the plug and it was black/dry, fouled. Could also be a valve seal. Could also be carb/mix screw related. The screws are all 1-1/8 out as specified for stock. I have a new manometer sitting in the box that should probably get used for a proper sync, although it could be related but I find it less likely. Float bowl/overflow on #2 sometimes leaves a drop or 2 on the concrete, could be higher than spec.

Question is where should I start and am I missing something?
All help is always greatly appreciated (I know we have discussed these topics a million times)

It's possible that the petcock has a bad diaphragm (if it's the stock petcock). The vacuum line from the carbs runs from the #2 carb to the petcock. This line draws vacuum on the diaphragm in the petcock when the engine is running and opens the petcock for normal fuel flow. However, if the diaphragm fails, which they sometimes do, the petcock can permit fuel to be drawn down to the carbs through the vacuum line. When this happens, that excess fuel goes right into the throat of the #2 carb and can cause a rich or fouling condition on #2 cylinder. You may be able to check for this problem by pulling the vacuum line off #2 carb and seeing if there is any fuel in the line - there should not be. Another alternative is to temporarily cap off the vacuum nipple on the #2 carb and run the vacuum line to one of the carb sync nipples on the carb holder of a different carb then put a new spark plug in #2 and see if it fouls. Ed

Yes it is the stock petcock. I will most likely check that air hose in the morning for gas.

650ed... a few months back the #2 overflow was spitting fuel at about 30 second cycles. I rotated the petcock several times and the problem went away. I'm going to bet 79 cents that air hose contains gas.

In the last few days I've noticed more backfires at idle that go away during cruise speed. Typical sign of a fouling spark plug. My rides have been mixed short and long distance, speeds below 50, some stop and go in the city and a very small amount of highway time. Wondering is going to a higher temp plug will help keep the carbon off the ceramic? The answer is yes if I don't have a problem elsewhere, but I think my rides have now become more than going around the block, so idle and low speeds shouldn't be the issue.

This morning had a few drops of gas from the #2 overflow tube on the garage floor.

I'm going with 650ed's diagnoses on the Petcock as the probable culprit. The spark plug will burn the excess gas for as long as it can before fouling, then an obvious rich gas smell when the cyclinder is no longer firing. All making sense.

Refer to note added to previous post.

jumping forward, should I order the rebuild kit for the petcock or look into a new aftermarket petcock (if it exists)?

Regarding the carb overflow -

Aside from the possibility of fuel passing through the vacuum tube causing an overflow of #2 carb, fuel coming out of the overflow hose is the common symptom of the 3 possible problems described below.

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

There was certainly gas in the Petcock vacuum line, so I proceeded to take a look. There is corrosion on the air chamber side of the valve (photo is after cleaning). The diaphragm is intact and I did a suction test that didn't indicate any holes. Overall dirty with some corrosion and wear, can be cleaned but I ordered a replacement just to be certain.

I'm now leaning to the "clear tube test" to determine if the gas level is set too high in the #2 bowl. (More on that tomorrow). Thanks 650ed for the suggestions.

Well, you never know what you are going to learn here! I have noted the same problem on mine. Colder number 2. Hadn't thought of the petcock but makes sense. I just spent the money on a dyna S cause I thought that was the problem and now I think that my problem was the same as yours. Funny, I just ordered another new petcock from Z1 because it leaked from the front and the PO told me he rebuilt it and just couldn't get it to stop leaking. I just never thought it through. Well, now I have a new ignition so oh well. I justified the purchase with the old "well it's old anyway" excuse. Now I think I may have a perfectly good stock ignition system sitting on the shelf. We shall see. I can't believe how much I learn just lurking around here.

Although at the moment with the tank off my bike, it upsets me I'm not riding. However on an equal level I enjoy wrenching and learning just as much (on rainy days).

A few months ago I had gas spitting out of the #2 overflow hose. Checked out the carb and everything else. Sat back and started to think about it and the fact the petcock relies on the #2 vacuum air for pressure and fuel delivery. Back then every time the carb needed fuel it seemed to get too much. At some point I ended up just rotating the PC about a dozen times and the problem went away completely. I had previously pulled the petcock off the tank to clean it. Took apart the front end but not the back end because the diaphragm was stuck down.

The fuel nipple on the PC also started leaking a few weeks ago when I installed a new fuel hose and gas filter. I didn't know this part was just fitted into the PC, thought it was fixed. Anyway, I moved it around and the leak stopped. Taking it apart I noticed there is a small groove on the inside end of the shaft (very small). I found a very tiny and thin o-ring type paper ring (photo to follow) that had a split end when I pulled the nipple out. Have read advice to cold weld it back on, but not certain it needs to be done that way.

I should have a new diaphragm on Monday and in the meantime will take the opportunity to do a clear tube test on all the float bowls and round that off with a carb sync. I've added 600 miles riding on my first season on 2 wheels and was holding off on these checks for another few weeks, My KZ both sounds and runs great, so I thought this could wait.

I'm also suspecting the #2 float level is slightly higher than it should be and pushing gas into the cylinder, especially after the plug has fouled and no longer burning in the chamber. The plug fouled about 300 miles ago and I replaced all 4 and the KZ was good to go.

This time I'm chasing the proper and complete fix so I don't have to deal with it for another 10,000 miles.

Since the topic of petcock repair has been the focus here I wanted to add a few more notes to this thread. Last night I reassembled the PC after receiving the new diaphragm from Z1.

The first image is the new diaphragm in place and I'm lifting a corner to show the positioning of the pressure release slot in the diaphragm spacer. I did not find any info in the FSM or the parts manual regarding orientation, so I placed it the way I found it. After setting the spacer, I flipped the diaphragm onto the PC and lastly placed the spring and cover and locked it down.

The second photo is the fuel nipple. No where does it say this piece comes off. About a month ago I noticed a fuel drip from the nipple after installing a new fuel hose. I took the opportunity to take a look at it and with just some easy pulling the nipple slid all the way out. I noticed a very small neoprene ring also fell out and a groove on the nipple shaft where it belongs. The ring was split and most likely the cause of the leak. I attempted to replace it with the smallest rubber o-ring, but there just isn't enough clearance to make it work. I looked around and decided to use basic sewing tread to fill the groove. This seemly worked and I will keep on eye on it for the next few weeks (and may result to a cold weld with JB weld).

Just glad to have it all back together while there is riding weather to be enjoyed.

Took her out for a 10 mile dinner. I'm very impressed - more power, smoother running engine, exhaust sounds fierce.

After spending a week with the petcock it's interesting how the vacuum hose connection can attribute to all sorts of issues with the #2 cylinder. As the diaphragm was clearly no longer creating a clear seal, gas was going directly to the top of the #2 carb and sucked into the cylinder, rich until fouling the spark plug. The other topic is the vacuum hose only produces suction to open the diaphragm and allow gas to flow from the tank to the float bowls of the carbs. The air is not used for anything else. With a leak/hole/puncture in the diaphragm this amount of pressure is changed and some extra air could also being getting introduced into the #2 carb.

We talk about air leaks being notorious for problems, I think this one is a sleeper since it's the last place to be looking for a fix. Now is this why many choose to cap the vacuum port and change over to a gravity fed petcock?

If you need help on this send me a message directly.

I expect to replace the diaphragm every 2-3 yrs or so. Some guys absolutely abhor vacuum petcocks & will say anyone is an idiot for not switching to a manual fuel valve.

Nipple repair. I used Permatex liquid metal on a petcock fuel nipple several years ago --- no leaks. And also to repair a leaky low fuel switch that was seeping fuel at one of the electrical terminals.

Seal-All is probably a good product to use (no mixing w either product).
I think the HomeDepot carries it --- it's on their website.

The petcock diaphragm certainly needed replacement. The vacuum hose is now dry after the engine has been running.

The second part of this equation was the points/timing. After pulling the points cover off I noticed the 2-3 gap was off and arcing. I had a new points/condenser kit on the shelf and decided to finally replace it all. Set it up to spec. Also replaced the spark plug connectors with a new set of NGK connectors, tested the coils again and wires (good).

Adjusted the air screws to 2 turns out (spec is 1-5/8) to avoid running rich, plugs are now just slightly on the grey side of the spectrum. My guess is somewhere between 1-5/8 and 1-3/4 will be the sweet spot. I was running the air screws around 1-1/4 rich.

Overall, the #2 is running hot and strong, thanks!