Danger's Ongoing Carb Thread

So tomorrow, given I can remove it, I was planning on hitting the advancer with some CLR.

Good idea? Bad idea?

Unless the CLR is corrosive I think you should be okay. I'm hoping someone else will speak up. I was fortunate my bike was garage kept by the PO (previous owner), so it had very little rust. Do you have a manual danger? There may be an available download in the file base.

Yes to both, but the manuals don't address removing corosion from the advancer.

Okay, the label on the bottle states to NOT USE on copper, brass, aluminum, or galvanized metals.

Are the advancers made from any of the above?

I think the advancers are generally brass.

CLR is corrosive. I would seek a different path.

So, I wasn't able to remove the pickup plate, the bottom screw.is just too stripped. So, I hit the advancer with wd40, and superfine steel wool, and a very gentle touch. I started the bike under full choke- 5k rpms, and it eventually bogged and died. A quick check of the floats were reading extremely low.

Also, someone I know has an air filter, and housing, and is willing to sell it and another set of carbs to me for $70. Good deal?

Forgot to mention-

When I blipped the throttle, it felt AND sounded like a piston wasn't firing. Advancer or lean mixture problem?

Here's my problem for today.

With my petcock set to PRI, my floats read very, very high. Almost like the needle doesn't seal completely, and I even get a steady overflow. After starting the bike, with Petcock set to ON, it idles for a bit, and boggs and dies. A check of the floats afterwards reads very, very low.

What is going on?

It sounds like you may have 2 different problems. The following assumes your bike has a vacuum activated petcock.

When the petcock is in the "ON" position vacuum from the carb pulls on a diaphragm inside the petcock which permits fuel to flow to the carbs. If the vacuum line is missing, clogged, or damaged, OR if the diaphragm is damaged, the petcock may not be permitting fuel to flow. This may cause the engine to stop running and the fuel level in the carb bowls to be low.

When your petcock is set to "PRI" position it opens an orifice to permit fuel flow. This means that fuel will flow from the tank to the carbs until the float valves in the carbs stop the flow. If the fuel level in the carb bowls is too high, you should 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