leaking gas into airbox & then engine

[nimblekat]

I am leaking gas into the air box & then into engine. My question is do the floats go badin the carbs or is the needle valve the floats push on going bad or both. I have 2002 Katana 600.

[92xjunker]

Float needles maybe worn or dirty, cheap to replace.

[nimblekat]

The fuel tap was not left on prime, or reserve. How do I check to make sure the diaphragm is working correctly in the tap?

[Purplehaze]

Remove the fuel lines. Turn the knob to the ON position, pointing toward the ground. Fuel should NOT flow freely out of the petcock. Suck on the vacuum hose (line routed to carb four). Fuel should come out of the petcock.

Smell your oil for fuel, if it has fuel it'll run like crap one warm and NOT be a good idea. If so, change your oil ASAP and do not run it unless absolutely necessary.

It's a fair gander to say your petcock and/or float system is incorrect/mal-adjusted or worn, respectively. You'll have to check your float heights, float needle condition, and sealing. The float should be seated properly with the O-Rings, and a bit tough to remove.

[92xjunker]

The petcock will not cause carb flooding, if your carb are working correctly it doesn't matter where it's set. The issue is the the needles and or seats, unless they were serviced and now they leak. A hole in the float is possible but, not likely. That would be a rare occurrence.

[Purplehaze]

The petcock will not cause carb flooding, if your carb are working correctly it doesn't matter where it's set. The issue is the the needles and or seats, unless they were serviced and now they leak. A hole in the float is possible but, not likely. That would be a rare occurrence.

True, but I've always erred on the side of why have two problems when you can have none.

[maniac1886]

I've seen a diaphragm go bad in a 81 suzuki gs550 and when the motor was running, the vacuum line would suck gas right out of the petcock. In the case of the 550 it definitely flooded the carbs, dripped out of the Pods, ran down the exhaust and leaked out of the seam between the down pipes and the muffler pipes, and filled the oil with fuel. I dont understand why you say a bad petcock wont flood carbs. IMO its totally possible. Like purplehaze said, suck on the vacuum line. if the diaphragm is bad you will know, just keep your preferred gas rinser drink nearby cuz you WILL end up with gas in your mouth.

[Badfaerie]

I've seen a diaphragm go bad in a 81 suzuki gs550 and when the motor was running, the vacuum line would suck gas right out of the petcock. In the case of the 550 it definitely flooded the carbs, dripped out of the Pods, ran down the exhaust and leaked out of the seam between the down pipes and the muffler pipes, and filled the oil with fuel. I dont understand why you say a bad petcock wont flood carbs. IMO its totally possible. Like purplehaze said, suck on the vacuum line. if the diaphragm is bad you will know, just keep your preferred gas rinser drink nearby cuz you WILL end up with gas in your mouth.

This isn't how it happens with Katanas. If you are getting gas in the crankcase or airbox on a Kat, you have something keeping the float needles from seating properly. You can bypass the petcock altogether and if your float needles are seating properly, you are fine.

If the petcock is not working properly, that is a completely separate issue with separate symptoms and diagnoses. In this case, fixing the petcock will mask the problem of the improperly seating float needles so the engine will only flood when it's running. Causing it to run rich and act like there is engine gremlins. It can lead to all kinds of mysterious problems.

So, fix the problem first, the float needles are not seating either because that circuit is dirty, the floats are set wrong, or the needles/seats are worn. Adding the petcock into the mix just confuses the issue.

[maniac1886]

thanks for the correction. that's good to know.

[Badfaerie]

There you go with a common misconception again

To explain the needle valves are not designed to hold back the full weight of a tank of fuel only to regulate it when the bike is running therefore if the fuel tap diaphram goes bad the weight of fuel above can overcome the float & depress it causing the fuel to flow freely hence the above problems

Another problem not specific to kats is fuel can drain down from the higher carbs if the bike is left on the sidestand, 750 slabby's are good at this

Um, no.

[ZukiFred]

The petcock will not cause carb flooding, if your carb are working correctly it doesn't matter where it's set. The issue is the the needles and or seats, unless they were serviced and now they leak. A hole in the float is possible but, not likely. That would be a rare occurrence.

You are half right. This will not cause it by itself, but is part of a multi failure. If the petcock is functioning properly then it will not allow fuel to flow and flood the carbs, so it is PART of the problem that needs to be addressed.

[Purplehaze]

Jesus ******* Christ. Why not just sort out the whole system? Yes, the floats need to be sealing properly and YES the petcock needs to be functioning properly, else the system WILL eventually flood.

Don't even bother trying to debate this, back when I left for college while my bike was still a project my bench-tested carbs (out of the boots but on the bike) overflew when I left my tank on prime after servicing the float system. The same thing would be achieved by a faulty petcock.

[jbo197]

If your bike sat for a couple of months ....
Welcome to the wonderful world of Ethanol!

Happened to me after the bike sat for 2 months, pulled the carbs apart and everything that was made of brass was corroded.

Will not put Ethanol gas back in her ever again no matter what low percentage it contains.

Too much work and aggravation.

[Kreylyn]

To explain the needle valves are not designed to hold back the full weight of a tank of fuel only to regulate it when the bike is running therefore if the fuel tap diaphram goes bad the weight of fuel above can overcome the float & depress it causing the fuel to flow freely hence the above problems

By this error in reasoning, every time the bike is running the floats would/could be "overcome" and flood the bike.


There is no flow regulation on a katana petcock. Vacuum does not control how much fuel flows. It's simply an on/off.


The reason an auto on/off with use of a vacuum is better for a bike not running is because fuel will evaporate out of the carbs since they are an open system. By not having fuel flowing when the bike is off, you prevent the fuel that does evaporate out from being replenished which could happen until the gas tank is empty, or the carbs are so full of deposits that it won't run again.


The number one problem is correcting the float needle issue so that fuel can't get past them. They ARE designed exactly for that. That is the primary thing to look for and correct when the air box or oil fills with fuel. These problems can happen with a perfectly function petcock as the fuel will flood when the bike is running, and also all the fuel that is in the fuel lines from the petcock down each time you shut it off. It may only be a cup full at a time, but it will still happen. Just takes longer for people to notice the symptoms when gas isn't completely draining out of the tank and onto the floor of instantly filling the crank case.


Allowing fuel to constantly evaporate and be replenished can be the cause of the needles stop sealing properly due to fuel deposits. So yes, you really should fix that petock as well if it's faulty... but the petcock is not going to fix the flooding issue, only addressing the float needles will.


When running, the petcock is always on.


Finally, it was mentioned prior that a faulty diaphragm could allow fuel to be sucked into the carbs. This is true, it could. The symptom for that though most times is a dropped cylinder due to only a single cylinder flooding. It's also only going to happen most times when the engine is running. Finally the petcock has a spacer with a hole... so if fuel was able to get to that point... you would have a visible external leak from the petcock, the plunger would probably not work very well at all since the vacuum would be released by that hole stopping/slowing the flow of fuel at all, causing the bike to not run. Honestly... it could happen, but the combined circumstances of the plunger being stuck open (or set to prime) with dual faulty diaphragms sheafs (the diaphragm has 2 layers separated), a clogged spacer hole to prevent the obvious external leak from that point, and then... draining into carb 4... Not very likely to happen on a Kat. It could... but that would be very specific and uncommon.


Fuel getting past the float needles is much more likely due to dirt/deposits.


Krey

[ZukiFred]

Jesus ******* Christ. Why not just sort out the whole system? Yes, the floats need to be sealing properly and YES the petcock needs to be functioning properly, else the system WILL eventually flood.

Don't even bother trying to debate this, back when I left for college while my bike was still a project my bench-tested carbs (out of the boots but on the bike) overflew when I left my tank on prime after servicing the float system. The same thing would be achieved by a faulty petcock.

Yeh, what he said....