starting flooded bike

2

2strokerfun

Member
May 19, 2006
1,500
1
Time to change or clean my float needle and seat. Couple of times recently flooded the bike by leaving the petcock on for 10 minutes or so when bike is sitting. Wondering what most people do to speed up starting a flooded two stroke. About the best way I've found is to remove the plug, blow it off, put the piston at lowest point and let it sit with the petcock off for 20-30 minutes with the plug out.
Anyone else got any better tips??
Meant to put this in 2-stroke forum. Oh well.
 
W

wake_rider

Member
Feb 21, 2007
481
2
I've always pulled the plug, laid a rag over the plug hole, then kicked it with the choke on multiple times to move air through the cylinder and evaporate the gas faster. I'm a bit impatient, though. However, I've always had the bike immediately start up after re-installing the plug. I've also drained the float bowl while closing the petcock and just starved the bike of fuel while kicking it a few times.

Either way seems to work, and it's just dependent on how much time you're willing to wait around. With both of these techniques, I've had the bike started within 2 to 3 minutes...
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
A trail bike, or any low compression motor/ small bore: Turn the fuel off, lay the bike over to drain the carb, choke on, throttle wide open and kick furiously, until it blubbers. Turn the gas on and the choke off, clear the motor out. Replace the float valve and seat asap. Vintage Bob
 
P

pesky nz

Member
Sep 13, 2010
296
0
If the motor will turn over I open throttle fully and kick gently at first and then full strength, if no go by about ten kicks remove plug and kick with stop switch off (ever since My boss set fire to a bike 30 years ago) and yes repair flooding problem before any damage occurs (I had to replace a bent conrod on a KX250 that was towed with a hydrauliced motor and have seen crank seals turn inside out) and turn off fuel whenever the motor is stopped for now. I have never found the choke helpful on a flooded bike JUst a wide open throttle
 
2

2strokerfun

Member
May 19, 2006
1,500
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whenfoxforks-ruled said:
Replace the float valve and seat asap. Vintage Bob
Click to expand...

I've got another brand-new mikuni in a box. I'll cannibalize the parts. Unfortunately, I noticed a huge crack developing in my intake manifold. Vintage, schmintage .......sigh....... I'll pay $75 for a $20 part when I finally find a good one.

pesky nz said:
I have never found the choke helpful on a flooded bike JUst a wide open throttle
Click to expand...
That has worked for me on cars, but so far, not on my bike. Draining bowl or laying on side to drain the carb is I believe the missing step for me. And, of course I should fix the freakin problem to begin with !!
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
If the float valve is bad enough, dropping it from a helicopter may not do the job. The Vintage parts, yes, brings chills up my spine. Even so called new parts from fleabay can be like the lottery. There are a few companies making new tech fancy colored manifolds, for some models. REASONABLE!
 
R

rmc_olderthandirt

~SPONSOR~
Apr 18, 2006
1,533
8
I am confused why float valve problem leads to flooded engine.

My bikes have all had a float bowel vent/overflow that led to a drain hose that routed the gas "safely" under the bike. I quoted "safely" as a stuck float would result in gas leaking out into the toy hauler or garage, neither of which was safe!

I have known people who have had a leaking float valve and attempted to fix the symptom (rather than the problem) by pinching off that hose or routing it up high. It keeps the gas from dripping out onto the ground, but now it will flood the engine instead.

The only time I have had a flooding issue is when the bike was laying on its side. Sometimes the bike fell over and I wasn't there to pick it up right away. A few times because I was trying to help someone and didn't take the time to find a spot where the kickstand would work. A couple of times because I had just crashed and picking the bike up was way down on the priority list (way below "restoring breathing" and even below "taking inventory of essential body parts")

When that happens the plug is generally fouled so it needs to come out anyway. Kicking it over a bunch with the plug out will generally clean it out, and then a new plug will fire it up.

Rod
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
A running engine, will draw the excess fuel into the engine. The angle of the intake and carb, of an unloaded bike, the fuel finds the path of least resistance. Some of those hoses, are not really over flow hoses, as much as atmospheric vents?
 
F

FNG

Member
May 2, 2008
97
0
Yes, when the float needle seals correctly the only place for fuel to go, IE when tipped over is out the vent lines.

But when the float needle does not seal the fuel passes it and goes directly into the engine.

The vent lines are above the bore of the carb so the fuel never reaches this point to drain out. The fuel comes right up the seat and past the needle and into your crankcase.
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
My bike was cursed, with the lay it over on its side, then it starts on the first kick, or floods hopelessly. I replaced the float valve, and it still done it. And still flooded the motor! I used an oem float valve. I switched out the carb with another newer carb, no more physical work out to start! I wish I had a microscope to inspect the float valve I purchased, I am sure it has issues!
 
R

rmc_olderthandirt

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Apr 18, 2006
1,533
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FNG said:
The vent lines are above the bore of the carb so the fuel never reaches this point to drain out. The fuel comes right up the seat and past the needle and into your crankcase.
Click to expand...


Not on any of the carburetors I have worked on.

Here is a link to an exploded view of a typical dirt bike carburetor:

http://www.sudco.com/CatalogJPG/046.jpg

Item "23" is the vent hose, which connects to the bottom of the carburetor. It connects to a "stand pipe" (opposite of a dip tube) which you can see in the float bowl extending upwards at about a 45 degree angle. The top of this tube is just slightly higher than the maximum level of gas in the bowl, but it is a long way below the throat of the carburetor.

If the float valve leaks, gas will rise in the float bowl until it gets to the top of this tube, and then it will run out the vent line. I suppose that if the float stuck wide open that gas could flow in faster than it could drain out the tube, and then a small amount would leak into the venturi of the carburetor and then perhaps into the engine.

A slow leak, however, should just drip out the vent hose.

If the bike isn't something close to vertical then there is an entirely different situation.

Rod
 
J

_JOE_

~SPONSOR~
May 10, 2007
4,697
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Rod is right, that's how it "should" work. However many people don't realize their carb vent tubes are plugged, in which case the engine may get flooded out by a poorly sealing float valve.
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Mine (PJ38) appears to be closer to half an inch above the bowl, and ends up into a cavity, just below the bore around 1/4". Was not clogged, BUT, I always turn my gas off, next time I will check, I am pretty sure it would dribble. I do know it starts on the first or second kick, with out the lay it over and let the fuel run procedure! That was terrible! And I do wonder if at idle would keep up with the dribble?
 
2

2strokerfun

Member
May 19, 2006
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It apparently doesn't take much straight gas or premix to flood an engine enough to make it difficult to start.
 
R

rmc_olderthandirt

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Apr 18, 2006
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It may not be that gas is actually getting into the engine.

There is a normal float height that allows sufficient room so that gas won't slosh around and make it out the vent tube. If the float valve is operating properly, it takes only a very light pressure to shut off the flow of gas. If the valve seat is worn it may take more pressure, which comes from the level raising up and the floats being submerged a bit more.

If the valve doesn't seal at all then the gas will raise all the way up to where it leaks out the vent line. This raises the float level significantly. The air/fuel mixture is influenced significantly by the float height, so having the bowl as full as it can get will make the mixture on the rich side.

If the bike is hard to start because it is too rich, try shutting the gas off, tip the bike over to spill some gas out of the carb, and then kick it.

Don't forget to turn the gas back on when it starts....

Rod
 

whenfoxforks-ruled

Old MX Racer
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Oct 19, 2006
8,129
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Merrillville,Indiana
How about, the fuel has an easier path through the pilot and main, possible some siphoning action, than higher into the over flow/vent tube? That vent tube, is also the culprit of floats out of adjustment, they do not go out of spec from normal use, imo.
 
P

pesky nz

Member
Sep 13, 2010
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0
Logic says

 
2

2strokerfun

Member
May 19, 2006
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whenfoxforks-ruled said:
... floats ... do not go out of spec from normal use, imo.
Click to expand...

I've been saying that for years. Only non-leaking floats seriously out of adjustment I've dealt with were made that way by somebody's ham hands.
 
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