MuncyBob
Platinum Member
Sounds like there is no need for the pics of my 422 carb, etc. But this is getting interesting!! That's one thing that is great about this forum...read & learn! /forums/images/graemlins/grin.gif
Vaporlock revisited
- Thread starter Phils
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MossRoad
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- South Bend, Indiana (near)
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- Power Trac PT425 2001 Model Year
Does the carb require pressurized fuel to fill the bowl? I'm not that familiar with small gas engines that have fuel pumps. None of my lawn mowers did. Heck, I don't even know if my Kohler has one. I'll have to look, now. I think the bottom of the tank is lower than the carb, so there must be a pump somewhere to get it up to the carb? Again, I'll have to look.
That's the trouble with this Power Trac forum... it keeps making me look at stuff! /forums/images/graemlins/tongue.gif
That's the trouble with this Power Trac forum... it keeps making me look at stuff! /forums/images/graemlins/tongue.gif
SnowRidge
Elite Member
The Kohler has a pump. It is mounted on the RH valve cover.
ClintBlake
Bronze Member
I had the same symptoms on my 422. It would start and run fine for a while and then start surging and sputtering until it died. Adding 1/3 to 1/2 choke would keep it running.
I pulled the solenoid needle valve on the side of the carburetor that shuts off fuel when the key is turned off. There was a small piece of brown fiber (looked like filter paper) in where the needle goes. After cleaning that out, it ran fine.
I pulled the solenoid needle valve on the side of the carburetor that shuts off fuel when the key is turned off. There was a small piece of brown fiber (looked like filter paper) in where the needle goes. After cleaning that out, it ran fine.
MossRoad
Super Moderator
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- Power Trac PT425 2001 Model Year
<font color="blue"> The Kohler has a pump. It is mounted on the RH valve cover. </font>
Thanks! I guess that would explain the fuel line going to my valve cover as it shows in this picture. According to the manual, I have a mechanical fuel pump. In all honesty, I thought it was part of the low oil shutoff system. Turns out, that is not how things work. There is no fuel shutoff associated with the low oil sensor. There is an electric switch under the breather. From the Kohler manual:
<font color="green"> "On stationary or unattended applications (pumps,
generators, etc.), the pressure switch can be used to
ground the ignition module to stop the engine. On
vehicular applications (lawn tractors, mowers, etc.) the
pressure switch can only be used to activate a “low oil”
warning light or signal." </font>
So apparantly it is not hooked up to do either from the factory, according to the manual. But that is for another discussion. /forums/images/graemlins/laugh.gif
The manual also states that the motor can be run without a fuel pump if the outlet of the fuel tank is higher than the inlet of the carb. I suppose as long as the level of the fuel in the tank is higher than the inlet of the carb, that would accomplish the same thing, so we could still eliminate the fuel pump from the system to see if the problem is with his carb or his fuel line.
Thanks! I guess that would explain the fuel line going to my valve cover as it shows in this picture. According to the manual, I have a mechanical fuel pump. In all honesty, I thought it was part of the low oil shutoff system. Turns out, that is not how things work. There is no fuel shutoff associated with the low oil sensor. There is an electric switch under the breather. From the Kohler manual:
<font color="green"> "On stationary or unattended applications (pumps,
generators, etc.), the pressure switch can be used to
ground the ignition module to stop the engine. On
vehicular applications (lawn tractors, mowers, etc.) the
pressure switch can only be used to activate a “low oil”
warning light or signal." </font>
So apparantly it is not hooked up to do either from the factory, according to the manual. But that is for another discussion. /forums/images/graemlins/laugh.gif
The manual also states that the motor can be run without a fuel pump if the outlet of the fuel tank is higher than the inlet of the carb. I suppose as long as the level of the fuel in the tank is higher than the inlet of the carb, that would accomplish the same thing, so we could still eliminate the fuel pump from the system to see if the problem is with his carb or his fuel line.
Keoke
Gold Member
Gravy, from the looks of Moss Road pic gravity flow to this carb is a long shot. It takes 2.3 feet of fall to generate 1 psi of pressure. In looking at the pic (a guess at best) it seems that the tank bottom is about even with carb. Most small carbs with your sized engine are happy with 2 to 4 psi at carb inlet. At high inlet psi there is a chance that the float will not put enough pressure on needle to stop fuel flow at idle. All of this depends on what is called the "wet area" of float. In short, small fuel bowls require low pressures and wide or deep bowls can take higher pressures.
In looking at the pic I feel for you guys. Having the carb so close to that muffler was not smart. With the muffler so close to carb there is a possibilty that fuel in the bowl it's self is boiling and causing starvation problems.
The fuel pump on the rocker cover may be of the "crankcase pulse" design. These pumps use crankcase pulses caused by the pistons going up and down to work a diaphragm to move the fuel along. Or it's possible that it is conventional pump running off the rocker arm or cam if it's an overhead cam engine.
If it is the crankcase pluse type then you would be better off going to a pluse type (self priming) elec pump. Watch the pressure thing when choosing the pump. You can also buy pressure regulators if needed to control a high pressure pump. Try without regulator first, if float needle holds at idle then you are ok if not use regulator.
The material used on cars as an insulator between carb and manifold is called a "phenolic" insulator and is made from phenol. However, in looking at you pic, the more you space the carb out the closer you get to the muffler. Thats a **** of a choice, none the less, there should be at least an insulator gskt between carb and manifold to reduce engine heat conductivity between carb and manifold.
One more thing, before screwing new elbow into tank bottom,
I would add a short standpipe (1/2" above tank floor) to keep the bottom junk out of your gas line.
lots of luck,
In looking at the pic I feel for you guys. Having the carb so close to that muffler was not smart. With the muffler so close to carb there is a possibilty that fuel in the bowl it's self is boiling and causing starvation problems.
The fuel pump on the rocker cover may be of the "crankcase pulse" design. These pumps use crankcase pulses caused by the pistons going up and down to work a diaphragm to move the fuel along. Or it's possible that it is conventional pump running off the rocker arm or cam if it's an overhead cam engine.
If it is the crankcase pluse type then you would be better off going to a pluse type (self priming) elec pump. Watch the pressure thing when choosing the pump. You can also buy pressure regulators if needed to control a high pressure pump. Try without regulator first, if float needle holds at idle then you are ok if not use regulator.
The material used on cars as an insulator between carb and manifold is called a "phenolic" insulator and is made from phenol. However, in looking at you pic, the more you space the carb out the closer you get to the muffler. Thats a **** of a choice, none the less, there should be at least an insulator gskt between carb and manifold to reduce engine heat conductivity between carb and manifold.
One more thing, before screwing new elbow into tank bottom,
I would add a short standpipe (1/2" above tank floor) to keep the bottom junk out of your gas line.
lots of luck,
MossRoad
Super Moderator
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Remember, I have a Kohler engine and he has a Robbin. There is probably a difference in the setup.
OP
Phils
Platinum Member
There is DEFINITELY a difference in the setup between engine brands!
The Kohler exhausts out the back, the Robin out the front then to the side then toward the back then down. It's that transit down the side that parallels the fuel line. The tub gets hot, and the fuel hose an inch or less from the tub then gets hot too. I'm convinced that is where the problem is rather than in the carb bowl. I also didn't notice an electric fuel cutoff solenoid at the carb inlet on mine, although it may be elsewhere on the carb and just not at the inlet.
Phil
The Kohler exhausts out the back, the Robin out the front then to the side then toward the back then down. It's that transit down the side that parallels the fuel line. The tub gets hot, and the fuel hose an inch or less from the tub then gets hot too. I'm convinced that is where the problem is rather than in the carb bowl. I also didn't notice an electric fuel cutoff solenoid at the carb inlet on mine, although it may be elsewhere on the carb and just not at the inlet.
Phil
SnowRidge
Elite Member
Gravity fed high powered motorcycles have been running fine for years with a foot or less of head, so I doubt that even 1 PSI is really needed.
No need to substitute **** for the word Hobsons, which is what I'm sure you meant. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
No need to substitute **** for the word Hobsons, which is what I'm sure you meant. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif
SnowRidge
Elite Member
Some Kohlers exhaust out the right side. I got rid of my PT built right side 'tank' muffler and replaced it with a rear exhaust Kohler muffler, just like the one that came on Moss's PT.