View Full Version : OT, Q re Lauson Carburetor

J Tiers
11-07-2004, 10:46 PM
I have a lauson on a chipper/shredder (a n old Sears) that has a 6 HP Tecumseh.

The unit works very well when it is working, we go through a LOT of leaves and other stuff for the big compost bin.

However, the (*&%*&^ carburetor is a POS. Every year, it has to be overhauled, with new diaphragm and "float" (gas inlet) valve. it usually has to have the main jet washed out with solvent also.

We run it out of gas every time of use, and use regular 87 octane in it. The fuel filter is OK, and no grit or other F.O. can be found in the gas inlet valve.

That valve, and many other parts have been replaced each year for years. When replaced, the unit runs fine for a while but the following year (spring if overhauled in fall) it will be as bad as ever.

The problems it has are that it will intermittently either just let gas through, flooding (literally), or else it will have the main jet ball check valve stick.

If it floods, there will be gas dripping out of the intake and exhaust. Plug will be full of gas, engine of course won't start until the valve is jiggled and the engine dried out.....

If it sticks, it has to be run at a point between full choke and regular power, a point for which there is no detent......makes life interesting. That seems to be a case of balancing airflow to fuel manually....

Usually it will do one when started, and the other if stopped and a re-start is tried. Which it does at what time may swap...today it was the setting when started, and after a shutdown to handle selling a machine, it was flooding.

This is the only Lauson carb I have ever had, are they all this bad?

Any idea what could be going on?

Alcohol in gas a problem? (bad if so, it all has it in)

Any other carb likely to work? Im ready to adapt a B&S vacu-jet to the (*&%^$%$ thing, except it probably won't work with a 6HP.

Thanks for any advice....

11-07-2004, 10:59 PM
Put some Sta-Bil in the last tank of fuel for the year. Maybe drain the float bowl and clean the needle and seat at the end of season instead of waiting until the next.

Sometimes cheap little carbs are kind of touchy. Head off the potential problems before they are problems, and all should be well.

J Tiers
11-08-2004, 09:50 AM

Since I run it OUT of fuel every time I use it, I don't think "sta-bil" is gonna do much......correct?

No float, its a diaphragm type, but has a similar valve setup for fuel inlet.
The valve, a conical part that hits a rubber seat, intermittently leaks abundantly for no clearly visible reason.

11-08-2004, 02:02 PM
Sometimes a float that has absorbed fuel has its weight changed and will cause trouble you mentioned. The black plastic floats are notorious for this. We used to
weigh them and were suprised to find how far off their weight was.

11-08-2004, 03:02 PM
Dirty Rusty dry fuel tank each year? You'd be surprised to see what comes out of a Harley tank left dry and painted, then gas poured in.
I have a chrome SU off a Jaguar, same problem. It has a touchy float and a kickstand angle to contend with. It is a wonder it has not burned to the ground.

Put some Stabilizer like they use in winterizing chain saws in gas. leave gas in it.


11-08-2004, 03:15 PM
While I am not knowingly familiar with the specifics of Lauson carburetors, running an engine out of fuel seldom removes all the fuel from the system. It appears that some probably remains to gum up your system, and the addition of Sta-Bil might be all that it takes to solve your problem. Having to clean out the main jet leads me to believe that this is probably your culprit.

Additionally, or alternately, you can partially disassemble and spray everything down with carb cleaner. If the inlet valve leaks after functioning properly for some time, the problem can be: 1) Dirt on the sealing surfaces (I assume you are using a ‘decent’ fuel filter plumbed right before the carb). 2) Gumming from fuel residue. 3) Incorrect spring tension, (if it is the type that uses a spring to maintain sealing pressure). 4) Hardening or distortion of the rubber seating surface. If you suspect that #3 is the cause, and it often is, try a different brand of valve next time, or just try using the sta-bil ‘without’ draining the system. I would bet that this last suggestion will work, and it is also the easiest to try. Of course you need to run the motor until you are sure that the treated gas thoroughly displaces all of the remaining fuel. Fuel stabilizers work quite well, give it a try.

[This message has been edited by Joel (edited 11-08-2004).]

11-08-2004, 07:52 PM
The problem is in the float valve and the problem is your drying out all the gaskets including the rubber tip on the float valve if it has one.

Me I don't worry about bad gas over the winter.I leave maybe a pint of fresh gas in the tank over winter.Come spring I add in a cup or so of rubbing alchol,then open the throttle and lets some into the bowl.Then I just clean and gap the plug and run it.When I get down to just about empty I top off the tank with fresh gas.Never have any problems.

J Tiers
11-08-2004, 10:11 PM
Him don't got no float.

This is the ONLY engine that has the problem.

Did it just as bad if I left in fuel

Apparently the units often do this.....someone else posted that he has the same problem, with the same unit. He tried "Sta-bil", didn't do squat.

Must be the "Lausony" carburetor.

J. Randall
11-08-2004, 10:33 PM
J Tiers, try running a small amount of marvel mystery oil in your gas, won't hurt a thing and will give everything a bit of lube. James