Koehler command 12.5 engine, choke over fuelling?

[chrisgixer]

Hi, wonder if anyone can help…?
Westwood T1250 ride on mower. UK. Koehler command 12.5 engine, runs ok, but lately has started throwing neat fuel out the exhaust when starting on choke from cold. But get the engine spinning on the starter, then apply the choke slowly then back the choke off once it fires and it’ll run fine, with minimal splutter and smoke from cold. If giving full choke it seem close to hydro locking and the starter motor will struggle, it will splutter badly, and heavy grey smoke is evident until it clears with choke off.
Any advice before I fiddle with it and cause more issues?
It’s running 10w 40 oil at the moment, as the manual says is ok to use, but does advise starting will be more difficult in cold weather, which it is. But ok in summer now. The thinner oil (5w 30? ) will go back in soon before it gets colder.

it will also stall on minimum throttle, where it used to be fine.

Ta

 

[chrisgixer]

Cv1259T seems to be the engine model

 

[bertsmobile1]

Check the oil level
Probably will be high.
Float is sticking in the carburettor allowing neat fuel to drip into the engine
It will get worse and can destroy the engine

 

[chrisgixer]

Check the oil level
Probably will be high.
Float is sticking in the carburettor allowing neat fuel to drip into the engine
It will get worse and can destroy the engine

Ok thankyou… yeah I had a DT 125 that did that…come back to it after a lay up and it would be hydro locked, so you had to take the plug out and kick it over until it cleared the fuel out the plug hole.

…on the Koehler though, fuel out the exhaust only happens on choke. Spin the engine without choke from the outset and nothing unusual happens. Open the throttle lever a bit further, still nothing, then you get to the choke range of the throttle lever and all the fuel arrives at once and out the exhaust comes near fuel….I’m just thinking If float was sticking would it not drip fuel all the time and have fuel in the cylinder from outset, rather than just on choke. ….? But no matter, really. Into the carb we go.

 

[Born2Mow]

1. Your float system is bad, which allows an immoderately high fuel level. Not high enough to leak, but higher than required so that the choke draws in too much fuel.
OR
2. Your air filter needs replacing. Inability for air to enter means that more fuel is ingested, in the place of air.

 

[Chrisgixer2]

Sorry chaps had trouble logging in

yes you were correct with your diagnosis. Took the air cleaner out and there was fuel sitting in the inlet. There’s a depression in the ventrury allowing fuel to puddle. With choke open the air speed through the crab isn’t quick enough to pull that puddle of fuel through. But apply choke the air speed quickens and whoosh all the fuel is dragged through.

fairly easy to pull the carb off to clean the float jet, blow thorough and test by blowing and sucking through the fuel line inlet by mouth to confirm it’s seating well. Good vacuum with the carb the right way up suggests to me the float valve is seating.
But I’ll whip the air filter out and check it again before next start up to be sure it’s stayed fixed and haven’t leaked though again.
I’m a bit concerned how to get the jets out thought. A new float needle I’m sure can be purchased and replaced but if it’s the seat that’s worn there appears to be no way to unscrew the seat/jet to fit a replacement ?
Is it a case of a new carb? That might be considered disappointing if so.

thanks for advise though. Oh and oil was on the upper mark? Too high?

 

[Born2Mow]

• Most jets are cleaned in-situ. Those few that unscrew are obvious from their hex shape or screwdriver slot.
• Most modern float needles are tipped with soft viton, making float needle replacement MORE common, and float needle seat wear a thing of the past.

 

[Chrisgixer2]

Hi thanks for reply

came back to the machine today. Popped the air filter out and fuel in the carb inlet clearly visible again

new float needle it is
If I can find one

 

[Born2Mow]

The fuel level should be about 1/8" below the float bowl gasket, which would place it about 1/4" below the interior of the carb.... So YES, your float level is WAY too high.

A good rule is to turn OFF the fuel when you finish mowing and allow the engine continue to run as you walk back to the storage shed or garage. This pulls the fuel level down, which drops the float, which then releases the pressure on the float needle, which makes those delicate viton tips on the float needle last longer. This procedure requires the presence of a manual fuel shut off valve, which is s a very good thing to have. About $8 anywhere.

I my personal view, if your mower/ tiller/ generator has an external 'rubber' fuel line, then you should have a manual fuel shut off valve AND a fuel filter. Having those 2 items would end about 40% of the common issues associated with small engines.

 

[Chrisgixer2]

• Most jets are cleaned in-situ. Those few that unscrew are obvious from their hex shape or screwdriver slot.
• Most modern float needles are tipped with soft viton, making float needle replacement MORE common, and float needle seat wear a thing of the past.

Unless they are recessed with a screw driver slot…. Or no slot as in this case ?