Rich Run Condition, Briggs Intek 10HP / Gen

[Cranky]

Problem, Runs very Rich with black exhaust, also will not come up to speed (Sputters / Backfires as well)

I did a top end with new gaskets and valve stem seal due to heavy carbon in cylinder, and Intake valve sticking issues
I have gone completely through Carb. (Nikki - bs# 699966) all ports and transfer tubes are clean and not enlarged, float and seat are functioning.
I have checked Spark which is consistent and installed a new plug as well, Cleaned a set Magnatron and coil gap. Still No Change.


If I turn off the fuel, after about 1-1 1/2 mins. as the fuel level gets low it starts to come up on rpm and smooths out ?

The plastic Transfer Tube Assy. inside the Carb looks good along with the gasket / O-Ring type seal.
At the price of this carb I don't want to replace it on try and see basis, rather explore other possible options first.

1# Could the Transfer Tube Base be warped enough to cause more fuel to bypass the main jet ?
2# Could Timing cause the rough run and fuel flooding effect ? ( Have not checked the Keyway but TDC looks good at the Mag.)

3# Is it possible the Genset is binding up after starting up ? ( It starts Fast and easy for a 10HP)


Coleman Powermate 6250 PM0545007.01

Briggs Intek 10HP 204412-0156-E2

Weather = Hot and Humid

Thanks' Cranky

[HondaG100]

You have an obvious carb/mixture problem. I cannot speak from experience with this exact model but either your needle and seat are leaking, the air filter is plugged or you have an internal leak letting to much fuel into the engine. If no fuel drips from the engine and into the filter or crankcase when it's sitting then my money is on bad O rings or something warped.

[bgsengine]

Problem, Runs very Rich with black exhaust, also will not come up to speed (Sputters / Backfires as well)

I did a top end with new gaskets and valve stem seal due to heavy carbon in cylinder, and Intake valve sticking issues
I have gone completely through Carb. (Nikki - bs# 699966) all ports and transfer tubes are clean and not enlarged, float and seat are functioning.
I have checked Spark which is consistent and installed a new plug as well, Cleaned a set Magnatron and coil gap. Still No Change.


If I turn off the fuel, after about 1-1 1/2 mins. as the fuel level gets low it starts to come up on rpm and smooths out ?

The plastic Transfer Tube Assy. inside the Carb looks good along with the gasket / O-Ring type seal.
At the price of this carb I don't want to replace it on try and see basis, rather explore other possible options first.

1# Could the Transfer Tube Base be warped enough to cause more fuel to bypass the main jet ?
2# Could Timing cause the rough run and fuel flooding effect ? ( Have not checked the Keyway but TDC looks good at the Mag.)

3# Is it possible the Genset is binding up after starting up ? ( It starts Fast and easy for a 10HP)


Coleman Powermate 6250 PM0545007.01

Briggs Intek 10HP 204412-0156-E2

Weather = Hot and Humid

Thanks' Cranky

The main nozzle installed correctly into the fuel transfer tubes? o-ring on it not leaking? Pressure test the carb - those nikkis can easily develop leaks due to careless assembly - Have a peek at the article on this website's content pages http://ppeten.com/two-minute-drills/pre ... nd-simple/ - see if you can get a pressure tester and test it out for leaks.

Just had that exact model/spec of engine in with the same problem - the owner tried to clean carburetor, and lost the main nozzle jet completely. (tiny brass nozzle that fits in the transfer tube - thats your main jet, goes in o-ring end towards the bowl.)

[Cranky]

Fresh oil in CC and no fuel dilution, also no drips from carb or wet-throat syndrome.

This Nikki has a Plastic Transfer tube assembly that is held against the sealing O-ring gasket by means of a spring, and although I do not see any signs of cracks or warps I suspect it could be leaking by. fuel level seems ok in the bowl ie' a little over half full when bowl is removed.

Also main jet is intact, it was clean and back in its place.

The nozzle that goes up into the throat from the main jet also seems ok, this one appears to be glued into the body casting.
The page you did on the nikki pressure test was very good, it will be of help to many... thanks for the link.



I appreciate the responses, Thanks

[Cranky]

I went out and examined the carb again, no pressure loss on the inlet or needle seat.

The Gasket sits in the body casting on this model and it appears to have some very small scratches, but nothing that looks like it could cause fuel fouling.

The transfer tube body does appear to have some staining between the low speed, inlet and emulsion tube ports.
looks like there may have been fuel seepage across the gasket, and maybe the gasket has actually shrunk.

I will order a gasket first and if that shows improvement ? I'll go for a complete carb.

[KE4AVB]

As mention main jet o-ring could be faulty. Not available separately that I know of so main jet replacement is the only to get it.

Another possible is that someone could put in the wrong jet. All depends if this one have worked on before now. I don't have the jet size on this jet as I have not needed one yet.

[Cranky]

As mention main jet o-ring could be faulty. Not available separately that I know of so main jet replacement is the only to get it.

Another possible is that someone could put in the wrong jet. All depends if this one have worked on before now. I don't have the jet size on this jet as I have not needed one yet.

Main Jet and O-ring appear original, fits into bottom of tube very snug as it should.

A friend owned the genset since new and he stated it was beginning to run rough, and got to where he would have to use starting fluid to start it.

I did notice that the plastic choke shaft looked like it was partially melted and warped from heat, other than that the whole carb looks great.

I ordered the gasket and will update when installed, not going with a new tube assembly as its half the price of a new carb.
If the gasket works well then I will stay with that for now, but will probably put a new carb on it soon.
The genset is worth $100 investment in parts, and maybe my friend will throw in some cold ones for the effort.

[Cranky]

Update 9/02

Ordered and installed the new O-Ring in carb and had no effect, then ordered a new carb complete.

Installed new carb and low speed perked up slightly, high speed is still suffering and blowing puffs of black smoke.

re-checked spark condition, mag setting and then keyway. All OK

Rechecked Valves for clearance, leakage and binding. All that appears OK

Then noticed a slight difference in the rocker arm travel of the valves, Ex valve is only moving aprx.
2/3rds of what the In valve does. After stripping the genset / armature and CrankCase........ Flat Cam strikes again...

So now waiting on more parts and the mailman, we will see"

[Cranky]

"And now for the rest of the story" .... RIP Paul Harvey ...

Turns out Timing was the overall cause, the EX. cam lobe had worn enough to cause shorter exhaust periods.
Inturn acting like a clogged muffler, causing the engine heat to build affecting the choke shaft and other carb distortions.

After installing the new Cam and Tappets and re-assembly of the genset it fired right up, but the high speed was extremely high.
I called the owner to get more info on the the running condition prior to the problems, and told him about the over-speed.
He told me it has always run wide open since day one and he thought that was what it was supposed to do, Hum ??

Today I went back out and checked the original Gov. adjustment, shaft was way CC of the set point against the mechanical Gov pin.
I adjusted the Governor to initial setting and now it runs smoothly and holds load changes, actually works like new should work.

New Carb, Top End renewed and De-carboned, New Camshaft and Tappets plus misc gaskets and seals.

The Popping and black exhaust, as well as the fouling under load and lack of acceleration are all gone.
Even put the old carb back on just to see the difference, other than a slight rich odor and darkening of the plug, it runs well also.

I am putting the new carb back on it, do a overall clean up and calling it good to go..

Thanks to all who replied,