550ex running rich

[bertsmobile1]

Got this in to the shop before I took crook.
Fuel pouring out of the carb so it got a bath in the ultra sound and got the fuel to shut off & the upside float holds against 5 psi which is my usual "test"
Thing had no spark so replaced the maggie a week back.
Now it is running very very rich & I can not see any reason for this.
Also the auto choke takes better than10 minutes before it opens fully and while in the 1/2 off / on state the butterfly swings wildly between the open & closed.
Is this normal ?
When finally warm it runs so rich it will not achieve full speed .

This is the model with the auto choke on a bracket off the exhaust and no air vane to over ride the choke .
It is also spewing fuel back out the carb so when it cools down going to open up the inlet lash to delay the valve opening.

According to the owners, the plug gap is .020" , seems a bit small .
Now in the back of my mind I can remember some one with more knowledge than me mentioning there was some tricks to these no prime /auto choke engines but for the life of me I have can not remember what it was or if it was relevent to the 140cc 09p702-0122 engine.
The choke lever had been fouling on the carb mount & I have already relieved that .
I really need to get it & the other old job out of the shop so I can reopen.
Thoughts about what I have missed ?
Thanks guys.

 

[Hammermechanicman]

I am not much help. I had one of those in the shop and i went through 3 OEM carbs till i got one that worked. I know those engines are particular about the valve lash. Every one of those engines i get in have carb problems. Hard starting and surging. Those are the worst carbs i have ever seen. You can replace the white jet to see if it works. There are 2 different ones i know of. I have had to replace the choke thermostat on one. Good luck with the POS.

 

[bertsmobile1]

Thanks.
The jets are not stocked down here so I will have to wait for them to come from the USA and according to my IPL there are 6 of them depending upon the serial number .
Unfortunately this particular engine is from China so it has a different type of serial number to those shown in the IPL although we are only at 100' for the altitude jets can be excluded.
Just the same I really don't want to spend $ 90 + freight buying 3 jet blocks to keep 2 for stock.
The carb is available locally but at $ 120 it is not really an option as it has a bill of $ 170 at the moment so I really need to get it running properly and sent back.
I doubt the owner will spring for $ 290 on a $ 400 mower that is 5 years old .
Not my favourite engine either . "
it is fitted to the locally assembled Victa 19" cut and these got such a bad name that Victa is now fitting USA made engines and put a really big sticker on the new mowers to that effect.
Tried opening the inlet lash to .010" in 0,002"incriments , made no difference .
Got the carb sitting hooked up to a tank that is hanging from the rafters to triple check it s not flooding .
I am starting to think that the valve timing is out ,
Do these have a plastic cam gear that can come loose on the shaft ?
The blow back out of the carb is strong enough to soak the air filter after about 10 minutes which is about how long it takes to fully open the choke.

 

[Rivets]

As Hammer said these carbs Most of the time have a lean running problem, not rich. I know that you know your way around engines and have probably done all of these things, but I’ll list what I have found in the past. 1. Linkages not hooked up correctly, most often choke linkage on the wrong side of choke butterfly. Also stretched spring. Personally I’ve never replaced the thermo assembly on one of these units. Posted video at the end, 3/4 of the way through, has a good pic. 2. White jet assembly dirty or not installed properly. Have seen the DYI try to install 180 degrees off. 3. Jet assembly not fully installed or missing O-ring. 4. Had one where the check ball in the jet assembly was loose, had to replace the assembly. 5. Square bowl gasket, wouldn’t fully seal, don’t ask me where the DYI got it from. 6. Had a DYI improperly install the carb bracket, allowing the carb to sit at an angle. Bert, I know you know what you’re doing and none of these would apply to your situation, but I’m posting them for anyone else who runs into these carbs. In your case if you have a used carb around, I would start by swapping out the jet assembly and pull off spring. Good Luck. Just saw you replied before I could post. Personally I’ve not run into an internal engine problem yet.

 

[ILENGINE]

The running rich sounds like the high speed jet issue. The spitting fuel back into the air filter maybe a secondary issue from the rich problem. Also from what I can find that camshaft does have a plastic gear, but I haven't seen any problems with the cam or the thermo chokes like Rivets mentions. I have seen the jet issue, the clogged jet on the carbs. Most of the issues I see with that engine is the water in the fuel like half a tank sometimes, thank you ethanol, or in most cases the engine will not start or run on the customers fuel. The new push mower engines from briggs are extremely fuel quality picky. If I get one in the shop that doesn't start the first thing I do is dump the customers fuel.

 

[Hammermechanicman]

Dont know about the cam. If it gets to that point i tell customers to cut their loss on the cheap mower. At $35 for an OEM carb here it is worth it. But at $40/hr + parts not worth tearing into a $250 old mower.
Try disconnecting the choke and blocking it open then start engine. Does it still blow back?
Drain the carb and spray a bit of starting fluid in the carb and see if it gives the normal start, rev, die.
Possible intake valve sealing issue?

 

[bertsmobile1]

Thank you gentlemen .
As no one has seen any internal faults with these engines I will make the big mistake & assume all is well with the timing.
So now I will bite the bullet & get a new carb , suppose having one on the shelf can not be a bad thing, just not needed right now.
I can not see any of my customers springing the $ 100 for it but at least I can tell ( and show if needed ) that their carb is gone.
When I got it fuel was pouring out the carb and being plastic it only ever got detergent solutions .
When the magneto was ordered I got two of them so I might try swapping it .
The more I think about it , the more it looks like an overly retarded spark .
Downside of that is I had to get the magneto retail so there is no return on it .
These are too new for my aftermarket suppliers to have aftermarket parts yet and it looks like Briggs Aust is no longer supplying either of them with genuine engine parts as they have been dropped from the new printed catalogue.

FWIW , starts first or second pull , smokey right away , runs about 1/3 speed blowing lots of smoke while choke is fluctuating sounds like 8 stroking.
When choke is fully open it gets to about 2/3 normal speed for a couple of minutes then goes back to 8 stroking & drops to 1/2 speed.
Stuck my finger under & checked governor, it is open fully . Does exactly the same with or without air filter .
Did not think holding choke fully open from the get go so will wire it open & see what happens.
I do not see man of these carbs in the shop , a bit new for my customers . It is the cheap version of this mower for the big box stores which comes with 550e engine .
The same mower is usually fitted with the 163cc 625ex engine for mower shops and these are the only ones I have touched previously.

I ruled out a leaking inlet as generally that will cause a lean burn situation not a black smoke one

 

[ILENGINE]

As far as timing I would check the flywheel key if you haven't previously. maybe it is sheared and throwing the spark timing off.

 

[bertsmobile1]

As far as timing I would check the flywheel key if you haven't previously. maybe it is sheared and throwing the spark timing off.

Thanks,
Been there but a second check won't hurt .
This thing is doing my head in .

 

[bertsmobile1]

To close this thread.
Got a new carb and noticed the choke return spring was a lot stronger than the origin so tried that,'
Almost ran to an acceptable level
Tried the new carb, chalk & cheese so it looks like I will need to keep a few of these carbs in stock.
Ordered on each of the 4 different part numbers , will see what turns up.