OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Brand new mower - major rich problem!

Hi Guys

I found this brand new Victa Vantage with Briggs 450 outside my unit complex. Being a qualified motor mechanic, I figured I'd be able to fix whatever was wrong with it. Boy, was I wrong! It runs (barely) super rich - belching out black smoke and misfiring like nothing else. I've removed the fuel tank, drained and refilled with fresh fuel (thought someone had put 2 stroke fuel in it), removed the carb and blown out all orifices (removed & blew out main jet), checked the diaphragm, air cleaner, new sparkplug, everything is new and spotless clean - now it's just driving me crazy! It was slightly over filled with oil so I drained out the excess and it's spot on the full mark now. I removed the throttle linkage and governor springs and I can get it to idle ok (no smoke) with the throttle plate fully closed. When I open the throttle past about 1/4 it smokes and farts like nothing else. I've heard this is a common problem but it's got me stumped! Any information would be very much appreciated!

Chris

Hi Chris, welcome to Outdoorking.

Please post the full set of numbers that will be in a visible place on the engine, probably on the cowl but possibly on a sticker on the crankcase. There will be three groups of numbers, called Model, Type, and Code. We need all of them, so we can try to find a parts list.

The problem will obviously be in the carburetor, so we need to find out exactly which carburetor it is. Hopefully we can get all of that from the three groups of numbers.

Thanks Grumpy

I'll post pics of the other numbers tomorrow night.

Chris

That carb is the pulsa primer carb.

You didn't mention having checked whether removing the air filter element cures the problem. Some types of sticky-coated filter element don't have to look dirty, to restrict the flow of air into the engine. A restriction of the air intake, such as an obstructed filter element or filter housing, gives an excellent match to the particular symptoms of this problem (engine runs properly at idle and gets increasingly rich at higher speeds). Hence I suggest you test the mower without the entire air filter before trying anything else.

On the old PulsaJet for vertical crankshafts (horizontal crankshaft version has a very different fuel pump and does not have the problem) major flooding was commonly caused by leakage from the pumping chamber into the intake area, bypassing the jet. This was typically either due to the carburetor body being bowed, or the diaphragm being damaged/displaced. The Briggs manual does not mention any equivalent sensitivity with the Pulsa-Prime, but you might try laying a straightedge across the carburetor body to check whether it is low in the center. Remember also to tighten the attaching screws in the correct sequence:

Hi Chris, once you've checked the carby body, replace the diaphram(they're fairly cheap) and take off the blower housing and make sure the manifold bolts are snug, The manifold runs under the coil and bolts up on the near side of the block with 2 1/4" bolts.
Good luck and let us know how you go.

Sorry I've taken so long to post this information!

Model - 01502
Type - 3152 H1
Code - 11102751
Dom (?) - Oct 2011

Can someone please recommend a good parts supplier in western Sydney?

Removing the air cleaner had no effect. The only way I could get the engine to run any better was to remove the throttle and governor springs and fully close the throttle butterfly. It then would run without misfiring, but only at idle! I managed to get my grass cut this way, but didn't it take me ages!

I stripped the carburettor again this time removing the primer bulb and found the tiny spring that holds the check ball against its rubber seat was mangled. I am assuming this could be the problem I have been searching for?

When I get the carby kit I will do those other jobs, like checking the manifold bolts and checking the fuel tank for trueness.

Chris, that Model is incorrect, and Briggs denies all knowledge of that Type as well. It might perhaps be a Model 09T502 for example, but I can't even guess the Type.

The carburetor's primer bulb is supposed to work like this:


If the ball is not held closed against its seat, the primer pump may not work at all. The Briggs troubleshooting chart does not reveal any way that a primer malfunction can make the mixture rich, though:
http://www.briggsandstratton.com/support/frequently-asked-questions/~/media/Frequently%20Asked%20Questions/Engine/PDFs/carburetion_troubleshooting_detail_reference_guide.ashx

You will need to fix the primer malfunction anyway - let's see what effect it has on the rich mixture problem.

So my "Briggs" is a fraud? I'm hoping genuine parts still fit! Grumpy, can you give me an idea of how much a carby kit is?

The Code indicates it was made on 27 October, 2011. The manufacturing plant code, 51, is not actually a manufacturing plant, it is a facility located at B&S head office and is described as "TBS", whatever that means. I suspect your engine was actually made in Plant 28 in Chongqing. Briggs' manufacture of small side-valve engines in the US was pretty much phased out by 2011. This involved closure of a number of US plants.

The numbers are not clearly stamped. I think that is 9T502-3152-H1. If so, here is the illustrated parts list for it:

http://bsintek.basco.com/BriggsDocumentDisplay/18kvuIXSnfBhU7y.pdf

Here is some information on carburetor parts from the Outdoorking on-line store.
https://www.outdoorking-forum.com.au/index.php?main_page=index&cPath=193_195_203

If you can't find what you want, I suggest you send a Private Message to Bruce, the site owner - he'll be able to help.

Thanks Grumpy, my mistake.

Chris, are you really sure you have installed the carburetor's diaphragm correctly? Here is the assembly diagram:




I may be missing something, but a messed-up diaphragm is the only thing that seems to really fit the symptoms.

Yeah I had the diaphragm oriented correctly. Haven't had the cowl off yet. Will get a carby kit tomorrow. Going to work on it again on Wednesday, will post an update then.

just want to add that if you have the aircleaner (one that sits atop the carbie)off you must still put its bolt back down the carbie hole for the choke to work properly.aparently these things are notorious for diaphragm problems. i have one with similar prob to yours and i just put it aside for a later date. so maybe your prob when solved will eventually help us all in the long run.cheers bazz

Gizmo, on this carb there is no choke, having the screw in there or not may make a negligible difference but I have never experienced one. It would be the diaphragm at fault, chances are its either sat with a little fuel in hte tank (its a 2011 model chances are it might have been tried once or twice when new, or the dry weather has simply cooked the diaphragm

Yeah I had the diaphragm oriented correctly. Haven't had the cowl off yet. Will get a carby kit tomorrow. Going to work on it again on Wednesday, will post an update then.

Be sure you put the diaphragm directly against the tank top, and the gasket on top of the diaphragm. Check that the diaphragm lays flat, no wrinkles, bumps or misalignment.

As Joe said, if you tried to run the old Pulsa-Jet without the air cleaner mounting screw in place, it ran vastly rich, but the Pulsa-Prime is a different animal.