OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Problems with Briggs and Stratton Engine

I have a Briggs and Stratton engine attached to a Victa lawnmower with the following specs:

Model = 92908
Type = 5175 01
Code = 82072308
Horsepower = 3.5
CC = 148CC

My mower has not been starting for quite a long time. I got it from a friend and it would not start, I cleaned it and it started but was very unstable, then after a while it had no spark anymore, so I replaced the spark plug and magneto and it started. I took it to mow the lawn I mowed about half the lawn and then it ran out of petrol. I refilled it and then it would not cut the grass without stalling. Then after that I tried to tip the lawn mower on it side to get petrol in the carb, but then oil came out of the air intake and went in the cylinder and it still does not start, but has spark.

Also I am trying to replace the carb diaphragm but I cannot get the spring into the seat on the diaphragm.

Another thing to note is that most of the screws on the mower are stripped, the thread holding the tank to the mower, the thread holding the pull start to the mower and the bolt holding the auto choke cover on.

It is a complete mess, can someone help me?

Thank you in advance.

Hi Lachiepower0402, and a warm welcome to the forum. It's great to have you aboard as we all like to learn new things and tinker here.
Thankyou for posting such concise information on your engine...some pics of the engine would be appreciated as well. Instructions for using the forum 'Inline Uploader' and be found HERE
Grumpy is our resident guru on Briggs and Stratton, and I sure will chime in here and give you advice on how to proceed.

Once again, to OutdoorKing.

Hi Lachie, welcome to Outdoorking.

Here is the Illustrated Parts List for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6nmsFVJ1DajI.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/msowGK-K_ny7tH217FzoPu.pdf

The engine was made on 23 July 1982, so it will be one of the first Briggs engines to be fitted with Magnetron electronic ignition (no breaker points or condenser).

There are rules for which way you can tip a 4 stroke lawnmower. If you tip a Briggs engine toward the valve chest, the valve chest will fill with oil and it will go through the breather pipe into the carburetor when you start it. Always tip it in the other direction so that the cylinder is upward.

So far as getting your engine running is concerned, the first thing to suspect is that when you ran it out of fuel, it sucked up a bunch of garbage from the bottom of the fuel tank and blocked the filter-screen on the fuel pickup tube on the bottom of the carburetor. While you are fixing that, it makes sense to strip the carburetor and clean it properly. It will probably need a new diaphragm after all those years. The 92908 is very unusual in that it has a Pulsa-Jet carburetor with an automatic choke, and unlike other older Briggs carburetors, this means the carburetor has to be serviced, and in particular re-attached to the fuel tank, carefully with the instructions from the workshop manual open in front of you. If you do not preload the diaphragm correctly when re-attaching the carburetor to the fuel tank, the choke will not work. So, you need to get a copy of the Briggs and Stratton Service and Repair Instructions 1984, though you can get by with a copy of the Single Cylinder L Head tech manual.

The stripped bolts are your main problem, and if you can't solve it, there is little point in worrying about your carburetion problems and the oil sloshing around in your combustion chamber. There are two ways to deal with a stripped bolt. The cheaper and easier way is to tap the thread to the next larger size. The more expensive way, which is mandatory for collectors' piece projects, is to fit a helicoil so each repaired thread ends up the original size.

Frankly, unless you are something of a mechanical hobbyist, you have a fairly difficult job in front of you repairing the stripped bolts, and it isn't really worth doing unless you aspire to becoming a mechanical hobbyist.

Thanks for the manuals, they are quite useful. I will definitely be looking at the stripped bolts first. I am able to fix a stripped thread and I have done it once on a motorised bicycle engine. But my main problem is money, to fix the stripped threads I would have to buy three different kits.

I will have to have a look online for the repair manual.

So I found the manual on this website, but it says that I don't have access, how do I get access?

Thank you in advance

The manuals are in a "subscription only" area of this site. For details of how to go about subscribing, please refer to this thread:
https://www.outdoorking-forum.com.au/forum/u...ords=subscribe&Search=true#Post53305

Sorry if I sound like I'm cheap, but did not want to spend money on the 1984 repair manual, but I did find the Single Cylinder L Head Manual Online

http://evanosaurus.com/ebooks/270962%20Single%20Cylinder%20L-Head%20BRIGGS%20&%20STRATTON.pdf

You won't get any disagreement from me on the desirability of being cheap, Lachie. The job can be done with the later manual, but it will be more difficult. You need to start on page 48 of 336, and remember, your engine is a 92900 series. In particular, it is not a 92500 series: that has a Vacu-Jet carburetor, still with an automatic choke, but with no diaphram and consequently less complexity. I suggest you do not follow the overhaul procedure as such, since that would require various new parts that would be difficult to get. The objectives are to inspect the diaphragm and replace if necessary; to clean the fuel intake screens, especially the one on the longer tube which is the fuel pump pickup - but only removing the tubes if they are the screw-in type; and to clean out the jet and the metering holes, plus miscellaneous fuel and air passages. You will need a spray can of carburetor cleaner, complete with the long thin tube that comes strapped to the outside of the can.

Remember that your engine has an automatic choke, not an all temperature automatic choke, it has a Pulsa-Jet carburetor, not a Vacu-Jet carburetor, and it has a pneumatic governor, not a mechanical governor. At this point I can't tell you whether you have a zinc (metal) bodied carburetor or a Minion (plastic) bodied carburetor, but I think by 1982 most of them were Minion.

I suggest you now read the manual, identify the sections which actually apply to your carburetor, and remove the fuel tank and carburetor from the engine. Then remove the carburetor from the fuel tank, take some pictures without doing anything else, and post them here. Then we can discuss the situation before proceeding. I'm hoping you'll find a bunch of grass and crud blocking the intake screen of the long tube. If you do, we can talk about how to clean it without having to buy parts to put it back together.

Here are the images of my mower, tell me if you want anymore photos.
















[img]https://www.outdoorking-forum.com.au/forum/uploads/usergals/2014/11/full-8567-18398-img_4426.jpg[/img]

Also I noticed that the intake tube was a bit wobbly when I took the carb off it. By the way the oil getting into the cylinder only happened yesterday.

Thank you in advance

You can only include 10 pictures in a single post, Lachie. After that you have to start another post.

There is an O ring that sits in a groove in the carburetor, where it slides over the intake port. A small amount of movement between the carburetor and port is normal, to allow alignment when the fuel tank is secured to the engine: that is what the O ring is for. As long as that O ring is intact, it should seal adequately against intake air leaks.

Your fuel intake screens seem to be reasonably clear, and are not the cause of your problem. You should clean the screen on the long tube with carburetor cleaner now that you have it dismantled, and you should clean and inspect the mixture adjustment needle and the metering holes behind it at the same time.

Then I suggest you concentrate on assembling the carburetor to the fuel tank correctly. It will be very difficult to do this by using the post-1984 manual, so I suggest you just read from an on-screen version of the pre-1984 manual, starting with the right-hand column on this page:
http://recoveryvehicles.tpub.com/TM-5-4240-501-14P/css/TM-5-4240-501-14P_98.htm
Use the "next page" arrow at the top to move to subsequent pages.

If you read through those instructions and then come back to this thread, we should be able to get the it correctly assembled and working.

Thanks I didn't know you could only have 10 pictures.

Those instructions seem a lot easier to follow, I have read through and it seems easy enough. The only thing I'm worried about is that the bolt that holds the cover on for the choke shaft, which has a diaphragm is stripped, which means that it would not be very air tight.

So do you want me to completely remove the mixture screw and clean it and the holes behind and also clean the long fuel pickup tube.

Thank you in advance

First, you have several threads to re-tap to make that engine usable: the one for the auto choke cover is one of them.

Second, it is not essential to remove the long pickup tube. You can spray the carb cleaner across the mesh, and clean it that way.

For the mixture screw, begin by checking how many turns it is screwed anticlockwise, from fully in. Be gentle doing this: you will ruin it if you screw it firmly against its stop. Just turn the screw clockwise gently, counting turns, until it bottoms lightly. Report how far it turned. Then unscrew it completely. Inspect the tip as described in the manual, and clean the screw with carb cleaner. Inspect the metering holes in the bottom of the hole the screw comes out of, without touching them, then blow carb cleaner through each hole in turn, noting where the liquid comes out. Then put the mixture screw back in, adjusting it to the standard setting given in the manual. You'll adjust it for best running when you actually start the engine. Then check the bottom of the carburetor, and the matching part of the top of the fuel tank, for flatness as shown in the manual. Note the specification for flatness: it is quite critical.

I will have to purchase the tapping tools, which costs money, which I will have to find before I can work on them.

But for now I will clean the pickup tube as you said and then I will count how many turns it takes for the mixture screw to bottom out and then clean it and the holes inside. Lastly I will check the surface of the bottom of the carb and surface of the top of the tank for flatness. I will post the results when I have completed it.

I screwed in the mixture screw and it was 1.5 turns out from fully in. Then I undid the mixture screw and sprayed carb cleaner in, but I cannot see more than one hole in the hole for the screw. Anyway the carb cleaner came out of the intake for the cylinder and out the bottom of the carb.

I cannot check the flatness because I don't have a feeler gauge.

Thank you in advance

1.5 turns is the standard setting, so nobody has been messing about with that adjustment previously.

I'm slightly confused at the moment because those Pulsa-Jets normally have a screw-out fitting the mixture screw goes through - see red circle:


When you screw out the hexagonal fitting, a large space becomes visible, with the two metering holes at the bottom. Sounds as if you have some kind of Mark II version there. If there is only one hole, and it passes carb cleaner freely, all is well.

You can tell whether you can see daylight between your straight edge and either the carburetor and fuel tank top. With that model Pulsa-Jet, if there is any space there worth mentioning (that is, more than 0.002") the carburetor will flood continuously.

When you have checked the flatness, I think it will be time to reassemble the carburetor in line with the instruction manual.

Their is no hexagonal nut of any sort where the mixture screw is. Can I just use a flat metal ruler to check the flatness.

FYI, I screwed the mixture screw in 1 turn from the bottom after a cleaned it.

Thank you in advance

You can use the edge of a flat metal ruler (not the flat side). The mixture screw should be opened 1.5 turns, not 1 turn.

I'll try it with ruler this afternoon and report back what the results are.

What size thread repair kits in metric will I need for the 1/2" thread in the middle of the fuel tank, the other thread that holds the pull start in place and the thread that holds the automatic choke cover on.

Yes I know the thread are imperial, but I would like to convert them to metric.

Thank you in advance.

I take it you are planning to heli-coil the stripped threads. This is an expensive process, but it can give good results. In this case, it keeps you from having a problem with the strength of the starter casting around the bolt holes if you used an oversize bolt.

Since there is no M13 standard bolt size, you would have to use M12x1.5. You would not need to use the "special drill" provided in kits, since in this case it is 12.4 mm diameter, and the stripped hole is already 12.7 mm (1/2").