OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines fuel to oil ratio for Mpsport craftman 435

You should start by looking for cooling problems: restricted air flow from the fan through the cooling fins, especially on the cylinder head, and an obstructed muffler. The classic cause of both problems is a wasp nest that has been built while the engine was out of service for a long time.

If it is neither of those problems you will need to look at whether the mixture is lean or the ignition system is breaking down when it gets hot.

Leo, it sounds like your engine needs a good overall service.

Im sure you would like it to start reliably and run well for this growing season and more to come.

If that engine came to me, I would flush out the fuel tank, clean the carby, clean the air filter, clean the spark plug or replace it, clean the magnet faces & magneto armature faces and reset them, clean all excess carbon from the head.

Plus check the things Grumpy has said & more.......

Joe earlier on offered to service it for you.

If you want to service it yourself step by step we can do that to.

hi Grumpy

I totally agree with you that it is most possibily that the cooling system causes the engine shut down. Could you please advise me the detail how to check them? Thanks

Hi Mark

Thanks for your sugestion, and I do not know how much should I pay for Joe. I would like to try to service it by myself. The question is that where should I get the manual of this engine.

Sorry but I think you should just pay what it costs and get it fixed by someone that knows what they are doing.
You are now more than capable of checking the oil and keeping on top of that, so once you have it serviced and fixed it will be good to go for quite a while with just regular oil top ups.


I appreciate that you want to learn. I would actually welcome that you do that. If you google or youtube about how engines work I am sure that you will come up with hours and hours of reading and watching. You need to understand how it works before you can fix it. Otherwise you are flying blind. Learning takes time.
The issue you are having could be any number of things.

Sorry leo, but the post with the arrow and circle got me. The yellow is the back of the crankcase and the red is the muffler.
Yellow, yeah that gets hot, not being experienced you would not be able to tell too hot, from hot, from not hot enough. If the motor has been running for a few mins, too hot to hold your hand on is normal.
Red, thats the muffler/exhaust. Hot hot very hot, dont touch.





Cheers, Bob.

Leo, to go through the steps with you to find and fix your engine fault is likely to take quite a while, you will have to buy tools if you don't have them, and the mower probably won't be in running order while all this is going on. If you want to learn about mowers, this is all do-able and we can give it a try. Expect it to take quite a lot of work and frustration, and cost more than getting your mower fixed by an expert, or throwing it away and buying a second-hand mower in proper working order. You will also have to follow the process closely and take the steps you are asked to take, without making your own experiments or leaving out steps. It is your choice to make. We've gone through similar processes several times before at Outdoorking, and succeeded, but we've also occasionally had someone drop out along the way, and at least once the person was very unhappy and noisy about it when he made that decision.

Hi Grumpy/Bob/Guys

Thanks for your reply and suggestions, and I will start to learn now.

Leo, please post the long string of numbers stamped on the cooling air cowl of the engine - that is, the pressed steel cover over the upper part of the engine, with the Briggs sticker on it. The numbers are usually on the vertical left side of that cowl when viewed from the operator's position, near the top. The numbers will be in three blocks, marked Model, Type and Code. We need all three blocks. That will give us some details of the engine, including its date of manufacture. Then I'll be able to suggest an overhaul manual for you to look at as background, while we go through the maintenance process. (The Briggs overhaul manuals are all available in the manuals section of this site - we can talk about it when you've posted the string of numbers.)

Grumpy, thanks. And I will post the pics requested tomorrow.

Hi Grumpy

Here are the photos, and I could not find the long string of numbers stamped on the cooling air cowl of the engine.

g'day leo , the numbers should be above the muffler stamped into the steel cover (engine cooling cowel) model 92908 type 1919-01 code 79112828 . not those numbers though , just an example so far i havnt found them in another place Dave

As Dave said Leo, the numbers are Briggs and Stratton numbers, not mower numbers so they are on the engine, not the mower frame. They are stamped on the black cowl (cooling air duct) that wraps around the top of the engine, with a hole in it where the air intake grill cover spins around. The numbers will be on the vertical surface on the left side of the cowl when viewed from where you stand to operate the mower. They will be in three groups, just like the example Dave gave you.

Hi Grumpy/Dave

I think the numbers are lost since I saw there were two holes at the area of engine you talk about. this mower is a used one.

unless someone ground them off they are there leo , ont the tin top (coweling) just above the front of the muffler on the side of the engine , grab a rag n give it a good wipe down 1st then use a torch ? might be hard to see but they are there .
dont worry about this muffler its different , but numbers will be there . maybe its been painted , so look close

Leo.

The picture you put up on page 2 with the red circle on the hot bit. I saved that and blew it up. Im pretty sure I can make out a 5.

Above the muffler, about the same height as the throttle cable, on the black engine cover/cowling, there is a number.


You are not making it easy for anyone to help you.

Hi Guys

Thanks for help me to find the numbers, and I will double check it, maybe tomorrow.

Hi Guys

I finally fund the numbers: Mode 02908 Type5671-01, code:86060902. I am not sure I got the correct No. since It is hard to see. And I will post pics soon.

That isn't a possible model number, Leo. See if it is by any chance a 92908 rather than 02908, and post a picture of the engine so we can verify that its appearance matches the number. (The picture will also be useful later in this thread.) If there is dirt on the number, wiping it with a rag wet with petrol or kerosene should clean it up.

Hi Grumpy

here is the pics

Thanks Leo, your engine is a model 92908 made on the 9th of June, 1986. It is 9 cubic inches displacement (148 cubic centimeters), a third generation design, with a PulsaJet carburetor, plain main bearings, and a recoil starter. The 92908 had a vertical pull geared starter, and an automatic choke.

The first thing you will need to check, is that your engine's flow of cooling air from the fan on the flywheel, is not being obstructed. To do that you need to remove the cooling air cowl (the black piece of sheet metal with the numbers on it). The cowl is retained by 3 small, horizontal, hex-head screws, one on the "front" (just above where the speed control cable attaches to a steel plate at the top of the carburetor) and two at the "back" (at the two bottom corners of the cowl, at the points most distant from the front screw). The three screws are all identical. However you cannot get access to one of the back screws until you remove the vertical pull starter. The starter is retained by two horizontal screws. The back screw is the same size as the three cowl screws, and the front screw (deeply recessed because it is just above the top of the fuel tank, in front of the fuel filler) is a size larger. Note that all Briggs and Stratton screws are inch sizes, not metric. When you remove the two starter screws the starter can be lifted off the engine. The cowl cannot be removed until you detach the speed control cable from it: it is retained by a single screw on the front of the cowl, right near the front cowl attaching screw. After freeing the cable, the cowl can be lifted off. Please post pictures of the areas under the cowl. There will be a lot of cooling fins, and we want to establish whether they are obstructed by things like dry grass and/or wasps' nests.

I have one of these on the bench at the moment, I have taken some shots that may help.

Thanks Mark - I don't even have a Briggs engine these days to take pictures of. Leo, here is that picture with the fasteners and their locations marked:

The fasteners for the starter, resting on the ground right adjacent to where they attach, are circled in green. The fasteners for the cowl, again adjacent to where they attach, are circled in red. On the picture of the engine beside them, the position of the front cowl screw is circled in yellow, and yellow arrows point to the positions of the back cowl screws. - They both attach down below the flywheel, on the sides of the crankcase.

Is the pulsa jet the plastic carb with no bowl in the top of the tank???


Usually they are not too bad.


I would say the issue with this mower is that the valve clearances are closed up. When it gets hot the valves do not shut and it stops.
Then once its cooled down a bit away it goes again.

Bob, Briggs has had two "suction" carburetors (fuel tank below carburetor, so no gravity feed). One of them was called VacuJet: that one had no fuel pump at all, just used venturi suction to lift the fuel from the tank to the venturi. It worked fairly well on the shallow fuel tanks on the vertical crankshaft engines, but was poor to unacceptable on the deep fuel tanks often used on the horizontal crankshaft engines. The other type was the PulsaJet, which had a little fuel pump in the diaphragm between the carburetor and fuel tank: the diaphragm was operated by intake suction pulses. The PulsaJet worked with either shallow or deep tanks and was a better device than the VacuJet, but the diaphragm had to be handled carefully because its built-in flap valves were sensitive.

Both the VacuJet and the PulsaJet were made in both metal (aluminium I think) and plastic (Minion) forms. In the third generation engines (second part of the model number was a 2, because they started with zero on the first generation) both VacuJet and PulsaJet had an automatic choke. Leo's carburetor is an automatic choke type. In my experience the choke works extremely well - but it does make reassembly of carburetor to fuel tank a bit trickier, since you have to preload the diaphragm.

For information, once we establish that Leo's cooling system is OK, the muffler will be next then the tappets will be the third thing to check. By the time he's through those three areas, he'll be more experienced and we'll be able to look at more complex stuff.

Hey Guys

Thanks for your help, and I will check the engine this weekend and post pics.

hye guys

Good news is that the mower works well, and it did not cut down any more(i did not do anything). My question is should i still need open the mower to check?

When you get a "new" old mower there are a few simple checks I would normally make in case it has a fixable fault that will damage it if you keep using it. Ordinarily that would mean checking that it has the correct amount of clean oil in the sump, the air filter is clean and correctly fitted, the cooling fins are clear, it has adequate spark, the compression feels OK, it starts easily, and it runs well through the whole speed and load range without any odd noises. I would probably check the tappet clearances as well, but that is just me. At that point, with an old mower like yours of no great value or collectibility, I would go ahead and use it, watching for odd symptoms starting to show up. None of those checks involves dismantling the mower beyond taking off the cooling air cowl and removing the spark plug.

hi Grumpy

Thanks for your detailed explanation. Now, I excatly know what should I do. Again, thanks for your help.

Leo, I don't think anything has been done to clear the fault that caused it to stop after it had been run a while, so that fault may come back. On the other hand it may have just been a result of running it on 2 stroke fuel when you first got it, resulting in some blobs of oil floating through the system, one of which lodged in your carburetor's main jet for a while. It could also have been one of many flying chunks of half-burned oil sticking in your spark plug for a while. If it was either of those things that caused it to stop, now that you have run it under load on the correct fuel (straight petrol) for a while, you should have burned away the original problem, and there would be no reason for the problem to recur - it should be back to perfect health. Those old Briggs engines have an excellent reputation for reliability and durability, provided you keep their sumps filled to the correct level with clean oil. It should be changed every 25 or 50 hours' running, depending on operating conditions.

I will close this thread. If anyone needs to post to it, just PM a moderator.