OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk SB Model 45 - Clutch and Engine Problems

I have replaced the cam shaft gear as described. Still getting stuck when I pull the cord. On closer examination it appears the main source of friction is when the piston is at the top of its stroke. ie when it is furthest from the crankshaft. The gasket was ruined when I took the crankcase cover off, and after some advice from a mower shop, i used sikaflex to take the place of the seal. Where to from here?

Stuart, as I told you previously, the Briggs and Stratton engine relies on the thickness of the crankcase cover gasket to set the end-clearance of the crankshaft. First, you should not have taken the crankcase cover off in the first place - all of your problems since have stemmed from that mistake. Second, it is not unusual for gaskets to be ruined when you dismantle an engine - when it happens, you have to fit new gaskets. Your crankshaft is jammed because of the absence of the gasket which provides its end clearance. Buy a gasket and fit it properly. I suggest you do not ever go back to that mower shop: it appears the person who advised you has probably never dismantled a mower engine, since most of them rely on that gasket to set crankshaft end clearance. There is nothing wrong with him not knowing anything about mower engines, but there is definitely something wrong with him giving stupid advice to a customer when he is consulted as a professional. The people serving at the counter in mower shops usually know nothing about mower engines, but normally they have enough sense to refrain from giving advice on the subject. They have a mechanic in the back room who (hopefully) knows about engines, but his time is worth too much to have him waste it talking to customers.

Thanks Grumpy and wilco. I have cleaned up the surfaces of the engine and cover and will now purchase a gasket. I have fitted the cover back on loosely and the pull cord seems to be working reasonably freely with the only real resistance coming when the piston is at the top of its stroke. I have looked for a gasket on the Outdoorking website but there are so many. What is the exact name of this gasket? The engine is a B&S 3hp model 80202.

To find the part number for the gasket I need the full string of numbers stamped on the cooling air cowl of your engine, right above the muffler. The Model is 80202, but I need the Type to identify which variant it is. The third group of numbers, the Code, will tell us the engine's year, month and day of manufacture.

The gasket's name is Crankcase Gasket. The standard (i.e. 0.015" thickness version) gasket for a generic 80202 is Part Number 270833. There are two thinner versions available, to adjust crankshaft endfloat, but you probably will not be able to buy them in Australia. The correct procedure is to fit a standard gasket and measure the end float with a dial gauge, then either fit a thinner gasket, or add a thin one to the standard one, to achieve the required endfloat of 0.004 - 0.008". However I doubt you have a dial gauge, so for this purpose I suggest you assemble the engine with a standard gasket and feel whether there is endfloat but not much of it, and the crankshaft rotates freely with the spark plug removed from the engine. If so, it will be fine. Incidentally I think you will probably find the resistance to pulling the starter when the piston is close to the top of its stroke will not exist when the spark plug is removed. It is a very bad idea to pull the starter with the spark plug installed and without the crankcase cover installed, since a substantial vertical force is applied by the compression, and the crankshaft is not supported to resist it.

Yes thanks, all resistance gone now I have removed the spark plug. The engine type is a 4016 01 and the code 90021303. Thanks for your patience.

Here is the illustrated parts list for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6ntABVJ1DajI.pdf

I can confirm that the standard thickness Crankcase Gasket for your particular engine is P/N 270833.

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/flivAJX-nfBhU7y.pdf

Your engine was made on 13 February, 1990. That is long after Rover took over Scott Bonnar in 1980, but if I recall correctly the Scott Bonnar plant continued to operate for some time after the takeover, before Rover moved all production to their own plant. That is a matter for Deejay to clarify.

I think the next step is for you to check the tappet clearances, in case you interchanged the intake and exhaust tappets when you reinstalled them after they fell out when you removed the camshaft. To do this you will need the crankcase cover installed - do not tighten the screws since that would lock up the crankshaft. You must have the cover installed though, because it supports one end of the camshaft, and the camshaft has to be supported for the valve clearances to be correct. Look at this illustration from the parts list:

The red oval shows you where the valve cover/breather attaches to the engine, directly below the muffler and carburetor. It is attached with two screws, and has a breather valve built into it. Do not touch the breather valve when you remove the valve cover: it is fairly delicate. Note the black gasket which keeps the cover from leaking oil: do not damage it - if it becomes damaged it will have to be replaced.

Look behind the valve cover: you will see two coil springs, and just below them, the junction between two metal parts: the tops of the two tappets, and the bottoms of the two valve stems where they emerge from the coil springs. To see how the valves operate, pull the starter very slowly with the spark plug removed: you will see each valve in turn rise and fall. Turn the engine to Top Dead Center at the end of the compression stroke - both valves will be closed. At TDC or very slightly past it, you need to measure the valve clearance, which is the very small gap between the top of the tappet and the bottom of the valve stem. To do this you use a set of "feeler gauges", which are very thin strips of hardened steel. Each gauge is marked with its thickness. The intake valve clearance should be 0.005-0.007". The exhaust valve clearance should be 0.007-0.009". If both clearances are about right, reinstall the valve cover, ensuring that the engine still turns smoothly and freely afterward.

If the valve clearances are correct and the camshaft timing gear mark aligns exactly with the crankshaft timing gear mark, you are ready to reinstall the crankcase cover with its gasket.

OK, Looks like I have to remove the Fuel tank first? to get to the valve cover. But to remove the fuel tank I need to remove the air filter. I am a bit wary of removing anything considering my last efforts. Are there any tricks here?

I think you can do this just by removing the carburetor, fuel tank and air filter all in one piece, Stuart, though I haven't done it. There are just three nuts/screws to remove: the two holding the carburetor to the cylinder's inlet port, and the one holding the bottom of the fuel tank. See the red circles on these two diagrams from the parts list:



The speed control cable from the handlebars will still be attached to the fuel tank, but I think there will be enough slack in the cable to allow you to put the whole assembly to one side while you access the valve cover.

Since I haven't actually done this, I hope Joe Carroll or someone else will chime in and confirm it can be done this way.

Thanks. Given that I have a 50% chance of having the tappets in the right position, what will happen if we work towards getting the engine started. Will it be obvious if they are the wrong way around and if so can I then take the gasket cover off and change swap the tappets over. It may cost me another gasket but is it better than taking the other things apart? One of the guys at the auto shop where I bought the feeler gauges also mentioned gasket paper. Is this an option?

If the tappets are the wrong way around, most likely one clearance will be more than it should be, and the other less than it should be or no clearance at all. The other possibility is that by luck, the two tappets are the same height and so the clearances are the same. If you had experience in this, I would suggest that you start the engine and listen to it, since a substantial difference between the two tappet sounds would be obvious. However since you are not accustomed to the sound, I do not think you would notice: you would just hear one tappet sound, and not be able to compare it with the usual two sounds.

Remember that to start the engine you must clamp the crankcase cover into position. After that if you have to remove the cover again because the tappets are the wrong way around, it is possible that your new gasket will be destroyed. This is additional to the possible replacement of the valve cover gasket.

If the tappets are the wrong way around, and as a result one of them has far too little clearance - or perhaps none - sustained running of the engine in that condition will cause one valve to burn, requiring another engine job to be done: lapping (if you are lucky) or replacing the burned valve. If you were unlucky, the valve seat would be damaged as well, requiring a somewhat more difficult replacement.

These risks are not unmanageable, and I think quite a few competent home repairers would "take the punt" and run the engine as it is - but those are people who would notice if it suddenly had uneven tappet sounds.

The decision is yours to make, Stuart. I am personally biased toward "doing the whole job" in cases like this because if you compromise the outcome to avoid removing those additional parts, you will end up being frightened of engine jobs in future. It is traditional to advise people who are thrown by a horse, to get back on it immediately and win the psychological battle with themselves.

great advice grumpy , a lot of folks do get worried by things mechanical . most learn from mistakes , a lot of trial and error but all but a few things work out in the end and a good lesson to be learned , once bitten ? most of/ almost all mine is learned the hard way too . pull it down , work it out then fix it . if still not working ask someone or if all else fails ....... read a book

OK thanks, I will proceed with the valve cover removal. Have a nice Xmas and I will talk to you again after new year, when I have got hold of a new gasket.

Stuart.

Hope you all had a nice Xmas. Rather than take the valve cover off I have borrowed a set of .000 inch digital calipers and measured the tappets. One tappet measured 1.278 inches and the other 1.280. Using the feeler gauges and your clearance measurements, both measure out at 1.286 therefore I have determined which tappet is which without the need to take the valve cover off. All I need to know now is which tappet hole is which. Can you please advise whether the exhaust tappet is the closest or furthest from the piston?

Look (once again) at this picture of the cylinder and crankcase:


The red circle shows that one port - the one closer to the crankcase cover - has thread in it, the other one does not. Briggs taps a thread in the exhaust port of most of their small engines, and screws the muffler directly into the port, because this is a cheap, reliable way to mount the muffler. In other words, the exhaust valve tappet is the one closer to the open side of the crankcase, where the timing gears are, and where the crankcase cover mounts.

Note that neither tappet is closer to the piston than the other, they are both equidistant from it, because they are lined up along the camshaft, which runs parallel to the crankshaft. The piston is almost exactly above the center of the crankcase, when measured along the crankshaft.

Yes sorry I meant the crankcase cover, thanks for the info. Ready now to closer her up and turn her over. Last time I tried this was before I took the engine apart and it did not want to turn over. I have a new spark plug, filters, oil. Anything else to help the engine out? I will study the Operating Manual about some of the adjustments and let you know how I get on. I was going to make sure she runs smoothly before I re-mount the engine on the mower chassis. Is this OK?

Without knowing more about your engine's history and condition, that sounds like a reasonable preparation for starting it for the first time. Running the engine without mounting it is a marginal thing to do in terms of safety: when you pull the starter the engine could easily tip over, and amazingly complicated things can then happen in the heat of the moment. The safe way to run an engine is with it bolted down somehow. One solution would be to remove the engine-side part of the mower's clutch, so you could mount the engine on the mower deck without the output shaft being coupled, but at this point it would be preferable to leave the mower alone and just get the engine working. Can you bolt the engine down to a box or something?

Easy, I have put some tech screws thru the mounting holes into a substantial piece of timber which keeps the engine stable and will allow me to start it with safety. The engine was always regularly serviced, didn't blow smoke and always started for us. It was after a period of 3 months, after I got the initial quote to get it fixed and before starting with my own reno, that I couldn't get it started. Once the new gasket is installed and I have tried to turn it over, I will let you know the results.

OK, engine is back together wi8th new gasket,fuel oil and spark plug. Everything turns freely but still no joy in getting it to turn over. Where to from here please?

Stuart, the next process to to check each of the basic functions of an internal combustion engine: fuel, spark, compression. First, remove the spark plug, reconnect the ignition lead to it, and clamp the metal body of the spark plug to a metal part of the engine - usually one of the cylinder head cooling fins is the most convenient. Then set the speed control in the start position, and pull the starter handle briskly whilst closely observing the gap between the two electrodes, shown circled in yellow:

(Ignore the apparatus holding the spark plug - that is what you do to make it easy to clamp the spark plug to the cylinder head, if you do this fairly often and don't want to have to mess about each time.)

As you pull the starter, you should see an evenly-spaced (in time) series of blue sparks across between the spark gap circled in yellow. If you do not (you see no sparks or red sparks), we have found a good reason why your engine does not start.

If the sparks are blue and regular, the next step while you have the spark plug out, is to put a teaspoon-full of petrol into the spark plug hole in the engine, then immediately reinstall and tighten the spark plug, connect the plug lead, and pull the starter. The engine should start and run briefly. If it stops after a couple of seconds, we've learned that your carburetor is not supplying fuel to the engine. If it starts and keeps running, we have reason to suspect that your starting problem is intermittent, or is just something simple like you forgot to use the choke. If it doesn't start, we will have to suspect a more serious mechanical fault in the engine, but we won't accept that as a conclusion until we repeat all of the tests a couple of times.

Please go through that series of tests and post the results. A picture or two would be helpful.

Thanks, Spark plug is fully functional and the engine starts when I place the fuel into the spark plug hole but, as you predicted, stops after a couple of seconds. Looks like the carby then. Are there any specific parts that require photos of?

Your engine has the Pulsa-Jet carburetor, which is both the best and the most complicated carburetor Briggs had in those days. Here is Briggs' check list of possible faults to be considered in your situation:

1. Leaking carburetor mounting gaskets
2. Gummy or dirty screen or check valve (Pulsa-Jet and Vacu-Jet carburetors)
3. Inlet valve stuck shut (Flo-Jet carburetors)
4. Inoperative pump (PulsaJet carburetors)

You can ignore Item 3, since you have a Pulsa-Jet not a Flo-Jet. Hence there are three probable causes of the problem. The first one is fairly easy to check. You may recall that I suggested earlier that you unbolt the carburetor, air filter and fuel tank from the engine to get access to the valve cover. The two carburetor mounting bolts are the two I showed circled in red on a sketch of the engine cylinder. To deal with possibility 1, you need to check that both of those bolts are done up firmly, not rattling loose. It is not all that likely a cause for your problem, but it is very easy to check. If it isn't that, you are going to have to remove the air cleaner, carburetor and fuel tank from the engine, so it makes sense to check it first.




The picture shows an 80202 about the same vintage as yours, but they are not all the same, so first, post a picture of your air filter, then remove it from the engine. For the one in the picture, you just unscrew the large screw in the center of the top of the air filter (circled in yellow), then you can lift off the entire air filter from the carburetor. If the filter is substantially different (e.g. a later one with a paper filter) you may have to remove the top cover to access the mounting screws. Post a picture of the carburetor (immediately beneath the air filter housing) when you have done this, so we can discuss the following steps.

OK, Mounting bolts are secure so we proceed to problems 2 or 4.

Thanks DJ, looks like you have a paper air filter. Now, the next step is to remove the carburetor and fuel tank from the engine. On many B&S engines the fuel tank is just suspended from the underside of the carburetor and supported by the carburetor's two mounting bolts, but deep tanks like yours will probably have an additional support screw. I identified what seems like the right screw previously in this thread:



You need to remove that screw and the two carburetor mounting bolts, so you can simply take the carburetor and fuel tank off the engine. Be very careful of the governor spring, circled in yellow below:

That spring is delicate, and if it is damaged it will have to be replaced with exactly the right spring.

The speed control Bowden cable will still be attached, but that should not be a problem at present. Please remove the carburetor and tank, put them on a suitable support that holds them steady while you work on them, and post a picture or two. When you have that done, we get to the important parts of the job.

Hi grumpy, I think you replied to the wrong member mate, this is Stuart's thread, not DJ's....

Thanks Deejay, I think I actually used DJ's name in replying to Stuart. I seem to be working from the right illustrated parts list for Stuart's engine. As my critics would say, "Lucky he got that close!"

Some more pics

Thanks Stuart, we have to remember now to plug that aluminium breather tube back in at the lower end (I usually disconnect them at the top, so that is where I usually look when I'm putting them back together).

All is good so far. I see you've removed the control panel - I'll still post the Briggs instructions for doing that, so this will be a complete archive:


The next job is to separate the carburetor from the fuel tank. It isn't nearly as tricky with horizontal crankshaft Pulsa-Jets as it is with vertical crankshaft ones, but you still have to be careful of the fuel pick-up tube, circled in red in the disassembly instructions:



On the bottom of that tube is a flared-out section, which you have to thread through the hole in the top of the fuel tank without damaging it. Do not try to remove the tube from the carburetor. Note you have already taken care of item 2 of the instructions. Don't discard the gasket unless it is damaged.

Now we get to the serious part. We need a picture of the flared-out section of the fuel pick-up tube, showing the fine mesh on the bottom of it. This will tell us whether Problem 2 (see earlier post) applies. We also need a picture down into the fuel tank, showing whether it is full of grunge or sparkling clean. Let's discuss the results of all that before taking anything else to pieces, especially the fuel pick-up tube.

Once we clear up those questions, we can talk about Problem 4.

The bottom of the mesh was coated in a lot of 'lint' like material which I have now cleaned off. The other small metal tube/pipe


with the brass end had a lot of rusty colored grunge on it which I have also removed. Looking into the fuel tank I can clearly see the bottom and it looks free of material. The well where the brass ended tube sits in, has the rusty colored gunge in that was on the end if the tube

The burning question is whether either the lint-covered mesh screen at the bottom of the long tube (the fuel intake screen), or the small brass item at the bottom of the shorter tube (the main jet) was actually blocked rather than obstructed. If so, that will have been the cause of the problem. If they were merely obstructed, it will be necessary to clean them both properly then go on to Problem 4. Both because we don't know the answer to that, and for practice and thoroughness now that we've gone this far, I suggest we should go the rest of the way anyway. Of course the first thing you need to do is to clean out the little well in the top of the fuel tank below the main jet, if you haven't already done so. Then, turning to the carburetor itself, step 1 is to clean both the mesh screen and the main jet with carburetor cleaner, which comes from your local auto shop in a spray can and may be called carb cleaner, throttle body cleaner, or some similar name - the counter jockey can point you to the right stuff. Wear safety glasses when you use it. In the case of the mesh screen, you might try squirting it across the screen first in the hope of blasting some of the remaining crud off and out rather than through and in. You will later need to squirt some directly through the screen, but it's best to do that during our pursuit of Problem 4, because of where the displaced crud has to go. In the case of the main jet, just squirt cleaner through the tiny hole in the center. After doing that, push a small strand of copper wire through the hole to verify that it is clear, then give it a short second squirt with the carb cleaner. I recommend that you do not dismantle the carburetor further except in pursuit of Problem 4, which I will now get into.

The Pulsa-Jet carburetor has a built-in fuel pump, which is subject to two main forms of deterioration, particularly during periods when it is unused. The first is blockage from the same crud you've seen in the Problem 2 investigation. The second is deterioration of the rubber-like diaphragm which is the heart of the pump. From the crud you had in the carburetor it sounds as if you may have used fuel that contains ethanol, and if so there is a good chance the pump diaphragm is damaged - we'll find that out.

On what might be called the back of your carburetor is the fuel pump cover, circled in red:



You need to remove that cover and dismantle the fuel pump - carefully:

Note the roll-pin (circled in yellow) which is being used as a dowel to locate the pump cover accurately. You will have to lift that side of the cover by using something like the sharp edge of a knife blade - which would be easy except that you'd prefer not to ruin the diaphragm (which acts as a gasket) and have to replace it - though you may have to do that anyway.

The objective when you open the pump chamber is to take pictures of the components, inspect them, and clean the compartment and the components with carburetor cleaner. You will also need to squirt carb cleaner through the screen on the end of the long tube (see Problem 2 above) in the hope that it will blast straight out into the pump cavity, carrying the crud with it. (Remember about wearing the safety glasses.)

Aside from getting the crud out, we want to know if the pump diaphragm, component 3 in the diagram, will sit flat with its little flaps laying flat on the ports they have to seal (one port is on the carburetor body, the other on the cover). We want to know whether the flaps were sealing before the cleaning operation, and also after it. There are two main issues in whether the pump works or not: whether the flaps seal, and whether the little cup, or piston (Item 2 in the diagram), is stuck in the bore.

Photos of disassembled pump chamber before cleaning. No apparent restriction in piston movement.