OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Reel Lawn Mowers, Atco & Villiers etc. Cant start my old Briggs and Stratton

Hi,
i am trying to start an old Briggs and stratton 2.5hp on an Scott Bonnar. I have had it running 3 times since i started working on it but only for about 15 - 20 secs each time and only at idle.
I have spark and have fitted new plug. i thought it was lack of fuel so i have cleaned tank out and fitted new diaphram to carby and new gasket between carby and tank. also new gasket between carby and cylinder head. but just can not gett it started... the carby is drawing fuel from the tank as after pulling for what seemed like a life time the fuel was running out the back of the carby. The cylinder did not seem to be flooded though as the plug was not wet.. Does anyone have an idea of what to check next???
the engine numbers on the side are Model 80202 Type 0568-01 code 80060401 if that helps.

Any advice would be appreciated

Thanks

From your symptoms it seems you probably have a blockage in the carburetor. If it had been too rich you should have a wet spark plug. You can verify that it is lean, not rich, by removing the spark plug and putting a spoonful of petrol into the plug-hole, then reinstalling the plug, reconnecting the lead, setting the controls in the start position, and pulling the cord. If it starts but will not continue to run, you have a carburetor fault, and if it isn't the diaphragm its most likely a blockage. The next step seems to be to take a look at it. Navigate to this page:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_103.htm
You can see earlier and later pages by using the "next" and "back" buttons near the top of the page. If you go back to 99 (back 4 pages) on the following few pages you can see how you should have gone about replacing the diaphragm.
If you have questions as you go through the process for cleaning and setting up your carburetor, just post them here. However, if you are able to replace a diaphragm, you probably won't have any problems following the manual. Please let us know how you go, even if you find a huge clod of dirt in the main jet and everything is fine after you remove it - we all like to know what happens, and we may be able to help.

and if there is nothign wrong with the carby, then it could be a blocked valve.

One other check you might make before taking the carburetor apart: take off the air cleaner and start it (using the fuel-in-the-plughole method if necessary) to find out if its puffing air and fuel back through the carburetor. If it is,remove the muffler and see if that cures everything. Once in a while some insects build a nest in there and block everything up. It is also possible for a huge clump of carbon to build up, then shift so it's suddenly in the way of the exhaust stream. Blocked exhaust is a fair fit for your symptoms.

Thanks guys
i will try these tonight and post the results

Hello again,
well, i have made some progress.
i started by taking the muffler off to see if it was blocked. Due to the shape of it i needed to take the carby and take off to do it (there may be an easier way but the muffler is oval shape so it was the easiest way i could see)
the muffler was clear, no blockage, i could blow straight through it, and see light through it. (i didnt try to strart it as you suggested Grumpy because as it was clear i assumed that would not be the problem.) i pulled the carby off the tank and cot it ready to clean but ran out of time.

Tonight i started again but before i started on the carby i realised my brother has an edger with a Briggs motor that runs like a dream and as luck would have it it is the same motor. So we took the carby and tank off his and raced it back to mine and fitted it. pulled and pulled and the best we got was a backfire with some flames blowing back through the carby..

so i have drawn the conclusion that it is not a carby/fuel problem.

that leaves me with Tezza98 suggestion that it could be a blocked valve.

With Tezza's suggestion in the back of my mind, when we took that carby back off, we slowly turned it over by hand and looked into the ports to check if the valves were moving. The intake valve seemed to be rising and falling about 5mm which was easy to see as it had a clean spot, but the exhaust valve was alot harder to see as there was no clean spot to gauge it. it was however, moving up and down as it should so definately not jammed but not sure if it was actually moving as high as the intake (i may just be confusing the matter so disregard it if you think it is not note worthy)

anyway.. i am again looking for suggestions.. is it worth taking the head off to check the valves. ?? can you still get had gaskets for these old motors??

you help and suggestions are appreciated..

Its well worth taking the head off to inspect the valves and valve seats, so long as the gasket comes off in once piece you can use the old gasket for now until you sort your problems out. They are still available it it may be that your local mower shop needs to order one though.

If you got flames back out the carby it is also probably with checking out the key on the flywheel, a sheared flywheel key can significantly affect your ignition timing.

I agree with Joe: it is routine to check the aluminium key that locks the flywheel to the crankshaft, since they are prone to shearing if the mower suddenly jams in a big way. This is fairly common on rotary mowers though I think less so on reel type mowers. Since it is not the carburetor or fuel system, and it is not the muffler, the only possibilities left are loss of compression, or ignition timing. The ignition timing will be correct if the flywheel key is intact, so after checking the key, you need to check the valves. Before removing the cylinder head you should check the compression. Briggs and Stratton recommend you do this by rotating the flywheel backwards (not forwards) until you feel compression, then move the flywheel slightly forward, and flip it backward against the compression. If it bounces back, the compression is OK. If it doesn't, you have either a ring-sealing problem or a valve sealing problem. However if rotating the flywheel backward does not indicate any compression at all, you have a stuck valve, very badly blow head gasket, badly burned valve, broken piston or connecting rod, or something along those lines. You can conveniently do the B&S compression test while you have the air cowl off to check the flywheel key. Remember, though, disconnect the spark plug lead first.
If there is no compression at all, you need to remove the cylinder head and take a look at the valves and piston. If there is compression but it fails the B&S test, do another test before you remove the cylinder head. Remove the spark plug, put about a spoonful of engine oil through the plug hole, reinstall the plug, and either repeat the B&S compression test or operate the pull starter to see whether the compression has improved markedly. If it has, your piston rings are shot.

hi fella's
i havent had a chance to try these suggestions but tonight when i was walking past it i decided to put some fuel in the cylinder as you suggested Grumpy and this time it started on the 2 - 3 pull... it ran long enough to burn up that fuel the stopped.. i was excited so tried it again and couldnt get it to fire. maybe flooded then..
What does this indicate ??? while the plug was out i put my thumb over the plug hole and pushed down hard while i pulled the started and it had enough pressure to force past my thumb (i know that is a crude way of testing and there is no way of know what pressure is there but i was pushing down hard and it forced past my thumb so i at least know it has some compression)

Anyway grumpy, what does the fuel in the test tell you??

fuel in the cylinder test i meant :-)

it tells you that there is no fuel getting through to the cylinder - which is caused by a blocked carby or a blocked valve. your engine still starts tho so it can be fixed

If adding fuel to the cylinder without changing anything else makes it go until that fuel is used up, then the only fault with the engine is that it is not getting fuel from the carburetor. The possibilities are: no fuel in the tank; a fairly large air leak into the inlet pipe; the fuel pump isn't working; or there is a blockage somewhere in the carburetor. You can easily tell whether there is fuel in the tank. If there is, it looks as if you will have to remove the tank and carburetor (they are screwed together) from the engine and work through a process to find the fault(s).

If the bottom of the tank is completely clean, the most likely single cause is that the fuel pump diaphragm has deteriorated, but there are other things that are also reasonably likely. Probably the best solution is to go through the carburetor repair procedure in the B&S manual:
http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_99.htm
Use the "next" button near the top of the page to access subsequent pages: you'll find there are quite a few pages that you need to read. Please report back here to keep us posted on your progress. Essentially, you probably just need to inspect (and almost inevitably in view of its age, replace) the diaphragm between the fuel tank and carburetor, then clean the carburetor by following the procedure. Be careful to follow the directions when installing the diaphragm.

g day! all been bloody hot anyway my 2 bobs worth on the above make sure the spark plug is doing its job regards steve....

In these cases the main thing we have to do, is get the symptoms clear. From what has been posted, the engine started once when primed with petrol, but did not start when the experiment was repeated. It could, as you said, have been rich the second time, but if you pulled the starter two or three times, it should have cleared that and started. Hence deviosi's concern that your problem might be weak ignition.

It is easy to test the ignition system. Just set the controls in the start position. Remove the spark plug from the cylinder head. Reconnect the lead to the spark plug. Clamp the metal body of the plug to the cylinder head. Pull the starter cord while watching the gap between the two electrodes on the end of the plug that is normally inside the cylinder head. You should see a rapid, even series of blue flashes across the gap. If the flashes are red, or uneven/intermittent, or if you only sometimes get flashes at all, some part of your ignition system has failed and that is probably your only problem. In that situation the first thing to try (after making sure you did the test correctly) is a new spark plug. If that doesn't cure the problem, come back and tell us, and we'll take it from there.

Hi grumpy, I particularly like the idea of clamping the plug to the cylinder head....I have been zapped plenty of times...not a pleasant experience!!
As an aside, I once had a toe-cutter Victa which had the exposed end on the spark plug, and whilst mowing, my neighbour would jump the fence, sneak up behind me, grab the plug and my leg simultaneously, giving me one hell of a shock!

I have a 3.5hp briggs on an old victa outside on the bench at the moment which made me think of this thread, problem is:

Will not start unless a bit of fuel is dropped down the carb it would run for a few seconds before quitting.

Carby is fine and ignition is good the actual problem is there was no exhaust valve clearance at all, I opened that gap up a little to around about 10thou or so and now its perfect, I may post a video later on it, depends how many upload mbs' I have left on my internet plan.

It sounds a bit strange, Joe. A single cylinder engine with a tight tappet will be hard to start, and down on power, but should run all right once it starts. I once actually ran a Honda postie bike like that for months before I figured out what was wrong. It went from needing rapid kicking to start it, to starting first kick after standing for three months, and suddenly felt like a MV Agusta instead of a mo-ped, but with the tight tappet it had never been known to quit, let alone fail to start. Are you sure you aren't missing something, like an intermittent fault somewhere? Fixing the tight tappet would make it run way better, but I don't see why it would quit after starting, when you'd primed it.