Flymo Briggs and Stratton engine

[Peter.N.]

Hi

I have the above mower and can't get the flywheel off, it has two holes on the top of the flywheel with arrows pointing to them, are these to put rods down to push with a thick washer under the nut? I can't see any other way of getting it off without damaging it. Any suggestions?

Thanks

Peter

 

[r896neo]

are you sure you don't need a specific fly-wheel puller for it.

 

[Peter.N.]

There probably is one but I have found several videos on You Tube which seem to indicate that you need brute force, which I was trying to avoid.

Thanks anyway

Peter

 

[Burnerman]

Those holes are actually for a puller to screw on to, Peter......however, if you pass screws through them, make sure they don't bear down on the coil etc below the flywheel it has been done!
I find by undoing the nut or pull start pawl - whichever your engine has - two screwdrivers levering gently under the flywheel followed by a sound thwack on the crankshaft end normally pops them free.
The woodruff keys are fragile on these, and often shear, causing a timing upset.
Are you trying to access the points below? Must be an old motor!
I've replaced numerous bent crankshafts on these.....lots of people adore mowing manhole covers
Regards
John

 

[Peter.N.]

Fancy seeing you here John That's what I thought originally about the holes but they don't have a thread in them, I had thought of self tappers but dont think they would be man enough. I could try tapping a thread - if I could find my taps It's on a flymo John, didn't know they made a four stroke, I only paid £25 for it and new ones are £400+ so I thought it was worth a go - no spark.

Peter

 

[Burnerman]

Flymo use a few B&S engines on some of their (cheaper) rotary products - usually the plastic decked ones....It was only the original hover flymo that used the two stroke, where crazy angles could be cut without fear of oil starvation.
The holes you mention are often threaded....coarse thread if I recall so its probably a UNC one. The extractor bar - with a threaded hole and bolt in the centre - was then fixed to the flywheel and released from the taper that way.
Are you still struggling with it? As I said, it must be an early motor if the points are beneath the flywheel.
John

 

[Peter.N.]

I only think there are points and a condenser John, I shan't know until I have got it off - watch this space

Peter

 

[Burnerman]

The problem with the points type Briggs.....the cam that opens the points does so via a pushrod that sticks in its aluminium housing. The points / condenser wires are held in a hole in a peg on the end of the condenser, kept secure with a spring, and the points gap is adjusted by sliding the condenser along its clip - if memory serves.
There's usually enough crankshaft end float to lift and hold the flywheel when the crank end is struck.
Looking forward to the outcome! At least, you can still get the bits- if you need any.
John

 

[Peter.N.]

Hi John

Well that's better, once I decided to get my hands dirty it all became clear. The flywheel came of easily, a screwdriver under each side and with my third hand a sharp tap on the end of the crankshaft with a soft hammer.

I expected to find the points rusty but just the opposite - covered in oil, courtesy of the top crank seal I think, took them out and cleaned them, lost the spring that holds the wires fortunately I have a box of misc springs in the TV workshop so soon fixed that, adjusted the points by sliding the condenser under the clamp - how crude is that! Anyway I now have a nice fat spark.

I will put it back together and put some fuel in it tommorrow. I think the engine has had a hard life, the oil looks like the original but at least it has some in it, and there is compression escaping through the inlet valve, hopefully only the valve adjustment, if it has one. I think its good enough to run though.

Peter

 

[Burnerman]

Aha an engine once used by Noah, no less
You can hook the old oil seal out from the top, and the valve clearances are set by grinding a bit off the stem they are easy to lap in, too. There may be the usual collets or a pin holding them in. These side valve engines aren't used to having much compression!
You may find the dip pipes from the carb into the tank a bit crudded up as often steel tanks are used and they are elderly by now. Posher ones were aluminium.
Later models have a plastic tank that wraps around the engine -and the petrol taps are guaranteed to leak.
Have fun!
John

 

[Peter.N.]

Grinding a bit off the stem eh? Takes me back to the old Ford engines, my first car was a '39 Prefect.

Peter

 

[Peter.N.]

Its up and running now but I still have a problem. Runs OK at part throttle but when you run it flat out it starts to misfire and eventually stops, it then won't start again because the plug is sooted up, the mixture seems about right but it smokes when it misfires suggesting it stops sparking, I thought maybe the points were to wide but closing them up has made little or no difference. That leaves condenser or coil?

Peter

 

[Burnerman]

Sure it could be, but I'd go for a new plug first I think.
Whats the air cleaner like - is it the foam type on top of the carb?
Some of these motors had an auto choke that blocked off the venturi when the engine is stopped, and this flipped open when the engine started to run.
Try running the motor with the air cleaner off, looking for a plastic choke flap that could be in the way. I seem to think that the air cleaner cover screw actually passes through it.
If there is one mixture screw on the side, this has to be turned anti clock when the engine is flat out until it just starts to eight stroke, and then turned back in.
John

 

[Peter.N.]

Hi John

Tried a new plug, just happened to have one lying around The air cleaner is not to bad, I am running it with the filter off anyway, and yes, it does have the spring loaded choke affair, in fact I could only get it started by jamming it open, once running I can let it go and its OK, runs fine until you get it near full revs then it starts to miss, let it slow again and it runs fine. If you keep it at full throttle it misses and slows down then picks up again, definitly sounds as though the ignition has cut. Tried the mixture screw in all positions but have now left it where it ticks over best.

Peter

 

[Burnerman]

Well, you've surely checked out most things, Peter. The only thing I can really add is that the carb pumps its fuel up from the tank courtesy of crankcase depression, so that rubber pipe leading to the carb venturi has to be intact....
Between the carb and the tank is a thin diaphragm incorporating flap valves that control the fuel delivery, and these don't last forever. There could also be one in the carb side, if its the pulsajet type.
If you've removed the carb from the tank, there should be 2 dip pipes with filters on the end. If these are brass, then they are truly ancient! Either way, the filters need to be clean - rather awkward though as they are a push fit in the housing, not threaded.
John