Another Mower Thread

[slug_burner]

OK after seeing the great response 5teve got on his Not another chainsaw thread .. a mower thread or what ever it was I thought I would try my luck.

I would love to have bought a Honda but got talked out of it by the sales person at the mower shop. I should have stuck to my guns but hey that is another story..

I have a Masport 12J802 0819-01 if that means anything to anyone. It is a cast iron bore and has a 60 on it which I suspect means 6hp (probably wishfull thinking, I think it is just a 190 cc 650IC B&S and whatever hp they deliver). It is a four stroke and it has gone pretty well for the last 10 years probably more. It has a Briggs and Stratton motor. Is a little down on power from when I first got it but has done the job.

The problem:

It has a priming button/diaphragm that you use to prime the carby when first starting the mower. Last time I used it, it took a bit of effort to get started and when it did it would cut out soon after, eventually kept going but did not rev as high and the engine was surging. Got a bit of lawn done but once it stalled one too many times I gave up.

Yesterday was Cup Day Holiday, I thought I would give it a go again. Once again starts but cuts out soon afterwards irrespective of what I do with the throttle lever. After much mucking about I found that the only way the mower could be kept going was to keep hitting the priming button. Everytime it it ran for a few seconds after the pull start and then would falter, if I primed it before it stopped it would keep going. I was not going to be able to do the lawn like that but figured that the mower was not pulling the fuel through the carby and it might mean something to someone who knows something about mowers.

TIA for your help.

[LandyAndy]

If you dont want to mess with fixing it,buy a can of Aerostart or Startyoubastard. May get you around the priming of the fuel system.
GOODLUCK
Andrew

[Fluids]

Sounds like a blocked main jet. Petrol doesn't have much storage life anymore. Carby ends up getting gummed up as the fuel oxidizes. Mower been sitting idle for some time with fuel in the tank ?

Only fix is to dissmantle the carby, clean it, probably a good idea to replace the carby gasket/rubber too.

Don't store/hold your petrol more than 30-60 days ... or use a fuel stabilizer to help prevent oxidization.

[slug_burner]

If you dont want to mess with fixing it,buy a can of Aerostart or Startyoubastard. May get you around the priming of the fuel system.
GOODLUCK
Andrew

It is not the strating that is the problem it is keeping it going after it has drawn the fuel in that was supplied by the initial prime. For me to keep it going I waited for it to falter which was 3-4 sec then hit the prime button and it would keep going for a few more seconds.

If Aerostart was going to do it I would have to put the can on like an oxygen mask so the mower would keep going.

It might be something simple like a sticky float, that's if they have one. With my previous mower I was surprised to find that it did not have jets but some rubber sheet with little holes/cuts to control fuel.

Don't know if it is a pull it a part job DIY or take it to the mower repair place.

[slug_burner]

Thanks Fluids,

Probably a gummed up jet.

I did have the fuel in a large container 10 litres or so but also put fuel stabiliser in it.

Yes the mower had fuel in it from previous time about 4 days before. But I have not made a point of empting the fuel out on previous occassions, it just works out that sometimes I just run it dry and call it a day. It has probably just caught up with me that I have not religously followed a protocol of ensuring that no fuel was left in the tank.

Thanks

[p38arover]

I had the same problem with my Tecumseh-powered mower - when it used to start. I'd have to keep priming it to keep it running until it got really warmed up. Then it would be fine until the next time it was needed some weeks down the track. I tried cleaning the carb and jets but it made no difference.

Now it doesn't start at all.

I guess I'll be taking it to the forum member who owns a mower and chainsaw shop here in Western Sydney. He told me I should have bought a Honda.

[slug_burner]

Sounds like a blocked main jet. Petrol doesn't have much storage life anymore. Carby ends up getting gummed up as the fuel oxidizes. Mower been sitting idle for some time with fuel in the tank ?

Only fix is to dissmantle the carby, clean it, probably a good idea to replace the carby gasket/rubber too.

Don't store/hold your petrol more than 30-60 days ... or use a fuel stabilizer to help prevent oxidization.

Is this bronze coloured little hole on the left in focus in the first pic the main jet or is it that thing in the centre in focus in the second pic near the butterfly?





I flushed it with RP7 and it appears to flow ok.

I pulled the fuel bowl out and I can see where the air from the diaphragm/button used for priming ends up. Goes through that hole in the casting on the left side under the bolt hole, then through the body and into the centre of the fuel bowl where there is a little chamber formed by the bolt that holds the bowl in place. This bolt is like a banjo bolt and picks up fuel from the bowl. That chamber is also where the brass tube near the butterfly originates.

Tried to draw it



The red bit is where the diaphragm appears to take the air and then I think it pushes fuel up through the blue bit up into the throat of the carbie. I suspect that somewhere in the red path there is a link to that brass coloured round bit with a tiny little hole in it as per the first photo in focus (brass thing on the left of picture).


What is the normal process for cleaning out the built up gum? Do you soak the carbie in injector cleaner? What disolves the gum? Or do you replace the jets somehow?

TIA

[DiscoMick]

My Briggs and Stratton also surges but keeps running.
Have you tried emptying the fuel and putting in fresh fuel each time?
I just swear at mine and it keeps running (doesn't dare stop).

[slug_burner]

We had a fuel chemist from BP come and speak as a guest at our club. The problem with older fuel according to him and this can be more of a problem in summer is that the lighter fractions evaporate off making it harder to start an engine when cold. Apparently by mixing in some fresh fuel you can make it easier to start.

None of this gets around the gum deposits, that is what I need to find a solution for. Might give Google a try.

[slug_burner]

And the answer is "Carburetor Cleaner" disolves gum. Many other chemicals mentioned in my search such as acetone, alcohol, etc.

Found this little clip which is marginally useful, however would be better if the guy used the zoom to get in close on bits and pieces particularly in some of the other clips in the series.