Anyone know anything about lawn mower engines?

[vauxtillidie]

its a briggs n stratton 35, it runs but the rev fluctuate alot to the point where it will almost cut out and sometimes does but will start again.

It was doing this last year when i had it out but only just got round to actually trying to do something about it.

it may be scrap but trying to see if i can get it going properly before buying another one

[Cavalier342]

We've got a Mountfield one. Tinkered with that before, it's only a carb basically. Have you checked the spark plug? No blockages in the fuel tank is there?


So much better than the shite electric ones that run over their own cables

[vauxtillidie]

haha yeh i love it real mans mower!

plug is black ive cleaned it but could probably do with a new one think its running rich and it does bellow some black smoke intermittantly

ive just took the air filter off and it was filthy ive cleaned that up waiting for it to dry out and ill try again that may explain the richness


edit not sure on any blockages

[Cavalier342]

Ye that wouldn't help. It will suck in grass one way or another.

[vauxtillidie]

Air filter hasn't helped the problem.

I tried running with the filter off and it's no different.

I did notice the thing by the carb moving on its own I guess this the engine speed (I don't have a throttle on this)

I know these do adjust engine speed depending on how tall grass is but should it be doing this when its not even under load?

Vid below

http://i57.photobucket.com/albums/g207/ ... 0b4172.mp4

[vauxtillidie]

ok apparently there should be tension on the governor springs i have zero tension this must be what the problem is

[Cavalier342]

governor sounds like it's to do with choke or throttle, so it could be that it's confusing itself if the springs keep moving, i.e. the fluctuating throttle. If I'm right then you just need to replace the springs.

[planetc]

If it's the same as mine, a Mountfield with a Briggs motor then the carb has a diaphragm similar to the old Ford vv. If it has a pinhole in it then it runs erratic and rich, almost stalling. Replacement diaphragm fitted and it was fine again.

[planetc]

Oh yes, and from the research I did it's quite common too.

[vauxtillidie]

I had read about that and as you say very common not sure where to get one from there are some on eBay but I don't know if they are right for mine Briggs and Stratton 35

[gazza1701-a]

Defo the diaphragm, fixed a few Briggs 35's with that prob, old petrol makes the rubber loose it tension. be careful with the springs on the governor as they can be dearer than the diaphragm kits if you break or stretch them, replace your blade to as your about it, it will cut grass so much better.

ebay item 360628960200 should be what you're after.

[carlos_canter]

Tinkered with mine the other day oddly enough.

My mower suffered from running problems too, very erratic and rich running.

Did away with the governor spring and part of the mechanism under the air filter. I used RC car parts, threaded rod and a spring to hold the throttle.

Now ticks over and for a 2 stroke, sounds lovely, still needs a little fettling.

[vauxtillidie]

Defo the diaphragm, fixed a few Briggs 35's with that prob, old petrol makes the rubber loose it tension. be careful with the springs on the governor as they can be dearer than the diaphragm kits if you break or stretch them, replace your blade to as your about it, it will cut grass so much better.

ebay item 360628960200 should be what you're after.

cheers for the heads up on the ebay item, ill get that and see where i go from there

[btcctroy]

The ford vv carb. I killed a few of them. They were utter garbage

[planetc]

My diaphragm came from ebay but it was a while back.

[vauxtillidie]

got the diaphragm today fitted it and it started straight away and ran perfect! Didnt look like there was anything wrong with the old one but doesnt matter its fixed! well kind of...

decided i would tip it up to change the blade not realising that oil found its way into the carb and coated the filter. Ive cleaned it all up best i can and its still running just very smokey hoping that will clear up.

lesson learnt altho all the guides i looked at online say just tip it on its side

Thanks for all help in sorting this!

[planetc]

Good stuff. Mine looked fine visually too when I got it out. Mine also smokes like a bastard if I tip it up for any reason but it soon clears.

[Barney]

Hi,

Ive got the same mower and had the same issue.

You need to buy a carb refurb kit as it the rubber gasket in the carb thats casuing the issue.

Takes about ten mins to sort.

[gazza1701-a]

got the diaphragm today fitted it and it started straight away and ran perfect! Didnt look like there was anything wrong with the old one but doesnt matter its fixed! well kind of...

decided i would tip it up to change the blade not realising that oil found its way into the carb and coated the filter. Ive cleaned it all up best i can and its still running just very smokey hoping that will clear up.

lesson learnt altho all the guides i looked at online say just tip it on its side

Thanks for all help in sorting this!

You should always tip these mowers backwards so the spark plug is pointing straight up, you may have to fold up the handles to do this though, then the oil won't fill the carb.

[gazza1701-a]

now your mower is working good now......maybe it'll work as good as mine, here's what i did at work today

[planetc]

I gave up trying to produce stripes like that when the dog count reached 2. With 3 of them tearing round on it I'm struggling to keep any grass at all!

[TurboDan]

So how are stripes like that made? Is each one a differant length or do you mow in opposite directions?

[gazza1701-a]

So how are stripes like that made? Is each one a differant length or do you mow in opposite directions?

stripes are made by the way the grass is rolled by the mower, bit like when you brush velvet in different directions. You also get better stripes using cylinder mowers, rotatory blade mowers are not so good for striping unless they're really heavy.

[planetc]

I bought a vintage Ransomes for making stripes, then spent weeks chasing it round the garden at speed as it became clear that it was too big for the area I have to mow! Tempted to strip the thing and make a go kart but it seems criminal as it is a piece of history.

[vauxtillidie]

got the diaphragm today fitted it and it started straight away and ran perfect! Didnt look like there was anything wrong with the old one but doesnt matter its fixed! well kind of...

decided i would tip it up to change the blade not realising that oil found its way into the carb and coated the filter. Ive cleaned it all up best i can and its still running just very smokey hoping that will clear up.

lesson learnt altho all the guides i looked at online say just tip it on its side

Thanks for all help in sorting this!

You should always tip these mowers backwards so the spark plug is pointing straight up, you may have to fold up the handles to do this though, then the oil won't fill the carb.

yeh i realised it needed tipping backwards after i made the mistake, wont do that again