lawnmower (petrol) engine - fix it or buy new?

Service what you've got, unless you like contributing to landfill ?

A new filter will always be a good idea, then take out the sparkplug and check its condition - that can tell you a fair amount about how it is running.

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Changing the plug and overhauling the carb fixes most problems with a brigs motor. Parts cost about a tenner

Service what you've got, unless you like contributing to landfill ?

Going back to my karting days here but I'd suggest a new plug and a carb rebuild. Should sort out most problems. For something that popular there should be loads of videos on Youtube on how to do the carb.

What passes for a carburetor on a Lawn Mower is a pretty simple device so I would also suggest taking it off/apart and cleaning and checking over the carb'

Check that the throttle plate moves through it's entire range and also check that the 'throttle' cable moves freely and has the intended full range of movement.

Replacing the spark plug can only help - so I'd do that as well.

In most areas there will be someone who buys up non-runners from boot sales and the like, refurbs them and flogs them on Gumtree. Have a look on there for someone selling more than one, or with a history of repeat sales. They will be happy to service it for a lot less than someone who does it as a full time job. If you were in South Yorks I could give you numbers of a couple of guys.

thanks chaps, just been looking at a few carburettor vids on youtube. all they seem to do is change the diaphragm and gasket, nothing else to it?

ill probs have a look at mine, see if i can start stripping it and what the air filter and plug look like too.

ebay the best place for new plug/filter/carb parts? and what sort of oils in there if i change that? oil filter too? not sure how much to do to it for a service......

thanks a lot

Agree with above. Get the carb off and take it into the kitchen, some isoproyl alcohol and clean it right up. Check the gaskets are ok. Clean the fuel/replace the fuel lines, tip out the fuel tank and clean it, fuel filters (mesh cap on the end of the fuel line inside the tank), pop a new plug on, replace the engine oil.

If it still acts up after this, just get it into a local machine shop and ask them to specifically sort that issue out. It'll be worth it I'm sure.

Normally I'd be all for repair as the environmental option but petrol mowers are terrible in general for the environment and a poorly running old one especially so.

i agree in principal but given that the mower will see what 30minutes use once a week/twice a month.... how long till it balances out with the materials/energy needed to make a new one and ship it all the way across the world.....

also my parents had this on a briggs and stratton powered mower.

was simply a choked up air filter.

REmove filter and run it (but dont go cutting grass or it will suck the grass in...) and see how it is .... theirs ran fine so we rplaced the foam filter and its still running today. 10 years sterling service - far better than the
plastic fantastic electric mower that didnt last a season.

Given most mowers dont get serviced - they are pretty robust.

mine was doning this for a bit last summer. Cleaned carbs and plug etc etc, eventually Got some EGR cleaner from Halfords and gave it a blast, lots of black smoke and engine running like new now. (coked cylinder).

REmove filter and run it (but dont go cutting grass or it will suck the grass in...) and see how it is ....

ill start taking it to bits, whats the worst that can happen 😉

Where are you?

If you're in Nottingham, I'll happily whack the carb in my ultrasonic cleaner for you.

I love tinkering with and rebuilding small Honda generators - the usual problem is fuel being left in them over time. This leaves a hard layer in the carb jets. Ultrasonic cleaning is usually the only way to clean them properly.
Other than a carb rebuild it's usually air filter, plug and oil change.
Empty the fuel tank when not in use though even if only for a few weeks.

[url= http://blog.lawneq.com/push-mower-lose-power ]try this[/url]

A couple of years ago I bought a John Deere mower that wouldn't start for £30. No compression and pulled over too easily. I took the head off and found that the exhaust valve seat had come away from the head, so I put it back in place and peened around the edge (as per internet advice) to hold it in.
It's still working great and is worth 5x what I paid for it!

People are far too quick to throw stuff like this away - the engines are simple and quite fun to play with. As you said punky - what have you got to lose?

I bet you fix it.

good link sharky, thanks. ill try and check as many of those as possible with my limited knowledge/skillzz.

Where are you?

If you're in Nottingham, I'll happily whack the carb in my ultrasonic cleaner for you.

started with the stripdown. took the air filter off, didnt look tooo shabbly...

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until i turned it over .......

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so that could well be the culprit, altho now im on a roll i want to do what i can.

taking the petrol tank/carb off, i realised i hadnt noticed where one of the springs went. can you enlighten me? its the real skinny spring at the back. doesnt matter too much at the mo but i need to know for when i put it all back. also the 'moving part' fixed to that bigger springs pretty stiff, im sure that spring wouldnt move it on its own if thats whats sposed to happen. dont think its related to my problem but is it all sposed to move really freely?
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carb off and i looked at the diaphragm and thought hmmm that looks 'blown'. but then when i took it apart i realised the diaphragms really thin and theres a spring pushing onto it, so thats normal yep?

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ill certainly get a new kit for it anyways, just not sure wheres best. ebay?

and is it ok to give the carb a good clean in soapy water? i know sobrietys ultrasonic cleaner would be better, but is water a half decent substitute or does it want to be soaked in petrol or somethings?

thanks

Assuming that the engine isn't overheating and seizing (it has got oil in, hasn't it??) and that the speed control vane that works the throttle isn't jammed, it's likely muck in the carb, or a failed diaphragm/gasket.

(BandS carbs are "odd" - the diaphragm also acts as a fuel pump. May not run at all without the air filter on.)

FWIW, I'd replace the diaphragm (£5 ish)and clean out the carb while I was at it.

[EDIT] Just seen your post above - don't clean the carb with water. Use diesel / meths / white spirit / proprietary cleaner or petrol (carefully).

Replace the diaphragm - our local mower place keeps them in stock (no good to you, though!)

this is the little spring that i dont know where it went

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just taken the spark plug out, looks black and charcoaly/oily. havent got a set of feelers for gap, but can get access to some easy enough i should think.

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From your OP I thought "it's running too rich."

Looking at the plug I thought "it's running too rich."

Looking at the air filter I thought "and that's why."

(I am not a mechanic and know nothing about lawn mowers.)

That looks very, very rich. I'd say cleaning the carb and replacing that horrible air filter will sort it out.

That or the piston rings are gone and it's burning oil, which is the other reason it'd be struggling. But Carb/air filter is more likely to be honest.

As to the spring, no idea. Did you take pictures of it in situ before you started pulling it to bits?

Edit: What he said. Also, if it were burning oil you'd have blue smoke coming out of the exhaust and an oily-burning smell to go with it.

T'interweb usually has a pdf manual with exploded diagrams in if you google the model number of the mower/carb...

As to the spring, no idea. Did you take pictures of it in situ before you started pulling it to bits?

i went out with the best intentions of doing so, but er.....

We all do it, some of us more than once.... 😳

New plug time!

Remember to soak the new air filter in oil then squeeze out the excess- foam alone doesn't filter

New plug time!

Remember to soak the new air filter in oil then squeeze out the excess- foam alone doesn't filter

this little 'well' in the casing..... had some shite in it. scraped a lot out with screwdriver but still a bit dirty. thought it was a filter at first but its solid metal i think. whats that for, just a 'holding area' for fuel? and does it need to be squeaky clean? the pic below is after id been foraging, but obviously cant get it spotless with a screwdriver.

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thanks a lot

Squeaky clean, all 3 of those holes/bowls/basins.

so ill have to bin the petrol and soak the whole casing in somethings? soapy water? petrol? WD40?

thanks

The petrol is probably 'off' modern fuel doesn't like being stood, as the ethanold content absorbs water and rusts things.

You might be lucky, but for the couple of quid a tank of fresh stuff costs, it's worth it.

To clean the carb I'd use carb cleaner, brake cleaner or wd-40 in descending order of 'goodness'

All good advice so far.

That small spring looks like it is part of the throttle arrangement. It will probably clip onto a plate that is moved by the throttle cable and will cause the throttle to return to a lower operating speed when the governor (within the pull cord assembly) says the crank is turning fast enough.

Plug gap looks massive. Also with no lead in petrol these days, you can't rely so much on plug colour....but that to me screams running rich and I'm sure a clean up, new air filter, new or cleaned plug and fresh petrol will have it running as new. Change the oil whilst you are at it.

Soak the filter in clean engine oil and squeeze the excess oil out. You can get specific foam filter oil but engine oil is better than nowt.
The oil traps the light dusty stuff that would pass through the pores of foam.

Are you wearing a suitable shirt while working on the mower? 🙂

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This might help you with the small spring

[url= https://c1.staticflickr.com/4/3836/33211455771_ab1642c5da_c.jp g" target="_blank">https://c1.staticflickr.com/4/3836/33211455771_ab1642c5da_c.jp g"/> [/img][/url][url= https://flic.kr/p/SAMoJp ]Briggs[/url] by [url= https://www.flickr.com/photos/83002503@N00/ ]mtbjeff[/url], on Flickr

So you set the throttle, and then the pneumatic governor works based on wind pressure off the fly wheel. Big load = no wind = more gas

FWIW, my mower came off freecycle - carb needed a good clean and a new plug and has been fine for 2 years now.

tbh While in the past I've rebuilt 2-stroke engines I CBA with our lawnmowers 4-stroke so just take it every other year to a local horticultural engineers and they service it plus stick a new blade in etc.

[I]Normally I'd be all for repair as the environmental option but petrol mowers are terrible in general for the environment and a poorly running old one especially so.[/I]

What should I use instead, and electric one - got one with a 100m cable?

This might help you with the small spring

Are you wearing a suitable shirt while working on the mower?

[url= https://www.lawnmowersdirect.co.uk/product/briggs-stratton-992230-service-kit#description ]this the service kit id need?[/url]

[url= https://www.amazon.co.uk/d/DIY-Tools/Briggs-Stratton-Carburettor-Diaphragm-795083/B0038U3IG2 ]with this diaphragm/gasket set?[/url]

thanks

When the diapragm leaks, the engine runs **very** rich under load (enough to stall it eventually).

Air filter won't help, either!

If you soak the foam in oil, you need to squeeze it out after. FWIW, I would just put a teaspoon full of oil to the cleaned filter and massage it to spread the oil around.

Insides need to be squeaky clean. Don't use water, or it'll be a bugger to get it out of the small drillings and jets in the carb. That recess is part of the fuel pump.

Not quite up to [url= http://singletrackmag.com/forum/topic/car-woes-new-engine ]Mowgli standards[/url] but you'll still be well chuffed when you mange to repair it yourself. 😀

PS - that diaphragm is goosed, under load you are using more fuel yet with that diaphragm the carburettor cannot lift enough fuel to supply the demand, and that filter will be choking the engine thus making it lift even more fuel and spitting it onto a huge plug gap that eventually oils up the cylinder.

Looks like the right kit you've listed.

That engine looks the same as the one in my mower. The diaphragm kit you linked to (795083) is the same one I have purchased. If find it fails every second year and gives a steady rise and fall in revs called "hunting" when its perforated.

I wouldn't bother with the new sponge just wash in soapy water and re-oil. I just use whatever I have typically 5W30. Do this every year. Fresh fuel also helps especially if its been stood all winter. A replacement spark plug would be code RJ19LM.

the filter comes with a kit thats cheap enough anyway mate, so i should be able to get everything i need for under £20.

just rang a local lawnmower shop who says he should be able to supply the lot for around £11 so ill go see him tomorrow.

thanks a lot

Next step... [url= http://www.blmra.co.uk/ ]this[/url]

Did you bloody well have to? I've just had to go and cut the grass in the spring sunshine after reading this... 🙂

Punky, you do know we're going to need a video of the running engine once you've completed this might task 😛

i think i can do that, watch this space 🙂 at work from tomorrow for 5 days so will hopefully have it serviced and back together on wednesday.

EDIT: jus wundrin..... imgur for hosting photos, does it do vids too? or will i have to upload somethings to youtube say?

Yay, thanks to this awesome thread, I've just bit the bullet and had a play with mine, which I haven't serviced at all for years - it's now got a cleaned up spark plug, air filter and oil change. Runs lovely and a warm sense of satisfaction that it was easier than I thought and I didn't break it! Cheers guys - you lot are always helpful for absolutely everything!!

Not sure if lawnmower's are ripcord/ pullstart (I'm guessing they are) but don't just go flalling away on the cord - SLOWLY pull and turn the engine over till at TDC (maximum resistance on the cord), let the cord go back in, slowly take the slack out then give it a good pull. Repeat until started.
Pull cords will thank you.

Couldn't be bothered with my old mower any more so I bought a new one 🙂

Quite looking forward to it actually. New one is £600 instead of previous £1300 and before that £1800. So I only want it to last a year. New one is 35kg instead of 70kg. The only thing is it doesn't have a BBC but I'll get by with that.

🙂 Handy few features such as a fuel cap with a clutch so you can't overtighten it, and a nice firm deck height adjust with only 5 positions.

New one is £600 instead of previous £1300 and before that £1800. So I only want it to last a year.

Have they put fibreglass decks on a decent cutting lawnmower ?

We used to get through a 1300quid honda every 3 years due to Ali deck rot depsite washing the grass off the undersife regularly.

Also had an fibreglass etasia . It was a great mower if you were doing acres but was on wheels and was shit for doing gardens.

And we had a hayter for doing the walled garden and tennis courts.

Are you wearing a suitable shirt while working on the mower?

Is that a young James May?

Trail_rat - how about a Stiga ?

My mum has an acre and a half site, mix of paddock and lawn and a 2nd hand Stiga Park is excellent and seems very well made.

I'm no longer in that industry so don't need one now but a quick look at stigas shows their self propelled unit has an alu steel deck same as the Honda's.

The spring will be under your fridge. Sure someone hasn't been using 2 stroke in it :p

The mower man is picking mine up this morning.... He's basically going to do what you guys have suggested and sharpen/balance the blade for £110.

So well done to the gents who've save themselves a pretty penny.

Next time I'll have a go myself (I hadn't read this thread before arrange for the service)... but having only ever replaced the spark plug once in 9 years I reckon I can "afford" to let someone who really knows what they are doing give it some loving care to my Hayter Sprint 41.

But I am going to have a go at the strimmer.... It's a 4 stoke so I'm guessing the principles are the same.... It's ticking over ok but cuts out when you rev it up.

for the strimmer my first check would be a leaky fuel pipe especially if you have left it sitting with fuel in.

ironically the fuel pipes on most hand power tools - strimmer-hedge cutter-blower - chainsaw use a rubber pipe from the tank to the carb that degrades when fuels left in and goes brittle. picks up a hole - idles fine but when you stick it on throttle the sucking of fuel increases and it sucks in air through the hole.

Used to keep a roll of it in the van for when we got the symptoms you describe as it wasnt really practical for us to drain all tools after each use.

Thanks TR ... that'll be the first thing I check

update! failure..... 😥

its maybe even worse than before

im sure i put the carb/gasket/diaphragm back together ok, and a new air filter rubbed in oil.

anyone care to hazard a guess? 😕

thanks

Sounds like it may be a fuel supply issue.

There's no smoke so I'm presuming the compression is good and rings are not worn.

Shouldn't you have a cable running from lever on 'handlebar' to the black lever attached to the spring in that last vid?

Shouldn't you have a cable running from lever on 'handlebar' to the black lever attached to the spring in that last vid?

The springs look roughly right, but there's something wrong as the linkages aren't moving freely - the throttle (turny thing in the middle) should spring back fully clockwise, and it should take very little pressure on the linkage to close it (turn it anti-clockwise). Everything should move like a Swiss watch - it relies on the breeze from the cooling fan to close the throttle when the engine is up to speed and the springs to open it again under load. Be gentle with them! The carb is probably OK.

The link by your finger isn't in its hole properly, and is probably binding:

[IMG] [/IMG]

Disconnect this and check that the arm near your finger (connected to the vane inside the cowling) is also moving very freely - may need a bit of a clean up. Provided it is, connect the linkage properly and check that the whole thing moves freely.

Have a look at this for inspiration:

Edit: You may need to take the carb off again to get that linkage in right - don't force it!

The link by your finger isn't in its hole properly, and is probably binding:

Provided it is, connect the linkage properly and check that the whole thing moves freely.

Have a look at this for inspiration:

do you think these springs are they key to solving this issue?

EDIT: just watched the vid again and see what you mean about the doobery springing back clockwise, need to try and work out why mine isnt. done a close up of it again and looks the same as mine :-/

I think the springs are right - 99% sure that the binding is the issue. Look how freely the linkage moves in that video, and how it always snaps back to the same place.

I think you will need to take the carb off again to get that linkage hooked up correctly. It needs to be put in place as you fit the carb back on to the engine so that you have enough movement to wiggle everything into place. It's not right as it is now.

yep, will do then, but one things baffling me. as you rightly say, the doobery springs back to the right every time until its pulled to the left and then springs back. but i cant see anything at all that would put any tension on it to keep it to the right. anything thats connected to it is to the left of it so youd imagine the opposite happening.

[url= http://tinypic.com/view.php?pic=29clzwi&s=4#.WMbj-JCLTrc ]found another pic.....[/url]

I did the filter, carb, oil, plug thing to mine. It was still crap.

Sold it for £40 and bought a brand new Honda.

Never looked back.

I did the filter, carb, oil, plug thing to mine. It was still crap.

Sold it for £40 and bought a brand new Honda.

Never looked back.

yeee ha, fixed it!!

I think the springs are right - 99% sure that the binding is the issue. Look how freely the linkage moves in that video, and how it always snaps back to the same place.

I think you will need to take the carb off again to get that linkage hooked up correctly. It needs to be put in place as you fit the carb back on to the engine so that you have enough movement to wiggle everything into place. It's not right as it is now.

thanks a lot for your help, much appreciated, this place is great.

Good stuff. Now for the most important thing; a picture of your lawn with fresh stripes! I love a stripey lawn. 🙂

Well done - and a nice view of the field!

Result! Well done 🙂

My lawn is available for extended trials...

ingwerfuchs - Member
Good stuff. Now for the most important thing; a picture of your lawn with fresh stripes! I love a stripey lawn.

POSTED 7 HOURS AGO #

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holy thread resurrection batman.

just asked the mods to re-open this but it says i can still post, so lets see......

lawnmower seems to have given up the ghost now, wont start at all.  its done a few cuts this year already but mrs ex-p cant start it at all, and now i cant either.

i'd go over all the above again and service it again but ive noticed that the squidgy priming jobbie spurts petrol out when pressed too, so not sure how much of a deal-breaker that is.

as with the OP 7 years ago 😱 mrs ex-p is desperate to buy another, whereas id like to keep it going forever, the 'triggers broom' of lawnmowers 😆

is it finally time to lay it to rest do you think?

cheers

Any trigger's broom is a challenge to keep it going forever. You don't just retire a trigger's broom when a small part can be replaced or fixed.

Fix it!
Fix it!
Fix it!
Fix it!
Your wife is having a 7year lawnmower itch!

excellent, my wifes soooo chuffed to bits with your answers 😀

and that squidgy prime button that leaks doesnt mean death to the lawnmower then no?

and i just need to service as above all those years ago, assuming that the links still work of course?

thanks

I have just done mine.

Gasket and diaphram, springs and plug, primer bulb, fresh petrol and good as new.

Ebay for the kit, Youtube for the how to. Mines the 35 too.

Ebay for the kit, Youtube for the how to. Mines the 35 too.

would you mind linking me to the exact kit that you bought then please mate?

ta

Love this thread. I have the same engine in my mower! I've had it for 22 years now and never serviced it, other than giving the spark plug a clean every now and then. I've never even put oil in it! Oh, I did just put a new throttle cable on it last week.

It's struggling a bit now and the plug gets choked sooner so I think I'm going to have to strip and service it. Will read this thread in full with great interest!

Great thread. Fix it. It's the right thing to do for the planet, for your personal pride and satisfaction, for your bank balance, as an antidote to the 'bin it and buy more shit' culture etc. etc.

You know this. Your wife will come to know this. Everyone on STW is now rooting for  sadexpunk's unkillable zombie mower. You simply can not let us down!

Seeing as we've lawnmover peeps in, I'm having a bit of trouble with mine....HOT starting.

Fires first time from cold, stop to empty the grass cutttings and it won't restart. Have to wait 10mins before it'll start again. Any ideas?

Last year it had plug, fuel filter and new carb. Emptied fuel over winter.

Mine's a Webb WER400

Another saying fix it – I have a B&Q special but it has a B&S engine and had a couple of issues with it – once I smashed the throttle linkage against something and bent bits and snapped a return spring, but YouTube and a few new parts and it was right as rain. Then it started running roughly and leaking fuel as the carb gasket had split - replaced that and it was still doing it then I realised it was actually the carb base that had warped (it's only plastic) so replaced that and all is fine. They really are easy to work on.

https://www.ebay.co.uk/itm/186353812114