Dry Brigg & Stratton

[peter]

Clive, can you help?

Everything in the shed decided to sulk & be uncooperative when asked to work this weekend.

Sorted the rotovators, fitted one new spark-plug & need one new spark-plug-cap, then tuned the carbs to get the mixture right.

The cheapo rotary mower started with a change of plug from my hayter.

The Hayter won't start at all, despite a full fresh tank of fuel the plug is showing completely dry, so I assume I have a fuel blockage. The carb seems semi-intregal to the tank, is it a strippable device or is a replacement needed? This a a Hayterette, solid alloy flat-deck 3.5 B&S, fully exposed on all sides.

Is modern fuel gummier than a few years ago?

I ask because I'm trying to sort my MTD engined shredder, where all the fuel p!$$&@ straight out the tank, thorugh the carb and flooded out the air filter. On stripping the carb its innards were covered in dirty yellow film/scum, which I think had stuck or sunk the float. Fingers crossed and fire extinguisher at the ready .

[John]

Hello Peter
I'm sure that Clive will be on this case pretty soon.
In the meantime I'd just like to say that over the last couple of year I've been using a Briggs & Stratton fuel additive (I think it's added at 5ml to 5 litres - bit more for overwinter)and I reckon that starting is much better especially after long periods of non-use. Its supposed to prevent the fuel gumming up.
I know you should keep your fuel tank dry through the winter but this is easier said than done and anyway I like to fire up the mower sometimes in the winter just to show the grass that I'm still around.

John

[peter]

Thanks for that John.
I agree its all well and good talking of dry tanks when they are al-la Kohler or Suffolk and have a fuel tap with attached hose that can be put into a receptacle. But draining a B&S with the integral low mounted tank is a bugger.
The MTD shredder has a capacious fuel bowl on the carb, and having removed the carb I would hesitate to take the bowl off while the carb was on-engine as the float dropped and pulled the bowl inlet fuel needle out on its little hairspring , quite difficult to re-insert with the carb free in my hands, never mind attached to all that metal.

[John]

Hello again Peter
Just struggled in from the garage during a snowstorm. I noticed the bottle of fuel additive that I mentioned. Its called B & S Fuel Fit. I use it for 2-stroke mixes and in my can of 4 stroke fuel. Its £2.95 for 125 ml but as you normally only need 5ml per 5 litres I suppose that's not too bad a price. It seems to do a good job.

John

[Clive.]

Hello,

Just back from a weeks NT Working Holiday in the Gardens at Beningbrough Hall near York..a sort of Busmans Holiday.??!!

I recall the Hayterette with 3 or 3.5hp B&S and carb as you describe can sometimes be a bit different to start than the similar engine in another application. I summise this has something to do with the auto choke and/or the large blade disc.??..unless yours has the smaller saucer disc and conventional blade which was an option on some.

It is often the case if this has the automatic choke engine that a start can be acheived with the throttle set at a position just above tickover instead of the full throttle position...well worth a try..and then let the revs slowly build.

With the air filter removed and the air cleaner screw replaced the operation of the choke disc can be checked... the disc can get blackened and not move freely. It can also wear at its pivot. A bent air cleaner screw can upset things.


Perhaps put a couple of squirts of oil from oil can into the spark plug hole to see if that effects a better seal of valves to give an improved compression in case a valve face has rusted over winter.

There is an "o" ring that can dry out in the carb mounting onto the intake tube that is above the cylinder...also the tube itself can shake loose in its alloy elbow. The elbow at the join with cylinder block can work loose and its gasket be damaged.. All these can upset the draw of fuel/air mix.

Another try may be to check carefully the position of the main fuel jet screw.. then open it by quarter of a turn..then attempt a start... this may help if some slight corrosion or gumming has occurred. By noting the screw position it is possible to return it accurately to the original position.

The older engines may have a choke applied by the throttle cable travel but most "middle aged" light green Hayterettes with red engines will have the auto choke with fuel pumped from tank up into a carb chamber from which it is then drawn through the main jet to the engine.
5Hp engines mostly had choke applied at the end of cable travel...these often did not quite choke fully and needed a little help to push the choke link full over to acheive a start. More recent 5hp (c1995 on??) had the float type carb as will the current 4Hp? types.

The carbs should mostly be able to be serviced..with parts drawings available online from the B&S website using the engine model, type, code numbers.
Service books are available to purchase.

The auto choke carb' is not easy to describe in a few words how to service.
Those on Hayterette will have a diaphragm that acts both as a fuel pump and choke operating mechanism. On replacement of the carb body to tank the diaphragm has to be preloaded by holding the choke disc over centre as the carb mounting screws are tightened.
The carb has to be checked for warpage...there is a fix with teflon washer to assist if this is suspect..I have also faced them flat, unofficially, with pipes removed.

The auto choke spring and rubber diapragm needs checking for condition.
There is a pump spring and washer that needs to be in the correct place to pump correctly.

Sorry, it's not easy to be specific....I have sat and typed through a few Hayterette ailments that I can recall from way back when I was in the machinery business.

If in doubt...then all garden machinery repairers will be familiar with B&S and Hayterette..although they will be into the manic busy season given a few sunny dry mowing days..

Take care,
All the best,
Clive.

[peter]

Clive, thanks for the advice, had some family problems which delayed me trying it out.

However managed it today (Weds), carefully screwed the main jet in as far as it would got, counted turns, then removed it.
Seemed clean.
So put it carefully all the way back in, wound it out the correct amount and tried to start.
No joy, plug still dry as a bone.
So, by half turns, wound the jet out and tried starting.
At about four full turns beyond "setting" it started.
Warmed up and started to sputter, so wound the jet in until the revs rose, continued till they started to drop, then back out a half turn.
Went and mowed the allotment paths and after a refill 3/4 way through it started to sputter again, so wound in a bit and all OK.

Heaven knows what it must have been, gum I guess and some use has washed it through.


BTW non-original engine, the original had zero compression, replaced with a £10 off local mower shops "heap", white engine with the pull-cord operating a "bulge" to the side of the flat "spinner" on top of the engine.

Many thanks again, now to sort the shredder......