Hard Starting B&S Lawnmower

[crash]

I have four stroke B&S lawnmower (Sprint 375 which is about 9 years old)which has become a pain to start.
It use to start on the third pull unless the air cleaner was dirty.
The only way it will start now is if I take the air cleaner off, and once running put it back on and it runs fine. I have changed the air cleaner to a new one but this has not helped.

I suspect that the rings are going bad as it has started to use oil, and the inside of the carb entrance is oily. If I take the the crank case vent off of the carb it does run better, and after running for awhile oil spills out of it (it needs a provent!)

I have sprayed carb cleaner down it a couple of times, and the spark plug is reletively new and is in decent shape.

I am open to suggestions.

[bee utey]

If it has the fuel tank under the carby, strip it down, there's a simple rubber diaphragm in there that acts as a fuel pump. They shrink with age and cause all sorts of running problems. They're quite cheap to replace from memory.

[Fluids]

What he said !!

About $10-12 and a piece of cake to change .... Clean fuel tank as well whil it's apart.

[crash]

Went to the mower shop and got B&S part no 5083.

Includes gasket, diaphragm, diaphragm spring and filter all for $12.00 plus some free advice on fitting.

When I took the carb off I was very surprised at the amount of "mud" at the bottom of the filter. Filter was clean though.

Have yet to fit the new kit - will let you know if it fixed the problem or not.

[d@rk51d3]

Check the valve clearances too.

A mate who does small motors for a living, reckons it's the main problem he finds with the Briggs.

[Avion8]

My B&S lawn mower will never start if the fuel is stale - even one month old. So now I always run it dry & put fresh fuel in every time it is needed, and then it starts first pull.

[JDNSW]

My experience, with multiple motors over many years is

B&S = hard start

John

[crash]

Put the new kit in, and started right away. Now the darn thing will not come up to proper running revs.
When it first starts it will reach proper running revs for about 5 - 10 seconds then it will slow down and run rough. Have checked all the linkages and are set properly.
Even took everything apart and double checked things were installed properly.

[rovers4]

Is the choke coming off?

In my case I have a mower that was running well, but then stopped. Would not restart. New plug, new fuel, new carby cover, seal, new needle valve.

[Aaron IIA]

When it first starts it will reach proper running revs for about 5 - 10 seconds then it will slow down and run rough. Have checked all the linkages and are set properly.

Have you tried adjusting the fuel mixture screw?

Aaron

[bee utey]

Have you tried adjusting the fuel mixture screw?

Too true. When I have had the misfortune of working with a BS engine a screwdriver was always at hand to fine tune the beggars. Since the advent of the Honda engine on my mower tuning has been totally unnecessary. :)

[crash]

Too true. When I have had the misfortune of working with a BS engine a screwdriver was always at hand to fine tune the beggars. Since the advent of the Honda engine on my mower tuning has been totally unnecessary. :)

This is a push mower with the carb above the fuel tank.
No adjustment screw on the carb (not that i can find).

Choke is coming off.
New fuel as well.

[bee utey]

This is a push mower with the carb above the fuel tank.
No adjustment screw on the carb (not that i can find).

Choke is coming off.
New fuel as well.
1. I lose track of how many vertical shaft BS engines I've worked on, most were old and cranky and all of those have the carby on the fuel tank, which is why I mentioned carby diaphragms in my first post. Instead of a needle and seat they have a constantly overflowing chamber in the top of the tank, pumped via crank case pulsations.

2. All BS engines I've seen have a mixture screw. From memory they sometimes hide in a hole in the throttle cable bracket.

3. The choke is designed to run with the air cleaner on, perhaps it isn't on properly.

[crash]

Ended up putting in a 2nd carb kit.
When I installed the first one I some how got the diaphragm missed aligned and one of the screws damaged the diaphragm - I think it was sucking air. After putting the 2nd kit in it is starting easily and running properly.

[PhilipA]

Geez I am missing out.
My old B&S 375? Rover Craftsman was bought about 20 years ago second hand and it had several years on it then.

I change the oil every few years, and treated it to a new spark plug and air filter a couple of years ago.

It has always started first or second pull and run properly straight away.

I am hoping it will die one of these days as I would like to justify a new Lithium lightweight mower as it is a bugger to lift and push up my hill.

Similarly when I was a kid I did lawns with a Rover B&S and it lasted 15 years and started easily until submerged in the flood of 74 in Brisbane.
Regards Philip A

[crash]

Geez I am missing out.
My old B&S 375? Rover Craftsman was bought about 20 years ago second hand and it had several years on it then.

I change the oil every few years, and treated it to a new spark plug and air filter a couple of years ago.


Regards Philip A

I do not change the oil any more - I just keep topping it up!
Growing up I would hate to know how old the lawn mowers were we use to have. Topped up the oil and filled with fuel and then away you would go. I am sure they were B&S too.

[Marty90]

I had a one-man lawn mowing business which I sold about four years ago,and I had two self-propelled Rovers on board,20" and 22".Both had Briggs engines which I serviced religiously weekly.The engines were great until they experienced a little compression drop,then if you switched them off when hot you would throw your shoulder out trying to start the bastards.I soon woke up and got my mowershop to fit Honda engines when time came to replace engines or complete mowers.You only needed half a pull to start.Beautiful.They then started to build the Hondas and Rovers in China.They look identical but the quality was gone in both.

[Tins]

Too true. When I have had the misfortune of working with a BS engine a screwdriver was always at hand to fine tune the beggars. Since the advent of the Honda engine on my mower tuning has been totally unnecessary. :)

Got three Hondas. The first one I got was a GXV (?) 120 on a Big Bob deck. The thing is about 35 years old and it starts first time, even if it has sat all winter. Blows a bit of smoke when first started but that's all. The only time I have ever had trouble with any of them is when I got some water in the juice.