Mountfield SP454 running issues

[ipbr21054]

Ive been cutting grass for a few years now & all my neighbours think im a mower man repair guy hence why ive been given another mower to look at.

This time its a Mountfield SP454 & overall its in very good shape / condition.

Lady told me it just died & wouldnt start again then left in a dry garage for a month.
I drained the fuel into a clear jar & i could see water & other jelly fish type algae etc not to mention it did smell like turps as opposed to petrol.
I removed the carb & confirm the float works fine also the needle jet below moves up / down fine.
The main jet down the long brass tube is now clear & free to blow through.
The inlet pipe where the fuel pipe connects is also clear to blow through.
The air filter has been washed, cleaned & dried.
A new plug has been fitted.

It has a red primer bulb with a hole in the top & it fits into the air filter which when i press it feels like nothing is happening.
If i then press harder / deeper so i can feel the plastic case to which it connects i then hear a noise in the fuel tank & i then feel a different feeling.
So much so i can say its now doing what its supposed to do BUT only because im pressing harder / further into the bulb.
This cant be right as i wouldnt expect a women to do it like ive been doing.
Second pull the mower starts but it runs for say 10 seconds & then dies.
If i repeat the same process it does the same thing.

So it will not continue to run & just drink the amount i pump then dies im saying that as i cant see tickover beeing low as lady owner wouldnt of known what to touch.

Does this seem like the gasket between carb / air filter not creating a seal so no continuous vacuum or do you know if these primer buls have an issue.
I dont see any leaks from primer bulb BUT now & then i do see fuel on the mower deck right below carb / air filter

I dont see any pipes connected to primer bulb so it must just work through a series of holes to get fuel from tank into carb


I would of done a short video clip but doesnt run long enough for me to do so

 

[ipbr21054]

Ive been out & deck is dry.
Ive pumped the primer say 10 times & now i see deck below air filter housing is wet with fuel

 

[Burnerman]

The primer bulb on these shoots a momentary shot of air into the float chamber.......this allows a jet of fuel to shoot out of the jet and into the carb venturi - just to give a temporary fuel enrichment .
Just like a choke really! Excess priming causes fuel to leak out.
These engines do like a good seal between the air filter housing and the carb, and I'd suggest that the carb itself would benefit from a good clean.......especially the main jet and emulsion tube area.
John

 

[ipbr21054]

Carb & main jet & emulsion tube has been apart & cleaned.
I am them pumping too many times hence the fuel on the deck.

I will order a carb gasket.

 

[ipbr21054]

So going by reply above the dripping fuel from below carb / air filter was due to me pushing primer bulb numerous times thinking it was squirting fuel in.
So now I take onboard it’s just a squirt of air I press it once or twice & go to start mower.

Today the gasket arrived & I’ve now fitted it. I press the primer twice & pull the starter rope. Same as before where the mower starts but only runs for say 5 seconds & then dies.

Fuel filter in tank has been cleaned.
New fuel pipe fitted from tank to carb.
Pull off pipe at carb & petrol fun’s out fine.
I can blow through carb pipes & jets so nothing is blocked.
Air filter is clean.
New spark plug.
Fresh fuel

Today I even removed the exhaust just to rule out it being blocked but same issue.

Lost & confused as to what it can be.
I supply some photos should you see something wrong or missing.

Also can I screw anything in or adjust anything to at least get it to run longer as to rule things out ?

Thanks.

 

[Burnerman]

Can you see in picture 2, the round plastic tick over screw?
Below that is the plastic slow running jet which can be prised out for a clean, after the tickover screw is removed.
Plenty of carb cleaner needed here, compressed air helps too!
John

 

[ipbr21054]

So remove & clean item by blue arrow

 

[ipbr21054]

OK
ive removed that plastic part & the small hole is blocked

At the bottom is a brass part, i assume that needs to be clear

 

[Burnerman]

Yes it does, and there is a drilling connection from one of the small holes shown in picture 1.
Squirt plenty of carb cleaner down there!
John

 

[ipbr21054]

Wont budge.
My needle jet cleaner will go in so far & thats it.
So not sure if its same size hole all the way through or tapered.

Compressed air does nothing

 

[ipbr21054]

It’s well blocked.
I’ve removed it from the plastic part as had no choice.

Any reason why I can’t leave it out & just refit the black plastic part ?

 

[ipbr21054]

Done.
I cut away a little of the plastic that the brass jet passes through.
Managed to get a hole through it & see daylight.

Put it back into the black part & touched edges with soldering iron & made a good contact with black plastic & brass part.

Short video.

Dropbox

www.dropbox.com

 

[Burnerman]

I’ve never removed the brass jet before, or altered the plastic insert!
I can’t access your vid just now, so how is the engine running?
John

 

[ipbr21054]

Running fine

 

[Burnerman]

Another triumph!
Seems to blow a little smoke though - maybe the oil level is a little high?
John