Hi all,

So my father tasked me with repairing his gf's mower. I'm not sure what the problem was before, but I cleaned out the carb and the tank with carb cleaner and gave the tank a flush out with fresh petrol. It's running, probably better than before but is still revving in and out. What else do you think could be the problem? Thanks.

Hi KawasakiKBH, and welcome to TGMForum.

Do you know what B&S engine it is? Just so I know what carb is on it.  Maybe attach a photo or two of it might help.

Cheers, will do!

It's a Briggs & Stratton 450 series 148cc

Quote from: KawasakiKBH on June 26, 2025, 03:32:33 PMIt's a Briggs & Stratton 450 series

Thanks.  So the one with plastic carb bolted directly on top of fuel tank?

As apposed to a 450E with plastic carb on the left, and fuel tank mounted behind it.

First things to double check if you're sure the carb is clean.

Make sure that the intake tube where the carb pushes onto is not loose on the engine or cracked. And that the O-Ring and plastic retainer is seated correctly where the carb meets the tube. Any air leak can cause it to hunt and run rough.
 

Plastic carb bolted to the tank absolutely.

I have thoroughly sprayed both the carb and the tank out with cleaner. I will take the top of the mower off and will check the intake tube tomorrow.

Can I just ask in which order is it with the white plastic ring and rubber washer?

The diaphragm on the carb is knackered, btw, so I have bought a replacement.

I would try just changing that diaphragm and gasket kit to start with and see if that improves the running.

The rubber O-Ring goes into the carb first, then snap the plastic retainer ring in.   

Also forgot to mention, please make sure your using fresh fuel and not stuff that's been sitting in a can from last year.

Ok, so now is basically running even worse. It has stopped surging, but gets to the point of conking out almost immediately.

So to summarise:

Changed the gasket and diaphragm.
Cleaned the carb out with carb cleaner.
Cleaned the tank.
Checked the mesh on the carb, seemed fine.

Put it all back together, filled it up with Aspen 4 stroke.

What am I missing?

Many thanks for the help.

Is it now running too rich, as in belching black smoke when its running. 

You have got the air filter on? or at least the air filter screw otherwise it can suck fuel.

It's a shame I can't see and hear it running.

Is there any way I could get a vid to you?

Quote from: KawasakiKBH on June 27, 2025, 05:21:53 PMIs there any way I could get a vid to you?

Do you have YouTube, or Facebook

https://www.youtube.com/@TGMForum
https://www.facebook.com/TGMForum/

Unfortunately I don't have the server space on here to allow video uploads

Sent a private message to the group's fb page.

Thanks. 

Hiya, have cleaned it all again from the ground up still running rough? Any further ideas? Many thanks.

That's not good.  Is there any chance you could show me a video of the throttle linkage when the engine is running. On facebook again if poss.