9 replies to this topic

[blacktulip]

Hi, I have been given a petrol lawn mower as it's been running or not running in this case. I hate to bin it and was wondering if anyone on here has a bit of knowledge on how to help fix it. It's a cheap challenge extreme 123cc 3.5hp. I think all of the settings are wrong. I've changed the plug and checked the oil, filter and fuel supply. I can get it to run but it will cut off then not start for a while. Any ideas on what I can do?

[imack]

Id remove the carb and clean it and blow out the jets with an airline. Replace the gasket between the carb and the fuel tank, this has the pump diaphragm in it - no actual pump as such, it just works on pressure pulses.

[blacktulip]

There's a little wire spring not attached to anything. I wonder if this is the problem. Do you think the black screw is the idle?  DSC_1205.JPG   54.37K   7 downloads

[Itsaminithing]

Looks like a governor spring, revs will be unstable without it connected & it's likely to cut out occasionally.

Fix this problem first before fiddling with the settings.

Plenty of youtube vids/info on the net for repairing lawnmowers though can't find anything specific for a 'challenge extreme'.

This might help https://www.briggsan...lving-tips.html

[mab01uk]

A new spark plug every couple of years usually fixes my Honda engined mower from cutting out but you have done that, also use new petrol as modern unleaded fuel goes off over winter months and then causes running problems.

Edited by mab01uk, 28 May 2018 - 08:20 AM.

[Itsaminithing]

In my geriatric Briggs&Stratton i only ever use old fuel that i wouldn't use in the Mini. Could have a couple of whiskies before bed, wee in the tank the next morning, & it would still run.

[Archived2]

Get the carb off and stripped.
The old fuel turns to varnish in the emulsifier over the jet.
Loads on YouTube how to strip and clean little carbs like this.
Don’t forget to pay attention to the idle fuel circuit else it will hunt on the regulator

Edited by minihobbymini, 29 May 2018 - 07:39 AM.

[blacktulip]

Stripped the carb out but the jet won't come past the bridge. It was raised around 5mm above the bridge. Is this normal?

[Archived2]

Stripped the carb out but the jet won't come past the bridge. It was raised around 5mm above the bridge. Is this normal?

Can you post a pic?

[elf66]

Usual problem is the fuel pump diaphragm that forms part of the rubber gasket between the two halfs of the carb. If there has been any contamination in the fuel the rubber will expand or go hard. They are cheap and easy to find on ebay.