Honda Izy GCV135 stalling full throttle

[_Jonesy_]

Hi all

Just picked up an old Honda Izy lawnmower with the GCV135 4 stroke engine. I stripped the carb and cleaned it thoroughly, replaced the spark plug, oil and air filter, and drained and replaced the petrol with some fresh stuff. It starts easily on choke and runs ok at idle, but keeps bogging down and stalling at full throttle. I've also tried running some carb cleaner through whilst it's running but still can't get it to run wide open. The cables are all operating fully and seem to be correctly adjusted. Any ideas gratefully received!

Cheers

[GreenV8S]

_Jonesy_ said:

I stripped the carb and cleaned it thoroughly,

Was it running OK before you did that? Stalling under load suggests a mixture problem, and it would be easy to have introduced an air leak, mis-adjusted a jet or accidentally left some dirt / sealant in the wrong place.

[_Jonesy_]

GreenV8S said:

Was it running OK before you did that? Stalling under load suggests a mixture problem, and it would be easy to have introduced an air leak, mis-adjusted a jet or accidentally left some dirt / sealant in the wrong place.

Thanks Green V8S

No, it had the same symptoms hence deciding to take it apart. I counted the turns to try and put the screws back exactly as they were, but did wonder if one of the old gaskets might no longer be sealing properly?

[stevieturbo]

carb maybe needs adjusted for more fuel. There will likely be a screw somewhere.

[GreenV8S]

_Jonesy_ said:

did wonder if one of the old gaskets might no longer be sealing properly?

If you're rebuilding a carb, best to do it with a rebuild kit that will include all the seals and gaskets that need replacing.

For small, high volume engines you may even find it's economically sensible to simply replace the carb, daft as that sounds.

[Richard-D]

_Jonesy_ said:

Hi all

Just picked up an old Honda Izy lawnmower with the GCV135 4 stroke engine. I stripped the carb and cleaned it thoroughly, replaced the spark plug, oil and air filter, and drained and replaced the petrol with some fresh stuff. It starts easily on choke and runs ok at idle, but keeps bogging down and stalling at full throttle. I've also tried running some carb cleaner through whilst it's running but still can't get it to run wide open. The cables are all operating fully and seem to be correctly adjusted. Any ideas gratefully received!

Cheers

That sounds to me like your idle circuit is working correctly but the main jet is plugged. This could cause it to run so lean on throttle that there is not enough fuel to support combustion.

[Scrump]

I have the same engine in my mower.
Last year it was running poorly and I looked to buy a carb rebuild kit. I found a service kit including a new carb for about £12!
Mower runs great with the new carb.

[_Jonesy_]

Thanks everyone, will keep working with it.

Scrump said:

I have the same engine in my mower.
Last year it was running poorly and I looked to buy a carb rebuild kit. I found a service kit including a new carb for about £12!
Mower runs great with the new carb.

Is that the GHS one by any chance? Heard good things about their pattern carbs

[Scrump]

_Jonesy_ said:

Is that the GHS one by any chance? Heard good things about their pattern carbs

I am not sure, I don’t recall. Will see if I can find a receipt.

[Maxdecel]

_Jonesy_ said:

................keeps bogging down and stalling at full throttle. Cheers

Fuel starvation ? Blocked filter, what's the flow from the feed pipe like? May have an internal gauze filter.

[Bainbridge]

Is the plug gapped correctly?

Might be worth tightening it a bit to see if it improves running when up to temp.