Stihl FS70 running issue

[Changy]

A friend dropped off a Stihl FS70, complaining of starting issues and difficulty keeping it running once it started.

It's only been used about 10-15 times since new and is in good condition. I stripped it down and did the usual fuel filter after filling it with fresh fuel. The purge bulb felt strange, and I discovered the metering diaphragm was very stiff. I removed it, and the gasket also looked poor.

I replaced both, and it started, but only on choke. If you release the choke, it settles, but it bogs down after a short time. I checked the exhaust, and it is fine.

It seems to be a fuel delivery issue, and it only runs on the fuel provided after a purge.

Could it be a carburettor issue? The machine is like new, which is why I am uncertain whether the carburettor is causing the issue.

It's stumped me to be honest.

Perhaps my brain is addled and I'm too old for this stuff 

All thoughts are welcome

Changy

[Mick]

Sounds like you still have a carb issue to be honest.  It's usually the ones that haven't been used much that suffer worse from fuel issues.

I would usually give them a sonic clean before reassembly, but I realise not everyone has that facility to hand.  It also doesn't work every time, but That's what I would do before throwing more money at it..

Also make sure the gasket between carb and manifold is correct and the correct way around so the pulse hole isn't restricted.

Might be a daft question, and I don't want to insult you. But did you get the gaskets and diaphragms in the right order and the correct way around?  https://www.lsengineers.co.uk/stihl-fs70-carburetor-c1m-s208-c1m-s146-california.html

[Changy]

Sounds like you still have a carb issue to be honest.  It's usually the ones that haven't been used much that suffer worse from fuel issues.

I would usually give them a sonic clean before reassembly, but I realise not everyone has that facility to hand.  It also doesn't work every time, but That's what I would do before throwing more money at it..

Also make sure the gasket between carb and manifold is correct and the correct way around so the pulse hole isn't restricted.

Might be a daft question, and I don't want to insult you. But did you get the gaskets and diaphragms in the right order and the correct way around ?  https://www.lsengineers.co.uk/stihl-fs70-carburetor-c1m-s208-c1m-s146-california.html

Trust me Mick, I have made the mistake with the gaskets in the past  They were fitted in the correct order on this occasion.

I think I need to remove the car and try a clean. I don't have a sonic cleaner unfortunately