MANY times, (most actually from China) aftermarket parts do not hold up as well, or is not manufactured as well as OEM..   
 
OEM usually costs more but you get what you pay for...
 
.
 
 
 

So what can be wrong with the actual parts I have?
Yes, thinner than the old one.
But I just went an hour ago and bought a OEM gasket kit for $25 and measured the thickness. It is also as thin as the aftermarket one. OEM now is not same as OEM way back either.
 
I am still keen to find out what the actual problem is in this case.
I am surprised nobody here has encountered this issue before.
 
Best regards
 Bernt

Those diaphram carbs are extremely reliable and trouble free-besides being extremely
simple.  
 
There's obviously still a problem.  I'd closely compare your carb and tank 
to the one that works.  
 
 
.
.

What if I told you that 2 people, who are not idiots, have had several looks and comparisons and the parts look exactly identical, no faults visible, except for an extra 1.15mm jet in the input hole under the primer bulb of the good one. It is not clear if that should or should not be there. It was definitely not in there and not lost during disassembly.
 
So many things are simple in principle but then in practice, that is not always the case, when a problem like this presents.
The simple solution is to replace the tank and carb, which is what most would do, but that is cheating!
 
 
 

As we don't have the model # for the engine, have you looked at the parts diagram itself
for that jet?
 
As that jet is the only difference (I don't remember seeing it), I'd be looking at that.
Can you put that jet in yours and see what happens?  That jet would likely control fuel flow and W/O 
it, let MORE FUEL thru the carb....  
 
I don't know the history of the engine, new to you, just started acting up, someone else was playing mechanic, etc...
 
.

Hello, thanks for the reply.
I had this since new. It is 16 years old and over the years had several services, oil changes, blades, cracked inlet tube, the lot.
It has started playing up with this problem a couple of months back.
 Regarding that jet, no, I cannot take it from the other carb as it is a one way press fitting, permanent. It was likely hever fitted.
 
Regarding engine model no, I cannot find it and the mower shop yesterday had a look at all pictures I took and cannot find it either. Who knows.
 
Pity I can't post pictures.
 
Best regards
Bernt

Go to Post Image and open a free acct.:  https://postimg. 
 
Upload your pictures, then use the link for "Forums"
 
As your fairly new, it may take a couple of days for admin to allow it to post.
 
IE:

Ok, thank you.
I can also not post links here though. They get scrubbed / removed almost instantly.
But if you copy this to your browser, you should get to pictures.
 
This is my carb, note, no jet in that hole:
 
postimage.me/image/20250516-144013.7KwXXO
 
Picture of the other carb, note jet in that hole:
postimage.me/image/20250516-144006.7KwmPD
 
Here are pictures of the mower and engine in the hope someone knows where to find the model:
postimage.me/image/20250512-103201.7Kwd20
postimage.me/image/20250512-103138.7Kwsrf
postimage.me/image/20250512-103126.7KwuHd
postimage.me/image/20250512-103118.7KwDTJ
postimage.me/image/20250512-103040.7KwKZk
 
Best regards
Bernt
 
 
 

The "new" carb.  Is there a jet that pop's in that hole or just that o-ring and "restrictor" plate?
 
Seems to me you should have that o-ring and what ever is behind it.  I'm guessing  but 
possibly it popped out..
 
Also, the model # may be visible under the plastic pull starter cover, stamped in the metal housing.
 
.

Sorry, I am now not sure what O-ring you mean.
 
There are no O-rings involved here. The "good" carb simply has a cup shaped metal jet pressed into that hole and mine does not.  The off centre hole at 8 o'clock, not the one with the green/red.