Briggs 5.5hp Intek hard start

[Riick]

I have a older Toro 21" GTS Recycler mower, (built in 2001) with a 5.5 Briggs engine. This engine uses a rubber bulb to prime the engine with gas.

Once mower would start on 1st or 2nd pull, but has been getting progressively harder to start. Cleaned the carb, new gaskets & float needle, no change, still hard to start.
Installed a brand new aftermarket carb, fuel line, fuel filter, cleaned & re-gapped the magneto, still hard to start;
Just like with the old carb, will only start if I spray some carb cleaner near the air filter.
Once it starts, runs fine, no surging, and warm, re-starts on 1st pull.
Anyone with an idea that might improve things?

 

[Scrubcadet10]

Engine model number?
If it's the engine I think it is, the air filter base could be warped or the primer passage clogged.

 

[Rivets]

Aftermarket carb may be the problem or the gasket between the air filter body and carb is leaking due to the plastic warping.