When you pull the lever of the IP into the start position, the IP will inject a very large amount of fuel into the engine (even more than the full-load position), so the throttle positionn doesn't matter during starting.

You can remove the bottom plate of the IP, so you can clean it, but you probably need a new (rubber?) gasket when you replace the plate.

On the other hand, there are no oil channels which can get blocked, so some dirt in the IP is not that bad.