Need Help Please... 3.5 hp Briggs

[SnowdogShae]

Hey Everybody!!! I'm New to this forum....Have read many threads already, but I still can't find what I need....
My neighbor gave me a 3.5hp Briggs mower(one of the cheapest around)...It runs, but there is black smoke coming out of the exaust...and it spits and sputters like crazy!! I've taken the gas tank/carb off and cleaned everything...although there is a spring missing off of the (I don't want to sound too stupid, but here goes)---plastic thing coming out of the side of the motor...I'm assuming that this is some kind of govenor arm since it moves... this engine doesn't have an adjustment for idle....just one speed....
Could the spring missing have anything to do with it running too rich??
ANY HELP would be greatly appreciated.....THanks!!!:

[Mr T]

Could be that spring. Get a repair manual or parts sheet for that engine. I think ive seen parts diagrams on the web. Search for your engine model. See if its on there.

Check the oil and plug. If the oil and plug have been changed recently and look bad, it could be a sign that the engine needs a rebuild.

Check your mixture adjustment (needle valve) If its way off you can get a horrible engine. Set it back to it's 'origional' setting and try to adjust it from there. The engine should at least start with that setting.

[Bumblerazz]

I'm surprised that it doesn't have an adjustment for motor speed, but if it doesn't then it is likely that the missing spring is for the choke. It could possibly be the cause for it running "rich".

Black smoke could also be:
- oil or debris in the air filter,
- gas bypassing the cylinder head and coating / igniting around the spark plug.

[SnowdogShae]

Thanks for the info....unfortunately it's storming outside....so I can't go try it out now...but will as soon as I can. I can atleast look up on the computer tho' and see if it's the choke lever...kinda makes sense tho...:D

[SnowdogShae]

okay, can't find any good links to get a good picture of this engine, I suppose any 3.5hp briggs will do....any help??