Vacuum Check!

[skynyrdcat]

I couldn't find this topic in the FAQ boards.
No specific engine in mind, but I was wondering if someone could give a basics course on typical vacuum realted engine problems (what performance issues generally are diagnosed as a vacuum problem, and what's the best trouble shooting method)?

Hopefully this isn't too vague to cover, just throw out what comes to mind!


Thanks in advance!

 

[tashasdaddy]

Re: Vacuum Check!

fuel restriction, clogged tank vent.

 

[Frank Acampora]

Re: Vacuum Check!

On 2 cycle engines, the piston compresses the air/fuel mixture in the crankcase to pump it up into the cylinder through the bypass ports. If the piston skirt is worn, reeds are broken or not seating, or the crankcase seals do not seal, then proper secondary vacuum and pressure within the crankcase will not be acheived; The engine will start and idle well, but will not produce much power at all. Additionally, the diaphragm vacuum/pressure 2 stage fuel pumps will not deliver sufficient fuel. Not sure what secondary vacuum should be but I am relatively certain that crankcase compression should be up aroung 6 PS!.

 

[skynyrdcat]

Re: Vacuum Check!

On 2 cycle engines, the piston compresses the air/fuel mixture in the crankcase to pump it up into the cylinder through the bypass ports. If the piston skirt is worn, reeds are broken or not seating, or the crankcase seals do not seal, then proper secondary vacuum and pressure within the crankcase will not be acheived; The engine will start and idle well, but will not produce much power at all. Additionally, the diaphragm vacuum/pressure 2 stage fuel pumps will not deliver sufficient fuel. Not sure what secondary vacuum should be but I am relatively certain that crankcase compression should be up aroung 6 PS!.

Very good, that's the kind of info I was looking for. I understand the principals but not always te best way to check / test it.