VF4 Wisconsin vacuum

Duner Wi

Well-known Member
Is it possible to get an even vacuum reading out of an odd fire VE4/VF4 at 5-600 RPM? High RPM it jumps 1 inch ,between 14-15 inches. Low rpm it is 5 to 15. Compression is 85-90 all cylinders.
Thanks!
 
I suspect a sticking intake valve. Old gas will varnish the intake valve stems. More pronounced on aircooled engines. When the engine is idling fog some penetrating oil in the intake or some 2 cycle mix for fuel.
 
I thought the same thing about sticky vales so I have been running engine out of 1 QT gas container. Pumped marvel Mystery Oil thru the intake with engine running, Same oil in the gas.
Removed the valve adjusting covers and oiled valve stems and springs with pump oil can with engine running. Same deal ,nothing changed. Still would like to know if uneven fire/odd fire Wisconsin can have a even vacuum reading at 500/600RPM?
 
Maybe not possible. However, I would try to pinch the hose to create an orifice between the guage and the manifold. Pinch it enough and eventually you will dampen out the bounce. At least that is my theory. Could do the same with a needle valve.
 
I did like you said and it evened out the bounce at low RPM. AT high RPM the bounce goes away too except or the 1 inch fluctuation.I assume that is a bad intake valve.
 

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