1990 Pro V 150 no vacuum at idle top cylinders

[iammarcuse]

I have a 1990 PROV150LD. that stumbles at idle and often coughs and stalls. I rebuilt the carbs and set every thing to spec. The motor is running great off idle and turning 5500 rpm at wot. After tinkering with the idle adjustments I noticed I was getting almost no vacuum in the top 2 cylinders, I can put my hand over the throttle body and there is little suction and the motor does not change rpm at all. As a result there is little fuel entering the throttle body. Basically I am idling on the bottom 4 cylinders. Once I crack the throttle I get good vacuum and the motor runs fine.

I ran a compression test and I am 95-100 across all 6. I looked in the intake and the reeds that I could see looked like they were sealing. Any ideas would be greatly appreciated?

[boscoe99]

Reeds would be my guess.

[iammarcuse]

Problem solved. Carbs were just slightly out of sync. Made all the difference in the world and idled perfect. Thanks.

[99yam40]

Told you to check link and sync on the other site , and you said you did it already.

Glad all is well now