Yamaha ProV running like crap. Have run out of troubleshooting ideas. Reeds?

iammarcuse

Petty Officer 2nd Class
Joined
Oct 15, 2007
Messages
131
I have a 1990 PROV150LD. It idles poorly and stalls and will not make full power under way. Sometimes it runs better than others and but always surges even if running better. I have run through most troubleshooting procedures. Compression 95-100. Good spark, new plugs, good fuel pressure, new lift pumps and filter. Thoroughly cleaned carbs. No obstructions. Floats set to spec. Pilot screws set to spec. Carbs synced.
Ruling out electrical and fuel, I am beginning to think that the problem lies deeper, as in reeds. The reason being the middle carbs at idle seem to be breathing very hard compared to top or bottom (which barely have any air movement when you put your hand over them while running.) The motor has a muffled sound while idling and does not sound clear like it used to run. I am open to suggestions. Not sure what to do next. Thanks.
 

iammarcuse

Petty Officer 2nd Class
Joined
Oct 15, 2007
Messages
131
Re: Yamaha ProV running like crap. Have run out of troubleshooting ideas. Reeds?

Well, it seems I left a screw loose in the float bowl when I did the carbs. Created a vacuum leak and cylinder 3 was getting no fuel. Seems to be running fine now. Hard to believe a loose screw could cause so much grief!
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
Re: Yamaha ProV running like crap. Have run out of troubleshooting ideas. Reeds?

Just curious......were those fuel pumps cracked?
 

iammarcuse

Petty Officer 2nd Class
Joined
Oct 15, 2007
Messages
131
Re: Yamaha ProV running like crap. Have run out of troubleshooting ideas. Reeds?

No, fuel pumps were fine.
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
Re: Yamaha ProV running like crap. Have run out of troubleshooting ideas. Reeds?

Why were they replaced?
 
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