99 yamaha 25 running on 1 cyl

av8erdunn

Seaman Apprentice
Joined
Oct 8, 2014
Messages
43
I have a 99 yamaha 25 that has started running on 1 cyl. It started with me forgetting to vent the fuel tank. We were running from a storm and I barely made it back to the marina About the time the bulb collapsed and it started running like crap. Now it's only running on one cyl. The oil was low as I just got this engine and was debating disconnecting the oil injection and was running pre mix. It's almost like its running in a safe mode for low oil but the light didn't come on nor is it ever on while running. It's run great for the last 6 hours I have used it up until now. I run a compression check and she is sitting at about 116psi on the dead cyl and about 112psi on the working cyl. I have taken off the carb and checked it and it was perfectly clean. Reeds looked good from looking through the intake and I replaced spark plugs hoping I had a bad plug. I even went as far as swapping the coils to see if the dead cyl woul follow but it didn't. The odd thing is if I put the motor on the hose and rev it up in gear it will run on 1 cyl until it gets higher up in the rpm range then you can hear the second cyl kick in. It's got me puzzled for sure. Any ideas?

Also how do wire up the wires on the oil tank level so they will not throw an alarm without he oil tank being on the motor? It's just a ping and black wire as shown in the pic.
 

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robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
drain carb float chambers onto a clean white rag to check for debris/water/etc....maybe a plugged carb jet?
 
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