2008 Yamaha 50 HP 2 Stroke far

lsumedic2005

Recruit
Joined
May 13, 2009
Messages
3
Good evening. Looking for some assistance with an issue I am having.

To start, purchased the rig about two months ago. Initially it ran flawlessly. Would crank right up and run all day with no issues.

Probably about two trips ago, motor would crank right up, however when applying the throttle to get on top, engine would stall out. Would crank right back up and idle smoothly and die again when throttle was applied, however after reving the engine in neutral for a short period of time it would get on top and run fine.

This did not last long and it eventually stopped starting at all.

what I’ve done thus far:

Changed all fuel lines from tank to engine to include all connectors and filters. New fuel pump.

Completely taken apart all three carbs and thoroughly cleaned every aspect of them. Didn’t find any junk in them, however I did notice the needle screw and spring for the middle carb was missing. I believe this is for the air/gas mixture. Thankfully I searched the engine area and was able to find it and put it back in place. I looked up the recommended adjustment which was 1 1/2 turns from seated position.

after completing the above, engine fired right up and ran very smooth. This was in the driveway with water hose hooked up.

Thinking i I may have fixed the issue, i took it to the nearest launch to take it for Test run. Engine would not start yet again, unless I placed my hand over the top carb and revved the engine up. Once I would bring it to idle it would die.

What am I missing? I am by no means a mechanic but I am stomped on this one. Any help would be appreciated.
 

Yahman

Cadet
Joined
Aug 5, 2018
Messages
10
If your engine has the Prime start system (found on middle carb), remove the 2 small phillips screws at the top of the valve and pull out the needle. Measure the needle for movement with the ignition on for a few minutes. (There are a few YouTube videos out there if you need them). Needle should extend a few millimeters after a few minutes with key on. If so, prime start is working. Next shoot some carb cleaner into the needle orifice before reinstalling the needle. Now try starting the engine. I bet it starts right up. I have had to do this every so often with my Yammie, the Prime start gets gunked up and then takes forever to start. A blast of carb cleaner fixes it for me.

Also check the fuel line and fittings between the gas tank and fuel pump. If there is any leakage it may allow air into the line which will not allow the fuel pump to reach full vacuum. Usually this condition is accompanied by a bulb that will pump up initially but goes soft again with running. Ethanol is to blame for the majority of fuel line failure. On mine the hose was swelled at the below-deck tank fitting and causing me all kinds of grief until I replaced the line.

Hope this helps you (or someone else). Andy
 
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