Motor Conk-out Question

S

Steve O

Active member
Any insight into this dilemma is greatly appreciated:

Purchased an old 5 HP Nissan 2-stroke engine. Had it professionally tuned.

Then ran it for about 20 minutes until it died mid run. It would start right up again fine, but almost immediately conked out again.

Took it back to tune up person, who returned it to me after running it 1/2 an hour on my gas tank with no problems, so I doubt the fuel is a problem.

Took it out 2 days and ran it about 4 miles each time without having it die (though it did sputter once or twice)

Next trip, went about 5 miles when it again decided to do the conk out routine. Managed to coax about 2.5 more miles out of it at much lower speed, when it conked out again.

Rowed back to ramp 2.5 miles (lots of fun).

Hope to bring it tomorrow to the tune up person, but I'm hoping somebody here can offer some insight I can share with him to help solve this riddle.

Thanks.
 
Try opening the vent on the gas tank. Don't mean to state the obvious, but sometimes its just too obvious. I've done it.
 
Try opening the vent on the gas tank. Don't mean to state the obvious, but sometimes its just too obvious. I've done it.
Click to expand...


I was going to suggest nearly the same thing. Try a different tank, maybe something is not letting it vent all the time. That's about as far as my mechanical knowledge goes.

Tim
 
How does the motor run cold? Will it idle? A couple have mentioned fuel system venting. That is a good possibility, especially after a bit of a run. It your engine 2 or 4 stroke?
 
the other thing that is easy and sounds like a possibility is an almost clogged fuel filter. It'll run at idle but it'll be rough or starve out at higher rpms.
 
I've made sure each time to open the air vent, but maybe something is causing it to seal. Probably worth investigating in any case. Thanks for the suggestions.

Right now the tune up person has the motor. I'm really hoping he figures this out. It's a nice little motor.
 
One more thing I have run across is the fuel pick up tube in the gas tank can be plugged or suck air. You can check for this by checking your fuel blub while running. If it flattens it is being fuel starved. I tried fixing that problem and created another it sucked air. Time for a new fuel tank for me. This problem after installing a new fuel pump.
 
Try opening the vent on the gas tank. Don't mean to state the obvious, but sometimes its just too obvious. I've done it.
Click to expand...

I've done it enough times to almost become legend.
 
Wispete beat me to it, so I'll second checking the fuel line and the bulb. If any connections are going bad and you're sucking air, you're SOL...
 
You know, this got me to thinking about another possibility. This is a flat bottom boat, and this happened not too long after some bumpy running where there were waves. Maybe the jostling around on an approximately half-full tank introduced air into the fuel line.

But on second thought, I don't recall much if any wave action the first time this happened. Still, perhaps the gas sloshed around with an abrubt speed change.
 
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Took the motor back to the person who tuned it up, and he went through it. he reports that he found some type of fiber inside (I think he said the fibers were clogging the fuel jets or something like that). He did not determine what the fibers were made of, but wondered whether they indicated a no-good fuel filter.

The fibers were removed and the fuel filter replaced. On 2 trips since then, the motor has run well. Hoping it continues to do so.

Thanks to all folks who offered helpful thoughts and suggestions in response to my question.
 
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