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Old 04 October 2006, 11:59   #1
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contaminated fuel?

hi all
just a quick plee for help.

I am having some issues with getting the engine to run properly.
the only way it will start is with full throttle and choke, then, when i take off the choke and slowly reduce the revs it just coughs then stalls.
ive cleaned the plugs and made sure there is no contaminated fuel in the tank. i get the feeling its got something to do with the carbs.
but i dont have the guts to dismantle it because i have no means of getting it out of the water and i wouldent want the bits to sink to the bottom of the river (which would invitably happen)
engine: yamaha 80aeto autolube 2-stroke c.1995
all suggestions appriciated
thanks
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Old 04 October 2006, 12:06   #2
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what kind of tank/s are you using?
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Old 04 October 2006, 14:43   #3
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Sounds like the idle jets in the carbs.

Taking them off and cleaning them out is an easy job, although I woulnt fancy doing it with the boat in the water....

Do you have a fuel filter/serperator fitted? If no then it might be worth putting in to stop it happening again.
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Old 04 October 2006, 16:40   #4
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i wonder if its sucking air though a lose hose clip or perished bulb?? Its worth checking to see if your fuel line is all tight before taking carbs apart etc.
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Old 04 October 2006, 17:19   #5
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Timing advance

Had a similar problem with a 90hp Mariner 3cyl carb engine.

Turned out to be the timing advance mechanism - worked on the throttle linkage and should have returned under spring tension. Springs corroded. If the mech was reset the engine would start and as long as you only increased the throttle setting it would run OK. As soon as you tried to slow down it would run rough and stop.

Sorted springs and all well.
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Old 13 October 2006, 11:55   #6
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thanks for replies.
craig, im am using 2 of the external barrus mod type tanks.
someone did mention something about the jets to me,they said just dismantle the carbs and blow out the jets. going to try that this weekend.
oh and no fuel separator apart from the small primary one under the cowl
but it looks pretty clean.
cheers
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Old 15 October 2006, 03:38   #7
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Quote:
Originally Posted by richardjawilson View Post
i wonder if its sucking air though a lose hose clip or perished bulb?? Its worth checking to see if your fuel line is all tight before taking carbs apart etc.
I have just had this with a 90's Suz DT 65, I pressed hard on the fuel bulb and smelt petrol. I traced it to the fuel filter which had a hairline crack.
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Old 27 October 2006, 10:47   #8
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I had something similar t this once on a Honda 50. It turned out to be the choke sticking on. The little solenoid actuator arm for the choke had slipped on its clip forcing it permanently on. May be worth a look.

Keith
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Old 27 October 2006, 18:48   #9
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no,i dont think its that.
the engine seems "addicted" to choke, because when take it off, it stalls.
also is it normal to have one of the carb drain ports sealed off?
because on mine the bottom and the top ones are fine but the middle port appears to have been sealed off with some kind of plastic.
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Old 28 October 2006, 02:43   #10
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Blocked jets,bad timing, dodgy fuel pump or a serious air leak. If it's an air leak that badly you'll hear it when the cowl is off.
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