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engine surging


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OK guys i need opinions as to where do i go now  engine surges

 

Cleaned carbs   new primer bulb    new separator    new fuel hose from separator to motor     new fuel pump    new filter

only happens sometimes.  when its not happening engine runs great  yamaha 115 2 stroke  2004

 

 

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after fishing a spot for 30 minutes, give it throttle and wont take off like it should.( sluggish  ) back off throttle and goes like hell. didnt happen until end of day.

got on plane fine in the am.  dont know where else to look.  Yamaha 115  2 stroke  2004

 

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Could be a sticky anti-siphon valve on the fuel tank.  When I took one off my tank to check it out, a while back, I may have accidentally punched out the ball and sleeve ;).  Just for the heck of it, I reinstalled it as it was.  The motor never ran better.  Installed a manual fuel cutoff ball valve 8" down on the fuel line for safety, until a new ASV could be installed.

:D

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2 hours ago, vinnybugs said:

is the anti siphon you r talking about the pick up tube in the tank?

It's the fitting on top of the tank that the fuel hose (supply line to the motor) connects to.  It's made with dissimilar metals (aluminum, stainless ball, spring and sleeve), so it's prone to corrosion in a salt water environment.  Looks like this:

 

 

ASV.jpg

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22 hours ago, RacerxV6 said:

I would get an exterior tank and run it and see how it reacts by bypassing the fuel cell in the floor.

This is my recommendation as well, put known clean/good gas in the portable tank and run direct to engine bypassing all external fuel systems.

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Ok guys  upsate on this surging thingy

Changed anti siphon. old one was nice and clean

Well got the tech here and went for a ride with remote tank. Same issue

Check everything on motor, spark coil and whatever else he did. No good

When he took off plugs they read b8hs10. Well this motor calls for brhs810. Didnt have plugs with me so thats next. He feels thats the problem.

We had already did the carbs.  Will keep u all informed  Motor yam 115 2 stroke  2004

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Ok Guys

Correct plugs in. Ran it today and little hicup first hole shot than ran like  a bullet for 45 minutes.

Let it sit for 10 minutes and it  surged again but i pushed choke and it caught up and ran great.

NOW WHAT?  Leave it and go fishing??? lol

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If your going to run it and hope it gets better run seafoam through with a 6 gallon remote tank. It might clean it up. Sounds like your loading up with fuel while at idle. And I know you say the carbs are good because your guy was just in them. But one little piece of trash in a jet or a float not sealing off is all it takes to create issue 

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Are the gaskets/boots from the carbs to the block fresh? Sounds like you're sucking air (lean) after the engine is cycled then cools some. The heat cycle could be opening the leak. Next time you run for a bit then shut it off, fire it back up with the cowling off and spray some starting fluid around the boots and gaskets, if the engine idle speeds up, you've found the issue. Please don't try to drown if with that stuff, a little vapor off it will do. 

If it's not that, it's a low speed circuit issue...vent on the carb clogged, vent tube pinched off, trash in the needle/seat, low speed jets or something along those lines. I'd check out the simple stuff before I pulled the carbs back off. 

Good luck! 

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What about the black box (CDI ignition)? I had a similiar problem on my 90 2 stroke and it drove me crazy. It was intermittent like you described and impossible to find. I had a friend who had the same motor and we swapped coils, carbs, etc (yes, he was a good friend) and finally the box and it ran fine. I located one on ebay and problem solved. They are expensive so I would try to borrow one first. This is just a guess but you seem to have tried almost everything else.

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  • vinnybugs changed the title to engine surging

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