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Author Topic: Two-stroke engine issue...  (Read 4537 times)

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Offline CLAY

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Two-stroke engine issue...
« on: January 07, 2014, 07:17:01 AM »
So on my buddy's 1980 340 Yamaha Enticer there is this weird issue.  It was running poorly, so I went through the carb and cleaned it- all good.  The only thing it has now is this:

When running full speed and you let off the throttle, it ends up dying.  You can sometimes recover it by feathering the throttle, but it just acts fuel starved, bogs down, and about half the time, dies (if you can't recover it by feathering the throttle).  Once you stop, you give the cord a pull and it fires right up.

Any ideas?
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Offline Cablebandit

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Re: Two-stroke engine issue...
« Reply #1 on: January 07, 2014, 07:37:44 AM »
Never let go of WOT.  Easy fix.

Online Black Hills

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Re: Two-stroke engine issue...
« Reply #2 on: January 07, 2014, 08:06:49 AM »
are you sure there isn't some crap stuck in the pilot jet?
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Offline CLAY

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Re: Two-stroke engine issue...
« Reply #3 on: January 07, 2014, 09:06:03 AM »
It was clear before, but if the pilot jet was plugged it wouldn't fire up and idle nice, would it?  I can check it again, it's not a big deal to pull the carb on these things.
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"The wider the road, the worse the food." -Coho
Let's do some science.

Offline Max Wedge

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Re: Two-stroke engine issue...
« Reply #4 on: January 07, 2014, 10:44:22 AM »
How long will it run at full throttle? Is it a vacuum fuel pump?
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Online Black Hills

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Re: Two-stroke engine issue...
« Reply #5 on: January 07, 2014, 11:08:06 AM »
have you checked for an intake leak?
the above are merely the ramblings of a hamfisted fuckwit who has broken too many helmets.

Offline Jim

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Re: Two-stroke engine issue...
« Reply #6 on: January 07, 2014, 11:24:12 AM »
An "out there" item...

Fuel pump diaphram leaking into the vacuum port / case of the motor?
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Offline chornbe

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Re: Two-stroke engine issue...
« Reply #7 on: January 07, 2014, 11:25:42 AM »
Two very good suggestions. The ever infamous and often non-specific "air leak" seems to be at play here. I like the diaphragm suggestion.
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Offline mxvet57

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Re: Two-stroke engine issue...
« Reply #8 on: January 07, 2014, 11:36:03 AM »
There's a fuel filter in the tank on the pickup.
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Offline mxvet57

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Re: Two-stroke engine issue...
« Reply #9 on: January 07, 2014, 11:38:07 AM »
have you checked for an intake leak?

If it was an intake leak the thing would be running WFO.
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Offline giaka

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Re: Two-stroke engine issue...
« Reply #10 on: January 07, 2014, 12:17:16 PM »
Have you checked the mixture by supporting the track and going WFO for five seconds then killing the power? Pull the plugs and make sure they are chocolate and are the same tint. Have you tried new spark plugs? Sounds like a small air leak but with a 2 stroke it can be several issues. Is the enticer a single carb setup?  After checking the mixture I would look into that air leak especially to the fuel pump. Also double check the float level in the carb(s). Make sure the needle and seat is good, the needles will eventually wear and a ridge will show up on them. Check the needle in the slide as well, make sure its anchored and not floating up and down in the slide.
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Offline bomber

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Re: Two-stroke engine issue...
« Reply #11 on: January 07, 2014, 02:05:42 PM »
When I was flying chainsaws for a living, I found that the float setting was very important (and easily fubared) . . .

This may not apply to the Enticer, especially if the engine is not run for an extended period of time inverted.
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Offline Max Wedge

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Re: Two-stroke engine issue...
« Reply #12 on: January 07, 2014, 02:21:58 PM »
Possibly a leak between the chambers in the fuel pump? Or an air leak between the case and the pump? Floats set wrong or an obstruction at the inlet?
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Online Black Hills

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Re: Two-stroke engine issue...
« Reply #13 on: January 07, 2014, 02:50:03 PM »
have you checked for an intake leak?

If it was an intake leak the thing would be running WFO.

my thought was a small leak that leaned it out only under high vacuum, when you chop the throttle from WFO, otherwise not affecting things?
the above are merely the ramblings of a hamfisted fuckwit who has broken too many helmets.

Offline CLAY

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Re: Two-stroke engine issue...
« Reply #14 on: January 07, 2014, 03:45:34 PM »
I'll try some of the standard intake leak checks, and take a look at the diaphragm fuel pump.  I'll let you know what I find.   Thanks guys!   :thumbsup:
"Most accidents happen when the meek meet the douchebags."  -Viffergyrl
"The wider the road, the worse the food." -Coho
Let's do some science.

Offline Max Wedge

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Re: Two-stroke engine issue...
« Reply #15 on: January 08, 2014, 10:00:02 PM »
I used to have to rebuild my fuel pump almost every year as regular maintenance. Parts were $5, picked the parts up at lunch and rebuilt it at my desk at work. EZPZ.
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