dirty carb or Bad spark?

countryboy73703

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Apr 23, 2014
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I've been doing a lof of searching on this forum, as well as other forums, and haven't had any luck. I'm sure my problem is out there but haven't got it found yet. With some friends and family counting on my boat to be running for a fishing trip, i'm running out of time and need to figure it out.

2001 yamaha 115TLRZ - 2 stroke

initially, during idle it would be rough and have a lean sneeze, and hit or miss it would cause it to stall and die, it would start right back up again until the same issue caused it to die out. Also with this, while on the water, sometime is would sputter and die while trying to get up on plane from ide, and some times it would work just fine and get up and go. This to be pointed to dirty carbs, so I pulled them all gaskets looked good and all jets and passages were cleaned by hand with a carb cleaner spray. I reinstalled and the motor was a pain to start the first time, then it would sputter and die. Waisting no time i pulled the carbs back off and soaked them for a couple hours, then went and sprayed all jets and passages with carb cleaner again. and then sprayed about 50 PSI air with a nozzle thru everything. I then reinstalled the carbs, it took a second to get fired up, but then once it did, it ran at idle on the trailer with no problems for probably 20 minutes. during this time I would just off the motor, and restart, and it would start with just half a crank, and old RPM no problem. I thought the issue was fixed, so I buttoned everything back up and came back out 2 days later and it again, fired right up and held. Over the weekend, I went to start it up again just to keep some fresh gas in the carbs (trying not to have to clean them again) and it started up, and about 10 seconds later cut out. I cant get it to start and stay running now. it will start and sounds like it fires on 2 or 3 cylinders and then dies. very frustrating as I'm sure some of you know. I'm familiar with the boat and motor, and prefer to do all of my own work, so a boat shop isn't an option, plus I"m tight on cash right now.

It seems like maybe one of the carbs got clogged up again, but it I would think it would have atleast ran rough before not wanted to run at all... Filters are also clean. I thought about checking to see if I had spark, but why would it be running good, and then all of the sudden not at all. I willing to get an ultra sonic cleaner and clean the carbs again, but I have little faith that it's going to get the trick done, especially if it's something other than my carbs...

Help is appreciated. Thanks

2001 yamaha 115TLRZ - 2 stroke

Edit: i forgot to mention that I noticed my timing adjustment screw at idle appeared to be backed out quite a bit. I did make some adjusting to it, and it did help the motor smooth out at idle. I"m not sure what the exact time is, or what it was, however, I even took the time to adjust it back out to where it had been and motor will still not idle. I don't believe that the timing is the issue, however the only reason I say that it was backed out was because evidence of thread lock that was there. Thanks again.
 
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schematic

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Jan 12, 2008
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1,102
check the fuel pump for cracks and ruptured diaphram. Poor quality screws used in these pumps rust up and crack housings
 

countryboy73703

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Apr 23, 2014
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I haven't check fuel pump yet because it won't even start with fuel bowl full right now. Before I mess with carbs it ran, not perfect, but it ran, and even at high RPM's. if it was running for a bit and then cut out, with a soft primer bulb then I would consider the fuel pump. Obviously i'm not a marine mechanic, but I don't think that fuel pump is the issue at this point... atleast not yet.

as I'm doing more research, it does seem like everytime i've checked the plugs they are wet/oily (this was when it was running). On this part i'm a little confused though, because since it's a 2 stroke i'm not sure if that would be normal or not, since it's burning oil too... I haven't pulled the plugs out yet since this new issue that I originally posted about, I'm assuming they "look" fouled but thats how they have always looked...
 

schematic

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Jan 12, 2008
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1,102
have you checked for spark quality while cranking?

water in fuel?
 
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countryboy73703

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Apr 23, 2014
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no, I haven't checked spark quality yet. I just moved to a new city and don't know anybody here to help me fiddle with things. So basically I don't have somebody to crank it while i"m looking at each plug. I do think it's possible that I have a spark issue, but if I do then it's intermittent. I was just reading another form right now, and they mentioned that if the plugs are wet/foulded then they are done for on a 2 stroke. Not sure how much I believe that though because they have always been wet. I do wonder though if maybe I cleared out the carbs so good they are allowing more fuel and causing a rich mixture, but I don't think they would run fine one day, and then a couple days after not run at all...
 

robert graham

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Apr 16, 2009
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6,908
Does your motor have the Primestart enrichening device on one carb?.... If so, then is red lever in correct position?.....
 

99yam40

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Sep 7, 2008
Messages
9,225
Most Yamaha techs change the pumps when cleaning the carbs as any thing inside them or the fuel lines and filter can and will hit the cleaned carbs once started up and run.

It could be that something has gotten into the carbs and plugged things up again.
But you will have to check to see what is happening as we can not see or do any troubleshooting
 
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