Super Jet Issues w/my 2008 superjet + factory pipe - vapor lock perhaps?

Greetings -

I purchased a 2008 superjet from a fellow forum member - it is stock except for a B-pipe, jetted and T-adjusters on the carb. It was basically in perfect shape but now that it is getting warmer out it just isn't running right and in some cases it just won't restart after it is warm. One of the problems I have is that the engine appears to be running hotter then I expect (cylinder/head, not so much the pipe). Anyway, I can run the ski hard for appx. 20 to 30 minutes and if I have to restart it, well, it just starts real quick then bogs and dies. I can immediately pull the choke and it starts but then dies again. After that it won't run for sometime.

My current theory is that perhaps I have vapor lock as I have pulled the plugs and they are pretty dry at this point. Great spark, but pretty dry. They don't look too light brown in color (ie. too lean) but they aren't black either. So, could I have a situation where the ski is heating up and the fuel is basically getting cooked?

There are other things that I have noticed - he ran a different premix oil then I use, and when I took the screens out of the top of the carb they feel as if they are almost oily/sticky. I am going to pull the carbs and check them just to make sure nothing is gummed up, but like I said this issue of not starting after running for 20/30 mins is very repeatable. I don't think the head temp sensor is doing it, but I just don't know.

Thoughts? I appreciate any help!
DaveR
 
WOW - I solved my problem tonight!!!! WAHOOOOOO!!! So, my logic was sound but it wasn't vapor lock. Basically what I was experiencing was fuel starvation, and it would only happen after the ski would pressurize the fuel (20/30 mins into my ride). What I found was that the guy that installed the B-pipe ran the vent line UNDER the gas tank, and it crushed the line. I took it off and tried to pass air through it and could not. Then I noticed it was pinched and "glued" together. I rolled the air line, and it opened right up. I ran the vent line above the tank and tested the ski for a 45 minute ride - NO PROBLEMS at ALL!!!

Problem solved - I hope this helps others if they have a similar problem. Now I need to dial my pipe and carbs back in as they are just not right anymore....wahoo

DaveR
 
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Man, you have NO idea how much of a bummer this was until I found root cause, but I truly hope others will search and find this and solve their own issue. I went in so many directions - carburetion, heat issue, pipe issue, intake clogged, fuel bad, etc...now it SCREAMS like day 1. I have a 1991 RN that is heavily modded and still runs great, so for anyone out there that is running Yamaha know that they run forever or so it seems!
 

SXIPro

JM781 Big Bore
Nicely done dude! Glad you found it, and it's amazing how simple something can be. Glad you're up and running.

Ain't that the truth. My neighbor was trying to get his SeaDoo Islandia running this year after it was de-winterized. He was cranking and cranking and cranking. Wore down his battery, lots of swearing, etc. Finally I had a chance to walk over, took a look, and said "Hey Steve, plug in the lanyard". Problem solved.
 

Tyler Zane

Open Your Eyes
when i finally got my fuel system right i knew it as well. my problem was a missing gas cap gasket thou so i wasnt getting the pressure i needed. then my primmer was acting funny so i ditched that. no problems since and i prob will not put the primmer back on.
 
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