Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened fully
pxctoday

» Log in

User Name:

Password:

Not a member yet?
Register Now!

» Find OEM Parts

» Jobs

» wallpapers

Page 1 of 2 12 LastLast
Results 1 to 10 of 14
  1. #1
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened fully

    Hello. Hoping there is common knowledge of how to fix this issue.

    Issue: Motors won't start without WOT when hot.
    We have two skis doing the same thing. Both will start cold and idle and accelerate. However after a few minutes of riding they both won't start unless the throttle is opened up to 3/4 - full. Then we have to crank them for like 20 seconds or more to get them to fire and a few more seconds holding the throttle open to get them to rev. Once that happens they take off and are fine until we stop, then it's a repeat.

    Data points:
    JS550 pisser inconsistent, sometimes flows good, sometimes not at all. Has a factory half pipe.
    js550 pop off was about 12 when rebuilt over the winter
    js440 pop off was about 20 when rebuilt over the winter
    Both start and idle fine when cold on the water or on the trailer
    Tested bottom end for pressure/vacuum holding before reassembly
    Cold compression testing OK - around 120 ish on all.
    Heads torqued to 18 ft pounds

    Theories:
    1. engine loaded up with fuel when stopped and requires clearing out to restart?
    2. maybe warping heads are causing low compression but only when hot?

    Just wondering if there is a "go to..." solution for this situation.

    Thanks!

  2. #2
    Resident Guru Durhamgoat's Avatar
    Join Date
    Jun 2008
    Location
    Jasper IN
    Age
    56
    Posts
    839

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    My 440 with a bn38 did this exact same thing. In my case when I stopped riding it would dribble fuel into the intake manifold and flood it so when I went to restart I had to pin throttle until it started. My guess is that when you stop riding, pull the hood and arrestor, and take a look, you will see this dribble.
    I seem to recall this was a common issue with these carbs. I tried loosening the filler cap when I stopped and this was an improvement as it released any built up pressure. Ultimately I switched to a sbn and never looked back.
    440 JS Stock
    440 PJS ski with ported cylinders, shaved head, pjs exhaust, pjs pump and exit nozzle, etc.
    550-750 Build...http://www.pwctoday.com/showthread.php?t=397055

  3. #3
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    Duramgoat - I see you are in Jasper IN. I grew up in Princeton, boating in the Patoka Reservoir. In fact I remember when they were filling it - had to watch out for stumps! Got a ticket once on that lake for skiing 5 people behind a bass boat. Also saw a boat lose an outboard at speed, hit a stump. Broke the transom and the outboard sank. Funny thing was they had just circled us and threw a beer bottle at us (we were stopped because of engine issues). We laughed as we idled back by them on our way to the ramp.

  4. #4
    Resident Guru Durhamgoat's Avatar
    Join Date
    Jun 2008
    Location
    Jasper IN
    Age
    56
    Posts
    839

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    Patoka is pretty much where I ride nowadays, once in awhile Lake Barkley. The south end of the lake has a lot of stumps for sure and a good share of idiots on the weekends, I usually ride weekday evenings only to escape them.
    440 JS Stock
    440 PJS ski with ported cylinders, shaved head, pjs exhaust, pjs pump and exit nozzle, etc.
    550-750 Build...http://www.pwctoday.com/showthread.php?t=397055

  5. #5
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    UPDATE: Appears a leaking needle/seat in the carb was the issue on the 550. I disassembled the carb to test the popoff pressure and the assembly would leak completely down in about 5 seconds or less. Put in a new seat and needle with rubber tip and that stopped the leaking. Popoff pressure was about 15 so I let it go at that. Readjusted the carb (idle, then low, then set high to spec) and took it out. Runs fine. Starts when hot right away now. Theory is the leaking seat was draining the gas into the motor when the engine was stopped and it was just enough to flood it - hence the starting with WOT necessity. Ordered a second seat (1.5) for the 440 and will test my theory again .

  6. #6
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    61
    Posts
    2,971
    Blog Entries
    6

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    Just curious, what year is the 550?


    Bill m.
    Horsepower == Speed, RPM != Speed



  7. #7
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    It's a 1988, factory half pipe, BN44, rear exhaust converted but still using OEM waterbox, STD OEM pistons with fresh lower end seals and fresh rings (and hone).

  8. #8
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    Oh, and the seat/needle is a 2.0.

  9. #9
    PWCToday.com Is My Home Away From Home wmazz's Avatar
    Join Date
    Jul 2013
    Location
    Riverside, CA
    Age
    61
    Posts
    2,971
    Blog Entries
    6

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    I was curious because the 1986 550's 44BN had a problem
    leaking fuel into the engine, because the pilot circuit was
    poorly designed.

    It was fixed for the 1987 550.

    The 44BN's from 86 thru 89 had a minor defect in the pilot
    circuit that contributes to the 550's tendency to idle and
    die (while circling back to the rider), and hard starting.


    Bill M.

    But I was hoping you were going to say you were a 82' - 85'
    550, because they are one of my favorites.
    Horsepower == Speed, RPM != Speed



  10. #10
    PWCToday Regular
    Join Date
    May 2008
    Location
    VA
    Posts
    64

    Re: Help Troubleshooting: 440 and 550 won't start when hot unless throttle opened ful

    UPDATE: after watching these carbs when the motor is turned off I discovered that both of them feed fuel (or air) backwards from the return line through the carb and back to the tank. Given 15 seconds or more they fill with air. I can see this in the fuel lines.

    Fix:
    So... I put a one way check valve inline between the gas tank and carb to test. Bingo, stopped the fuel from leaving the carb. Took it out and tested yesterday starting and stopping several times. 1 second of cranking and it fired right back up every time. Problem solved. So I ordered an in tank check valve and will be installing shortly.

    Question: is there a part of the carb (BN 38 and 44) that should stop this from happening? It would have to be in the pump I think.

Page 1 of 2 12 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBadvanced CMPS v4.2.0