Results 1 to 7 of 7
  1. #1

    Fuel Pump Check valve questions

    Okay I have a couple questions wrt fuel pump check valve tolerances...

    I have the inlet and outlet check valves leaking when they should be sealed per the manual. The manual states that they should not leak at all w/vacuum on inlet test and pressure on outlet side. I have a small leak on both - the discs were replaced during carb rebuild and I have confirmed that the grommets are good and discs are not ripped. However I suspect that the discs may not be the same quality as the originals (customer brought in rebuild kits that he wanted used)

    I have read in a couple threads online where they talk about small leak being acceptable?? However manual and other threads state no leakage...

    reason I ask is that the ski (92 XP) bogs off idle and I have gone thru and checked everything:

    Pop-off - 25 psi and 26 psi for ea carb
    Needle valves good and hold 10 psi for 30 secs
    diaphragm checks good at 4 psi for 10 secs
    Cleaned out carbs and verified Pilot jets and channels are clean and free flowing (carb cleaner run through).

    Came back to fuel pump and noted a small leak when under vacuum on inlet side and correspondingly pos pressure on outlet side ==

    If pump check valves are leaking would this not cause a rich condition in carbs and corresponding bogging problems off idle to mid range?

    I am wondering if the actual sealing area on check valves is too corroded to make a good seal and pump body needs to be replaced. I cleaned them with just fingernail as I was not sure if I would damage area using xacto knife balde, scrapper or emery cloth. I have included a few photos to ask for opinions/ recommendations.

    I also ordered OEM Mikuni kits to see if replacing discs to OEM will rectify the situation...

    Any help/advice greatly appreciated.

    Click image for larger version. 

Name:	20140811_145530_resized.jpg 
Views:	53 
Size:	87.0 KB 
ID:	338576Click image for larger version. 

Name:	20140811_145544_resized.jpg 
Views:	45 
Size:	86.0 KB 
ID:	338577Click image for larger version. 

Name:	20140811_145608_resized.jpg 
Views:	49 
Size:	75.7 KB 
ID:	338578

  2. #2
    wkuadam07's Avatar
    Join Date
    Feb 2013
    Bowling Green, KY
    I use scotchbrite on them when they look like that. Never a blade or stiff sandpaper... They will never seal perfectly, and they don't really have to... I also check them with oil on them, they will not seal very well dry at all.
    Your problem will most likely have to be fixed by backing out the low end needles until it doesn't bog off idle anymore, then reset the idle stop, then check your RPM and determine how to adjust the high end needle.

  3. #3
    Okay - I went back in and cleaned up the pump seal surface and they seemed good to go after press/vacuum test. Also had a 94 XP that the pump had the same problem when rebuilding the carbs and cleaned them up also...

    So I reinstalled everything and brought both seadoos to lake and put trailer in to tune up carbs at idle and see if bog/hesitation went away.

    Nope same problem on both doos - right off idle it dies out. I tried opening up LS screw on each set thinking fuel starvation?? - did not seem to have any effect. I even removed the fuel filter I had installed thinking maybe it was constricting fuel flow??? Still same...

    I am attaching a couple of video files so maybe someone can point me in right direction - seems like it should be something simple that I missed as both sets are doing the same thing - so I must be consistent in my rebuilding error....

    For some reason I am having problems with these two sets.... did not run into same problem on my 95 GTX rebuild.

    I went back and reread info here from GroupK threads on carb tuning and the stickys as well as some other online references - and I confirmed I had completed all the steps (no gray lines on either Doo [except one pulse line on 94 Xp] - they were replaced by previous owners sometime in past)

    When I got back fm lake I pressure checked both fuel systems again thinking maybe there was an air leak I missed - chkd 4.0

    Any assistance or verification as to what I am dealing with from notes/video greatly appreciated.

    Or should I start a new thread ....

    M Meyer

  4. #4
    Here is link I forgot to insert

  5. #5
    Myself's Avatar
    Join Date
    May 2007
    North Central Arkansas
    Did you thoroughly clean out the fuel line fittings? I usually use a tiny screwdriver to scrape out the goo followed by a half stripped down q-tip soaked with carb cleaner. Verify the tiny pilot holes into the carb throat were clear? Dis-assemble and clean out fuel switch? Replace clogged up old fuel lines?

  6. #6
    wkuadam07's Avatar
    Join Date
    Feb 2013
    Bowling Green, KY
    Have the rotary valve covers been off? Honestly it sounds like they are out of time in the vids to me... Have you confirmed your fuel line plumbing? If the second PTO carb isn't getting fuel that's also what it sounds like. Is the gasoline fresh?

  7. #7
    Yep - been thru both fuel systems - both systems no longer have the gray lines in the system - redone by previous owners in the the past. Cleaned out both gas tanks and verified fuel baffles were good to go (In fact 92 Xp fuel baffle was just sitting in tank - not even pushed in)

    Have cleaned out the pilot jets on both sets with carb cleaner and re-verified today by another person.

    Rechecked and verified fuel flow thru switch again today

    94 Xp - rotary valve not off as the carbs just unbolt from intake....
    92 Xp - verified rotary valve timing was correctly set (especially after finding fuel baffle not installed)

    rebuilding/verifying carbs tonight on 94 and then reinstalling ...

    thanks for the input ...

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Mikuni Carb Fuel Pump Check Valve Install
    By OsideBill in forum Yamaha How To & FAQs
    Replies: 9
    Last Post: 08-17-2015, 09:33 PM
  2. Fuel Pump Check Valve Query
    By steelroe in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 05-19-2010, 08:50 PM
  3. 44mm i body fuel pump check valves
    By billy's gpr in forum Yamaha PWC Performance (2-stroke)
    Replies: 9
    Last Post: 03-19-2009, 08:24 PM
  4. Wrong fuel pump check valves?
    By kingstretch in forum Yamaha Old School Skis
    Replies: 18
    Last Post: 09-15-2008, 11:48 AM
  5. fuel pump check valves?????
    By martybess in forum 2-Stroke Performance
    Replies: 2
    Last Post: 07-12-2008, 03:12 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts