Page 1 of 3 1 2 3 LastLast
Results 1 to 10 of 24
  1. #1

    Join Date
    Apr 2005
    Location
    Logan Township, NJ
    Posts
    280

    stage 2..dropped to 7400 rpm

    ski runs and pulls like a rapped ape....but only goes to 7400. I changed the plugs. Oil is fine. Supercharger is chugging along. I don't have a boost gage. The old plugs that I pulled were lite(running lean). Full stage 2. Stock ecu...I believe it is a boost leak. Anything else to check. Thanks

    Peter


  2. #2
    Moderator The Bandit's Avatar
    Join Date
    Jul 2006
    Location
    Wilmette, IL
    Posts
    8,373
    Its a boost leak.

  3. #3
    JFizzleJR's Avatar
    Join Date
    Aug 2005
    Location
    FL
    Posts
    8,628
    +1
    808
    I have to disagree. That could be the case, BUT, have you checked the supercharger slip before you mentioned the S/C is 'chugging along' ??

    I had the same problem this week (still isn't fixed). RPMS went from 7750 to 7450. Changed to a prop that is 2mm less aggressive AND changed from 81 to 83mm ring. I thought that would put me into the ballpark of 8000-8100. Boost is 5.9 lbs at 7450 STILL. I am SURE there are no significant leaks because I just went through all that BS for the longest time and a week ago was running 9 psi+ at 7950. Supercharger was BRAND NEW less than 10 hours ago. Spring washers, metal washers, ceramic bearings, green wheel..

    My point is, the only thing I can think of is the slip moment is extremely low (probably from breaking in the S/C in my case).
    My advice is to thoroughly inspect your supercharger health (atleast do a slip test) and THEN go hunting for all the wonderful boost leaks if the slip moment is in spec..

  4. #4
    I didn't think a ski pulled "like a raped ape" if it had a boost leak?

  5. #5
    Moderator The Bandit's Avatar
    Join Date
    Jul 2006
    Location
    Wilmette, IL
    Posts
    8,373
    Quote Originally Posted by JFizzleJR View Post
    I have to disagree. That could be the case, BUT, have you checked the supercharger slip before you mentioned the S/C is 'chugging along' ??

    I had the same problem this week (still isn't fixed). RPMS went from 7750 to 7450. Changed to a prop that is 2mm less aggressive AND changed from 81 to 83mm ring. I thought that would put me into the ballpark of 8000-8100. Boost is 5.9 lbs at 7450 STILL. I am SURE there are no significant leaks because I just went through all that BS for the longest time and a week ago was running 9 psi+ at 7950. Supercharger was BRAND NEW less than 10 hours ago. Spring washers, metal washers, ceramic bearings, green wheel..

    My point is, the only thing I can think of is the slip moment is extremely low (probably from breaking in the S/C in my case).
    My advice is to thoroughly inspect your supercharger health (atleast do a slip test) and THEN go hunting for all the wonderful boost leaks if the slip moment is in spec..
    You have a boost leak AND a slipping S/C

  6. #6
    Vman's Avatar
    Join Date
    Nov 2005
    Location
    NJ
    Posts
    4,363
    +1
    339
    First thing I would do is get under the ski and check out the intake to make sure nothing is wrapped around the shaft... then the prop, wear ring, all that good stuff you can check just by looking.

    I've seen plastic bags and such tightly wrapped around driveshafts- that'll rob you some rpm big time... simple stuff first.

  7. #7
    Moderator The Bandit's Avatar
    Join Date
    Jul 2006
    Location
    Wilmette, IL
    Posts
    8,373
    You have a boost leak AND a slipping S/C AND a plastic bag.

  8. #8
    Vman's Avatar
    Join Date
    Nov 2005
    Location
    NJ
    Posts
    4,363
    +1
    339
    Or a rope...

  9. #9
    JFizzleJR's Avatar
    Join Date
    Aug 2005
    Location
    FL
    Posts
    8,628
    +1
    808
    I know I don't ..

    Maybe he does though.

  10. #10
    Moderator The Bandit's Avatar
    Join Date
    Jul 2006
    Location
    Wilmette, IL
    Posts
    8,373
    You have a boost leak AND a slipping S/C AND a plastic bag with a rope inside.

Page 1 of 3 1 2 3 LastLast

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Riva stage 1 RXTX only revving to 7700 RPM
    By stevea99 in forum 4-Tec Performance
    Replies: 14
    Last Post: 11-15-2014, 11:47 PM
  2. changed to 160mm rpm dropped !!!
    By isa alnoaimi in forum Yamaha PWC Performance (4-stroke)
    Replies: 4
    Last Post: 02-09-2013, 10:17 AM
  3. Gp1200r drops To 5,000 rpm
    By Almost in forum Yamaha PWC Performance (2-stroke)
    Replies: 0
    Last Post: 05-27-2011, 08:07 AM
  4. RIVA Stage 1 installed! Down to 7700 RPMs. Any pointers?
    By sgaaap in forum 4-Tec Performance
    Replies: 15
    Last Post: 10-01-2005, 10:56 AM
  5. Boring Out Venturi to Regain RPM's?
    By johnD in forum 4-Tec Performance
    Replies: 27
    Last Post: 07-11-2005, 08:06 AM

Posting Permissions

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