SBT Jetski Engines, Parts & Accessories

Results 1 to 5 of 5
  1. #1
    Joined
    Apr 2019
    From
    Watertown, NY
    Posts
    5

    Default 95 Seadoo SP 587 Backfire/Misfire

    Hi All,

    New to this forum, but have been searching and lurking trying to figure out this issue with new 587 short block just installed in the SP.

    Basically, got everything installed and it idles well, but backfires when you try to give it gas both out of exhaust (bit of flame noticed at one point) and pops out of the carb too. I had checked the exhaust for restriction (none). SBT Tech recommended new valve and valve cover. Installed both and timed per spec; no change.

    I turned to focusing on the electrical system as I had put a timing light on it and it seemed to flicked and go dark sporadically at the higher RPMs so figured it was loosing spark. Went down the electrical road, checked voltage (13v) at idle seemed ok, unplugged rectifier anyways didn't change anything. Clipped plugs back, no change. Battery was weak so replaced that; no change. Got a complete ebox off ebay (used) installed that no change. I had also cleaned the flywheel as there were some metal shavings in there from the starter. Thought that may have been shorting the stator/flywheel as there was a couple very slight scratched on the stator. Also replaced stator after that; no change. So only thing lefty on electrical system is flywheel not sure how it could be that. The only other thing I was thinking was maybe the start button is possibly shorting....?

    Puzzled at this point and looked other directions. Searched and sawt that backfire could be caused by lean condition to ran off of fuel bottle. That seemed to help it run a bit better but still had a hesitation. Changed plugs at the same time, went back to backfiring, but at least I think I got some clues that maybe its fuel related. So thinking about rechecking the carb to make sure that its pumping correctly and the replacement jet was the right size. Had rebuilt originally and adjusted everything to spec. Pop off was a bit low but hadn't worried about that at the time. Had noticed the high speed screw was out a few turns on rebuild. Its at 0 now.

    I guess I am going to look at the on/off/start switch and recheck carb. I am running out of options...? Any ideas? I would appreciate them. Thanks.

    Ryan

  2. #2
    Joined
    Apr 2019
    From
    Watertown, NY
    Posts
    5

    Default Re: 95 Seadoo SP 587 Backfire/Misfire

    I retested the start/stop button and the lanyard/safety switch by disconnecting each while running. Still did the same thing.

    I re-pulled the carb and RV cover. I even found exact TDC to be sure (not screwdriver method). All lined up right on for both valve open and close per the manual. I then took carb off and tore it down again. This time I rigged up a pressure testing apparatus so tested things there. Pop off was low (15 psi or so). Changed out spring to one that got me to like 25 psi so think that is better. Also pressure test on pulse line seemed fine. However, when I did the testing of the fuel in/out lines I discovered a pretty good leak between the diaphragm assembly and the carb housing. I am wondering if that contributed to the possible lean condition at high rpms. Basically the more vacuum at high RPMs would cause it to pull air through this leak. Going to try and fix that soon and see what happens...

    Ryan

  3. #3
    Joined
    Apr 2019
    From
    Watertown, NY
    Posts
    5

    Default Re: 95 Seadoo SP 587 Backfire/Misfire

    I retested the start/stop button and the lanyard/safety switch by disconnecting each while running. Still did the same thing.

    I re-pulled the carb and RV cover. I even found exact TDC to be sure (not screwdriver method). All lined up right on for both valve open and close per the manual. I then took carb off and tore it down again. This time I rigged up a pressure testing apparatus so tested things there. Pop off was low (15 psi or so). Changed out spring to one that got me to like 25 psi so think that is better. Also pressure test on pulse line seemed fine. However, when I did the testing of the fuel in/out lines I discovered a pretty good leak between the diaphragm assembly and the carb housing. I am wondering if that contributed to the possible lean condition at high rpms. Basically the more vacuum at high RPMs would cause it to pull air through this leak. Going to try and fix that soon and see what happens...

    Ryan

  4. #4
    Joined
    Apr 2019
    From
    Watertown, NY
    Posts
    5

    Default Re: 95 Seadoo SP 587 Backfire/Misfire

    Trying to post for like 5th time...

    Anyways checked lanyard safety switch and start stop switch while motor running and unplugged no change

    Found true tdc with stop I had to check valve timing looks right on

    Pulled carb off and changed spring for pop off as it was low 15 psi...now 25 plus


    Also pressure tested fuel in and out lines

    Both dont hold pressure as there is a pretty good leak between carb housing and diaphragm

    So wondering if this could cause it to suck air at high r's...

  5. #5
    Joined
    Apr 2019
    From
    Watertown, NY
    Posts
    5

    Default Re: 95 Seadoo SP 587 Backfire/Misfire

    Now they all pop up...ha

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. 97 XP misfire
    By pwctech253 in forum Sea-Doo
    Replies: 2
    Last Post: 05-09-2012, 11:55 AM
  2. 89 seadoo sp fustrating misfire!
    By lovemysan in forum Sea-Doo
    Replies: 3
    Last Post: 08-08-2010, 11:15 AM
  3. seadoo gtx,rfi 1998 backfire
    By Ray007 in forum Sea-Doo
    Replies: 3
    Last Post: 03-23-2010, 06:18 PM
  4. Xp Di Misfire
    By MAD MAX in forum Sea-Doo
    Replies: 1
    Last Post: 01-07-2008, 09:33 AM
  5. Sea Doo Misfire / Backfire SBT Motor
    By sspracing in forum Sea-Doo
    Replies: 1
    Last Post: 06-07-2007, 09:26 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
  •