SBT Jetski Engines, Parts & Accessories

Results 1 to 9 of 9
  1. #1
    Joined
    Jul 2001
    From
    Baton Rouge, LA
    Posts
    33

    Post

    I searched this forum before starting this topic, but it seems each problem in unique in its self so here is mine.
    Waverunner with twin carbs, still with oil injection. Ski is about 4 years old and has 55 hours on it. Once started the ski runs fine at idle and low throttle speeds. When you get the throttle to 1/4 - 1/2 squeeze it boggs like it has something in the pump or starved for fuel. On the trailer the motor runs perfect WOT but once the pump is loaded in the water you can not get past 1/4 - 1/2 throttle without it bogging. Sometimes it kills. Every once in a while I will get to WOT but the motor doesn't increase in speed it just gets louder. I can get past 1/2 throttle and hit my primer once or twice and the ski takes off but then within a few seconds it is back to bogging down. So I thought it may be a fuel problem. I dried the tank and refilled with high octane. Even after running it down a 1/4 tank there was no change so I thought maybe carb is off a little. I made adjustments on both the high and low speed screws (even though low speed has been fine). Never made a difference. I put the screws back to factory settings and rode the ski back to the launch. Only time I got any speed was to hit the primer with the throttle squeezed. This ski is not used much and the owner lets it sit up over the off season with the fuel in it (without stabil). My thought now is the carb needs to be rebuilt/cleaned. But I had another thought, could it be the carb fuel pump is not performing? Since the ski runs fine with fuel delivered through the primer that maybe the fuel is not getting pressured to the carb. I guess either way it means pulling the carbs. I wouldn't think it would be a vacuum or other fuel hose leak, but could it. Should I vacuum/pressure test the lines and tank before pulling the carbs? I did notice that when I open the fuel cap the tank is not under pressure just after a run, but when trailered and I fill up, it is pressured then. I guess there are just too many possibilities for the cause. I didn't want to pull the carbs and find that it wasn't the problem. But then again, leaving fuel sitting in the motor for 10 months leads me to think thats got to be the culprit. Any advice would be appreciated.

  2. #2
    Joined
    Feb 2001
    From
    Clearwater, FL
    Posts
    7,358

    Post

    ou have a pump on each carb, and need to rebuild both completely - you either have clogged internal filters, worn pumps or just junk inside. Grab a couple SBN rebuild kits and go for it.

  3. #3
    Joined
    Jul 2001
    From
    Baton Rouge, LA
    Posts
    33

    Post

    Thanks Bryan. I knew of a pump at each carb but I didn't want to spend close to $100.00 for rebuilds if there would be other culprits that I could eliminate first.
    When I rebuilt my own carb last year I saw that the screen in the carb had some stuff in it. How does this junk get past two filters (tank pickup filter and line filter)? I know the filters are only paper element but you think they would be a little more efficient. I know some of this stuff probably gets in there from sources between the filters such as rubber dust from new hose lines and such.

  4. #4
    Joined
    Feb 2001
    From
    Clearwater, FL
    Posts
    7,358

    Post

    The tank screens are just for debris like snad. The main filter is a very coarse element, and the internal screen filters are the last resort.

  5. #5
    Joined
    Jul 2001
    From
    Baton Rouge, LA
    Posts
    33

    Post

    Bryan, OK, I tried ordering carb kits from your sales dept. through email, that was two days ago and still no response. I will have to make a phone call I guess.
    Anyway, for the technical stuff. I pulled the carbs (twin carbs). One screen had a little trash the other was approvingly clean. On the regulator body side on each carb. One was filled with fuel, the other was dry. The one that was dry had the clean screen but I noticed the N&S were sorta stuck. I want to rebuild the carbs and I know the kit only comes with the basic stuff. I am going to replace the N&S on both just because of the one sticking. This is a totally stock motor. What N&S should I use, would it be the stock size? Mikuni manual states use the smallest possible. Now for the spring, which would you recommend and what pop off pressure should I be trying for? I looked through the forum for pop off settings but most recomendations are for mods.
    Is SBT going to sell more stuff for carb work besides the rebuild kit, such as N&S, springs and pop off pumps?
    Thanks!

  6. #6
    Joined
    Feb 2001
    From
    Clearwater, FL
    Posts
    7,358

    Post

    We don't do email orders, as it is not secure whatsoever, I hope you never transmit cc info over email...

    Please call in to order.

    No we aren't going to carry all those small carb parts - there is no need for us to when there are so many dealers out there.

    Use our old springs if you don't have a pop off pressure gauge, which is what you need to tune if you change springs.

    Your N&S has the size stamped on it - pull it out and look to order new sets.

  7. #7
    Joined
    Jul 2001
    From
    Baton Rouge, LA
    Posts
    33

    Post

    Bryan, It wasn't so much as an order rather a inquiry. Basically asking what the cost is for the list of items I gave and who I should call. But, I will go as you advised and just call.

    So I should keep the N&S size that is already in the carb?
    I want to go ahead and get the pop off setup since one side was sticking. You mentioned in other forums to be sure that carb pairs or triples should be a close to possible on pop off settings. So I replace the N&S and the springs. What should I go for in spring range and what pop off pressure would be the best for this stock motor. I checked for the specs in the manual for this ski. It doesn't get into that type of detail. It must be something in the R&R manual. The Mikuni manual wasn't much help either. I would appreciate input from anyone with experience with 760's and the best performance settings for the carb.

  8. #8
    Joined
    Feb 2001
    From
    Clearwater, FL
    Posts
    7,358

    Post

    It's probably set around 35 psi, and you need to leave them alone. It's not something that changes based on wear or age - if you were replacing your airbox with aftermarket you would need to change it but you are just replacing the N&S. Leave the springs alone.

  9. #9
    Joined
    Jul 2001
    From
    Baton Rouge, LA
    Posts
    33

    Post

    Bryan, I was replacing merely because of a sticking needle. I am down this far into the carb. If you were me, wouldn't you change the spring as well. I not looking into changing the range, I just want it back to peak performance. If you recommend 35 psi, then that's what I will use. The spring looks OK and maybe changing only the N&S is all that I need to do, but there must have been some water in the fuel and it sat in the carb (or trapped condensation), there was some corrosion in the regulator body. I may just order the springs but test p-o with the original ones and see what happens.
    Thanks!

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. 96 Yamaha Waverunner 760 Starting Problem
    By awadecki in forum Yamaha
    Replies: 9
    Last Post: 07-09-2007, 09:38 AM
  2. trouble over fuel pumps
    By xplayer2885 in forum Polaris
    Replies: 4
    Last Post: 03-26-2006, 05:32 PM
  3. 98 GSXL Fuel Trouble
    By njseadooer in forum Sea-Doo
    Replies: 1
    Last Post: 05-13-2002, 12:55 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
  •