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  1. #1

    Carb settings on SL650

    Good Day to all. I am Mark. I haven't been on the board for over 4 years! I just turned 70 and have recently relocated, but still reside in So Cal. Prior to moving, I completely rebuilt my Polaris SL650 which I purchased new in '93. It's repainted (USMC Theme) and everything is like new, in and out.

    After the rebuild, I took it to a local lake and had great difficulty getting it to idle properly and it was very "bogged down" and hesitated during throttle up. (I know those terms are indicative of different problems); anyway, I put it back in storage and just now am trying to get it going. I should mention that I removed the oil injection and have gone to pre mix since that was it's original downfall when an oil line broke and I fried the mag cyl. After this long lead in......

    I just went thru each carb and the pop off's were about 23 when it calls for 10-18. I changed the springs and now they all are at about 17. I have double checked the carb syncs and they are good. In order to get it to idle properly, I have the lows at 3/4 out when the book calls for 1/4 on all 3. It now starts immediately and idles very well. When applying throttle, it does well until 1/2 to 3/4 when it hesitates noticeably. Although the book calls for 7/8, 3/8, 5/8 for the highs, I have them almost twice that right now. This is because I want to be rich and then come down to a good 3/4 throttle +.

    I am starting and briefly running in my garage to try and get it within the ballpark before taking it out again. When I say "briefly", I mean 20 seconds or so. I'm kinda not sure why the lows would have to be wider that recommended, but I don't want to fry anything!!

    Primary question: Am I correct that If it idles well will reasonably accelerate to about 1/2 throttle, my low settings and pop offs are good. If I have difficulty beyond that, I should bring down the highs incrementally and see if that corrects the 3/4+ throttle response. I know that once on the water, I can pull the plugs and read them to assist in my high settings. I am also aware of the basics of piston wash reading.

    I am not looking for top performance!! I re-did the machine for my grandkids and primarily want a fun, safe PWC that is unlikely to burn up from lean settings. I know the new machines are really high tech and fast but I was always pretty pleased with my Polaris. We took it to lake powell every year for quite a long time!!

    Thank You
    Murrieta, Ca.

  2. #2
    I'm answering my own thread because I just got back form the lake. To begin, I have three semi related threads open. This one, one on low compression (90-100 on all 3) and a thread on mixed gas.
    4 years ago - all new top end; then sat for 4 years after short run on lake and problems getting the carbs set so it would run even close to normal.

    (within the last 3 months: )
    all 3 carbs cleaned and the individual restrictors drilled out and the return line restrictor inserted. (however, not having a spare jet, I drilled a aluminum rod **slightly larger than the recommended 95 jet size)
    All 3 heads removed and noticed that piston wash showed extremely rich from the runs 4 years prior before storage.
    Carbs set per the book; 1/4 out on all 3 lows and 7/8, 3/8 and 5/8 on the highs mag,c,pto

    Today, on the water:
    1. I let it warm up and took it out. Idles great. Approx 1300 rpm steady. Very sluggish at any throttle attempt. Even feathering the throttle didn't help.
    2. Back to shore, opened up the lows to 1/2. 5 mph back out and marked improvement upon applying throttle from idle. Still hesitation at higher throttle, but would take off intermittently.
    ** felt heads and they were very hot.
    3. Back to shore, opened up the highs about a 1/4-1/2 turn each. Back out and it took off like a rocket at all throttle levels, with an occasional need to feather the throttle a little, once in a while, but generally, I
    was very pleased. I removed the thermostat for the remainder of the day. Ran at a temp that was reasonable via touch.

    I just got back and have not yet checked the exact settings of each jet, but suffice to say the lows are approx double the book and the highs are likewise, open wider than the book. However, it ran very nice at the current settings. I do not know if my slightly "larger" restrictor in the return line can effect these settings or the drilling out of the individual restrictor ports??

    Final judgement from today: It ran about 90% like new. The occasional need to work the throttle a little still needs some fine tuning.

    I will pull the heads tomorrow and take a look at the pistons and post some pics. The plugs were oily and wet after the runs. I ran it at 32:1 today.

    Regarding the Compression. My old gauge showed 90-100 psi on all 3. With a new, relatively expensive name brand, gauge, it still showed 90-100 on all 3. It ran at speeds today that make me question any compression loss??

    Any responses would be appreciated.

  3. #3
    Click avatar for tech links/info K447's Avatar
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    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by ltmark View Post
    ... the individual restrictors drilled out


  4. #4
    There are numerous threads and posts relative to the benefits of installing a restrictor in the main return line and enlarging the individual carb restrictors. Having previously lost a piston due to broken oil injection line, I will do any modification that reduces the chance of engine failure!


  5. #5
    This is turning out to be my own little back and forth. Anyway, I removed the heads a few hours after my lake ride. Now, remember that I had to turn the lows and highs out from book settings to get to a pretty good throttle response. However, after removing the heads, there is almost complete wash on the mag, about 70% wash in Center and 50% wash on the PTO. Going to have to think a bit on this. ie., I had to add gas to get good throttle response and excellent acceleration, but the pistons show too much gas is being burned during combustion? I'm also still perplexed about the compression readings. At the end of the day, after all the low and high changes, it ran at speeds and acceleration that was, without doubt, equal to when it was new???


  6. #6
    Hi Mark,

    What condition are the carb diaphragms? Mine ran great one year and then sluggish the next. It turned out the diaphragms were distorted, likely from soaking in ethanol gas too long. $15 later it was like new.

    Hope you get this sorted out.


  7. #7
    Hey names Kado I see you have posted a lot and are pretty knowledgeable. Can you help me with my 93 sl 650? Thanks

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