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  1. #1

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    Carb Adjustment Assistance

    Hello all, did some mods over the winter to a 2000 GP1200R. Here's the list:
    RIVA FA
    Rebuilt the carbs and went with the Oside Bill recipe for chokes intact: 110 Pilot 1 turn out on lows, 120 Main 1.5 turns out on highs, 1.5 N/S, 45-47 Popoff
    RIVA Stinger 1
    Boysen stuffers
    RIVA Grate and ride plate
    Pump shoe seal kit
    R&D Steering Nozzle
    Wave Eater Clips & Couplers
    Free Flow
    Premix 40:1
    Compression = 117,121,110

    Figured I'm now in the carb tuning phase and made my first attempt today. The temp was in the high 40s. I hope that isn't too cold to even make an attempt.
    I have read everything I can possibly read on the subject through GH, RIVA, Group K, and all the others I can find. I believe I understand the tuning sequence and I've got the idle set. It seems like it is lean on the bottom end. Anytime I give it any amount of throttle from idle up or 1/4 up, it hesitates severely. To the point it would die if I didn't feather the throttle. I can give it slow progressive throttle and eventually get to the point where it damn near jumps out of the water. I see the fruits of the mods when I get that point. It's getting there. I have played with the low speed adjusters, and it made only a minor difference. I have gone up to 1.75 out without much improvement. Should I go up even further? From what I read, the low speed adjusters shouldn't make any difference for a low end hesitation. I'm thinking either my Pilot Jet is too small or my pop off is too high. I also understand this could take some time, so I'm prepared with an extra dose of patience. A challenge I have is the ski is 180 mile from where I live and I only get there every few weeks. I am there now, but head back home on Monday, so if I need to rejet or adjust pop off, I'll want to pull the carb rack and take it home with me.

    So, could I get some feedback on whether to adjust the low speed jet, the pop off, or both, or neither?

    Also, I'm sure the water temp is in the 30s, and the air temp is in the 40s - Could that have a negative effect on the tuning process?

    Thanks!


  2. #2
    mudslanger's Avatar
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    Start out RICH then start tuning it down. check your plugs. if they are looking like they have been hot richen it up. dont idle it a lot before checking the plugs run it hard then drop then throttle then kill it all wile riding it so you want to be coasting to shore or your trailer. its better to have wet plugs when you start tuning it than DRY HOT plugs. I would suggest 2 1/4 to 2 1/2 on the high speed screws and 1 to 1 1/2 on the low speed screws to start tuning. it is easier to set the lows on the trailer with the pump in the water. make sure you ride it a little wile between adjustments open it up to full throttle.

  3. #3

    Join Date
    Aug 2006
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    You did not mention disabling the accel pumps, if you did not you would bog badly on the bottom. Disabling the accel pump is a big part of the carb mods for flame arrestors.

  4. #4

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    Nov 2011
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    I forgot to mention couple of things. Yes, the accel pump is disabled, and when I did a low end chop, the plugs seemed dry. New plugs - Dark mostly, but just a tad silver/white on the electrode. So adjusting the highs to 2.25 to 2.5 will affect the low end hesitation? I had the lows from 1 up to 2 with very little change.
    Thanks!

  5. #5

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    Well, I went up to almost 3 turns out on the low and high speed adjusters and it still has the bottom end lean condition although it certainly helped , but it screams pretty good on the top end. I will bump both the pilot and main jets by 5 and start at 2 turns out. Should I consider changing the N/S or the pop off? The N/S is the 1.5 and the pop off is 45-47. I will also pick up a Pet Tach to make sure I'm solid on the top. Is there any use for the Pet Tach in diagnosing/tuning the low end?
    Thanks!
    Bob

  6. #6
    Moderator OsideBill's Avatar
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    It is lean because of the pipe you have open the lows up a full turn to start with and open the highs at least a half turn more. That recipe is for a single stock pipe, the riva pipe needs more juice on the bottom end. You probably have relatively perfect air at this temp too so it will make it leaner.

    Your needle and seat will be fine going up on jets will help

  7. #7
    mudslanger's Avatar
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    It sounds like there's more wrong than just carbs out of adjustment if your 3 turns out on the hi and low. make sure the power valves are opening and closing and in the wright position when closed and check those wave eater connectors between the cylinders. the connectors can wear your shafts out the stock ones are better IMO. unless you can make some yourself. I would go back through the carbs and when you do the popoff test make sure just before it pops off the seat it doesnt leak down (say you want 40# of popoff if you pump 30# it should hold it and not leak down if it does find out were it is leaking and repair it).

    Yes a pet tach is a must when tuning and worth the money if you want to get all you can out of your boat and you can use it on many other boats.

  8. #8

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    OK - I'll go up 5 on the low and high speed jets and start at 1 turn out on both. I'll check the PV couplers, and go through the PV adjustment procedure in the service manual. When I put the jets in, I'll make sure there is no leak down when I check the pop off. It will be a few weeks, so I'll update when I get there.

    Thanks all!

  9. #9
    For the record, the Riva Stinger's actually require a slightly leaner setting for the low's and midrange, but richer on the top. And they require a larger gap/leaner setting for the accelerator pump. The pressure wave scavenging is more efficient at lower r's compared to higher r's for that pipe.

    (The other issue is; if you DID NOT advise Bill that you were doing those higher 'flow' mods, removing the accelerator pump is accentuating the leaness when you stab the throttle. Unless you completely compensate, remember: aftermarket F/A+Free flow+cold temps+removing pump+anything lower than 50:1 premix, that's a recipe for leaness/hesitation.) Just sayin.

  10. #10
    Moderator OsideBill's Avatar
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    Wow straight from the Riva pamplet. He is lean and he is not running an accel pump or stock airbox he definitly needs more juice on the bottom end. These pipes will lean the ski out if not jetted right I have seen it before. Actually picked up a ski pretty cheap once after the guy burnt down a couple pistons. Be sure and check your plugs and piston wash that's the only way to know what's really going on.

    Sent from my myTouch_4G_Slide using Tapatalk

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