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  1. #1

    GP1200 Needle/Seats?

    okay so i've gotten the running and dieing issue sorted out. now i've got a new issue. i was reading the service manual for these skis and they spec. 1.5 seats with w/e spring i've forgotten already but the genuine kit i got and the seats that came out were 1.2? i used someones recommendation on the turn outs for the adjustment screws but it bogs bad idle to 1/4 then comes alive and is happy.

    anyone have a good starting point for the adjustment screws? i think they were 1; 3/4; 1 on low and 1 1/2 on highs (don't quote me on this though)

    thanks


  2. #2
    The manual was actually wrong. The stock needle and seat that came with these are actually 1.2 instead of the 1.5 in the manual.

    As for your bogging issue, so let me first try to understand. So your following the settings for the 1.5 N/S with your 1.2 N/S that came with your rebuild kit?

    Did you change your jetting at all? OR did you just basically rebuild the carbs with all stock parts? Reason I ask is that that 1,3/4,1 setting on the 3 carbs are I think for basically stock jetting and all.

  3. +1 by:


  4. #3
    Quote Originally Posted by bford View Post
    The manual was actually wrong. The stock needle and seat that came with these are actually 1.2 instead of the 1.5 in the manual.
    Good to know, that is actually pretty funny.

    Quote Originally Posted by bford View Post
    As for your bogging issue, so let me first try to understand. So your following the settings for the 1.5 N/S with your 1.2 N/S that came with your rebuild kit?
    Stock rebuild 1.2 N/S did not re jet. If I remember correctly I saw a 105 & 130 maybe for the jets and did 1 turn 3/4 turn and 1 turn on the adjustment screws

    Quote Originally Posted by bford View Post
    Did you change your jetting at all? OR did you just basically rebuild the carbs with all stock parts? Reason I ask is that that 1,3/4,1 setting on the 3 carbs are I think for basically stock jetting and all.
    Did not change jets at all but I think the adjustments need to be leaned out for my altitude.

  5. #4
    If memory serves me right, I think the main jet for all 3 carbs are 130's. The pilot/slow jets on the other hand, stock unmodified, they came with 95, 97.5, 100 in some particular order - cant remember though.

    Yes sounds like to me that it's a rich bog. My recommendation to you is that you do a what they call a "plug chop" although at around that rea it it's not as effective since different fuel jets affect that area. What that means is that you ride the ski around right where it bogs (you say idle -1/4 throttle) for a bit. AND then shut it off quickly-pulling the lanyard key is the best way to do it. Then basically what you do is you check your spark plugs - take them out one cylinder at a time and look at it - read the spark plugs. THAT will tell you if it's actually rich or lean.

    Let me know if what you find out.
    Last edited by bford; 07-17-2015 at 06:12 PM.

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  7. #5
    quadzilla's Avatar
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    Hey there..

    A bit more information could help with diagnosing this issue..

    1/. did you stick with the stock jetting.
    - (if not what size jets are in there.? all three carbs hi and low)

    2/. did you check the pop off settings on them after you replaced the needle and seats..?

    3/. are you running the stock air-box or after market flame arrestors .?
    - (Staggered low speed jetting is ill advised on aftermarket F/A's)

    4/. Have you checked the compression on the motor lately.?

    5/. Are you aware of any modifications that may have been done.?

    6/. do you think you have a lean or rich bog when you hit the throttle.?
    - A lean bog is when you mash the throttle and it gets up and GOES only to fall flat on it's face after 10-20feet
    - A rich bog is when you mash it and it just gurgles for a few second that takes off..

    I should point out DO NOT attempt to do plug chops at anything other than full throttle..!!
    - Plug chops are for fine tuning the "MAIN JET" on a good running motor..
    - Plug chops are not for diagnosing problems.
    - (you could very easily lean seize your motor, if you have a lean condition)

    This is a good read from Group-K:. http://www.groupk.com/tec-carbs97.htm

    .

  8. #6
    Mpeavler's Avatar
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    97's had the 1.5's
    98-99-2000 65u's came with a 1.2

  9. #7
    Keep in mind these skis are ran at high altitude (5280 and higher) so I think they are just a bit too rich in the lower end since I followed stock needle adjustments.

    Quote Originally Posted by quadzilla View Post
    Hey there..

    A bit more information could help with diagnosing this issue..

    1/. did you stick with the stock jetting.
    - (if not what size jets are in there.? all three carbs hi and low)
    As far as I know, yes. I did not remove the jets. The main Jet is stamped with 135. Can not see the other one without removing, and it doesn't want to come out so I am not touching it.

    Quote Originally Posted by quadzilla View Post
    2/. did you check the pop off settings on them after you replaced the needle and seats..?
    Yes, All 3 carbs pop off was around 60psi (I did this weeks ago and not at home where everything is written down so I don't know the exact number, however, they were all 3 the same).

    Quote Originally Posted by quadzilla View Post
    3/. are you running the stock air-box or after market flame arrestors .?
    - (Staggered low speed jetting is ill advised on aftermarket F/A's)
    The ski is completely stock from intake grate to air handle bars.

    Quote Originally Posted by quadzilla View Post
    4/. Have you checked the compression on the motor lately.?
    Compression is at 105psi all 3 cylinders, which is spec at 5280 ft.

    Quote Originally Posted by quadzilla View Post
    5/. Are you aware of any modifications that may have been done.?
    They painted it with super-gay flames... other than that, stock.

    Quote Originally Posted by quadzilla View Post
    6/. do you think you have a lean or rich bog when you hit the throttle.?
    - A lean bog is when you mash the throttle and it gets up and GOES only to fall flat on it's face after 10-20feet
    - A rich bog is when you mash it and it just gurgles for a few second that takes off..
    Its for SURE a rich bog. It gurgles from 2-8mph then takes off like a bat outta hell and rides all day long no issues. Pulled plugs after 6 hours of riding and they are burning pretty nicely.

    Quote Originally Posted by quadzilla View Post
    I should point out DO NOT attempt to do plug chops at anything other than full throttle..!!
    - Plug chops are for fine tuning the "MAIN JET" on a good running motor..
    - Plug chops are not for diagnosing problems.
    - (you could very easily lean seize your motor, if you have a lean condition)

    This is a good read from Group-K:. http://www.groupk.com/tec-carbs97.htm

    .
    Haven't had any time to get them back out as I'm waiting for a fuel float for my 97 and don't feel like putting it back together. The only issue is getting to those damn adjustment needles with the stupid air box on is not happening.

  10. #8
    Quote Originally Posted by Mpeavler View Post
    97's had the 1.5's
    98-99-2000 65u's came with a 1.2
    I didn't look at my 97's jets when I had the carbs off but I will next rebuild since I used shitty SBT kits on it and the Mikuni kits I used on the 98 work much better. I'm just getting burned out working on these things.

    Both Mikuni kits I ordered, though, came with 1.2 N/S. So, I don't know. Either way, what would you do with a smaller seat? Increase adjustment needle?

  11. #9
    quadzilla's Avatar
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    Quote Originally Posted by Mpeavler View Post
    97's had the 1.5's
    98-99-2000 65u's came with a 1.2
    Think Yamaha dropped the 1.5 Needle and seat for the 98 and beyond models that ran the triple motors..
    - they just shake too much at idle and unseat the needles, leading to the carbs leaking through the main venturi (bomb site)
    - makes for poor off the line performance.

    Compression is at 105psi all 3 cylinders, which is spec at 5280 ft.
    I would say without any doubt you need to re-jet at that altitude.
    - Have your ski's always lived at this alt, or have you bought them elsewhere and took them up.?
    - Would seem unusual if they were always locally owned and Not re-jetted.

    Think your going to have to at the very least get the low speed jets out to check exactly what you have in there.?
    - Input from others who operate their craft at these sort of altitudes would be benificial..
    - You could be looking at coming down to. #1 95 low jet,. #2 90 low jet., #3 92.5 low jet (stock is 100/95/97.5)
    - Set them to 1.5 turns out to begin with. you may need to go in a little to get it perfect.?
    - You may want to stay with the 135 mains initially.? (you could end up at 130 though.?)
    - Stick with the 1.2 needle and seats you have (since they're new)

    Both Mikuni kits I ordered, though, came with 1.2 N/S. So, I don't know. Either way, what would you do with a smaller seat? Increase adjustment needle?
    The needles are all the same it's the seats that are differently sized.!
    - Adjustment is made by increasing their size, Or changing the springs to get your desired pop-off..

    If you don't have a copy of this already.?
    - You NEED to download it. it's very good indeed.
    Mikuni SBN Manual http://www.mikuni.com/pdf/sbn_manual.pdf
    Last edited by quadzilla; 07-24-2015 at 03:33 PM.

  12. #10
    Quote Originally Posted by quadzilla View Post
    Quote Originally Posted by Mpeavler View Post
    97's had the 1.5's
    98-99-2000 65u's came with a 1.2
    Think Yamaha dropped the 1.5 Needle and seat for the 98 and beyond models that ran the triple motors..
    - they just shake too much at idle and unseat the needles, leading to the carbs leaking through the main venturi (bomb site)
    - makes for poor off the line performance.
    Yeah they all dribbled after I rebuilt them for about a half hour then stopped. Annoying little *kers.
    Quote Originally Posted by quadzilla View Post
    Compression is at 105psi all 3 cylinders, which is spec at 5280 ft.
    I would say without any doubt you need to re-jet at that altitude.
    - Have your ski's always lived at this alt, or have you bought them elsewhere and took them up.?
    - Would seem unusual if they were always locally owned and Not re-jetted.
    They have been here for 8 years that I know of. I'm pretty sure the adjustment screws weren't out as far as I have them out right now, I was pretty pissed off when I put them all back together.
    Quote Originally Posted by quadzilla View Post
    Think your going to have to at the very least get the low speed jets out to check exactly what you have in there.?
    - Input from others who operate their craft at these sort of altitudes would be benificial..
    - You'll could be looking at coming down to. #1 95 low jet,. #2 90 low jet., #3 92.5 low jet (stock is 100/95/97.5)
    - Set them to 1.5 turns out to begin with. you may need to go in a little to get it perfect.?
    - You may want to stay with the 135 mains initially.? (you could end up at 130 though.?)
    - Stick with the 1.2 needle and seats you have (since they're new)
    Why do all 3 carbs have different jets in them? That seems a little counter intuitive as far as AFRs are concerned, don't you think?

    Quote Originally Posted by quadzilla View Post
    Both Mikuni kits I ordered, though, came with 1.2 N/S. So, I don't know. Either way, what would you do with a smaller seat? Increase adjustment needle?
    The needles are all the same it's the seats that are differently sized.!
    - Adjustment is made by increasing their size, Or changing the springs to get your desired pop-off..

    If you don't have a copy of this already.?
    - You NEED to download it. it's very good indeed.
    Mikuni SBN Manual http://www.mikuni.com/pdf/sbn_manual.pdf
    [/QUOTE]

    Each kit came with that same manual from Mikuni. I would like to know if there is a corrected yamaha service manual for the 65U equpped skis?

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