Page 1 of 3 123 LastLast
Results 1 to 10 of 21
  1. #1

    Join Date
    Apr 2014
    Location
    UK
    Posts
    212
    +1
    22

    GP1200 carb recipe

    Hi all, I'm about to fit GP1200 carbs on the Waveraider and wondering what jetting will work best. I dont have them yet but theres a full set incuding intake manifold and reedblocks ready to buy. Until I see them though I've no idea what's actually in them, are they 1.2 N/S with 100 lows and 130 high's stock?

    Lots of talk about the 'recipe', from Fercho? Searched a few times and never found it, could someone post a link please.

    The Raider is bored to 1200 and moderately ported, I'll be removing the chokes and fitting K&N's, would the stock 44' jetting be ok to start with or to high? Obviously need to fit two more pulse fittings as well

    Any old schoolers feel free to jump in with advice, opinions or ideas cheers!


  2. #2

    Join Date
    Oct 2013
    Location
    West Central Florida
    Posts
    178
    +1
    12
    Here is a copy and pasted piece of expert information posted by the late OsideBill. This may be of some help of where to start. Your ported mod may require different adjustments and/or jets but at least this is starting point....

    "The setup that is tried and true for a stock or mostly stock GP1200 engines with a aftermarket flame arrestor is the following: Use the 115 gram spring with the 1.5 NS to get a pop off of around 50 to 55 psi. Run all 3 carbs with 100 pilots jets and the highs should all be the stock 135. Run the low speed screws all at 1 1/4 out and the highs at 1 1/2 out. Thats exactly how I run mine and it runs perfect. Your higher compression has little affect on jetting/carb set up but do some minor hi/low speed screw adjustment if you feel you need to. 1.
    I moved to this to the old school section since this is a 65U 1200 npv motor in this ski. As for jetting I run the following in my SUV which is the same motor.
    1.5 N&S Gold 115gr spring 100 pilot jets 135 main jets chokes removed R&D power plenum F/A
    This has been a work horse for almost three seasons without an issue using this jetting".....

  3. #3
    quadzilla's Avatar
    Join Date
    Apr 2007
    Location
    LOCH NESS Monster-Land
    Posts
    1,178
    +1
    29
    Quote Originally Posted by Raider1200 View Post
    Hi all, I'm about to fit GP1200 carbs on the Waveraider and wondering what jetting will work best. I dont have them yet but theres a full set incuding intake manifold and reedblocks ready to buy. Until I see them though I've no idea what's actually in them, are they 1.2 N/S with 100 lows and 130 high's stock?

    Lots of talk about the 'recipe', from Fercho? Searched a few times and never found it, could someone post a link please.

    The Raider is bored to 1200 and moderately ported, I'll be removing the chokes and fitting K&N's, would the stock 44' jetting be ok to start with or to high? Obviously need to fit two more pulse fittings as well

    Any old schoolers feel free to jump in with advice, opinions or ideas cheers!
    Hey there Mate..

    The actual recipe you are looking for was from "OsideBill"
    - As has already been posted it was what he used in his workhorse SUV
    - He had great success with those settings on a basically stock motor with a mild bump in compression to 150psi

    What should come installed in the carbs you have a line on is.
    - 1.2N/S, 135 main jets in all 3 carbs, staggered low speed jets. 97.5 / 95 / 100

    Depending on how much Porting you have you might want to start with 105's on the lows
    - leave the Hi's at 135.
    - Get some 1.5N/S's and 135gram springs. that will put you around 55psi pop-off
    - (95 grams springs and 102.5 low's might be a little crisper off the bottom. will put you around 43-45psi)

    You Will want to double up the check valve on the valve body assemble (metering block) in the jet side of the carbs.
    - even tripling up isn't unheard of.! (part number BN34/107)
    You will also be wanting to do the drilled restrictor modification.

    Shoot me a PM about this carb setup.
    If you want to explore a slightly different avenue.??
    I have a spare 1200 intake manifold you are welcome too,
    your stock 1100 reeds are just as good as the 1200's (as long as they are still sealing correctly)
    A reed spacer is a good idea to get the stock reeds out of the crank turbulence and back from the boost port also adds a few RPM's on top.
    If these carbs come with the stock airbox (F/A) then I have a good mod for it.

    Good to hear your moving forward from the 38's..

  4. #4
    quadzilla's Avatar
    Join Date
    Apr 2007
    Location
    LOCH NESS Monster-Land
    Posts
    1,178
    +1
    29

  5. #5

    Join Date
    Apr 2014
    Location
    UK
    Posts
    212
    +1
    22
    Thanks guys, excellent detail!

    Great to hear from you Quad, excellent detail. Pretty much similar stuff to the 38's then. I drilled the returns on those and tapped/threaded a main jet into the return barb. Also doubled up on the check valves there too so it's all familiar stuff to do ��

    The new carbs are coming with adapters so hopefully my K&N's will fit, 70mm base approx.

    Ive got some spare 95g springs somewhere, pop off on the 38's was around 40psi also. I'll wait and see what N/S's and jets are in them before buying new. You never know, the previous owner may be a member here! I'll be going through them with beady eye anyway.

    Thanks for the offer of the manifold! I'll see what state the one is I'm buying, complete with reeds. It's an interesting point you say to use the 1100 reeds, I've got fairly new Boyesen Power dual stage ones but they are slightly smaller than the 1200's. Didn't a good mod back in the day be to fit 1200 cages and reeds in the 1100 manifold because they were bigger and flowed more air?
    I wonder if it would be a step backwards fitting my nice 1100 Boyesen's?

    Interesting info on the spacer. They're damn nearly impossible to find a triple one so I was going to buy two twins from FreeRide Innovations for about 60 with gaskets and fixings and chop one in half! Mixed reviews on performance gains because it slightly increases the crankcase volume? Good news for the reeds lifespan though!


    Right, thanks again for the excellent detailed replies. I'm going to grab a brew, sit down and read through the links posted above

  6. #6

    Join Date
    Apr 2014
    Location
    UK
    Posts
    212
    +1
    22
    "Shoot me a PM about this carb setup.
    If you want to explore a slightly different avenue.??"

    Intrigued! Would this be something like reverse jetting? Because that's way over my head!

  7. #7

    Join Date
    Apr 2014
    Location
    UK
    Posts
    212
    +1
    22
    Carbs arrived off a low 35 hour '98 GP with a blown motor. They're in really good condition.

    Pulling them apart, they do have 1.2 NS's 135 mains. The lows do look like 100, 95 and 97.5. Hard to make out though. The anti tamper caps were on the needles too. I've removed these and stripped the carbs down bare. Odd needle settings? The lows were 1 1/8, 7/8 and 1 turn out and the high's were 3/4, 0 (fully screwed in on #2) and 1/2. I'll go with the recommendations above, cheers.

    Choke plates removed and Mikuni primer fittings ordered and on the way along with new gaskets, seals, check valves etc. I had spare 1.5's already. Stripping the pumps apart I guess the check valves are all creased on one side (3 valves out of 6) wonder if the ski went lean and blew because of this? I'll be drilling out the returns later today
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	image.jpg 
Views:	83 
Size:	121.3 KB 
ID:	399390  

  8. #8
    quadzilla's Avatar
    Join Date
    Apr 2007
    Location
    LOCH NESS Monster-Land
    Posts
    1,178
    +1
    29
    Quote Originally Posted by Raider1200 View Post
    Carbs arrived off a low 35 hour '98 GP with a blown motor. They're in really good condition.

    Pulling them apart, they do have 1.2 NS's 135 mains. The lows do look like 100, 95 and 97.5. Hard to make out though. The anti tamper caps were on the needles too. I've removed these and stripped the carbs down bare. Odd needle settings? The lows were 1 1/8, 7/8 and 1 turn out and the high's were 3/4, 0 (fully screwed in on #2) and 1/2. I'll go with the recommendations above, cheers.

    Choke plates removed and Mikuni primer fittings ordered and on the way along with new gaskets, seals, check valves etc. I had spare 1.5's already. Stripping the pumps apart I guess the check valves are all creased on one side (3 valves out of 6) wonder if the ski went lean and blew because of this? I'll be drilling out the returns later today

    Hey Mate...

    You can bet your ass they went lean because of that..!!
    As well as someone Not accounting for the jetting changes needed when they added the F/A's

    Number 2 carb would have went lean the minute F/A's are added.
    - this is due to the Increased signal generated when the stock F/A set up in in use.
    - (that's why number 2 has the lowest low speed jet but the most turns out on the High speed circuit to compensate)

    Good to hear your in about them already..

    .

  9. #9

    Join Date
    Apr 2014
    Location
    UK
    Posts
    212
    +1
    22
    So... the carbs are built and ready to fit. They came with choke plates intact, that was the first job removing them and adding blanks and primer fittings.

    Next was a FULL strip down, clean and check everything, replace what needed replacing. Pump diaphragms, pump check valves and gaskets, new internal screws, double jet plate cover check valves, high and low needle O rings, alan bolts in pump body and diaphragm plates, drilled returns and 95 main jet thread-tapped into the last return outlet, reedblock to crank case gasket, carb top f/a adapters, drill and fit two new pulse nipples.

    I had three spare 1.5 n/s to fit and reused the new looking shiny silver pop off spring. Pop off comes out at about 43psi so they're 95g.

    The low jets I had two spare 100's already so now there's 3x 100's fitted along with the stock 135's. Screw settings are as above, 1 1/4 lows and 1 1/2 high's.

    Porting is fairly mild so hopefully the low jets will be ok at 100 with a tweak on the turns when it's running? I'll pay close attention to how it's running

    Lastly I've got hold of a 65U CDI and flywheel rather than the whole 1200 electrics and mag cover, changed the block connector over on the CDI to match the 63M one (easy to do, remove pins) but keeping the 1100 cover with stator and pick ups

    While all this has been going on I also bought a replacement jet pump stator as mine was badly beaten. It's off a GP1200 with the water strainer. I wasn't sure if it would fit but it all looks good. Just drilled and tapped a 1/8" x 3/8" water bypass for the jet works valve tonight. I've got the impeller set back as far as it will go too with a thinned down impeller spacer/washer. The gap between the stator and impeller hub is a gnats whisker! Prop is my trusty Solas Concord 13/19. I'm hoping the ski will go well enough to get this pitched higher from 19 to 20. We shall see soon enough, should be running by next weekend

  10. #10
    quadzilla's Avatar
    Join Date
    Apr 2007
    Location
    LOCH NESS Monster-Land
    Posts
    1,178
    +1
    29
    Hey Mate...

    Thought I'd follow up on the 1100 Vs 1200 Reeds conversation we had a few weeks back..

    I'd been away on holiday for a while there..
    - (back to reality now though.)

    So had no access to my parts..

    OK then...
    I've posted a few images of the 1100 and 1200 reeds side by side as well as a set of Boyesen reeds for comparison.
    - ( these Boyesen's are actually a complete reed system with there own reed cage design and funky stopper)

    As you can see there is very little if any difference in the 1100 and 1200 cage blocks external dimensions.
    There is a difference in the slightly longer petals used on the 1200's,
    -The 1200 reeds also use a considerably larger reed stopper.??
    - (I'm struggling to see the benefits of implementing such a large reed stopper, As it certainly obstructs the boost port somewhat)
    - The Boyesen's are quite a bit larger height wise.

    Looking in from the back of the cages.
    You should be able to make out the slightly larger bridge along the inside top of the 1100 cage.
    - The openings may be very slightly larger on the 1200 cage.? (need to measure to be sure)
    - The 1200 cages also have the corners at 45 degree for some reason.??
    - You can see Boyesen have went with an opening around the size of the 1200 manifold.? (someone has had a go a grinding on these ones.??)
    - There is some good theory on keeping the reed opening larger than the inlet manifold opening into the reed.
    - Both the 1100 and 1200 would have the same "theoretical" benefit on the 1200 manifold.
    - The Boyesen's also have a substantial central divider inside the cage. (as do most all aftermarket systems)

    I also have a couple of sets of Moto-tassinari original VF reeds and a pretty rare set of R&D M16's for a 65U motor.


    All this brings us back to should you use the 1100's with your Boyesen petals or the 1200's.??

    If it were me.? I'd..............








    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	1100(L) - 1200(R).jpg 
Views:	715 
Size:	83.7 KB 
ID:	400158   Click image for larger version. 

Name:	1100 reed +1200.jpg 
Views:	714 
Size:	48.7 KB 
ID:	400159   Click image for larger version. 

Name:	1100,1200 rear.jpg 
Views:	707 
Size:	54.7 KB 
ID:	400160   Click image for larger version. 

Name:	1200,1100,Boyesen.jpg 
Views:	703 
Size:	66.9 KB 
ID:	400162   Click image for larger version. 

Name:	Boyesen dual stage.jpg 
Views:	713 
Size:	69.2 KB 
ID:	400163   Click image for larger version. 

Name:	Boyesen, 1100, 1200. .jpg 
Views:	798 
Size:	73.6 KB 
ID:	400168  


Page 1 of 3 123 LastLast

Thread Information

Users Browsing this Thread

There are currently 2 users browsing this thread. (1 members and 1 guests)

  1. Ridetodie

Similar Threads

  1. gp1200 carb parts needed!!
    By SvrdRam in forum Yamaha Classifieds
    Replies: 40
    Last Post: 04-20-2009, 08:55 PM
  2. gp1200 carb questions
    By pilo704 in forum Yamaha Old School Skis
    Replies: 17
    Last Post: 09-14-2008, 11:11 PM
  3. gp1200 carb problem
    By pilo704 in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 07-22-2008, 02:04 PM
  4. Help! - GP1200 Carb Issue
    By 9t8gp1200 in forum Yamaha PWC Performance (2-stroke)
    Replies: 2
    Last Post: 07-05-2008, 04:36 PM
  5. 1998 GP800/GP1200 Carb Rebuild
    By DTV in forum Yamaha Old School Skis
    Replies: 7
    Last Post: 06-29-2007, 12:32 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
  •