Author Topic: GS1200SS Carb's...Need Info and Suggestions  (Read 12345 times)

Offline bstard

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GS1200SS Carb's...Need Info and Suggestions
« on: October 31, 2008, 08:35:09 PM »
Hi
I have a 2004 GS1200SS ...now this is a Japanese model so it has Keihin CRV32 carb's not the Mikuni's. I am under the impression that these carb's might have been used on the 600cc bike.

First thing I need is someone to identify these various bits on the carb's.






Then I want info on how to get rid of what feels like a lean condition that occurs around 3000rpm. Most likely there because thats round the rpm that they had to do their emission testings.
I'm sure you guys fix it all the time on the Mikuni shod bikes but I know jack shit about Keihin's.

Then I need info on what I am likely to have to change when I remove the standard highly restrictive muffler and put on a hand, made basically empty megaphone.
I assume that I will have to go up on the main jet but is there any thing else with these CRV32 Keihin's that I should alter ?
Looking forward to any info you guys can give me.
Thanks
Richard

Offline pmackie

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #1 on: November 01, 2008, 12:53:59 AM »
According to my Factory Service Manual for 2nd Gen 600 (GSF600/GSF600S) from model Y(2000) through K3 (2003) all use the Keihin CVR32SS and look the same as your picture...so

A) pilot jet
B) Starter (enricher) jet
C) Pilot screw
D) pilot air jet
E) main air jet

The jet at the 2 O'clock position from a) is the main jet.

You would not normally change D) or E) as they can be adjusted elsewhere and are pressed in, and on your carbs B) looks fixed as well, and would also not normally need to be changed.

As for your jetting changes, I would start by turning out the c) pilot air screw. Carefully turn the screw IN (clockwise) and count the turns they are now, and write it down for further reference so you can go back to stock if needed. The pilot jet(fuel)and the pilot air jet(air) basically control what is a rich mixture that is injected into the airstream downstream of the throttle butterflies. Turning the screw IN reduces fuel flow and makes the bike leaner, turning it out (counter-clockwise) makes it richer, as this screw is controlling the rich fuel/air flow in these Keihin carbs. Depending on what the factory setting is, I would start with 1/2 to 1 full turn out (richer) than stock, or somewhere between 2-1/2 and 3-1/2 turns out from seated. If you need to be over 3-1/2 turns, you should consider a 1 size richer pilot jet instead (A). The Pilot jet and Pilot screw have the biggest effect between 0-1/8 throttle, but do have a small effect at all throttle openings.

2nd, you can consider "shimming" the existing needles in the carb slides. Some commercial jet kits come with needle shims, or you can try and source them from a local electronics supply house or similar. You are looking for small dia washers, approx 0.5 mm thick, that will just fit between the clips that hold the needles and the slide that they seat in, in effect "raising" the needles. For your stock pipe, and/or to start with your modified pipe, use one washer at a time. On my 600, anything over two shims would not fit without some mods to the seating arrangements. I have 1 shim in mine now, but it would be too lean at sea level.

3rd, as you mentioned, you would need to go up at least one main jet size for your modified pipe.

Try to only make one change at at time and see if everything is working. This means you may need to have the carbs off a few times to make the changes as you go. The other option is to look for a commercial jet kit, which may have some other instructions

Let us know how you make out...
« Last Edit: November 01, 2008, 01:03:01 AM by pmackie »
Paul
2002-GSF600S, Progressive Fork Springs, B12 Shock,
SS Brake lines, EBC HH pads, Leo Vince Ex & Kappa bags.
Ex Bike Mechanic (late 70's), somewhat rusty
32 years in the Fuel/lubes industry(Retired)

Offline bstard

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #2 on: November 02, 2008, 12:16:36 AM »
Hi
Thanks for that info.. I have given the Pilot Screws a little tweak and on a quick ride today it feels slightly better at 3000rpm.
When I get a proper 90 degree tool I will do the adjustment again and see how it feels.

So when I build my new muffler I will need to go up on the main jet size...so who has the best prices for Keihin jets ?

Also if I remove the airbox completely and go for individual filters which filters are you guys using and how many main jet sizes do you go up...ballpark figure needed here.
Thanks
Richard

Offline pmackie

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #3 on: November 02, 2008, 10:58:42 PM »
In NZ you may just want to go to a savy, local shop and have him get you the jets.

You can order internationally from Jets R Us, but the international shipping is pretty pricy...

http://www.jetsrus.com/main_page.htm

Paul
2002-GSF600S, Progressive Fork Springs, B12 Shock,
SS Brake lines, EBC HH pads, Leo Vince Ex & Kappa bags.
Ex Bike Mechanic (late 70's), somewhat rusty
32 years in the Fuel/lubes industry(Retired)

Offline bstard

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #4 on: November 03, 2008, 12:15:37 AM »
Hi
Can you actually remove the Pilot Srews by unwinding them completely ?
I want to give them a clean out and one feels a bit tight on the threads.
Thanks
Richard

Offline pmackie

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #5 on: November 03, 2008, 12:51:07 AM »
Yes...you can take them out, just make sure you keep track of the parts. There is a spring under the pilot air screw for sure.
Paul
2002-GSF600S, Progressive Fork Springs, B12 Shock,
SS Brake lines, EBC HH pads, Leo Vince Ex & Kappa bags.
Ex Bike Mechanic (late 70's), somewhat rusty
32 years in the Fuel/lubes industry(Retired)

Offline bstard

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Re: GS1200SS Carb's...Need Info and Suggestions
« Reply #6 on: January 03, 2009, 04:20:55 AM »
Hi
Anyone have the specs on the 600cc  Pilot screw turns as standard ?
I think it is 1 1/2 out but does anyone have that info for sure.
thanks
Richard