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Author Topic: How to rejet the GT650 with photos  (Read 41774 times)

AdamTubb2506

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Re: How to rejet the GT650 with photos
« Reply #40 on: June 20, 2011, 05:14:26 PM »

Hey bud great DIY keep it up and you might be in show biz 8)
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Bretto

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Re: How to rejet the GT650 with photos
« Reply #41 on: July 14, 2011, 04:24:22 AM »

Ok I have had the bike apart for about a month now - no time and waiting for parts, got the Sigma 6 jet kit and from what i have read else were it has the same parts (mains 145 & 150) as everyone else so not sure what elavation has to do with their kits - we cant all live on the same level. So ive gone with 145 mains full open standard air filter as they state that these work better than the after market (and the fact that I am still waiting for my BCM filter, moved the neddle.
i had to wait for the slides as the previous owner filled the slides in with glue (not big fan of that). So hopefully will get to go for a spin this weekend and hook up fuel air ratio meter and see exactly what is doing and if it needs adjusting.
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2006 GT650R, derestricted, rejet, mod airfilter, Screaming demon exhaust, stainless braided brake lines, Metal Gear brake pads, Carbon fibre look mirrors with inbuilt blinkers and brake light modulator.

michaelbell85

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Re: How to rejet the GT650 with photos
« Reply #42 on: October 22, 2012, 05:57:59 AM »

what did you do with the air fuel screw which screw is the air fuel screw.
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Bretto

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Re: How to rejet the GT650 with photos
« Reply #43 on: October 22, 2012, 10:51:35 AM »

Not sure what you mean but the mixture screw relates to the air fuel mixture at idle and cant remember been 15 months since last rejet, will go over notes and see
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2006 GT650R, derestricted, rejet, mod airfilter, Screaming demon exhaust, stainless braided brake lines, Metal Gear brake pads, Carbon fibre look mirrors with inbuilt blinkers and brake light modulator.

michaelbell85

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Re: How to rejet the GT650 with photos
« Reply #44 on: October 22, 2012, 06:39:06 PM »

there is a air fuel cfrew on all carbs but on mine the supposely put  a small brass cap over it and 6 sigma sent a screw and a drill bit to drill it out to get to the screw. There is 3 screw holes on top side of the carb underneath the slide housing. I dont know which one to drill out 2 of them have caps over the screws.
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DrunkenMistake

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Re: How to rejet the GT650 with photos
« Reply #45 on: February 12, 2013, 10:52:47 AM »

Im not going to lie,
I am a lazy bugger..
I have an 06 Carbed 650R with the stock air filter and a free flowing exhaust,
Can someone recommend the right sized Jets to use? 
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weswho

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Re: How to rejet the GT650 with photos
« Reply #46 on: July 12, 2013, 11:11:36 PM »

We all know air + gas makes combustion, however, heat also affects the combustion process. As does altitude since air is thinner in higher altitudes. There are several factors that can affect how hot a bike gets, but I'll focus on just one here, the air/fuel ratio. Otherwise known as lean or rich. Lean means not enough fuel for the amount of air in the combustion chamber. Rich means there's too much fuel for the air to burn completely. A lean mixture leads to higher temperatures in an engine which is suicide.
 Hyosungs are really lean due to emmisions regulations. So, that means that hyosungs have TOO much air and not enough fuel. Jetting is the best way to bring down temperatures, increase power, increase engine longevity, and cut down exhaust popping. Putting on an aftermarket air filter or exhaust without increasing the amount of fuel to me is just counter-intuitive, even harmful.
For those that live around sea level; If you don't want to upgrade your intake or exhaust I still recommend getting slightly larger jets. (135s should work) Due to the thicker air, this exacerbates the lean problem. Sure you will get a hardly noticeable increase in power, but it's better for the engine in the long run.
But let's be honest, you want more power. So you wanna know what size jets to get. Sorry to say, there is no easy answer. There are several factors such as altitude, modifications, some say fuel economy, but that means you're not paying attention to the air/fuel ratio. Your best bet is to have someone dynotune or use an exhaust air/fuel meter using different jet sizes. Or if you wanna wing it you could add 5 for every mod you have done, (exhaust, air filter, desnorkel) don't include ais mod. then subtract 1 for every thousand feet over sea level...This is just a idea, not a scientifically proven fact. So if you have an exhaust and air filter and live at 2000 feet that's 10-2=8 add that to the stock numbers of 130, and you get 138, however, 137.5 and 140 work just fine.  22.5 is a good pilot jet size for almost all factors.
Of course learn how to check your sparkplugs. If your engine feels boggy, you might have too large of jets, could be lack of exhaust backpressure if only happens at low rpms. If you feel like you are running out of steam at higher 3rd of rpms you are probably running lean. Experimenting doesn't hurt anything, have fun, it's actually really easy to do once you know the mechanical function of the carbs parts. Lastly, I recommend cleaning the carb every year 1/2  two years, even the smallest particle can clog a needle leading to lean conditions. I also recommend header wraps to lower engine temps they also increase exhaust flow.
« Last Edit: July 15, 2013, 09:39:15 PM by weswho »
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SwedishKing

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Re: How to rejet the GT650 with photos
« Reply #47 on: September 12, 2014, 11:52:15 PM »

instead of putting on a new thread, i will ask for help here.

Now im no super duper mechanic, i can do most of the normal jobs, but not more.
Problem is i am not someone who has grown up learning about carbs that much at all. And i wanna leave them alone. But i do need to rejet them!

I have k&n airfilter and ixil xtrem shorty exhaust.

I was thinking of getting these small parts myself and letting a workshop do the rest, or a nice friend.

For a lazy bugger like me, what parts do i need?

Main jet, pilot jet...then what more? And what size? i live in stockholm, sweden. No idea of altitude :p
Im just looking to get rid of backfiring, and if possible getting a bit more midrange/lowend.

Just changing the jets is enough? or do you need to actually do every small detail?
« Last Edit: September 12, 2014, 11:54:16 PM by SwedishKing »
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zero

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Re: How to rejet the GT650 with photos
« Reply #48 on: January 03, 2017, 11:34:06 AM »

Just my thingies I did.
I bought a sigma kit, thinking it would be a stage 1 to 3 kit. Got fed up with 2 needle jets and 4 main jets, size 145 and 155. I have another exhaust ( Dominator ) but silenced it because it was way too loud.

Put in the 145 main jets, placed the needle 2 ticks higher and made 4 25 mm holes in the airfilter. Doesn't run like i want it to and smells a lot of gasoline. Now I bought just the main jets ( mind you, only 3 euro's each.... :-\...) in size 132.5 and 137.5. I will re-open the airbox a bit more and install the 137.5 main jets. Seeing how that will work.

Will let you know.
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zero

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Re: How to rejet the GT650 with photos
« Reply #49 on: January 09, 2017, 01:34:57 PM »

As promised. I made the exhaust a liitle bit louder ( by removing some of the exhaust stuff I put around the silencer, works perfect ) and did the snorkle removing. Wit the 137.5 mains it runs like a plumber on a housewife without money. :-\
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