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Author Topic: How to rejet the GT650 with photos  (Read 50886 times)

jabba

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How to rejet the GT650 with photos
« Reply #30 on: December 14, 2008, 01:45:15 PM »

For someone who hasn't really had much to do with bikes/mechanics before would you say this is better off left for a workshop or easy enough to go off the instructions??
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JoeB

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Re: How to rejet the GT650 with photos
« Reply #31 on: March 02, 2009, 12:10:55 AM »

I went off the instructions myself never having done this before to these carbys and it was pretty easy I think but if you have doubts then take it to the mechanics.
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razor

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Re: How to rejet the GT650 with photos
« Reply #32 on: April 05, 2009, 06:45:35 AM »

bretto I notice on your original you quote jets of 140-142.5 then on reply #24 you say you upgrade to and give the same sizes for the main jets ?
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tubs

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Re: How to rejet the GT650 with photos
« Reply #33 on: August 04, 2009, 02:33:31 PM »

Hey Bretto, excellent post however im sure you've heard that enough from everyone else lol what i want to discuss with you is 2 topics on the back of this...

Ok guys -I have been playing again and have updated the how to
I increased my main jet sizes rear 140 and front 142.5 and have also drilled an extra 4 x 3/8" holes in the air filter to increase air flow, and it feels a bit more toey in the upper revs.
I'm thinking of going with a full open air filter, just waiting for a couple of bigger jets to come in and will try them out.

1. Ive noticed that you've increased your jets here and are tossing up whether or not to go bigger, i understand that finding the right jet sizes is a matter of trial and error, which as you pointed out raises the issue of the higher oxygen demand.

2. This is where im calling on you to give your opinion on the optimal way to balance the air/fuel ratio. What do you think of these BMC filters? Are they worth buying if your only going to cut holes in it to get more air??
So all up with a short unbaffled exhaust, de-restricted slides, what size jets would you recomend (your original choice or 140/142.5)? How much of the original air filter would you drill out?

I am planning to Dyno the bike before and after the jets have been replaced, which will give me a more accurate ratio. I will post the results when its all complete.
Hope to hear from you soon, and again well done, i look forward to more posts like this in the future.

Tubs
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'07 GT650R
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Speedemon07

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Re: How to rejet the GT650 with photos
« Reply #34 on: April 08, 2010, 12:23:30 AM »

haven't seen anything on this for awhile. Did you get those Dyno results?
Hey Bretto, excellent post however im sure you've heard that enough from everyone else lol what i want to discuss with you is 2 topics on the back of this...

Ok guys -I have been playing again and have updated the how to
I increased my main jet sizes rear 140 and front 142.5 and have also drilled an extra 4 x 3/8" holes in the air filter to increase air flow, and it feels a bit more toey in the upper revs.
I'm thinking of going with a full open air filter, just waiting for a couple of bigger jets to come in and will try them out.

1. Ive noticed that you've increased your jets here and are tossing up whether or not to go bigger, i understand that finding the right jet sizes is a matter of trial and error, which as you pointed out raises the issue of the higher oxygen demand.

2. This is where im calling on you to give your opinion on the optimal way to balance the air/fuel ratio. What do you think of these BMC filters? Are they worth buying if your only going to cut holes in it to get more air??
So all up with a short unbaffled exhaust, de-restricted slides, what size jets would you recomend (your original choice or 140/142.5)? How much of the original air filter would you drill out?

I am planning to Dyno the bike before and after the jets have been replaced, which will give me a more accurate ratio. I will post the results when its all complete.
Hope to hear from you soon, and again well done, i look forward to more posts like this in the future.

Tubs
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2007 Black UM V2S-650R, Dowco Saddle Bags, Things wanting to add: Fender Eliminator, rim tape, Tank Protectors, Hugger, and a tinted double bubble screen.

Speedemon07

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Re: How to rejet the GT650 with photos
« Reply #35 on: July 08, 2010, 04:14:06 AM »

Anymore updates on sizes and dyno results?
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2007 Black UM V2S-650R, Dowco Saddle Bags, Things wanting to add: Fender Eliminator, rim tape, Tank Protectors, Hugger, and a tinted double bubble screen.

Bretto

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Re: How to rejet the GT650 with photos
« Reply #36 on: June 03, 2011, 10:01:08 PM »

Hey Bretto, excellent post however im sure you've heard that enough from everyone else lol what i want to discuss with you is 2 topics on the back of this...

Ok guys -I have been playing again and have updated the how to
I increased my main jet sizes rear 140 and front 142.5 and have also drilled an extra 4 x 3/8" holes in the air filter to increase air flow, and it feels a bit more toey in the upper revs.
I'm thinking of going with a full open air filter, just waiting for a couple of bigger jets to come in and will try them out.

1. Ive noticed that you've increased your jets here and are tossing up whether or not to go bigger, i understand that finding the right jet sizes is a matter of trial and error, which as you pointed out raises the issue of the higher oxygen demand.

2. This is where im calling on you to give your opinion on the optimal way to balance the air/fuel ratio. What do you think of these BMC filters? Are they worth buying if your only going to cut holes in it to get more air??
So all up with a short unbaffled exhaust, de-restricted slides, what size jets would you recomend (your original choice or 140/142.5)? How much of the original air filter would you drill out?

I am planning to Dyno the bike before and after the jets have been replaced, which will give me a more accurate ratio. I will post the results when its all complete.
Hope to hear from you soon, and again well done, i look forward to more posts like this in the future.

Tubs

Tubs

Sorry for delay - just after I posted my last message some one came into my workshop and offered me enough cash to buy my bike that it went out the door with him also we moved out of town and did not have internet access for 12 months, so I didnt get a chance to trial bigger jets or keep up todate with you guys, the more open the ait filter the bigger the jets you need - I have a portable air flow meter that I can ride around with and check if lean/rich or spot on - great for sorting dead/flat spots etc in the full rev range of the bike, so yes it can be a bit of trial and error to get the right jets for the right filter opening and also filter type.
BMC filters - Yes I like and use alot - Have one on my 3.0 litre common rail diesel Hilux with LPG conversion, snorkel and 3"exhaust, great for air flow and the fact you can clean, re oil and use again.
There is two ways to go about it - Open your air filter to the size you want and then change the jets until you get the correct mixtures or fit the jets you want and slowly open the filter up until the mixtures are correct.
Let us know of your results with the jets and dyno.
The reason Im back is I just purchased another Hyo 2008 LAMs model - been for a 5 klm ride only so far and some one else has already done some work to it, will give it a service before to long and pull it down and see what has been done and then see what I can do.
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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.

MotoUnion

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Re: How to rejet the GT650 with photos
« Reply #37 on: June 04, 2011, 08:35:43 AM »

Hi Guys, sorry to butt in, just thought I add my ten pennies worth, done some playing with jets on my 650 and we found that 132.5 jets offer a reasonable balance between fuel economy and performance. Currently my airfilter is de-snorkelled, but im thinking this is too much. Maybe I will experiment with drilling a couple of holes in the top first.

Cheers
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Bretto

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Re: How to rejet the GT650 with photos
« Reply #38 on: June 05, 2011, 11:35:03 AM »

how far did you desnorkel - im thinking of going all the way and getting jets to suit - not worried about encomony just raw fun
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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.

MotoUnion

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Re: How to rejet the GT650 with photos
« Reply #39 on: June 05, 2011, 12:51:47 PM »

Whipped the whole snorkel out.
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