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TOPIC: Jetting after a bore and cams

Jetting after a bore and cams 02 Feb 2020 03:10 #818389

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Hey guys, I just finished putting my 650 back together after boring to the wiseco 700 piston kit and putting on kz750 cams. I got her to run with the choke on, but my question is how many jet sizes for the pilots and the mains is typically in the ballpark after that kind of work? Btw, I also installed ape valve springs and have a 4 into 2 exhaust with open baffle.

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Jetting after a bore and cams 02 Feb 2020 03:28 #818390

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Leave the pilots alone and start at 2 or 3 sizes up on the main and work down .
If you are running no airbox and using pods or stacks you should really fit air corrector jets if not already installed.
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Jetting after a bore and cams 02 Feb 2020 03:46 #818392

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Air corrector jets? I am unfamiliar with these. Before I began with the bore and cams, I was riding it with air pods already. Do you mean that I need to install air corrector jets to run pods with the bore and cams, even though I started with pods prior?

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Jetting after a bore and cams 02 Feb 2020 03:56 #818393

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Sorry. I bet it would be helpful to know which carbs I'm running. I'm running the stock vm pumper carbs.

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Jetting after a bore and cams 02 Feb 2020 03:59 #818394

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With the pods you will most certainly have had hesitation or a flat spot just off idle at around 2k rpm and ideally the air jets should be fitted to cure this regardless of having the bore and cams fitted.
The usual patch is to lift the needles a notch but this is not the best way as it detrimentally affects other areas of the fueling.
If the flat spot didn't bother you or wasn't that noticeable then just go up on the mains as suggested.
If you feel that the flat spot is an area that needs curing here's a link to the Jet thread that explains the issue.
www.kzrider.com/forum/23-for-sale/611992...-round-slide-mikunis

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Jetting after a bore and cams 02 Feb 2020 04:01 #818395

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Bigz wrote: Sorry. I bet it would be helpful to know which carbs I'm running. I'm running the stock vm pumper carbs.


Are they the 22mm or 24mm ?

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Jetting after a bore and cams 02 Feb 2020 04:12 #818396

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WOW! You have no idea how helpful that is. I spent months tuning my carburetor to try to fix that flat spot. I finally got rid of it and thought that I had truly fixed it. No one, in everyone that I asked, has ever told me about this. This is mind blowing. Thank you!

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Jetting after a bore and cams 02 Feb 2020 04:13 #818397

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I believe they are the 22's

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Jetting after a bore and cams 02 Feb 2020 04:25 #818398

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Bigz wrote: WOW! You have no idea how helpful that is. I spent months tuning my carburetor to try to fix that flat spot. I finally got rid of it and thought that I had truly fixed it. No one, in everyone that I asked, has ever told me about this. This is mind blowing. Thank you!


Glad to be of help..
They were developed here in the UK in the late 70's and due to there being no internet at the time they hardly ever got known overseas so that's why no one you ask will know.
They have been out of production for over 30 years until I started making them again recently due to the resurgence in popularity of these bikes.

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Jetting after a bore and cams 02 Feb 2020 05:26 #818399

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I see an order for a set of these in my future. Those are going to make my life a lot easier. Can I assume that there are different sets of them for each style of carburetor? I have 2 kz650's, a kz1000g (that may get carbs), and 2 gs550's that may need them as well. Also, a kz1000i motor that I'm going to casually upgrade with performance mods on my bench for a while.

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Jetting after a bore and cams 02 Feb 2020 06:03 #818402

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Yes! different sizes depending on carb size and sometimes model but most big kwaks are the same jet.
I'm mainly only producing them for the 4 bank VM 24, 26 and 28mm carbs on kawasakis as that's my main interest and they happen to fit quite a few Suzuki GS's and Yamaha and some CV carbs too.
The VM 22's on your 650 will need a set making to order and also the GS550 depending on model.
We didn't get the smaller VM22mm carbs here on the 650 so no point having a bunch of those sat around that don't sell.
I have only done one set of those since i started.
Just Pm me if/when you want some and we'll sort it out.
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Jetting after a bore and cams 02 Feb 2020 06:49 #818405

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Very nice. Thank you very much. I will definitely contact you when I'm ready for a set.

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