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carburator boring 28 Jun 2020 14:43 #829229

  • TJKZ9er
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who has had any luck with carburetor boring and was it worth it and who does it ?

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carburator boring 28 Jun 2020 14:52 #829235

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Welcome to KZRider
Seek out advise from ZED1015

Original owner 78 1000 LTD
Mr Turbo Race Kit, MTC 1075 Turbo pistons by PitStop Performance , Falicon Ultra Lite Super Crank, APE everything. Les Holt @ PDM's Billet Goodies . Frame by Chuck Kurzawa @ Logghe Chassis . Deep sump 5qt oil pan. RIP Bill Hahn

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carburator boring 28 Jun 2020 15:08 #829239

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Welcome from Michigan... Hi!

Zed1015 is the local carb wizard, I second Street Fighter LTD’s suggestion...

I purchased a set of VM26SS from another member here that were bored to 30mm. He sold them because they just were not enough for his set up... he was happy with the way the preformed but just not enough... they are in my storage waiting for a big bore build I will be doing in the near future... my set was done by Wired George, but I don’t think he is doing them any more... you might still be able to contact him for advice... I don’t know every aspect of doing it but know It involves internal changes to the carb along with the bore to get correct operation from the set...
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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carburator boring 28 Jun 2020 15:17 #829241

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I took some VM26'S out to 29mm, really no issue doing it but you do have to cut the bottom of the slides after so they will seal off past the throat. Once you bore the throats your taking away some depth from that slide groove.

I also drilled out the hole bigger in the side of the body that lets the gas flow between the fuel tees, this is so the carbs will be able to fill the float bowls quicker.

Trimming the slides is the only thing you could screw up, you need to blue them and scribe the shape you need, its a compound curve so its a bit tricky. If it leaks at the bottom it screws up the tuning big time.

If your not comfortable using a lathe or milling machine maybe leave it up to somebody who is.

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carburator boring 28 Jun 2020 15:23 #829243

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I read that a special cutting tool is used to reach down through the slide bore and recut the seat... its a better way to re locate the slide... I’m not talking from experience but just what I’ve read... either way the needle jet and jet needle will need attention.
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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carburator boring 28 Jun 2020 15:31 #829247

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I was shown how to do it the way I explained by a old Kawasaki mechanic, I guess either way would work but there would be a greater risk of screwing up the carb body by re cutting the bottom thru the slide bore.
The method I explain works, there is still a groove there after boring it out, its only 1mm less. I guess if you going to put it out to 30mm then it may be required?
Yes, forgot about the needle jet/jet needle mods.

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carburator boring 29 Jun 2020 00:42 #829276

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I bore out my own carbs on the lathe.
The 26mm bodies are best as they are fractionally thicker than the 28's at the stub and there's more meat between the inside bore and the bottom of the boot groove.
All the details were in my Cafe racer thread in projects but Photobucket cut all the photo links so there's nothing to see and the posts can't be edited to post new pics.
Basically you straight bore the carbs to 30mm.
Make a cutting tool to re-instate the slide seat groove which is lost ( this has a slot up the side to allow the cutter to drop past the plastic guide for the slide )
You then need to spot face the now raised portion around the needle jet to allow the slide to fully seat and then lift the jet needle 2mm to put it back in the correct position in relation to the jet.
The slide type with the spring loaded needle and plastic spacers are the best for this as you only need to switch spacers and use a shim.
Once done correctly they out perform VM29 smoothies and are easier to set up.

Carb being bored


Before and after


Slide seat groove cutter with alloy guide that slots in after to keep it square
AIR CORRECTOR JETS FOR VM CARBS AND ETHANOL RESISTANT VITON CHOKE PLUNGER SEAL REPLACMENT FOR ALL CLASSIC AND MODERN MOTORCYCLE CARBURETTORS
kzrider.com/forum/23-for-sale/611992-air-corrector-jets-





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