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KZ440's with Mikuni VM carbs 17 Feb 2023 07:27 #880326

  • Sdaniels2010
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For those who have done this conversion, how much of a difference in gas mileage is there?
1981 KZ440 A2 LTD

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KZ440's with Mikuni VM carbs 18 Feb 2023 15:56 #880403

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I haven't finished the conversion yet, but I don't know if there will be a huge difference in mileage compared to a stock 440 if you keep the jetting that comes with the Mikunis.

BTW I'm assuming you're talking about VM30s that are pre-jetted for the KZ440 (like in the SpeedMotoCo kit) rather than 28s or 32s.
1979 KZ400 Gifted to a couple of nephews
1967 Yamaha YCS1 Bonanza
1980 KZ440B
1981 Yamaha XT250H
1981 KZ440 LTD project bike
1981 GPz550
2013 Yamaha FZ6R

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KZ440's with Mikuni VM carbs 19 Feb 2023 09:59 #880438

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I haven't finished the conversion yet, but I don't know if there will be a huge difference in mileage compared to a stock 440 if you keep the jetting that comes with the Mikunis.

BTW I'm assuming you're talking about VM30s that are pre-jetted for the KZ440 (like in the SpeedMotoCo kit) rather than 28s or 32s.
I know there have been several conversions to those 3 sized carbs so I'd be interested in any of them, but with particular attention to the 30's for the reason you stated.  
1981 KZ440 A2 LTD

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KZ440's with Mikuni VM carbs 19 Feb 2023 10:09 #880439

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It would be really nice if someone came up with a using a modern set of CV carbs too.  Several bikes I've owned that had jet kits made for stock setup, individual filters, modified stock airbox with a single, large filter that ditched the housing & they all worked.  Of course the newer CV's had quite a few differences compared to the ancient kz carbs.
1981 KZ440 A2 LTD

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KZ440's with Mikuni VM carbs 19 Feb 2023 10:55 #880442

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28s would probably give you the best mileage but I haven't looked at prices or availability or anything.

30s would be the easiest conversion, as you've seen.

32s are too big for a stock KZ440. From what I've read, you would need a cam and head work for 32s to make sense on a 440 (and possibly not even then).

I'm going with velocity stacks (with light filtration) and short gearing and expect to be winding it up most of the time, so I went a little richer on the mains.

Here is a screenshot of a spreadsheet I did 6 years or so ago:

 
1979 KZ400 Gifted to a couple of nephews
1967 Yamaha YCS1 Bonanza
1980 KZ440B
1981 Yamaha XT250H
1981 KZ440 LTD project bike
1981 GPz550
2013 Yamaha FZ6R
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KZ440's with Mikuni VM carbs 29 Sep 2023 17:39 #889904

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I'm a little late to the thread, but am currently debating between keeping the stock cv carbs or buying the speedmoto mikuni vm30 kit. I just don't know if the kit is worth the $430. Since you guys seem experienced with both what would you recommend I go with?

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KZ440's with Mikuni VM carbs 30 Sep 2023 03:41 #889911

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Hi id leave the stock carbs on unless they are unusable, if they were good enough for Kawasaki designers then why change? 
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KZ440's with Mikuni VM carbs 30 Sep 2023 05:45 #889914

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Hi id leave the stock carbs on unless they are unusable, if they were good enough for Kawasaki designers then why change? 
Agree.  Changing the carbs will be expensive, and there is no guarantee that they will run properly out of the box.  
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KZ440's with Mikuni VM carbs 01 Oct 2023 10:47 #889969

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Confucius he say if it aint broke dont fix it

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