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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 11:46 #852785

  • SteveKing84
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Whats the name of the port I need to install for my vacuum line?  I'm not sure how to find one

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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 11:59 #852787

  • Nerdy
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You alluded to this earlier, but my recommendation is that you swap the vacuum-feed petcock for a gravity-feed model. The gravity type will just have On, Off, and Reserve settings; On will be functionally equivalent to using Prime on a vacuum model, in that it will simply allow gas to flow.

A petcock swap will be MUCH easier than fiddling about trying to get the vacuum port installed, working, and not leaking.
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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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 12:36 #852788

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Yeah I'm going to go this route.  Much easier.  The pain in the d*ck part now is find a reducing tee from 1/4" fuel hose from petcock to two 3/16" outputs to head to carbs.  The kit only came with a 3 way 3/16" tee which is just going to let fuel leak like crazy.  I couldn't find a hose clamp small enough to attach the 1/4" ID hose to the tee.

edit: had wrong dimension in there

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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 15:52 #852799

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Whats the whole purpose of having a vacuum petcock?  This is my first bike that's had that.

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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 15:58 #852800

  • Mikaw
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1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 16:29 #852804

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I don't like that solution because you are taking your fuel line and reducing the flow by a little over 55% suddenly, then you are splitting it.  Whereas a proper 1/4" into two 3/16" reduction tee provides the room to reduce and split at once preventing any irregular flow.  Until I find a proper 1/4" into two 3/16" reduction tee I've manufactured this solution (attached) which is bulky, but works.  And I should be able to hide it somewhere.  It's just weird because "doing my vetting" I've found plenty of tees that take one 3/16" input and split it to two 1/4" outputs.  What scenario would that be necessary?  I do not know.  Seems the opposite would have more usage.

 
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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 16:38 #852806

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Do your vetting, was meant to say. I found parts but not going to just blindly tell you to buy from an unknown source. You vet the source. Good luck
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 18:10 #852813

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Those are well known sources, but thanks for your input.

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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 18:42 #852821

  • Nerdy
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Yeah I'm going to go this route.  Much easier.  The pain in the d*ck part now is find a reducing tee from 1/4" fuel hose from petcock to two 3/16" outputs to head to carbs.  The kit only came with a 3 way 3/16" tee which is just going to let fuel leak like crazy.  I couldn't find a hose clamp small enough to attach the 1/4" ID hose to the tee.

edit: had wrong dimension in there
 


I haven't tried this, but I wonder if you could build up the 3/16" using multiple layers of shrink tubing. Shrink one layer on a time until you get close to 1/4", then use a high-quality wormgear hose clamp.

Also saw that you have a solution lined up that should work just as well (or better).
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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Dual VM30s on a KZ440. Anyone done it yet? 29 Jul 2021 19:23 #852825

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Yeah I'm going to go this route.  Much easier.  The pain in the d*ck part now is find a reducing tee from 1/4" fuel hose from petcock to two 3/16" outputs to head to carbs.  The kit only came with a 3 way 3/16" tee which is just going to let fuel leak like crazy.  I couldn't find a hose clamp small enough to attach the 1/4" ID hose to the tee.

edit: had wrong dimension in there

 


I haven't tried this, but I wonder if you could build up the 3/16" using multiple layers of shrink tubing. Shrink one layer on a time until you get close to 1/4", then use a high-quality wormgear hose clamp.

Also saw that you have a solution lined up that should work just as well (or better).


 

Yeah that sounds like it would def work.  But it is most definitely not a long term solution.  I've figured there are two solutions to my problem (excluding the proper one).  The option that I did not choose to go with, which is a 1/4" tee all three ways, then run 1/4" line to carbs where I have two brass barbed reducers to 3/16" - and then my monstrosity of a brass tee.  It's been quite some time since I've taken Fluid Dynamics in college, but that's my thought on the subject.

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Dual VM30s on a KZ440. Anyone done it yet? 30 Jul 2021 06:20 #852837

  • TexasKZ
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Whats the whole purpose of having a vacuum petcock?  This is my first bike that's had that.

It is a convenience and safety device. It automatically shuts off the flow of fuel when you turn the engine off. 
When the lever is in the RUN or PRI (may be ON instead of RUN), fuel will not flow until the engine starts and vacuum from one of the carburetors opens the valve via an internal diaphragm and o-ring. When the engine stops, a small spring closes the valve, thus preventing any more fuel flow. If this flow is not cut off and one or more of the carburetor float valves is leaking for any reason, the engine and crankcase can fill up with fuel, and you will have a right good mess to deal with before the engine can safely be started again. There may also be a large puddle of fuel on and under the bike, presenting quite a fire hazard.
in case you are wondering, the third position, which is marked PRI, is only for priming the carburetors after they have been disassembled or drained for any reason. It should take no more than thirty seconds or so to fill them from empty, then the valve should be turned back to RUN or RES, depending on how much fuel is in he tank.
Ok, as long as I am on a roll, the RES (reserve) setting is to access the last bit of fuel in the tank while you frantically search for a refill station. The valve should normally be in the RUN (ON) position. When you notice a sudden drop in power or a bit of stuttering, turn the lever to RES and drive to the nearest fuel station.
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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Dual VM30s on a KZ440. Anyone done it yet? 30 Jul 2021 14:18 #852867

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You can run it on prime until you know you have everything working.





 

This is essentially like "ON" on a normal petcock?  I've almost got everything back together and would love to ride tomorrow if possible

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