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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 12:58 #852982

  • loudhvx
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One of the carbs will have an idle screw on the inside.  To make it easier to turn, go to a decent home center and buy a shaft-collar.  It's a metal doughnut that goes over the head of the idle screw, and has a tiny setscrew to lock it in place.  Measure the outside diameter of the idle screw head so you know what size collar to get.  This gives you a nice big knob to turn instead of the little screw.  Paint half of the knob so you can keep track of rotation to match both sides.  With the carbs off, and slides free to close all the way, turn the screws so both slides are just starting to move.  Then paint a mark on the outer idle screw that matches the paint on the inner idle knob.  Now when you turn one you can match the other one the same amount.

And if the knob is not enough to adjust with one finger, you can use a longer locking screw.  The extra length will act like a lever and will allow you to make adjustments by poking a finger in from above or below.

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 13:11 #852983

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One of the carbs will have an idle screw on the inside.  To make it easier to turn, go to a decent home center and buy a shaft-collar.  It's a metal doughnut that goes over the head of the idle screw, and has a tiny setscrew to lock it in place.  Measure the outside diameter of the idle screw head so you know what size collar to get.  This gives you a nice big knob to turn instead of the little screw.  Paint half of the knob so you can keep track of rotation to match both sides.  With the carbs off, and slides free to close all the way, turn the screws so both slides are just starting to move.  Then paint a mark on the outer idle screw that matches the paint on the inner idle knob.  Now when you turn one you can match the other one the same amount.

And if the knob is not enough to adjust with one finger, you can use a longer locking screw.  The extra length will act like a lever and will allow you to make adjustments by poking a finger in from above or below.


 

Excellent idea, thanks so much

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 13:18 #852985

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Also, I wouldn't be so hard on them.  Making a kit like that to cover so many different bikes which may or may not have been modified over the decades would be near impossible to make without flaws.  We went without a kit, but there were plenty of headaches.  Just simply finding any kind of decent throttle cable to fit at all took us days, and when we found it, we still had to do a lot of modifying and shortening.  Then there is the carb holders.  We used the original Kz400 holders, but they are far from ideal.  They barely grab, but luckily they seal.  It would have been nicer to have some new ones in a kit that just bolted onto the engine.  The Kz400 has offset bolt holes on the carb holders so most generic holders don't work.  You would have to go through dozens, one at a time to find one with the correct offset.  That could take weeks.  None of this addresses the biggest hurdle in such a project...the jetting.  To have a jetting formula all worked out for you is worth the price of the kit alone.  Jetting from scratch can take months of experimenting to get 100% ironed out.  If you've never jetted a bike from scratch, you don't know what patience is.  You have to wait for different weather conditions to see if a previous combination of jetting will work under different conditions, and if it doesn't you are starting over.

Oh, and if you really are going to be riding it, remember, when you are on prime, there is no reserve.  When you run out of gas, that's it.  I highly recommend topping it off every 50 miles or every 3/4 hour, which ever comes first... at least until you are more familiar with the fuel usage of the bike.  Some 400/440 tanks don't hold much.  If you open the cap, and slosh the bike around, and don't see fuel easily, buy some.  Don't rely on sound to tell you how much you have.

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 13:48 #852986

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Also, I wouldn't be so hard on them.  Making a kit like that to cover so many different bikes which may or may not have been modified over the decades would be near impossible to make without flaws.  We went without a kit, but there were plenty of headaches.  Just simply finding any kind of decent throttle cable to fit at all took us days, and when we found it, we still had to do a lot of modifying and shortening.  Then there is the carb holders.  We used the original Kz400 holders, but they are far from ideal.  They barely grab, but luckily they seal.  It would have been nicer to have some new ones in a kit that just bolted onto the engine.  The Kz400 has offset bolt holes on the carb holders so most generic holders don't work.  You would have to go through dozens, one at a time to find one with the correct offset.  That could take weeks.  None of this addresses the biggest hurdle in such a project...the jetting.  To have a jetting formula all worked out for you is worth the price of the kit alone.  Jetting from scratch can take months of experimenting to get 100% ironed out.  If you've never jetted a bike from scratch, you don't know what patience is.  You have to wait for different weather conditions to see if a previous combination of jetting will work under different conditions, and if it doesn't you are starting over.

Oh, and if you really are going to be riding it, remember, when you are on prime, there is no reserve.  When you run out of gas, that's it.  I highly recommend topping it off every 50 miles or every 3/4 hour, which ever comes first... at least until you are more familiar with the fuel usage of the bike.  Some 400/440 tanks don't hold much.  If you open the cap, and slosh the bike around, and don't see fuel easily, buy some.  Don't rely on sound to tell you how much you have.
 

Carb boots can be found on Amazon.  I have an extra set if someone wants them.  I purchased them before buying this kit because mine were badly cracked.  And time will tell if jetting is correct, I have little faith (but lots of hope) because of the set backs that should have been foreseen on a kit that could be put together on a small fraction of the cost.  It should have included something to deal with the vacuum petcock - either a new one, or a drill/tap/port.  They def should have foreseen the difference in fuel tube sizing, and dealt with it in some fashion.  And the damn throttle cable is too long.  And also the 15-18 feet of tubing I had to purchase so all the overflow hoses of the carb could reach an appropriate area to drip.  And then (geez this goes on), the engine vent tube that went into airbox.  I still need to figure out what I'm going to do about that now.  Maybe another long hose that drains where my carbs do?  Motion Pro makes custom cables, they should have had a custom cable for this custom kit.  I've got it in riding condition now, so I'm going to go for a ride.  Hopefully I don't break down.  I will be buying a new custom cable, because it looks stupid with a giant loop out the front of my bike.  I probably wouldn't be so hard on them if they hadn't told me the kit was a giant "Big Red Easy Button" and that's the reason for the high price before the purchase - but they did.  And it most certainly wasn't.

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 14:24 #852993

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Well, I still don't think the kit is all that bad considering you get actual Mikuni carbs and the problems with it don't amount to much as long as the jetting lets the bike run.  The Chinese knockoffs would not let the bike run at all without a complete rejet.  We did not find any online sources on how to rejet them, and all we really came across back then were warnings to not get those carbs.  It took a while to get the jetting close enough to ride, especially since replacement jets are not available specifically for those carbs.  After installing them and fooling around with fuel lines, you are already at the point of riding.  With the Chinese carbs you could be months away from that point.  BTW Motion Pro cables are not exactly the highest quality.  And a couple years ago their lead-time on custom cables was measured in months.  A factory OEM manufactured cable is always better if you can find one.  

I hope the ride goes well!

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 15:34 #852998

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One could assume that the longer cable is intended for a 440 LTD or something, with higher/pulled-back bars...and the petcock, who knows, maybe the bike they used for product development had a non-vacuum type. Assuming your bolt spacing is 44mm you can get something usable for like $15. It isn't that serious. 
1982 KZ750 Spectre - Dyna 2.2 coils + 8mm wires, WG coil relay, SH775 R/R, Mikuni BS34s - 40P/122.5M, Progressive fork springs/KZ900 rear shocks, Vance & Hines 4-1

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 17:57 #853008

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One could assume that the longer cable is intended for a 440 LTD or something, with higher/pulled-back bars...and the petcock, who knows, maybe the bike they used for product development had a non-vacuum type. Assuming your bolt spacing is 44mm you can get something usable for like $15. It isn't that serious. 
 

I've got the A model LTD with the tall bars.

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Dual VM30s on a KZ440. Anyone done it yet? 01 Aug 2021 18:03 #853009

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Anyway I took it for a test run, and I'm quite happy.  There is a noticeable power difference than from before.  And it even sounds louder.  I can feel where the cable seems to pull out of sync sometimes which sucks - not sure what to do about that.  Also there is probably a 15degree rotation of the throttle that is completely free.  I've played with the screw tops on the carb, and the long nut (about an inch long) near the throttle and havent' seen any change.  What am I missing here?

I've owned modern dirt bikes with carbs, and modern bikes with FI, but never had to check sparkplug conditions.  I've been lucky where everything has always been dialed in.   At what point should I take a look at my spark plugs to determine how my machine is running?  My bike also has a tick, of which I'm going to start a new thread for in the engine subforum.  I'm hoping its something stupid because the bike only has 4xxx miles on it.

Sorry for being a such a newb with this stuff.  I'm super appreciative of all the support yall have given me and am def willing to provide some moneys for your beer funds.

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Dual VM30s on a KZ440. Anyone done it yet? 02 Aug 2021 15:41 #853049

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Well, I still don't think the kit is all that bad considering you get actual Mikuni carbs and the problems with it don't amount to much as long as the jetting lets the bike run.  The Chinese knockoffs would not let the bike run at all without a complete rejet.  We did not find any online sources on how to rejet them, and all we really came across back then were warnings to not get those carbs.  It took a while to get the jetting close enough to ride, especially since replacement jets are not available specifically for those carbs.  After installing them and fooling around with fuel lines, you are already at the point of riding.  With the Chinese carbs you could be months away from that point.  BTW Motion Pro cables are not exactly the highest quality.  And a couple years ago their lead-time on custom cables was measured in months.  A factory OEM manufactured cable is always better if you can find one.  

I hope the ride goes well!


 

Who makes better custom cables.  I took my bike for about a 40 miles drive around town today and noticed that the carbs seem to get hung up a little around the 3k range at idle and just driving with my hand off the throttle while in various gears.  It's typically corrected by blipping the throttle a little, but I think it's due to the cable.

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Dual VM30s on a KZ440. Anyone done it yet? 02 Aug 2021 15:56 #853050

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I re-cut OEM cables.  Unfortunately, I haven't found a decent source for custom cables.  

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