Just noticed this boost bottle setup on ebay. It says it fits vm28-30.
Does this mean I can use my stock 28's now and still use these if I upgraded to 30's later on. I dont have a 30 to look at and wanted to verify this info on ebay.
https://www.ebay.com/itm/Yamaha-RZ-350-YFZ350-RD350-RD400-28-30mm-Manifolds-Aluminum-Boost-Bottle-NEW/172779478216?hash=item283a759cc8:g:-bIAAOSwc1FXbARc
You are better off using either the balance tube from the RZ or one designed for the RD350.
I think Superfund makes them, but I may be wrong...
John @ Economy Cycle can set you up with the first..
This doesn't make sense.
A VM 26 and 28 has a smaller spigot than a vm30
Quote from: suey1958 on December 29, 2019, 09:39:46 AM
Just noticed this boost bottle setup on ebay. It says it fits vm28-30.
Does this mean I can use my stock 28's now and still use these if I upgraded to 30's later on. I dont have a 30 to look at and wanted to verify this info on ebay.
https://www.ebay.com/itm/Yamaha-RZ-350-YFZ350-RD350-RD400-28-30mm-Manifolds-Aluminum-Boost-Bottle-NEW/172779478216?hash=item283a759cc8:g:-bIAAOSwc1FXbARc
It is a mis-leading ad, It does fit all RD's and RZ/Banshee 35mm spigot manifolds carbs.
The only 30mm carbs the UPP or RZ/Banshee 35mm spigot manifold will work on are what they call small body oem carbs that came like from snowmobiles.
Now I can machine the std VM 30's to fit the 35mm spigot manifolds all of the 30-34mm sized carbs come with 40mm spigot size.
That Banshee boost bottle is junk on RD's.... All wrong dimensions for the air-cooled engines.
Go with just the stock kit from John or you can email me for a kit with my TSR/Barlow designed boost bottle as shown in all my builds.
Like Economans RD350, Nicks RD400 build, Daves racebike build, Steve's blue puff and hundreds of other's over the last 16 years since Harry and I worked on a dyno for 2 days developing a boost bottle for the air-cooled engines using Tom Turner's boost bottle software.
(https://photos.imageevent.com/supertune/carbstuff/websize/Boost%20Capture.JPG)
(https://photos.imageevent.com/supertune/carbstuff/websize/20130425_111631%20_Medium_.jpg)
(http://www.2strokeworld.net/forum/index.php?action=dlattach;topic=1230.0;attach=3330;image)
(https://photos.imageevent.com/supertune/nicks76rd400/large/20190806_155647.jpg)
(https://photos.imageevent.com/supertune/homesteadfmrraraces121519/large/20191214_102305.jpg)
(https://photos.imageevent.com/supertune/homesteadfmrraraces121519/large/20191214_145107.jpg)
(https://photos.imageevent.com/supertune/homesteadfmrraraces121519/large/20191214_155951.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/Capture.JPG)
Machining a VM30mm carb from 40mm spigot to the 35mm spigot size to fit stock manifolds and the banshee manifolds.
(https://photos.imageevent.com/supertune/carbstuff/websize/20130202_135759.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20130202_140029.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20130202_133222.jpg)
(https://photos.imageevent.com/supertune/carbstuff/websize/20130202_135120.jpg)
Chuck
Hey Chuck,
How does it affect the tuning running the uni pod straight off the carb vs a spacer tube like on the white racebike?
Hardy
Thanks Chuck,... You always go the extra mile with clarification that any of us can understand. That is MUCH appreciated ! :righteous:
Quote from: Hardy on December 29, 2019, 10:12:07 PM
Hey Chuck,
How does it affect the tuning running the uni pod straight off the carb vs a spacer tube like on the white racebike?
Hardy
I like to do that when I can on RD350's with the shorter 54mm stroke, the intake pluses are closer together than the 400's with 62mm stroke and with stock small 28's where the air speed is faster, it helps with smoother jetting rolling on the throttle through the turns.
I always like finding the littles that then add up to a better package in the end.
Chuck
Quote from: SUPERTUNE on December 29, 2019, 11:59:52 AM
The only 30mm carbs the UPP or RZ/Banshee 35mm spigot manifold will work on are what they call small body oem carbs that came like from snowmobiles.
Chuck, wouldn't the small body VM30s flow better than the regular/ large body VM30s, due to a smaller diameter slide (less cross section area change)? Basically being a bit like the old VM29 Smoothbore carbs popular with the Z1 and CB750 crowd back in the day.
Also, some snowmobile Mikuni VMs are much lighter than other VM carbs, made from some aluminium or magnesium alloy, vs the more common zinc alloy. Weight savings is always a good thing, isn't it?
in my opinion , moving from small body to large body (which i did with 34's), the large body works better. it basically has a 'built in' velocity stack and just seem to flow better, especially down low.
Quote from: m in sc on December 31, 2019, 07:51:18 PM
in my opinion , moving from small body to large body (which i did with 34's), the large body works better. it basically has a 'built in' velocity stack and just seem to flow better, especially down low.
34 mm would be a different kettle 'o fish altogether...I was talking specifically about 30 mm small vs large body, as the OP's question was about manifolds for 28 and 30 mm carbs. I believe A.Graham Bell's book touches on this subject, where he actually recommends boring out carbs instead of buying the next size up, when the next size also means next body size, with a significantly larger slide diameter. Large body VM30 has the same slide as your VM34, so the cross section gets significantly wider in the slide area, which cannot be ideal. On the other hand, the VM34 should be the best one in this aspect since it is the largest carb in its size group (30-34)
I see what you're saying..I think you might be right regarding the 30s. I've run small body h2 vm30s on an rd, was good, can't say as I've played with the larger body 30s.
Quote from: Hardy on December 29, 2019, 10:12:07 PM
Hey Chuck,
How does it affect the tuning running the uni pod straight off the carb vs a spacer tube like on the white racebike?
Hardy
I don't know if you noticed, but it looks like that bike is a 350 engine in a 400 frame. And the spacer tube/velocity stack is pretty much straight. That setup would not fit in a 350 frame. Many, myself included, use the stock 350 "Y-boot" with a single large UNI or KN filter instead. Like this: https://www.economycycle.com/shop/yamaha-rz-350/fuel-and-airintake-yamaha-rz-350/air-filters/economy-y-boot-filter-kit-for-yamaha-rd250350400-r5-ds7-rz350/
look at the brake thread, runners on large vms on my white bike in a 350 frame. Just, curved a bit. :patriot:
Quote from: Dvsrd on January 01, 2020, 04:38:09 PM
I don't know if you noticed, but it looks like that bike is a 350 engine in a 400 frame. And the spacer tube/velocity stack is pretty much straight. That setup would not fit in a 350 frame. Many, myself included, use the stock 350 "Y-boot" with a single large UNI or KN filter instead. Like this: https://www.economycycle.com/shop/yamaha-rz-350/fuel-and-airintake-yamaha-rz-350/air-filters/economy-y-boot-filter-kit-for-yamaha-rd250350400-r5-ds7-rz350/
Very good eye...
Yes, it is a 400 chassis for the longer wheelbase. and was a freebie for the racebike build.