Eagler's Nest
Engines => 2 Cylinder => 1/2 vw => Topic started by: dz1sfb on February 23, 2016, 04:58:00 AM
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From looking through the forum there seems to be a leaning to dual Mikunis over the single Zenith. Are my observations correct?
If so, what would be the recommended size Mikuni and or model number? Also what about a pumper bowl vs. gravity bowl?
I am building/buying a 37HP 1/2VW. Is this suitable Mikuni assembly at Ebay (http://www.ebay.com/itm/Carb-Mikuni-28mm-Carburetor-Air-Filter-Manifold-Intake-Pipe-Gasket-Pit-Dirt-Bike-/161985050596?hash=item25b70fb7e4:g:HpIAAOSwDuJWvO7p&vxp=mtr)
Ken
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Ken,
Miks are gonna tune much more finely, and have better throttle response.
Try this search...
(https://groups.yahoo.com/neo/groups/EaglersNests/search/messages?query=Mikuni or Zenith)
https://groups.yahoo.com/neo/groups/EaglersNests/search/messages?query=Mikuni%20or%20Zenith (https://groups.yahoo.com/neo/groups/EaglersNests/search/messages?query=Mikuni or Zenith)
And this post:
https://groups.yahoo.com/neo/groups/EaglersNests/conversations/topics/29112 (https://groups.yahoo.com/neo/groups/EaglersNests/conversations/topics/29112)
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Dan,
Thank you for the direction. The Mikuni's seem to be the way to go I'm just looking to find out now what diameter bore I need to use for the 37 hp engine.
Ken
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Fw: [DEr's read Msg15985] Re: Mikuni Carbs
Steve Kiblinger:
Jun 26, 2013
Occasionally VM-28 roundslides show up on EBay as NOS (New Old Stock)...
There is a high time LE that has used TM-28 Flat Slides - the carb float valves had to be replaced at about 100 hours, otherwise all Ok... These carbs are available new in many places - just more expensive... Mikuni brought these carbs to provide better mid range response - doesn't matter much to us...
If you look at the Mikuni tuning manual there is a graph in there that calls out HP as PS (German for HP) as the carb sizing scale and can conclude that 24 - 26mm carbs are Ok for our purposes ( I don't know of anyone that has settled on this size and therefore am hopeful there will be feedback)... The VM26-606 is Japanese made and shows up in several vendor catalogs...
The bigger carbs are considerably heavier and will be at full power with the slide half open on a single cylinder - the upper half of the slide becomes a (dead zone)... The way the Mikuni is designed this makes tuning a daunting task because the carb ceases to function as described in the tuning manual due to the slide position determining which jets are in the driver seat - the Tuning Manual has a big diagram near the back that spells this out graphically...
There are a lot of zinc body carbs on the used market - you don't want them because of the weight...
Here's a link to the Mikuni Tuning Manual pdf:
http://www.mikuni.com/pdf/vmmanual.pdf
Tune for 1300 - 1400 F EGT static RPM...
Power will be low below 1300 F...
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Great information Dan!
Thank you again,
Ken
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I am using 28mm on my Eagle...guestimating 37-38 HP works fine! Leonard had 30mm and they work great also....
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The BetterHalf Plans states "I use 32mm size carburetors with 40mm spigots. The carbs are mounted on the heads with a rubber flange -- just like motorcycles have used for many years."