baz
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- May 26, 2010
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having had a pair of worn out 32 mm concentrics then brand new 32mm concentrics then a single 32mm concentric then a 32mm cv mikuni then a 34mm vm mikuni then a 36mm vm mikuni i now have a tm 40 mikuni all i can say is the way the bike performs is way better in real terms for a road bike ie it will pull well into the red if i want it too,it has better mpg it has better bottom end power ,way better mid range and the top end feels the same as the twin concentrics ,also going from a 36mm vm to a 40 mm tm is like comparing apples and oranges ,i have always thought that maybe the flat slide mixes the fuel up a bit better but i'm no expert on this cheers bazdennisgb said:worntorn said:Now that Amal Premieres with anodized slide and other improvements are available for relatively little $, I don't understand why anyone would spend money going the single Carb route and live with diminshed engine performance. If you happen to have the single Carb items on hand already, then it's a different scenario. However if you need to buy the manifold and Carb vs already have the manifolds for twin carbs, I think you could have new twin Premieres on there for the same cost or very little more. It is either free or very cheap horsepower.
Glen
My bike came with a single Mikuni VM. The carb was junk so I switched to a Mikuni TM flat slide because there is improved performance over a round slide carburetor.
From the Mikuni web site:
"Mikuni's TM Series flat slide carburetors provide a significant performance improvement over older round slide carburetors. Air flows faster and smoother through the TM Series venturi and jet blocks due to the flat slide design which helps create a smooth bore effect. The high velocity air flow means stronger vacuum at the needle jet for more precise metering, better throttle response."
This is true of all Flat Slide carburetors and from my experience the response improvement is obvious.
While these changes are not keeping with the perfect original restoration, the technical improvements in carburetion since the Amal design are worth it to me personally.
It's not totally about keeping it simple or cost.