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[kurt]

Here is a part of the figure from the bell book I'm refering to. I see I said 36mm in the previous post. It should have been 35.

Table 4.23 Recommended slide-type Mikuni carburettor sizes

Cyl. Displac. (cc) Recommended carb. size (mm)

125 - 150 24
175 - 200 28
225 - 250 32
275 - 300 34
325 - 350 34
375 - 425 36
500 - 650 35

(source: Four-Stroke Performance Tuning, Fourth edition, A. Graham Bell, page 158)

[kurt]

Sorry the last post didn't preserve the columns very well. If you look carefully, you will see a hiphenated number. that is the displacement range. Then a space, then the carburettor size in millimeters. The 125 - 150 is 24 mm and 175 - 200 is 28 mm.

[PeteF]

I would think 35mm is far too big unless you are tuning to the absolute maximum. That's half as much again in surface area.

[simon]

Yes there is a point where there simply isn't sufficient gas flow to operate the venturi. I thought my 1 1/8 monobloc (28.6 mm) on my 350 was pushing the line but it seems after endless fiddling to be fine. 36 mm on a 500cc machine should be ok as they put them on the Ducati 864cc machines which are basically two harnessed singles of 432cc each although the standard carbs were 32mm.