mikuni twinport specs

[stump magnet]

can anyone tell me the size and type of mikuni to run on a 250 twinport plus the jetting specs please cheers.

[090]

From memory you are in the U.K? Are you allowed to run any size carby?

[tony27]

Have a look here as a starting point, be interesting to hear how different Brad's settings are

http://www.braigasen.com/Mikuni_jetting_chart_two_stroke.htm

[stump magnet]

hi that chart is very usefull thanks wot size do you guys think is best standard is 30mm have been using a 30mm mk1 amal and runs great but sod to start and can nip up on the over run (ur club is looking at getting rid of its mikuni rule for this year hence the question) the inlet is around 30mm dia anyway so what advantage would the 34mm carb have over the 32mm?

[090]

I currently am running a 34 which seems to go okay but with the characteristics of the motor i.e. long intake, lower revving and port timing, I was advised to run a 28 or 30mm instead. The guy that advised me actually worked it out to a formula. I will be running a 28 as the rules are a bit fuzzy regarding what size you can run here in Oz and the 28 is widely accepted.

[GMC]

I will be running a 28 as the rules are a bit fuzzy regarding what size you can run here in Oz and the 28 is widely accepted.

In what way are the rules fuzzy?
You need to run a period style carby (round) but I have never seen anything regarding a restriction on the size of carby your allowed to run.

[090]

I will be running a 28 as the rules are a bit fuzzy regarding what size you can run here in Oz and the 28 is widely accepted.

In what way are the rules fuzzy?
You need to run a period style carby (round) but I have never seen anything regarding a restriction on the size of carby your allowed to run.

There is another rule in the main section that says what was available in the period and 34's weren't available. In the carby section (which is more specific) it's like you said. So depending on which rule you want to look at, you come to a different conclusion. Boag was chipped for having a bigger carby (at a different nat's) and he pointed it out to me, to which he said he wouldn't protest but! So to play safe and to probably make it run at its optimum, I will be fitting a 28.

[GMC]

There is another rule in the main section that says what was available in the period and 34's weren't available.

Really??
I find it hard to beleive that you couldn't find a 34mm carby in 64??

[090]

Apparently not a Mikuni.

[stump magnet]

we can run any size here in the uk so i think i will go for the vm32 as the chart shows a jetting spec for it unless someone has a spec for the vm30 which is closer to stock size any ideas? lets hope my club do away with the no mikuni rule its the only club in the uk that still bans them!

[Bamford#69]

Hi,
The GCR's for Classics , rule 18.6.0.4
Carburettors;
a) "Any round slide carburettor of a type available pre -75 may be used
    except the Pre-60 class where a Mk 1 Amal Concentric or period carburettor may be used"

 a pre 65 bike can use any size, make, model, round slide carb  that was available pre 75

cheers