Mikuni Choke Position

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Big Red

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Jul 23, 2022
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Hello all, I have a little problem with my Commando (haha). The choke won’t stay in the fully raised position, and slips or relaxes to a position about half way on. It is sometimes hard starting, catching but not staying lit. I had my son hold the choke in the fully raised position while I kicked and it fired right up. Is there a fix for this, or can it be adjusted? It has a lever not a knob. Thanks in advance.
 
If it's a VM, the diagram shows what looks to be a detent system (circled)
Maybe it is removable and can be adjusted to give stronger detent?
Could even be that it has fallen out of your carb?

Failing that - take your son with you wherever you go! ;)
Cheers
Screen Shot 2022-12-29 at 3.33.12 pm.png
 
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so, @Big Red , base on Les' advice above - have a hard look at parts 14 & 15 in the picture.
That "V" and the spring arm below it, that it acts on, are why your choke is dropping.
Maybe buy a new one of each?
 
When you go to the cable operated chokes on the Mik I seem to remember that the choke lever will operate "backwards" from the way it is with the Amals. Not a problem really.
Russ
 
Craig said:
I tried both setups , decided lever on carb best for me , any cable saving on bars is good ….
Click to expand...
I don't know about a commando setup but with a t140e the MK2 amals have the same enrichment plungers
And when converted to cable it enables you to give it full choke to start and then back the lever off until it's just above normal idle so you can ride off
 
baz said:
I don't know about a commando setup but with a t140e the MK2 amals have the same enrichment plungers
And when converted to cable it enables you to give it full choke to start and then back the lever off until it's just above normal idle so you can ride off
Click to expand...
That is the only slight niggle I have with the Mikuni, the lever is so far in tucked away under the fuel tank that I can’t reach it unless I’m knelt beside it to find it. A cable or even a longer lever maybe a good thing.
 
baz said:
I don't know about a commando setup but with a t140e the MK2 amals have the same enrichment plungers
And when converted to cable it enables you to give it full choke to start and then back the lever off until it's just above normal idle so you can ride off
Click to expand...
I have converted a few sets of MkIIs to cable operation for the Commando using the stock bar lever ...worked perfectly and made for reliable starting
 
Take the cold start off and slightly bend Item 15 Its in the form of a flat spring so giving it a bit more hold to keep the plunger up
 
Flatspot said:
That is the only slight niggle I have with the Mikuni, the lever is so far in tucked away under the fuel tank that I can’t reach it unless I’m knelt beside it to find it. A cable or even a longer lever maybe a good thing.
Click to expand...
It's even worse trying to get to the right carb with a twin Mikuni setup, unless you use the link bar set up from a Suzuki (say GT500).

Mikuni sell the parts you need to fit cable operation at the carb. MK- 412 from Motocarb, maybe other numbers elsewhere. 1 kit per carb.

Single Mikuni should work fine with an Amal style handlebar lever and a single carb choke cable.

(I have these parts on a twin Mikuni set up and have used Yamaha TR/TZ cables and one of Don Pender's thumb chokes, but you need to keep your thumb on it until the engine is warm enough to let the choke off)
 
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baz said:
I don't know about a commando setup but with a t140e the MK2 amals have the same enrichment plungers
And when converted to cable it enables you to give it full choke to start and then back the lever off until it's just above normal idle so you can ride off
Click to expand...
I understand that works, and I understand it is probably useful, as long as you don't leave it there too long, but it isn't really what Mikuni (or Amal) intended!

Using the fuel enrichment lever raises the rubber seal used in the mechanism off of the fuel way orifice/seat.

There are only two intended positions, on the orifice seat and off the seat, no enrichment fuel flow or enrichment fuel flow. Start up, warm up, close orifice!, ride away. So no riding with fuel enrichment on.

The 'choke' is either held with the orifice closed for normal running, by the internal coil spring, or held off of the orifice by the external detent spring (part 15 referenced earlier) for starting.
 
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