MIKUNI

[gunning]

Has anyone fitted a MUKINI carb to there arrow/leader ?,if so do you know what jets to use and needle position,they tell me they are very good on two strokes and helps with hot starting etc thanxs

[dave.owen]

Any new carb will help the starting and running of a well set up engine,Mukini have a reputation for less wear with age

Dave

[gunning]

Thanks Dave i don't have a lot of knowledge setting up a carb,any tips would be very welcome
Thankyou

[dave.owen]

Generally you should use the same jetting as the Amal,


Dave

[robin.parker]

Didn't a firm who supplied Mikuni advertise their willingness to set up and jet a carb suitable for whatever machine the purchaser nominated? If that still applies, your problem might be simply solved. (depends how much simple solution might cost) I think Allen's are the UK distributors.
Good luck,

[brenton.roy]

Hi, how did you manage to join without a name?
You'll get a much better response if you can sort this out.
Otherwise, welcome to our forum.

I'm not the current owner of a Leader or Arrow, so this is general stuff. Won't you lose the nifty choke?
If you are buying secondhand, try to get a carb from a small two stroke 125 to 250cc. From memory, the carb you need was used a lot on trail bikes in the 70's.
From the manual,
Choke 7/8 (22/23mm)
140 main or 170, without spray tube
30 pilot
105 needle
slide 3 1/2
A mikuni will probably be a little more efficient, and may end up jetted slightly leaner than these (monobloc) settings, but running lean is a good way to damage pistons.
So, I would start with the above settings (170 main) and move to leaner settings in small increments. Needle in the middle slot.
Running lean will show up as stuttering / misfiring in a rev range. Rich (lots) will show black smoke and poor acceleration. You'll smell it. Adrie can tell this by ear, but the rest of us are mere mortals! ...and have to work through this manually.
Reducing the main jet size will have the biggest overall effect.
Get it idling properly with the idle mixture screw (not the one with the spring). Assuming it revs ok in the shed, go for a ride. You'll need one or two main jets plus and minus from 170 (likely minus) and the tools to change them.
You'll need the motor under load, so you do have to ride it to sort it. Consider the carby as three parts, and use throttle accordingly. Idle, Mid - needle jet, main.
If it isn't right in one of these thirds, the corresponding jet will be need to be altered. i.e. If it idles OK, goes flat out OK and misfires under mid acceleration, raise the needle.
There are plug colour charts available on the internet. These will give you an idea of where you are at. To be of any use, you have to ride the bike for a while at the rev range you are interested in and cut the engine. Letting it go back to idle may give you a false result. This is called a "plug chop". Unless you do this properly, it's a waste of time.
Be aware of the possibility of fire. You may be dripping fuel over the motor when you change jets.
Brenton

[gunning]

Thanks for the helpful information ,iv'e bought a new mikuni from Motocarb ,main jet 140.pilot 30,needle jet 182 n-8,jet needle 5DP7,throttle valve 2.0,and main air jet 2.0.
Also supplied with,tunning jets,main 135,145 150
pilot 27.5,32.5
Very helpful folks they set it up best guess.

[gunning]

by the way brenton,my name is gunning,thanks for the help.

[Roger James]

Further to previous messages.
I have a friend who runs his Leader with a 26mm Mikuni carb fitted and after some trial runs settled on a 140 main jet.
Another friend who runs an Arrow fitted with a Mikuni carb settled on using a 150 main jet and 1.5 slide.

No doubt these minor changes have been made to suit the running of their engines so a bit of trial running and testing as with most carbs might be needed to find the best set up for that particular engine its fitted to.

Happy Spannering

Jess

[bh.sprint]

Re the hot starting. My Arrow with a Mikuni carb starts easily when hot. The Leader with a 376 carb, about 10 years old, usually starts well but after a fast run it can be slow to start . A fast kick on the kick start usually gets it going with the help of the electronic ignition.

bh.sprint