Hard to start mikuni 22
- Thread starter MiniBike Paul
- Start date
- Tags hard mikuni start
125ccCrazy and 66 Vette - you guys are absolutely correct.
I spent 1/2 hour on ther phone today with Mikuni's main carb guy. The pilot jet is very involved with starting; going bigger on an engine that will not start is the ticket.
Also, as you guys may know, screwing in the idle air screw (the vertical one just in front of the bowl) limits air so richens the mixture, also helpfut for hard starting, although he cautioned about leaving it out at least a turn.
I ordered 17.5's and a 20 (mine has a 15.) and will see if it fixes the hard starting
I spent 1/2 hour on ther phone today with Mikuni's main carb guy. The pilot jet is very involved with starting; going bigger on an engine that will not start is the ticket.
Also, as you guys may know, screwing in the idle air screw (the vertical one just in front of the bowl) limits air so richens the mixture, also helpfut for hard starting, although he cautioned about leaving it out at least a turn.
I ordered 17.5's and a 20 (mine has a 15.) and will see if it fixes the hard starting
On the 22mm Mikuni that screw is not an air screw. Turning the screw out will richen the mixture not lean it out.
With Mikunis there are two different style carbs in terms of the idle screw. If the screw is placed on the outlet side of the carb (towards the engine) such as the 22mm, it controls fuel. So open = more fuel.
If the screw is placed on the air filter side then is is an air screw, so open = leaner.
With Mikunis there are two different style carbs in terms of the idle screw. If the screw is placed on the outlet side of the carb (towards the engine) such as the 22mm, it controls fuel. So open = more fuel.
If the screw is placed on the air filter side then is is an air screw, so open = leaner.
no thats not correct
Mikuni carburetor operation and tuning
Mikuni carburetor operation and tuning
Yes,but a TRUE Mikuni Vm series has A/f on the side,the AGK/NR kind of mikuni has the A/f under the carb bowl it will be on the intake side. The Idle adjustment will be on the right side of the carb. Take a look,here is the one 95% of I seen ran on this site.
Affordable Go Karts - Carburetor tuning
Here is the VM
http://www.mikuni.com/pdf/vmmanual.pdf
Affordable Go Karts - Carburetor tuning
Here is the VM
http://www.mikuni.com/pdf/vmmanual.pdf
Right, both are air screws that regulate air mixture, depending if it's on the front or rear of the carb will determine if "IN" or "OUT" is leaner or richer and vise versa, one works opposite to the other.... Neither is a fuel screw, thats what the jets and the needle's jobs are.. I may be wrong but the only carbs I know of that have a fuel screw are diaphram style carbs and not float carbs..
After reading this post yesterday I went out and messed around with my carb. Its a 22mm with a 15pilot jet, needle with the clip one notch down from center (richer) and 127ish (its been drilled) main jet. The engine does start hard when cold, meaning about 5-10 pulls. After reading the above, this would leave me to believe the engine was running lean. I started the engine and warmed it up then tried turning the screw in to richen the fuel mixture, but anything less then 1.5turns out the engine would stall. It seemed to run the best at about 2.75-3 turns out, which indicates it is running too rich and a smaller pilot jet is required. This goes in line with AGK's recommendations of a 12.5 pilot jet. I wonder how it is some of you are able to use a 20 and have it run fine?
A check of the spark plug looks as though it is running lean overall, though I have not done a full throttle run and then checked the plug as my road has about 1/2 to 1 inch of sand on it right now and a 50mph run didn't seem like the right thing to do until it gets cleaned up. Its been about 50 degree's here lately. I'll need to buy some jets and start playing around some more, though I'll need to order them because they are hard to find around here, especially the pilot jet.
This all being said, the engine runs good once started and will idle nice and smooth all day long.
A check of the spark plug looks as though it is running lean overall, though I have not done a full throttle run and then checked the plug as my road has about 1/2 to 1 inch of sand on it right now and a 50mph run didn't seem like the right thing to do until it gets cleaned up. Its been about 50 degree's here lately. I'll need to buy some jets and start playing around some more, though I'll need to order them because they are hard to find around here, especially the pilot jet.
This all being said, the engine runs good once started and will idle nice and smooth all day long.
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