Mikuni on a 196 clone

E

ELT

Active Member
#1
#1
I have a 196 clone engine that I've installed a flat top piston and billet rod in. I added a 22mm mikuni from go power sports. The sent a 140 main jet and a 17.5 pilot jet that are supposed to be close to what I need for this engine. I can't even get the enine to idle without playing with the choke. I've gone all the way up to a 37.5 pilot jet. With that jet I can only open the idle air screw about 1/4 turn. I've checked for air leaks by spraying brake cleaner around the intake gaskets and all seems good. I rechecked valve lash and cam timing and that is fine. I need some more ideas on what I'm missing.
 
P

panchothedog

Well-Known Member
#2
#2
Bolt the makuni to the manifold with it off of the engine so you can check that the O ring is perfectly centered. It doesn't take much to make the idle go real fast. Once you get the carb centered and bolted down tight then bolt the manifold, with carb attached to the engine. I fought the same thing you are doing for 3 or 4 days until I got the same tip on assembly procedure.
It cured the problem and I was SURE I didn't have a leak.
 
E

ELT

Active Member
#3
#3
panchothedog said:
Bolt the makuni to the manifold with it off of the engine so you can check that the O ring is perfectly centered. It doesn't take much to make the idle go real fast. Once you get the carb centered and bolted down tight then bolt the manifold, with carb attached to the engine. I fought the same thing you are doing for 3 or 4 days until I got the same tip on assembly procedure.
It cured the problem and I was SURE I didn't have a leak.
Click to expand...
Centering up the carburetor did help a little bit. I'm waiting a larger pilot jet right now.
 
E

ELT

Active Member
#6
#6
I put a 40 pilot jet in yesterday
It idles great. The air screw is between 1 and 2 turns open. There's a 140 main jet in it now and it seems to be good but I can't really do any plug readings till the snow leaves. The pilot jet is much bigger than all my research shows it should be. I'm not sure why but it is running good.
 
ole4

ole4

#8
#8
Which type of jets does your carb have? They are either Mikuni or PWK style Kehin jets. If they are the PWK style then you are about right at 40 (If I remember correctly, which lately is not that often). First pic are mikuni style second are PWK type, which does yours have? You have to look carefully at the pilots as they look similar but thread is different. A lot of the carbs from GPS are PWK style and folks are having issues jetting them as most assume mikuni jets.
 

Attachments

ole4

ole4

#10
#10
That doesn’t help look at the thread diameter the mikuni threads on the pilot are smaller. Look at the first and second picture. The main jets are completely different, as is the numbering system.
 
E

ELT

Active Member
#11
#11
ole4 said:
That doesn’t help look at the thread diameter the mikuni threads on the pilot are smaller. Look at the first and second picture. The main jets are completely different, as is the numbering system.
Click to expand...
The jets I used have the correct thread. My set up came from GPS and I used the jets they sent with the carburetor. I'm a retired heavy equipment mechanic and I understand the difference in thread pitch and being sure to use correct parts.
 
You must log in or register to reply here.
Top