Help me out guys. Apparently I know just enough to get by. There is lots I don't know too. Take these holes for instance.
A) I assume is the pilot air hole. You can see the screw.
B) Factory block off
C) Not sure. Might have something to do with the choke. When I shot carb cleaner in here on the choked carbs, it sprayed in to the bore. On the non choked carb, it just ran out the other side. Not sure where but it left a puddle on the table.
D) not a clue
E) is blank. I assume this is for the pilot air screw being installed on that side. Hole A would then be blank
F) Again - No clue.
If someone knows what all these holes do, please list them so I can store them in my decaying memory bank. ---- Thanks!
I was born with nothing and still have most of it left.
This is what I think is going on there. The two left and two right are the same - for left and right side mounting.
A is the air intake for the pilot jet
B is a drilling through to the pilot jet and the outside is blocked off after it is drilled.
C is the air feed to the needle jet
D is the same as B but I don't think it is drilled all the way through
E is for right mounted screws
F is air intake for the choke (enrichment circuit)
What is pictured above is the center carb. The left is exactly the same. On both carbs, hole D is slightly over 2" deep, checking with a pipe cleaner. Seems pretty deep for something not used. The right carb is really different. A,B and F don't exist. C is there . D is a factory installed block and E is the pilot air screw hole. I get the mirror image bit, but don't understand why D is so deep.
On the right hand carb, D would / should be B, but it doesn't exist. This leads me to believe that D has something to do with the choke. It's late. Tomorrow I am going to fill hoe D to see if in fact it goes nowhere.
I was born with nothing and still have most of it left.
It depends where the pilot screw is placed determines if A and B or D and E are needed. D or B – long for it has to head down towards pilot jets.
If you don't have A and B, I think you have the cast surface for them (maybe not) just not machined. It looks like the center casting was machined to be used with either side pilot air screw, Here they machined only the one needed Pilot air screw.
Other carbs like Tillotson (early vintage snowmobiles) had Welch plugs to seal connecting passages versus the little brass Beebe like plug you see in B. The plug had to be removed to clean the passage. Many people did not do
If you remove pilot jet and push a fluid through A with air screw out a few turns and it flows out where pilot jet was B passage not plugged.
You need to explain what happened if you come off idle and use say 1/16 and 1/8 throttle. Will the cylinder that was at idle not firing now firing with a little more slide opening?
I have a j model with separate carbs. The bell mouth set up is exactly the same except I have a Beebe in the pilot air screw not being used as well. Also I have three choke enrichment holes too. If I spray carb cleaner into D it comes back in your face so it must be sealed
I see there is no cast boss on this carb for a pilot screw. That explains why there is no A and B. But there is no D (which would be B if the mirror image idea is correct)
I was born with nothing and still have most of it left.
OK. I tested hole D on the left and center carb. They do not go through. Now it all makes sense. So it's a dead hole. Why did the bother to drill it I wonder?
I was born with nothing and still have most of it left.
Yes, but in a two stroke with Primary type needle jet, the air mixes only through that large hole as fuel is discharged from the spray tube.
In a 4 stroke (or reed motor) there is a Bleed type needle jet/emulsion tube with a series of small hole that allow the air to mix before it is sprayed out.
Because they mix air and fuel slightly different places, a primary type tends to allow more fuel out at higher revs than a Bleed type - all other things being equal.
I can't see a mating hole in the needle jet bore, but there must be one. Also an assumption, this hole in the needle jet side must be for air, not fuel as fuel would be rising from the main jet.
Of all the carbs I have cleaned in the past, I have not removed this jet. It wasn't till a few years ago that I realized this was even a separate part. That includes the carbs I am fixing to use. So now I want to make sure this is clean and doing its job, without total carb dis assembly. Which hole in the bell end intersects this hole? Is it the large hole 'C'? I want to use carb cleaner and compressed air. Will I need to crack the bowls open to keep from collapsing the floats?
I was born with nothing and still have most of it left.
never mind. After re reading the first TZ response, I can see that 'C' is the corresponding hole. I figure the needle jet side hole must be clean as it ran and accepted throttle pretty well - except for the center cylinder not firing. I also figured out I need to remove the bowls and block the main jet to force the cleaner and air where it needs to go. Probably lift the slides all the way up too.
I was born with nothing and still have most of it left.
Another two important holes to ensure are Clear are the pilot hole and the pilot bypass hole.The bypass hole is just in front of the main jet, engine side and the pilot jet is a small hole in front of that this points toward the engine at an angle. I clean those with a single strand of clutch cable,then carb cleaner and finally comp air.
It's late. Tomorrow I am going to fill hoe D to see if in fact it goes nowhere.
