Help - Won't Run/Miss on 3 and 4

[oldyam80sg]

Having issues with my bike too at the moment but with the help of this forum wont be long.

[bikerphil]

I have been checking those little holes, but I don't remember where they come from. Anyone know?

They lead to the enrichment circuit, pilot jet, and air pilot jet in the back bell of the carb. To make sure they are all clear, blow compressed air thru the pilot jet tower and thru the pilot air jet covering those holes with your finger and letting go. If no compressed air is available, carb cleaner with the straw is the next best method.

[CaptonZap]

[QUOTE=Laptop_geek;399018]I have been checking those little holes, but I don't remember where they come from. Anyone know?

[QUOTE]

Here is something to think about, when wondering where the holes go.
The carb manufacturers cannot drill curved or crooked holes, and all holes are drilled from the outside of the body.
So you look at the holes, and say "where did they drill those from?" When you find the small round disc that covers a hole, you say "How would gas get to that disc?"
Lo and behold, there is what looks like a tube cast into the body. So you follow it, and see where it goes.
After a while, you can see all the passages that are used, and at that point, you can figure out where to apply compressed air, while covering certain holes with your fingers, and blowing out all of the passages.
Figuring it all out is almost better than a Tetris game.
CZ

[Rasputin]

They lead to the enrichment circuit, pilot jet, and air pilot jet in the back bell of the carb. To make sure they are all clear, blow compressed air thru the pilot jet tower and thru the pilot air jet covering those holes with your finger and letting go. If no compressed air is available, carb cleaner with the straw is the next best method.

Myself I prefer the carb cleaner as I can see it flow on those three tiny holes. Air pressure not so much. I use dental picks to poke through the three tiny holes to see if they are clean, if the flow is not enough. That can help if you are not getting a correct flow from them.

[TopCatGr58]

Took me a little while to find this again, but it might help to visualize things?



T.C.

[CaptonZap]

Myself I prefer the carb cleaner as I can see it flow on those three tiny holes. Air pressure not so much. I use dental picks to poke through the three tiny holes to see if they are clean, if the flow is not enough. That can help if you are not getting a correct flow from them.

Not to argue with you, knowing how you are, in your garage, but to advise someone to use dental picks, without knowing the persons mechanical knowledge, is a bit irresponsible, IMHO.
Aluminum is soft. Stainless steel, which most dental picks are made of, is not so soft, and generally tapers to a point.
Someone not familier with proper procedure, could be rooting around in there with the pick, and swedge out the holes, which alters their operational behavior. Enough to be a critical factor? Maybe, maybe not. But if one learns a "proper way" to do something, then to advise a less than proper way is not a good idea.
Better to use a soft copper wire, stripped from a stranded copper cable, or maybe a plastic bristle, taken from a toothbrush or kitchen brush, or even a toothpick, whittled down to fit.
(I don't advise wood, because it can break off in the hole, and then you have a problem).
Once again, passages filled with fluid, and allowed to soak, then blown out with compressed air, will almost always be cleaned to an operational state, without fear of mechanical damage to the carb. To clean carbs without compressed air is like trying to trail ride without knobby tires.
Don't have a compressor? A spare tire, filled at the station to it's maximum pressure, as molded into the sidewall, can be used as a source, with a hose from a tire pump screwed onto the stem, and a spritz valve hooked to the other end of the hose, used to apply the air. You will learn to be frugal with the air, but if you are using an LT tire, rated at 65+psi, you should be able to get most of it done.
Once again, nothing harder than aluminum should be used in cleaning carbs, at least not in my garage.
CZ

[BA80]

With 3 and 4 being the affected cylinders it almost has to be carburetion or fuel supply.

2 other REMOTE possibilities I can think of are bad plug wires or clogged exhaust on that side. As I said, REMOTE possibilities.

[skids]

Yeah I drew that a long time ago. It certainly is not to scale and I am not certain that it is 100% correct, especially for the later model carbies. I know the bowls are vented differently...

[Laptop_geek]

Alright, got a nice day where I'm able to work on the bike and got some compression numbers. Going from one to four I got; 160, 160, 125, 155. Note that I was able to get number four to fire and it was hot when these reading were taken, number three was not hot as I was unable to get it to fire.

Some other funny things I've noticed. When I got it warmed up and took off the choke it ran fairly good (besides the miss on three) and idled around 1200-1300 (haven't been able to set the idle yet). When I reved it up it idled above 2000 and took a while for the idle to drop again. What would cause this to happen?

I also noticed that the number three plug is not screwing in all the way (has about 3/32 left to go) in the cylinder head. I'm going to get a plug tap and fix the problem, just thought I'd give you the info.

Oh, almost forgot. My enrichment lever will not stay out for more than just a little bit. I'm not sure why this is happening but when you pull it out, it will stay out for ten or fifteen seconds, then it will go back in. I'm not sure if I'm missing something or not using it right but I'm sure its not supposed to do that.

[TopCatGr58]

Hey Geek,

Even at 125 psi, that #3 cylinder should be able to FIRE. The spark plug tip being recessed due to it not screwing in/down all the way could possibly be contributing to the lack of fire. Folks have recommended putting plenty of grease on the thread chaser to help catch/capture the shavings when you re-tap the spark plug hole threads!

Have you verified that you're getting spark on that cylinder? The plug is probably fuel fouled so after rechasing the threads, you should get a new plug. Then also swap the 2 and 3 plug wires/caps and see if the problem moves to #2 or stays with #3. IF still # 3 then you know it's fuel, if it moves to #2, then it's the spark plug wire/cap!

The hanging idle is a telltale sign that the carbs are not properly vacuum synched together, so they don't pull evenly, and will pull one another.

Forgot..the enrichener lever and arm/bar that connects all four carbs has a few detents on the side facing the carbs...on the #2 carb IIRC, and there is supposed to be a spring and small ball that will CATCH on those detents and hold the bar/enrichener plungers in place against the spring pressure of the plungers and lever. Sounds like someone got into the carbs, took them apart, and lost the spring/ball!

T.C.

[skids]

Hey Geek,
The hanging idle is a telltale sign that the carbs are not properly vacuum synched together, so they don't pull evenly, and will pull one another.
T.C.

What TC says is true, but if you are just running on the enrichener (choke) I would wait for the bike to warm-up. An air leak through the manifold boot connection(s) can cause hanging idle as well, or some other problem causing the lean condition. You can't really pass judgement on a bike running on the choke however.

Concerning the spark plug hole...if you hook a shop vac to blowing onto the exhaust, and turn the crank until air blows out of the plug hole, you can expell the cuttings pretty efficiently (watch the eyes). I just hope the hole is not buggered from a plug previously getting stuck. If the hole is not fixed by your method, you may need to use a helicoil kit. Antisieze compound is a must for the plug threads.

[Laptop_geek]

Thanks for the info guys. A lot of good stuff to think about. I'll take a look at these and get back when I can.

[GLoweVA]

Just for grins, check the 2 bolts that hold the intake boots on.
One time, I couldn't figure out why my #1&2 weren't getting hot and I couldn't figure it out for hours. Finally I had the vac sync rig hooked up and got almost no vac on #1 or 2. Come to find out, the intake boot bolts had loosened up and the boots came off the head a little and it was a huge vac. leak. Compression numbers were great, but it couldn't suck any fuel in due to the leak at the boot/head joint.

Just a thought, something to try.

[Laptop_geek]

Just for grins, check the 2 bolts that hold the intake boots on.
One time, I couldn't figure out why my #1&2 weren't getting hot and I couldn't figure it out for hours. Finally I had the vac sync rig hooked up and got almost no vac on #1 or 2. Come to find out, the intake boot bolts had loosened up and the boots came off the head a little and it was a huge vac. leak. Compression numbers were great, but it couldn't suck any fuel in due to the leak at the boot/head joint.

Just a thought, something to try.

I'll look at this too. I bought some stuff to do a vac sync on the carbs. I'm hoping that'll tell me what I'm missing.

BTW: I have got it to idle since the number four cylinder started hitting. It didn't seem to change anything when it got warmed up. I also switched the 2 and 3 plug wire and that didn't change anything either. Hopefully it'll warm up and stop raining so I can work on it again.

[Laptop_geek]

Alright, I had a chance to play with it tonight and 1+2 are missing now. Looks like I'm gonna take off the carbs and swap them with the 79 carbs. Hopefully that'll take care of some of the problems. I'll keep you updated on what happens.