Gonna get more carb removal and install experience

How sure are you that your pilot fuel jets aren't clogged? I am by no means an expert, but I would think that if your throttle shaft seals were leaking that you would most likely see your idle racing high by itself. As I understand it, while your bike is idling up to around 2k or so, all of the fuel comes from the enrichment circuit (if on) and the pilot jet. Since you need it to be above 3k, that seems to indicate that you aren't getting the necessary fuel until the main jets come into play. I am sure some of the more experienced members can chime in here. Do you have an inline fuel filter installed and/or the mesh screens on your needle valve assembly?

 

how about this THEORY, with the plates closed(idle) the fuel comes from the enrichment circuit (if on) and the pilot jet, but the shaft seals leak air but not in the right place to draw more fuel from the needle jet/main jet (lean and stalls) until the plates open more to draw air over the needle jet delivering more fuel (result, 3K rpm). Turning back the idle closes the plates, fuel from needle jet stops, goes lean, stalls.
or the pilot circuit may be dirty
of course by now Jack pulls the carbs just because there's nothing on TV

 

I did see in my reading that there are 3 holes for the idle circuit. The only one I remember seeing is the hole directly under the adjusting screw. It also seemed to me that the problem might be with the pilot circuit. Still have to pull the carbs to check that out.

 

This THEORY also makes some sense so I'll be checking the shaft seals as well as the pilot circuit.

 

I don't know how you would test the throttle shaft seals other than by using an unlit propane torch or spraying carb cleaner/starter fluid around them while the bike is running to see if the idle climbs. That you would need to do while the bike is running. As k-moe said in another thread, bad throttle shaft seals look like good throttle shaft seals except they leak (unless they are obviously stiff/brittle). Point being that they can look fine and still be bad.

 

Good point. I did that before, and found that the rubber boots or their seals were leaking. When I sprayed the carb body there didn't seem to be a problem but now that the boots and their gaskets have been replaced I'll try it again. I haven't pulled the carbs yet. Too many good shows on TV. lol

 

I would try it again but, yes, you will be pulling them again; either you discover the throttle shaft seals are the issue, or you don't and need to check the pilot s.

 

The pilot circuit is the idle circuit. Same passages, same thing.

 

if i had the carbs off, i might be tempted to connect one at a time to a shop vac and light a incense stick.
at least the garage would smell good

 

Great weather. The Maxim will be lonely today. I think a ride over to JP Cycle sounds like a good idea. I need a tube of handgrip glue and whatever sparkles and spangles that catch my eye. Of course a nice ride is always on the to-do list as well.

As I mentioned before, I only saw one orifice into the venturi from the pilot screw. In my reading I think someone mentioned 3 openings that needed to be checked. Is that true.

 

Had a few minutes to kill while my phone charges so started the old girl up and sprayed the shaft seals with starting fluid. 1 and 2 seemed ok, but 3 is definitely bad and 4 may be just sympathy for 3 or may be a little bad as well. Time to get new seals and also new plugs for the vacuum outlets on the intake boots.

 

How many holes there are depends on which carb you are working on. One of them is always the idle/pilot needle hole (in front of the closed throttle plate), and the rest are bypass holes (behind the closed throttle plate) that ease the transition from the pilot/idle circuit to the main jet, just like an accelerator pump does. Those holes are part of the idle/pilot circuit. During a bench-synch I use the idle/pilot mixture needle hole as my refrence for setting throttle plate position.

 

three holes, one is the pilot(idle, low speed), another is the enrichment(choke), i don't know what the other one is(doesn't matter here).
all you need to be concerned with is the one that is closest to the throttle plate as it stops closing
the one on the left

 

Been watching a couple YouTube videos about Pilot Circuits. For some reason I assumed that the pilot screw varies the amount of AIR going into the engine. What I found out is that if the pilot screw is on the airbox side of the carb it varies the air, but if it is on the engine side it is providing the gas that allows the engine to idle. So even though I took the screw out and made sure that the hole into the venturi was clean I didn't make sure that gas could get to the jet. Hence, the reason that the bike won't run under 3000 rpm. Does that sound right? Gonna go pull the carbs again and see if I can figure how the gas gets to the pilot jet.

 

Those caps on the vacuum ports don't seem to last very long for me.
But a short piece of vacuum line plugged on the end last for a long time

 

I'm trying to make sure I'm able to get gas to the pilot screw and here's what I found. (See Picture)
So the gas is picked up by that little brass tube that extends down into the float bowl which I tried to clean very thoroughly. It appears that the gas is metered through the hole at the end of the pilot screw, but is free flowing through the hole directly behind (towards the airbox). Any good ideas on how to ensure that the passages marked in green are as open as they need to be. Gonna try compressed air through the brass tube and see what happens.
Item 2: When I removed the pilot screws, only one had the o-ring and washer. going to have to see if I can buy those. If someone knew what size they were I might be able to pick them up at Napa or AutoZone. Otherwise I bet Chacal has them. I looked at the carbs from a maxim X that I have here and they don't have o-rings either. Are these something people throw away for some reason?
Item 3: I'm not sure about the Pilot Air Jet at the top of the orange line, but assume it also has something to do with the idle circuits since it's named Pilot....

 

Oops! My bad. The o-rings and washers were all there.

 

That skinny brass tube is the pick-up for the CHOKE (starter, enrichment) circuit, NOT for the pilot fuel circuit. The pilot fuel circuit picks up fuel from the brass pilot fuel jet that screws into the bottom of the carb body.

I bet you're right..........

People lose them when they remove the pilot screws (or, the parts remain in the bottom of the well, and people never knew they were there in the first place). The O-rings and washers are a specific and not-too-common size.

 

Progress...... Went back and recleaned everything in the pilot circuit that I could with my newfound knowledge guiding the way. It ran much better, (smoother) but still wouldn't come back to an idle without dying. Grabbed the carb cleaner spray and aimed it directly at the throttle shaft seals. I couldn't determine if there was a change in speed or not, so I moved on to the vacuum outlets on the new intake boots. Every one had a noticeable increase in speed, #3 being the worst. Went to Napa and picked up a pack of little rubber caps and installed them. The bike will now idle with the choke off. I'll pick me up a new air filter at the local Yamaha dealer and tomorrow I'll hook the balance gauge up and see what I've got.

 

I thought it would be a piece of cake from here. Brought the brand new air filter home, connected all the blankety-blank pieces of rubber from the airbox to the carbs, she started easily, but when you goose the gas the revs stay high for a long time. I says to myself, aha, I've seen this written up before. so I started working the pilot screws down 1/2 turn at a time. (they were at 2.5 up from stop). Got down to almost .5 turns up from stop before the engine returned to idle somewhat normally. Still a little slow coming dow. Now it idles at about 1200 for a minute or two but then dies. The plugs are new, but I'll pull them and check when I get back on it. Right now preparing for a trip. Be back first week in Aug. I suppose the next thing I'm going to have to learn about is "Cam Chain Tension" and "Valve Adjustment" Maybe I should study up while I'm on vacation ........ Nah.

 

You should net need to lean the idle mixture out that much. You are compensating for something.

 

Add "synchronization" to your list of topics and you'll be golden..................

 

The sync is on the money with my old four tube mercury based manometer. They remain in sync from 1200 to 5000+ rpm. Checked that first thing after installing the air filter. The float levels were checked/adjusted with the addition of your adapters and clear tubing. The choke/enrichment works as it should. There is a bit of clunking at slow idle that I am thinking is the cam chains. My compression tester is missing the proper adapter so I haven't checked that yet, but I'll get that resolved as well before continuing. Question: If there were a compression leak of some kind (valve, rings or piston) wouldn't that show up by making it almost impossible to sync the carbs?

 

Probably the main (starter clutch) chain, it is "tensioned" via an oil-pressure-actuated plunger system, and low rpm = low oil pressure = some slack = some clunking, which goes away as soon as rpm's come up a little.

Probably not. "Synch" refers to the engine, not the carbs (it is ADJUSTED via twiddling with the CARB THROTTLE OPENINGS, yes). The purpose of synch is to get the POWER OUTPUT of all cylinders equalized ("in synch" = "equal power output from each cylinder"), so while low compression will lead to REDUCED power output, you can still synch each cylinder to the lower output level (the vac pull from the cylinders will be lower, and the level of mercury in the synch tubes will be lower, but still EQUAL, i.e. "in synch").

 

^ +1 on the primary chain tensioner. The (long absent) 550 guru here reccomends that the idle speed be set to 1200 RPM to get rid of the slack. Won't hurt the bike any to do that.

 

Fitz? That's a tough void to fill.