Still Won't Idle! I think I'm done.

[UncleMike]

There ya go! Remember my anecdote about the "good" bench sync I did the other day which still resulted in one flapper being totally closed at idle? I have a new understanding for the sensitivity of the sync adjustments after that incident. At idle those flappers are supposed to be nearly closed anyway, and having one or two even a *tiny* bit off can mean they are basically blocked at the lowest throttle openings. That could easily account for the symptoms you've described.

Anyway, I bought one of those mercury vacuum sync gauge quartets (Motion Pro brand) off eBay for $40 and I will *never* rely on anything less now (if I want a bike that actually idles). Sounds like that's your next purchase as well? ;-)

Nope, that's what I used to give it a vaccuum synch. Twice.

Explain that.

[t3rmin]

Nope, that's what I used to give it a vaccuum synch. Twice.

Explain that.

Ack. Um...

Well barring some kind of a problem with the vacuum gauge (cracks in tubes, uneven length hoses, poor seal on the intake tap spigot thingies, missing some of those little plastic "restrictors" in the hoses, etc.), or a vacuum leak(s) in the carbs/intakes (torn slider diaphragm, bad vac hose/petcock diaphragm, torn or improperly-seated intake boot, etc.), then either the throttle adjustment screws vibrated themselves out of sync (did you get those locknuts good and tight?), or something in the motor is out of whack (valve lash?). Or I guess we could still be dealing with clogged pilot circuits or something. When I clean the carbs and spray carb cleaner in the holes, then blow it out with a compressor, I like to see whether I can observe mist coming out of the teensiest passages (like the pilot holes in the carb throat near the top of the flapper and the tube thingy in the float bowls). Can you verify that mist does spray out of these tiny holes when you blow out the appropriate jets and such with a compressor?

I think the first thing I'd do before touching anything is put those carbs right back on and hook up the vacuum sync gauge again. You want to find out if the mercury levels still look correct when you *know* the flappers are out of whack or whether the carbs are simply out of sync again somehow (evidenced by the mercury levels being all over the place). Also, are you syncing at idle or a higher RPM?

[UncleMike]

Well, the locknuts are tight, so I know they didn't vibrate out of synch.

Brand new fuel and vaccuum lines, as well as brand new carb to engine and carb to airbox boots.

Petcock tests fine and all the diaphragms look perfect.

Guess I'll stick the damn carbs BACK on and check that synch.

Thanks,
Mike

[r.t.snake]

Hi,

If you do get to the bottom of things I would love to know because I went through the same scenario with my 82 550. I got pretty much the same advice about clean carbs, intake leaks, throttle cables, and spark, and finally just left the bike at the back of the shop and rode my Honda. Started it up today with a faint hope that yet another cleaning and new intake boots and o-rings would help but, alas, same old thing....


RT

[UncleMike]

Hi,

If you do get to the bottom of things I would love to know because I went through the same scenario with my 82 550. I got pretty much the same advice about clean carbs, intake leaks, throttle cables, and spark, and finally just left the bike at the back of the shop and rode my Honda. Started it up today with a faint hope that yet another cleaning and new intake boots and o-rings would help but, alas, same old thing....


RT

Well, that's encouraging,...*

[r.t.snake]

Actually Mike,

I got pretty close to a solution last spring with a suspect carb synk tool. That was just before I quit.( Well took a break from it)

If there is a faint hope, I would say that it might be with synchronization.

Good luck!

[t3rmin]

Hi,

If you do get to the bottom of things I would love to know because I went through the same scenario with my 82 550. I got pretty much the same advice about clean carbs, intake leaks, throttle cables, and spark, and finally just left the bike at the back of the shop and rode my Honda. Started it up today with a faint hope that yet another cleaning and new intake boots and o-rings would help but, alas, same old thing....


RT

I wonder if you took the carbs off and examined the throttle flappers at small openings, if they'd look uneven like Mike's?

[r.t.snake]

Not really, I just double checked them with a wire guage before I put them on yesterday, they all measured out evenly (?)

[t3rmin]

Not really, I just double checked them with a wire guage before I put them on yesterday, they all measured out evenly (?)

Hmm. Have you tried the "hold them up to light and observe the slivers" method?

It's a stinkin' sensitive adjustment, though, so who knows...

[Commodus]

So, I pulled the carbs because honestly, what else am I gonna do on a rainy Friday afternoon besides clean my carbs for the umpteenth time while watching Frankenstein Meets the Wolfman?

Anyway, I held the rack up to the light, and even though I JUST did a carb synch, butterflies #1 and 2 are open much more than #3 and 4. I can see a nice big sliver of light beneath 1 and 2, but almost nothing beneath 3 and 4.

So that would indicate?

Well, there are always going to be differences - that's why we have to sync them in the first place.

I would certainly not expect those differences to be so large. This indicates excess cylinder differentiation (heh, look at me, I sound all technical) - I assume you've already checked compression and valve clearances, cuz there's no point in trying to sync a carb bank without checking yer valves.

If these check out, the carbs are not sealing. The ole "spray-em-with-WD40-til-you-kill-a-cylinder" trick should tell you where, and which.

It is also possible that the carbs are simply worn. How many miles are on this bike?

It would be very nice if someone with a working set of carbs was in your area and could try their set. Too much guesswork in this troubleshooting process right now.

[Commodus]

Note that I often find the choke plunger areas on these carbs to be problematic. Try the WD40 trick there, especially.

[bonanzadave]

Even tho you have new fuel and vac lines make sure the vac line is not kinked or is to thin walled and is colapsing under vacuum. Once the tank is on its like the old refridge light and the door. Does the light go off when the door is shut ? I guess if you ran it on the "pri" position it would eliminate the bad vac line possibility. Good Luck.

[KEITH KRAUSE]

The bike will start very quickly with full choke and idle at 900rpms. The rpms will then start to climb and reach around 2900rpms and stay there for about ten seconds, at which point the rpms will begin to fall until the bike stalls. No amount of messing with the choke will prevent her from stalling.

If I walk away for about 2 minutes or so and then attempt to start it again, she'll start right away with no choke and idle at 1100rpms, albeit not very strongly.

Now, when she's beginning to stall, I can prevent it by giving her light throttle and holding the throttle on for about a minute or two, at which point she'll idle on her own with no choke. But again, it's not confidence-inspiringly strong.

When riding, if I pull in the clutch and hold it, she'll often stall out on me. More often than not, actually, until I get her warmed up.

When she's FULLY warm, her idle jumps about 800rpms to 2000.

Just saw this as I'm going to bed. So just a quick thought.
Sounds like an intake leak. I know you say the manifolds are new.
Are you positive they're the correct ones? Are they genuine Suzuki? Does each manifold have to go at a specific cylinder on your model? Are you using the factory style clamps?
Barring an intake leak, the only other thing that can cause the rpm's to rise incorrectly as you describe is the diaphragm/spring assembly operation. Do you know if the springs are installed correctly and are they stock or look like they've been changed or modified by a PO? Are they colored?
Seems like your symptoms are a combination of two problems. Sure seems like an intake leak is involved though. An intake leak will cause the choke to have limited effect. An intake leak also starves the bike because the loss of vacuum means less fuel drawn up, most noticable when still cold/warming up. Stalling is then common. Once hot enough, the intake leak increases the rpm's and the bike can't stall even though the intake leak is creating a lean condition.
Just wanted to ask you the above. Maybe we can narrow this down. It's late, gotta get to bed.

[UncleMike]

Just saw this as I'm going to bed. So just a quick thought.
Sounds like an intake leak. I know you say the manifolds are new.
Are you positive they're the correct ones? Are they genuine Suzuki? Does each manifold have to go at a specific cylinder on your model? Are you using the factory style clamps?
Barring an intake leak, the only other thing that can cause the rpm's to rise incorrectly as you describe is the diaphragm/spring assembly operation. Do you know if the springs are installed correctly and are they stock or look like they've been changed or modified by a PO? Are they colored?
Seems like your symptoms are a combination of two problems. Sure seems like an intake leak is involved though. An intake leak will cause the choke to have limited effect. An intake leak also starves the bike because the loss of vacuum means less fuel drawn up, most noticable when still cold/warming up. Stalling is then common. Once hot enough, the intake leak increases the rpm's and the bike can't stall even though the intake leak is creating a lean condition.
Just wanted to ask you the above. Maybe we can narrow this down. It's late, gotta get to bed.

My bike takes the same manifolds for all four and they're genuine Suzuki, although the bike was doing this before I changed them as well.

The springs are installed correctly and they do not look as though they've been changed or modified. As far as I know, I'm the first person to have taken apart the carbuerators. The springs are not colored.

No amount of spraying has ever indicated an intake leak.

I appreciate your help, Keith. Thanks.

[KEITH KRAUSE]

My bike takes the same manifolds for all four and they're genuine Suzuki, although the bike was doing this before I changed them as well.

The springs are installed correctly and they do not look as though they've been changed or modified. As far as I know, I'm the first person to have taken apart the carbuerators. The springs are not colored.

No amount of spraying has ever indicated an intake leak.

Well, it sure sounds like the manifolds are OK. Only you would know if the carbs are positioned correctly into them and the clamps positioned and tightened correctly. I assume they are.
I'm not sure why you believe the carbs have never been taken apart but I'll have to assume you're right on that too. If so, the diaphragm/spring assembly should be fine since a failure here usually means a lack of throttle response or none at all instead of your high rpm problem.
So you've inherited the problem? No amount of carb or electrical work has any effect.
Have you ever taken a compression read? I'm thinking you may have a leaking head gasket. Has it been replaced or at the minimum, re-torqued correctly? Any visible signs of a leak anywhere?