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

[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.

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

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.

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...

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

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?

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!

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,...*

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, 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

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?

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.

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? ;-)

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?

You have a point there. ;-) Maybe turn your idle screw up a bit. The closer to idle the better, though, 'cause it's easier to hear roughness at lower RPMs (IMHO).

Indeed. She'll idle when fully warm, but then she's not "doing it" at that point, so it'd be kinda hard to diagnose, you know?