Topic: Blarg. Still hanging idle... 1976 CB550K

[HondaMan]

I'd suggest trimming 1/2 turn from both spark advancer springs, for starters.

[OldGreyBeast]

Those of you that keep saying to cut those springs, does that need to be done even on the electronic ignition kits?  The advancer thing is free and snaps back into place when i twist it with my hand.

I'm about at the end of my rope with this thing.  I spent the last 2 hours redoing the valves, cam chain, all that crap.  Now the carbs are out of sync again and nothing I do will make them happy.  This is the most irritating piece of equipment I have ever dealt with.

[Deltarider]

I'd suggest trimming 1/2 turn from both spark advancer springs, for starters.

I wouldn't recommend that for starters. A diagnosis comes first. Why not first check the advance with a stroboscopic timing light? If statically the advance was set at 5^o, it is not uncommon to see an advance of say 7 or 8 degrees when idling at around 1100 rpm. That in itself is no reason for concern. If the advance then is more or flutters, only then you might cut a coil and see if that helps. Having said that, my route would be to order new springs and be done with it. But a diagnosis comes first and the strobe will tell it all.

[dave500]

its not an irritating piece of equipment at all,without seeing how the carbs are set up once vacuum synced im guessing youve started the sync with the adjusters too high?theyll be close to closing via the spring but need a physical nudge to slow the rpm?leave the springs intact!

[OldGreyBeast]

What do you mean the adjusters too high?

The only thing that will slow the idle once it's gone  up is choking the engine off for a few seconds (if running on the stand) or if on the road I can just absolutely hog on the brakes and force it to slow that way.

[HondaMan]

Jetting is 110 (Keihin jets from jetsrus).  Idle jets are 40 because I just realized I didn't replace those when I had the carbs off this last time [rages internally].  I'm not sure if they're aftermarket or OEM.

#110 is mighty rich for a CB550. Normally that one is around #98 or #100. If too rich, the engine intake tubes get 'wetted' while running, and closing the throttle will do little to slow it down.

It does have electronic ignition, timing has been set to the stock values from the manual.  Cam chain and valves have also been adjusted per the manual.

What kind of electronic ignition does it have? Is it still using the OEM spark advancer? If so, see my earlier comment about the springs. This is universal on the 550 today (50 years old) and on the 750 as well.

[dave500]

if you start with the adjusters too high youll have the idle set screw backed out fully but the slides aint all the way down,to correct this youll have to back the adjusters off enough to lower the slides and repeat the vacuum sync again.

[OldGreyBeast]

Ok, so it sounds like I need to re-jet to 100/38 (do you guys think I can do that without pulling the carbs off?), as well as get a timing light and verify timing.

It has a Dynatec Dyna S electronic ignition on it, comes with it's own advancer.

I did the carb bench sync at the 49mm "german method" so the adjusters should be set per the manual.

[Scott S]

Ok, so it sounds like I need to re-jet to 100/38 (do you guys think I can do that without pulling the carbs off?), as well as get a timing light and verify timing.

It has a Dynatec Dyna S electronic ignition on it, comes with it's own advancer.

I did the carb bench sync at the 49mm "german method" so the adjusters should be set per the manual.

 It can be done, but IMO it's easier to pull the carbs.

 The Dyna S had it's own mechanical advance mechanism?

 I would pull the carbs and start from scratch on the slides. Use Two Tired's method of bottoming out one slide, then set the rest, then check the 49mm setting.

 Here's what the mechanical advance looks like...what everyone is referring too. I don't think any of the Dyna's come with this part.



 

[OldGreyBeast]

Oh I'm dumb.  The Dyna comes with the middle piece, but the springs aren't part of that middle thing.  I bought a timing light yesterday so I'll check on the operation of those and maybe trim them when I'm checking the timing.

I think I'd honestly rather set the bike on fire than pull the carbs off again, so I'll try to rejet them with the carbs still on the bike.  I got new NGK spark plugs as well so I'll be starting fresh there.  The existing ones have gotten pretty fouled from running rich.

[HondaMan]

Oh I'm dumb.  The Dyna comes with the middle piece, but the springs aren't part of that middle thing.  I bought a timing light yesterday so I'll check on the operation of those and maybe trim them when I'm checking the timing.

I think I'd honestly rather set the bike on fire than pull the carbs off again, so I'll try to rejet them with the carbs still on the bike.  I got new NGK spark plugs as well so I'll be starting fresh there.  The existing ones have gotten pretty fouled from running rich.

The O-rings that come on the Keyster mainjets are also too thin, and do not seal. This lets extra fuel slide right past those mainjets, which is known as "unmetered fuel". This will always wet the cylinders as soon as the carb slides are open above idle speed. If your OEM jets' O-rings have also been changed, make dead sure they actually seal in their holes. One way of checking this in these carbs with the little steel springs that hold the mainjets in place is to see if they will insert into their holes with the springs attached, and hang there. If they don't, then they are not sealing. In that case, PM me for a set of them so you can actually seal the mainjets.

[OldGreyBeast]

Thanks Hondaman, I used a set of your o-rings on the 110s I have in the bike now.  The set of jets I got from jetsrus came with o-rings on them.  Do you know if those are the proper spec?  If not, is it fine to pull the ones off of the 110 jets and move them to the new jets?

[HondaMan]

Thanks Hondaman, I used a set of your o-rings on the 110s I have in the bike now.  The set of jets I got from jetsrus came with o-rings on them.  Do you know if those are the proper spec?  If not, is it fine to pull the ones off of the 110 jets and move them to the new jets?

About 4 years ago I last used some JetRus non-Kehin jets (that the owner sent with his carbs, for me to rebuild) and they were not the right size O-rings. They just barely stayed in the mounts: that was when I got mad and went to the local O-ring supplier and ordered a whole bag of the right ones. That's the only way they can be had, as they are not a common size.

[95chris]

I'm in the same boat as the OP here so I thought I add my observations on to what HondaMan was saying about seals. I rebuilt my carbs using a Keyster kit for my '74 550 as well a few years back and it may be biting me back now. Kit# is 48-1907, stock jet sizes (Main #100, Pilot #38), float and needle are originals. Here's a short video I took that shows how the main jet wiggles about in its bore:

I can see how may be fuel sneaking pass the o-ring when revving up, keeping RPMs high and slowly returning to idle speeds. For reference, here's how my slides & nuts are adjusted on the outside. They were bench synced with a drill bit, forgot the number but barely lets light through the other side. Don't believe I had the idle knob in at all at the time of rebuild. I can see #2 may be slightly higher then the rest. If anyone thinks these could be adjusted better then let me know.

One way of checking this in these carbs with the little steel springs that hold the mainjets in place is to see if they will insert into their holes with the springs attached, and hang there. If they don't, then they are not sealing. In that case, PM me for a set of them so you can actually seal the mainjets.

Explain this! (I guessing the seal is JUST thick enough to hold itself up, or dirt/fuel is assisting)



Will be following this thread. In the process of cleaning up the original jets that were originally on (pilot jets giving me some trouble  ) and using spare Honda o-rings I had laying around.

[dave500]

if you have a decent truck type diesel pump and injector service centre close by drop in and ask them for o rings and copper washers etc,they usually have myriads of all weird types and sizes,for a few bucks ive often walked out with handfulls!often the actual carb is corroded or worn where the jets sits and even proper genuine o rings etc still may be wobbly?

[OldGreyBeast]

Mains are now genuine K-word 100s, idle jets are K-word 38s.  Re-bench synced.  Still doing the exact same thing.  I can futz with it until the carbs are all in sync on the meters, as soon as I give it throttle it will run to 4k and just sit there until I hold the choke on for like 10-15 seconds.  After that the carbs will be all out of sync again at idle and I'll have to futz with them again.

I haven't messed with that timing thing yet.  I guess that'll be the next step.  I tried verifying it on the old jetting setup and couldn't figure it out.  Was hoping it'd be calm enough on this one that I could try it there but it's still being weird.

If any of you guys live near north AL and want to buy a cafe style '76 550 shoot me a PM.  I'm seriously ready to just set it on fire.

[RAFster122s]

Is fuel being sucked in past the orings like HondaMan mentioned?

[OldGreyBeast]

I'm using his o-rings so surely not.  It was incredibly hard to even get the jets in there.

I set the static timing per this video -

I don't really understand what I'm supposed to do with the timing light.

[Scott S]

 Re: Timing light

 It helps to have a friend/helper/extra set of hands

 - Get the bike warm, choke off
 - Loosen the screws that hold the timing plate, then gently snug ONE of them back up. You want to be able to move the plate but don't want it flopping around.
 - Attach timing light to battery and the #4 plug wire (be sure no wires are touching the exhaust pipes)
 - Start bike, pull trigger on the timing light and point it at the window where you see the 1/4 and 2/3 timing marks
 - At idle, you should see the two II marks near the T.
 - Have your assistant rev the bike to about 2500 RPM and hold it
 - You should be able to move the plate L or R to get the II marks at the 4 (about 30 degrees)
 - When you get the marks timed, snug down the screw on the plate
 - Move timing light wire to wire #3, repeat above steps.

 Don't be surprised if you can't get them both *EXACTLY* the same.
 Don't worry about where the marks at the T are at idle. You spend most of your time riding above idle. Set timing for full advance.

[OldGreyBeast]

Ok wow yeah I was way off with what to do with that thing then lol.  Thanks for the write up.  I'll see if one of my buddies can come by one afternoon this week and do that procedure.

I feel like the timing should be fine since the bike ran pretty much perfect >5k rpm with the previous owner's pod setup on it but I'll check it out to make sure.

[Scott S]

 I edited the post and added the pic of the advance plate. You should see it around 0-5 degrees.... the T mark...at idle. When revving, it should move to the two marks at 30 degrees. Make sense?

[OldGreyBeast]

Perfect, thanks so much!  I've got a buddy coming over on Wednesday after work so hopefully we can get the timing confirmed.

[enwri]

The timing advance just needs to be able to return to full retard at higher revs than your high idle speed. That's what the spring shortening does.
Timing light will show if it does or not.

[maxheadflow]

I throw out how I do timing.  Probably done a few hundred when these bike were new. It was part of the standard service.

First thing is to make sure the mechanism is clean and moves freely.

Make sure that the springs are tight and that they hold the weights up against the cam.. If loose, tighten the spring by using a pair of short needle nose and crush the spring loop on the pin. (arrows) During the time I worked on them never had to clip out a loop and reform the hook (except when I worked in a real crappy indy shop but mostly on Honda twins) .  I'd expect that it would slow the advance curve sine the spring rate changes. 

Rough gap the points and set the timing to the back of the F mark  (8 deg?) See that at 1000 to 1300 RPMs that the timing is steady. If it bounces around, crimp the spring loop a little more..

With the timing set at idle see that full advance runs between the advance 2 lines. If not pull the points plate and using a hammer and a punch bend in the limit tabs.   

Bikes always ran well.  Came back to idle well. 

When the motor and carbs are in good shape.  You can set the idle mixture buy getting them all the same and after syncing, tweak them a little for best idle.   You can then blip the throttle.  If it comes back to idle slow, might need to richen up. If it comes back to idle and drops below, it's too rich.

[OldGreyBeast]

Timing has been verified, but it's still being super weird. New video attached shows how it's behaving.