Topic: 'Resetting' The Idle Adjuster??

[Dr. Frankenstein]

So I 'm out in the garage trying to synch my carbs with a Carbtune II, and I think I need to re-adjust the Idle Knob to a 'better' idle adjuster position - let me explain: when I first started the bike, it idled at around 1100 RPM; as it got warmer, the idle rose ( I know: air leak, I'm thinkin') so I tried to adjust it with the Idle Adjusting Knob by turning it out - but I soon had it ALL the way out and as I tried adjusting the slides and would blip the throttle, the idle would go up so I'd adjust the appropriate slide and eventually managed to get all the slides pretty even - except it's running at around 2K RPM, and the idle adjuster is literally all the way out!

So maybe you can see where I'm going with this - if I start over, WHERE should thar idle adjuster screw be - about halfway in from its little plate? ALL the way in?? - in order for it to have an effect on the idle?  I'm going to go out and spray some carb cleaner around the boots and see what happen, but what's a good way to give myself enough 'play' in the idle adjuster?

[Deltarider]

What bike?

[bryanj]

Your bench sync has set the slides too high

[Mark1976]

Your bench sync has set the slides too high

+++++++1

[Dr. Frankenstein]

Delta - 1974 CB550K

Bryan - I benched it with a 1/8" drill bit - and besides, even if it was too high, synching them with the Carbtune would have brought them all in line, right..?  Actually, I have them all pretty much synched, it's just the idle is too high - so how do I correct that/ get my idle adjuster working as it should?

Wait a minute, I see what you're saying - the idle adjust 'needed to be where it needed to be' (what - halfway??) when I benched the carbs - so how do I adjust that on the bike w/o taking the carbs out? Turn the idle adjuster In (to what point?), start the bike and then adjust the slides? 

[Mark1976]

Delta - 1974 CB550K

Bryan - I benched it with a 1/8" drill bit - and besides, even if it was too high, synching them with the Carbtune would have brought them all in line, right..?  Actually, I have them all pretty much synched, it's just the idle is too high - so how do I correct that/ get my idle adjuster working as it should?

Wait a minute, I see what you're saying - the idle adjust 'needed to be where it needed to be' (what - halfway??) when I benched the carbs - so how do I adjust that on the bike w/o taking the carbs out? Turn the idle adjuster In (to what point?), start the bike and then adjust the slides?

Its normally (for myself) the 1st thing to suspect, and are you sure that the cables and the throttle tube on the handle bar are returning all the way. Sometimes the pull cable can be adjusted improperly, post a pic of the sync adjusters, they don't really protrude from the adjuster body but 3-3 half threads (turns).

[bryanj]

On the bike no sorry

I did a write up years ago.
1/8 is too big
Wind the idle screw all the way out
Set all slides so they touch bottom
Wind in tickover screw till you can get a 1/16 (or smaller) drill shank under engine side of first slide that moves
Set other 3 same
Make sure with tickover screw all way out slides still touch bottom

[Dr. Frankenstein]

Well - I took off the carbs, reset them the way Bryan said - "...or smaller;" (I used a 1.25 mm piece of wire - 1/16 is 1.5 mm)  put on the throttle cables, adjusted them to the spec in the manual, and now it won't start at all. CRANKS great - but won't fire. So now I have to start all over again. Recheck everything - take the carbs out AGAIN; check for spark - AGAIN -

[HondaMan]

Well - I took off the carbs, reset them the way Bryan said - "...or smaller;" (I used a 1.25 mm piece of wire - 1/16 is 1.5 mm)  put on the throttle cables, adjusted them to the spec in the manual, and now it won't start at all. CRANKS great - but won't fire. So now I have to start all over again. Recheck everything - take the carbs out AGAIN; check for spark - AGAIN -

Bryan's way works for me, too, although I often do final startup of the 500/550 with the slides still 'fully' closed, making me the idle & low-speed controller until it settles in a bit.

The positions of the individual slide adjusters on these carbs can cause troubles: see that your adjuster screws are mostly out (on top) of the housings. If they are turned in too far, the startup can become problematic due to geometry issues with the individual arms, which widely affects the mixture opening between adjacent carbs. If the slides end up too far apart from the lowest to the highest one, the engine does a lot of spitback, killing the low-speed roll. Then it becomes hard to make it run enough to start checking timing with a strobe, etc.

Then, once it will (often ratty) idle I'll start on setting an idle speed, then work on the balance last (with gages).

[Dr. Frankenstein]

I'm currently trying this method I found on here from Bodi:

"You need to avoid having the idle screw unable to adjust the idle, that happens when you start messing with all four adjustments.
- loosen idle screw all the way
- pick a master carb (does not matter which one, but 2 & 3 are harder to adjust when running because of the frame so usually we pick one of them). Adjust it so the slide just fully bottoms and then maybe 1/4 turn further.
- Lift that slide with the idle screw to fit your bench sync rod in the slide gap.
- I lock this adjuster with nail polish, but maybe you don't use it. A bit of paint will do.
- Do not touch the idle screw again. Use the adjusters to set the other three slides to your gauge rod.
- Done. The idle RPM you get is unpredictable, depends on what size rod you used. But it will be adjustable with the idle screw.
- proceed to do a vacuum sync - after the valve lash and ignition timing is set up. You should set all the pilot screws to factory spec then make small adjustments (1/8 turn is good) equally to all four to get the best idle and minimal stallout on throttle opening. For the vacuum sync, DO NOT adjust that master carb: adjust the others to get matching readings.

The 'rod' I'm using (I assume he means the piece you measure the slide gap with) is 1.25mm, as opposed to Bryan's recommendation of 1/16 of an inch ("or smaller").


I had no problem starting it up before when I first synched it -I used a 1/8" drill bit to set the gap, as described here in this post:
http://forums.sohc4.net/index.php?topic=159210.0


Before I put this thing back on the engine, could the size of the gap be a factor in that no-start situation? 

[Dr. Frankenstein]

UPDATE: That was the synching instructions I followed, and it started right up! And as per the instructions, I was able to dial in the idle speed too, so...two thumbs up!

[bryanj]

It may not have started because the idle screw was not in far enough after adjusting slides

[Dr. Frankenstein]

Don't know; but it's running and synched, so...Yay!

[bryanj]

Well done, its great to get there in the end

[Deltarider]

As long as you have not deracked the 4 carbs, it's easy to achieve the right position. Could you communicate how much thread of the 4 sync adjuster screws is visible above their locking nuts?
If the carbs have been deracked, I can post a vid that shows how to set all adjustments prior to reassembly, but I hesitate to post it, because it may be an incentive for some to derack. Know that Honda/Keihin took great care so that deracking the CB500/550 carbs is never needed. As long as you don't leave your carbs drained for an extended period of time. Keep them in a natural state, which is wet, so no rubbers will shrink.