Topic: '76 CB 550 air screws / ignition *updated*

[prov431]

Well today I started digging into some maintenance...oil, filter, spark plugs, points gap, battery tender etc...noted something I thought was odd...none of my carb air screws are set the same,  they ranged from 1/4 turn to 3 turns..I'm no carb expert, but I think this probably isn't good? I wrote down all the values and then set them all to 2 turns out....wondering if my 1/8 throttle Stutter might improve? I have pics of the plugs...will upload later....and the good news is my carpy header is at the powder coater getting ceramic coated.

Thoughts?

[dave500]

see how it runs once the exhaust is on,setting the airscrews the same is the thing to do then take it from there.

[TwoTired]

Air screws should be set to same on each position.

These adjust how rich the idle is, and it should be a bit rich to compensate for the sudden leanness when the slides are lifted.  If it stumbles under load and one half throttle twist, they are set out too far.

This post assumes the carbs in question are for a 76 CB550K model.

[Deltarider]

Tip: Always, always write down in what position each screw was before you change anything!!! Most probably it was in that position for a reason. The same goes for whatever else is adjustable like needle clip positions etc. Start by mistrusting yourself and not the PO, not as long you don't know he ever touched things .
Many years ago I made the mistake of adjusting the airscrews uniformly to what I had found in a Haynes manual without writing down in what position each was before. I was ignorent.
 Although my bike performs well (both HP and top speed) I've never found back that super wonderful driveability I once had. Not that driveability is bad, but it used to be better. Colleagues blame it on the gas however, that has changed over the years.
According to a mechanic I once consulted, airscrew position may vary between the carbs. I don't know if this is true.
What I am personally interested in is to have an equal CO on all four say @ 5000 rpm under load and I'm willing to accept whatever idle is the result.
Hope to learn more.

[dave500]

technically each airscrew will be best at a similar but not exact position,a bit like syncing carbs,each cylinder will require a slightly different mixture to the others,its a hair line thing though,,also what about worn threads that let the needle wobble somewhat and draw air past them?some might use o2 sensors etc to set them,,just set them the same unless you want to fiddle with three fifths of #$%* all every day,you havent lost some perfect setting delta,your bikes just getting older,and memories are always optimistic and favour the good things.

[Deltarider]

technically each airscrew will be best at a similar but not exact position,a bit like syncing carbs,each cylinder will require a slightly different mixture to the others,its a hair line thing though,,also what about worn threads that let the needle wobble somewhat and draw air past them?

Yeah, that is also my understanding.

some might use o2 sensors etc to set them,,

When mine was on the dyno stand, it was my task to hold the sensor in the exhaust. Not easy (I screwed up, it's impossible to stick it in there deep enough). The mechanic explained that the O² sensor should be much further in.

set them the same unless you want to fiddle with three fifths of #$%* all every day,you havent lost some perfect setting delta,your bikes just getting older,and memories are always optimistic and favour the good things.

True, I'm a perfectionist. On the other hand I have managed to make things better. I've raised the needles by going one notch lower to compensate for gasquality nowadays. Worked but now a bit too rich. In between 3rd and 4th notch would be ideal I guess.
I'm still in the proces of learning. Having the original four mufflers it would be interesting to listen (at a bit above idle) to them and compare the sound they make. If any of you have suggestions... I like to learn.
Tip: avoid digital 4gastesters. They're impossible to work with: figures jump all over the place. The old analogue CO-tester is best. That is: if you can find one.

[dave500]

once your riding and always over 4000 rpm who gives a damn man?

[Deltarider]

once your riding and always over 4000 rpm who gives a damn man?

You are at the heart of the matter.
Never had complaints regarding starts nor top speed.
It is just the driveabilty (picking up) between 4000 and 5500 used to be better in the old days, even considering the flat spot 500/550s are known for. Raising the needles a bit has helped. So I agree with the mechanics: gas did got worse, that is: for our sort of bikes.

[dave500]

any 500 or 550 ive had ive always made any flat spot go away no trouble,if its even had it!we still have good fuel,ill send you some delta.

[prov431]

Well I'm finally getting back to the computer - did some good maintenance on the bike including oil, filter & o-rings, valve check/adj, cam chain adj, points gap, plugs, etc....here is the pic of the spark plugs I removed - they aren't very old; two look ehh, ok...the other two rather rich. The numbers next to them are which cyclinder they came from and the air screw turns outward as found. As mentioned earlier, I've set all of the air screws to 2 turns out although I haven't been able to run the bike because I haven't got the header back on yet (being ceramic coated).  Again, no plug chop or otherwise was done, in fact the last bit of run time was idle and low revs to warm up the oil before I changed it. Not sure how much of an impact this had on the plugs. Either way, time will tell if I made it better or worse with all my tinkering.

[dave500]

if you have a multi meter check the plug caps resistance,unscrew them from the wire,it should be 5000ohm,some older ones were 10000,if any look cracked replace them all,if they are the factory old ones replace them,you must have a properly sorted ignition before you tinker with any fueling problems full stop.

[prov431]

Not sure I'm following you 100% on the plug caps - My guess is to check the ignition coils (nice write up on them in the manuals from this site)...from what I saw today when I had the tank off it looked pretty darn original (with the exception of the actual plug wires, those look newish)
SO, if I do indeed have original coils from 1976, that certainly may be a culprit in poor performace to the spark plugs......what is a good resource to get replacement coils from?
Thanks for the replies!

[dave500]

the coils will be 99.9% ok,,the leads are captive within the coils and cant be replaced,they are solid wire and last longer than the dead sea scrolls,providing they are the stock honda coils,,the end has the bit that snaps onto the spark plug,thats the cap,itll unscrew from the wire,then you test it for resistance,,you might want to clip a quarter inch from the leads once you have the caps off,this will provide a fresh contact within the screw part of the cap.

[Deltarider]

What Dave said.
Sort ignition out first of all, check and doublecheck.
I agree with Dave again on coils. Can't believe how much coil replacing goes on in this forum. For some silly reason I replaced my genuine coils for 3 Ohm Dyna's. The genuine coils are still in good order. Of the Dyna coils one gave up already after 30.000 kms. Because I wanted an equal pair I bought a new Dyna. How foolish. I should have removed the other still working Dyna and returned to the Honda coils that had never let me down. A coil is a very stupid thing by the way, but because it deals with invisible powers like electricitry and magnetism, people are willing to project all kinds of (desired) mysterious power into them. In this field Dyna is more than helpful boasting their coils can produce 36.000 volts, where no one will ever need more than 10.000 Volts, unless you're in some sort of high tuned engines like those used in dragraces.

[dave500]

the honda coils last forever,for how ever meagre the output is compared to some super duper ones they are robust and ever so reliable,put your finger on the bare lead end and crank the motor over!some aftermarket electronic systems MUST use the specified coil though,,theres nothing to be gained from changing to a new brand of coil if the honda one hasnt failed or been proved to have an intermitent fault,thats fair dinkum mate!

[prov431]

Thanks very much for the additional info...that makes much more sense now. I'll pull the tank again hopefully this afternoon and check those caps out. Can you be more specific on what type of resistance values i may encounter and if i need to replace, where can i purchase just the caps? Thank you!

[Deltarider]

Caps should be around 5KΩ each and not much above 10KΩ. With both caps still attached to the coil expect to read between 23 and 26KΩ.
NGK has SD05f, XD05F and VD05F as options, all 5KΩ. Some prefer angled spark plugs, some like to have 2 of them straight.
Do a Google image search.

[prov431]

Well, I took the tank off and gathered some tools only to find I have no caps, at least that I can see. I also came to realize that the plug wires must also be original as they are straight out of the secondary side of the ignition transformer - no aparent way to remove them. See the pics...
Thoughts and suggestions most appreciated!

[dave500]

pull the connector from the spark plug,the thing with ngk written on it,thats the cap,roll back that short rubber weather seal and the cap will unscrew.

it looks like this.
http://www.davidsilverspares.co.uk/CB550F-SUPER-SPORT-1976-USA/part_70029/

[prov431]

Ohhh...got it, thanks for the clarification!

[dave500]

if you have a multimeter to test the caps you should also check the coils,they both have a black/white stripe wire to them,one will also have a blue wire and the other coil a yellow wire,unplug them and with the meter connected to the coloured wire and the bk/wh wire going into the coil your looking for 5ohms.

[prov431]

Got it, thanks!

[prov431]

Caps should be around 5KΩ each and not much above 10KΩ. With both caps still attached to the coil expect to read between 23 and 26KΩ.
NGK has SD05f, XD05F and VD05F as options, all 5KΩ. Some prefer angled spark plugs, some like to have 2 of them straight.
Do a Google image search.

Nice info - I finally found the NGK page with the data:
http://www.ngksparkplugs.com/docs/Resistor_Covers.pdf

[prov431]

the coils will be 99.9% ok,,the leads are captive within the coils and cant be replaced,they are solid wire and last longer than the dead sea scrolls,providing they are the stock honda coils,,the end has the bit that snaps onto the spark plug,thats the cap,itll unscrew from the wire,then you test it for resistance,,you might want to clip a quarter inch from the leads once you have the caps off,this will provide a fresh contact within the screw part of the cap.

Thanks Dave, I should have read and understood your post a bit better! I'm not new to bikes, but I'm new to OLD bikes!

[dave500]

lots of old bikes of any make have captive coil leads that you cant remove,,it can be done though with a dremel and a hack saw and some jb weld and a power drill and,its been done but is a pain,,you wont need to replace the leads unless they have been cut too short or have exposed centre conductor or other damage,they are a solid wire not a carbon type lead that wears out or even a spiral wound type,thats why the resistance is built into the plug cap to supress radio noise etc and also help with building some pressure to make the spark jump the gap more or less.