Topic: compression test 77CB550F

[scuba steve]

also - while using the timing gun I noticed the strobing isnt totally consistent. The light from the gun comes on somewhat intermintently. I am gonna try another timing gun to make sure i can duplicate this.  im pretty sure its good since i just bought it.

in other words if "tick" is when the light comes on it goes like this - tick tick tick tick short pause tick tick short pause tick tick tick tick short pause tick tick tick

since "tick" is the light flashing which is a spark firing, shouldnt this be totally steady? this is leading me to believe i have a problem elsewhere... unless this is all because im still not on yet with the timing

[TwoTired]

I haven't used (or seen) the Diachi points yet.  Hondaman says their construction geometry is wrong.  If the plate is fitting tightly on your example (I've had them need a .006 feeler to fit in the space on some), you may have to elongate the slots on the plate with a file, or compromise on the gap setting.

If the light isn't firing, but the engine doesn't change speed, then the spark occurred,  but the light's sensor didn't pick it up.  You could try "inverting" the clamp probe, as some trigger device designs are picky about sensing negative pulse or positive pulse.  The SOHC4 has both among the spark leads.  Autos usually have just one pulse polarity going through the distributor system.  Alternately, you could try the light's clamp on #1 instead of #4 lead.

Another thing you might try is swapping the condensers.  The condensers are supposed to increase the initial current flow during field collapse.  If they are leaking or not at full value, the pulse edge can be slower and the light trigger may get fooled by this.
Another thing to look for is the spark lead resistance or extra gaps in the spark circuit loop.  It can still fire the plug but the wave shape being sensed can be "funny" from the light trigger's perspective.

Check the spark plug caps for correct ohms.  The 550 came with 10KΩ from the factory.  Hard to find those these days.  5KΩ is a reasonable substitute.  The standard spark plugs don't have an R in the number.  But, if you have 5K plug resistance and 5K caps, it should work like new.
Always look for insulation cracks, and the wire ends where the caps screw in should be solid, leaving no possibility of an extra gap there.
Finally, look at the spark circuit in a darkened garage for visible arcing.  If so, that's a leak that must be corrected.

You do need to do what you gotta do to get both point gap AND point timing correct for both point sets.  Is it not possible to obtain ND or TEC points from any source?

Cheers,

[scuba steve]

I am using fairly new TEC points. I tried setting my point gap more on the .012-.013 side as opposed to the .015-.016 side of the allowable range and it seemed to get my timing closer to the F on both sets. Im really not that far off maybe 10 deg or less on both sets. When you are looking at || 1 4 || my timing is b/w the 1 and 4; same on 2-3. Should I settle for this? When you are viewing the timing marks through the peephole with the timing gun, the marks seem to jump back and forth. Is this normal? It seems to land on one setting more than any other, and thats the one im going on.

I threw in a fresh set of plugs and overall the bike is running really good. when Im accelerating it feels and sounds smooth as butter and pulls real strong. The only time it sputters is when im hold the throttle completely steady trying to maintain a constant speed and that is only like a putt putt here and there.

I intend to go through my carbs again but I want to make sure I have the ignition system as good as I can get it.  Only the 2 and 3 plug wires have resistors in them, they are 5k ohm, why does 1 and 4 not have them, are they missing or is this right? When i hold my plug on the block to watch the spark I get a blue one but I wouldnt call it a FAT blue spark, how can I tell if my coils are 100%? I ran it in the dark and there is no visible stray arcing coming off the coils or wires.

[TwoTired]

Are you confusing the labels with the marks for alignment?  If you are getting the light when the case mark aligns with the numerals, rather than the marks for which the labels are intended, you have it too far advanced.
In the shop, I wouldn't settle for anything less than correct, which includes at least .014" point gap.  A roadside repair is another matter.

Once I learned to set the points correctly, I seldom bother with a strobe timing light and my trusty CB550's.  I just use an instrument lamp clipped across the point and ground terminals.  After gap is set, the lamp comes on when the F mark aligns with the case reference mark.

Sometimes tools can be unworthy of trust. (quality issues)

Cheers,

[scuba steve]

Just tried a 12V bulb and jumpers across the point terminal and ground. This test shows exactly what im seeing with the timing gun. attached pic is 1-4 right when bulb comes on.

[TwoTired]

Well, at least you know the timing light isn't lying to you.

But, your picture shows near full advance.

Hmm, have you checked the mechanical advancer for sticking?

When you rev the bike with the timing gun, how far to the right does the light flash?

[scuba steve]

yes i pulled out the advance and it seemed to be free and working properly. I shot a little lube on it for good measure.

the light flashes about 25 deg to the right when I rev the bike, landing on the cotter pinned shafts on the advance mechanism

[Danno]

a common problem that is only sometimes noticed on these bikes is that the cam that drives the points block up and down sometimes has the pin it rides on slightly bent or out of square there is a faq on it on the forum here

[scuba steve]

thanks danno, I did check out that pin and it was nice and straight

[scuba steve]

I finally figured it out. The timing is now dead on.

For some reason I had it in my head that the point gap had to be set with the crank positioned on the F mark. Wrong. The manual says set it when the points are at their widest opening. This happens to be around a 1/4 turn past the F mark.

Ive read alot of the arguments here on HM ignitions vs dyna or other electronic ignitions and cant decide which is the best way to go. Alot of people say the electronic ignitions make there bike run better but I wonder if there points/timing wasnt working correctly before they installed one. Can the dyna or other electronic systems offer advantages over a properly adjusted and good set of points? Cost doesnt matter much to me, I want it to run as good as possible. I have no problem with having to adjust point gaps and timing as part of regular maintenance now that i can do it, its easy.

[TwoTired]

Points are pretty bullet proof and rather low tech.  Some electronic systems are not designed well and waste a bunch of the just-adequate charging system power of the cb550.

They do relieve the mechanic of frequent ignition attention, which some like to avoid like death.  I think that is their main purpose which, while superficially attractive, I don't value as much as the expense.

The high voltage claims claims/hype don't translate to power increases by themselves, especially the flashy bits on a bench which don't mean a thing in the combustion chamber.  But, if you think the light show is worth it, then spend away.  They do offer longer term consistency.  And, the expense is justified in many minds (especially after the purchase and the money is already gone  (Human feel-good psyche).

Lots go ballistic about this. (You'll see.)  I haven't found a seller worthy of my dollars yet, though some have mastered a sales hype common these days.
If you don't care about seller integrity and honesty, most are quite happy to take your money.

IMO
Cheers,

[scuba steve]

recent tuneup history:

1. took apart carbs, checked jet sizes to make sure everything was stock sizes and honda oem which they were, cleaned everything, replaced all o-rings and gaskets. the only thing i skipped was pulling the slides apart to see if the jet needles were factory spec and to see which clip setting they were on. I did look at each of them through the carb throat they looked in really good shape.
2. installed new coils, plugs and plug wires, and dyna s ignition module
3. set timing dead on. no problems here
4. synced carbs, set air bleed screws at 1-1/2 turns out from seated per manual

Bike was initially running okay after all this and then one night while in the shed I noticed the no.1 pipe was not super hot like 2,3, and 4 - even after running for 15 mins or so. I pulled the #1 plug and it was black and sooty. with the plug connected to its plug wire and the plug tip touching the engine while I fired it I got NO spark. I cleaned the plug and tried it again and shocked myself from the fat spark i was now getting. so then I pulled all the plugs, all were black and sooty, cleaned them all and put em back in. Seeing that it was running rich, I removed the air filter and ROOOAAR. Although my foam filter (not stock) looked clean it must be clogged. I revved it in the shed for a little bit (clearly now running alot better with the air filter out)  and then pulled the #1 plug. it was clean, no black soot.

So this am I got to ride around and got on it pretty hard. It runs great coming off idle with light throttle. If I really twist it hard coming out the hole, when I shift into second and third it sputters like maybe its backfiring in the carbs or exhaust  (kind of a light popping sound) and there is a noticeable loss of power.  If I stay kind of easy on it it pulls hard and smooth.

So I guess this is the point where I start pulling plugs after running the bike at different throttle settings to see where im rich or lean?
Or should I take the carbs apart again and double check everything?
The aftermarket Kerker 4 into 1 might be causing me to run rich or lean, Im not really sure if this exhaust system is more or less restrictive than the stock 4 into 1. I wish I could find a stock 550 4 into 1.
Also this means I did all this tune up with a clogged air filter, could that have any effect the carb sync or timing setting?

[TwoTired]

When you took the carbs apart, did you also clean the mains emulsion tubes that sit behind the main jets.

It would have been nice if you had stated what jet sizes you found inside the carbs.
And the needles set the mixture between 1/4 and 3/4 throttle positions. Which is what you use during 90% of driving operation.

I haven't re-read this entire thread.  Do you have confidence that the carbs are in stock configuration?  Could whoever put on the exhaust projected that the bike would need more fuel and raised the needles in anticipation?
I would expect a more open exhaust would, in effect, make the carbs seem too lean.  Certainly, in an otherwise stock configuration CB550F.

A foam air filter can be over oiled and the oil would block many of it's tiny air passages, making it behave as though partial choke was applied.

FYI, you should never be able to snap the throttle open from low RPM under load with this bike and carbs. The carb design won't allow it.
Mark your throttle position, the bike should respond smoothly and reliably form low RPM in any gear with up to 1/2 of remaining throttle travel.  Once the engine is above, say, 5-6000, then the throttle travel limitation is no longer an issue.  That's just the physics of the carb design.

Further, if the carbs were set up to allow snapping the throttle full open, then you can expect the spark plugs to soot frequently.

Cheers,

[lucky]

decided to go through top end. engine is still in frame, I have the cam cover off and am wondering if i need to mark something before I remove the camchain?

the head gasket definitely needs to be changed but the gasket below the cylinder block looks good. If I want to change the piston rings do I need to pull the engine?

Read the shop manual.