Topic: Trouble starting '75 CB550 - FIXED

[Patrick]

You also want to leave as much play in the adjustments nuts as you can. You will need it when you synch the carbs on the bike. You start out all even to get the bike running, then you have to synch with it running to account for the variables on each of the intakes. It's going to be really cool the first time you hear this engine roar.

BTW, did I read in this thread that you are trying to start this without an exhaust? If not, ignore the next sentence I'm too lazy to read back and be sure. But if you are that's a back idea. Asking your valves to contend with a fiery explosive on one end and outside air on the other is testing the temper. Always have at least the header attached.

Patrick

[c.tran]

Thanks for the advice. Looks like I'll be going back to square one. I think I shorted my wire coming from my killswitch to my coils too when I was checking my voltages....

Well hopefully I can track down the wire problem and get my carbs bench synced by the weekend. Then I guess I can worry about the ignition. This bike is turning into a real headache. I was hoping to get it going by March.

[Patrick]

You're not back to square one. Square seven or eight on a scale of 10, I'd say. Don't worry, you likely will become proficient at pulling and remounting the carbs by the time this is done. It gets easier. One clue? Use a heat gun or a hair drier on the rubber parts when you put the carbs and the airbox back on. The old rubber still has some flexibility when you warm it up.

Patrick

[c.tran]

I'm pretty sure I bench synced the carbs correctly this time.  However, when I tried seating the slides all the way down to the bore, there was a very tiny gap remaining (looking from the engine side).  It couldn't have been any wider than a pin needle.  I screwed down the individual adjuster screws as far as they would go.  The main idle screw was backed all the way out too.  Is this normal?

Well, since I couldn't do anything about the tiny gap, I turned in the main idle screw a bit to raise all of the slides and went ahead and used a 1/8" drill bit to "gap" the slides from the air box side.  After getting all of the slides pretty close to uniform, I backed out the main idle screw so it wasn't placing any pressure on the throttle linkages (is that what it is?).

[Patrick]

You want the slides as far down as you can get them. As you adjust the synch on the bike the slides are going to come up. You are going to end up with a gap. You want it as small as possible. If the adjustment nuts are at or close to the top of their adjusters, and the slides are moving as close to tandem as you can do, you're ready to try again.

Wiring also is not hard, it is just time consuming. If you have a multimeter and some very fine sandpaper cleaning the whole system is only an afternoon of tedium.

Patrick

[c.tran]

Alright I think the carbs are ready then.  I just tried doing my timing for my ignition (with the Daiichi plate and points) in order to rule out (or verify) that the Daiichi products are the problem.  When I use my 12v lamp, it glows very dimly when the points just begin to separate.  I have it grounded to the engine case and have the probe touching the metal arm of the point.  It glows brightly when I use it to test continuity everywhere else, so I don't know why it is only glowing very dimly at the points.  Voltage at the points is about 10.8v or so.  I don't think this is the cause though, because other wires that register a similar amount cause the lamp to glow brightly.

Because of the above issue, I used the spark plug grounded to the cooling fin of the engine to time my points.  I use the spark from the plug to indicate when the points are beginning to open.  However, when I use this method and turn the crank slowly, I get multiple sparks.  For instance, when I'm testing the 1-4 point, I am approaching the F mark on the advance plate.  About 1mm away from reaching the mark, I get a spark.  When I continue to slowly turn the crank, it sparks again, but stronger, when the F mark is aligned.  Is this supposed to happen?  I replicated the results multiple times to make sure that it was a recurring event.

[Patrick]

I do not believe you can static time an ignition with Mark's ignition installed. No juice running through the points. Gap your plugs and you can set the dwell and timing after it starts. It should be close enough to start, even if it does not run well. You can always disconnect the Hondaman ignition to set the static timing. Only takes a couple minutes.

Patrick

[Duanob]

Stating the obvious but are you getting gas out the fuel tap? If you only have a gallon in your tank that might not be enough especially if the internal tank screen is dirty. Pull the fuel lines and see if you're getting fuel flow first.

Check the obvious first. Fuel + Timed Spark + Compression = ignition.

[c.tran]

Ah I didn't know I couldn't set static timing with Hondaman's ignition in.  I'll take it off and give it a try.

Yes, I have a new fuel filter and there is most definitely gas going through.

Thank you everyone for all of the input and advice!

[c.tran]

UPDATE:

She lives!!!  After readjusting the carb slides and setting my timing without Hondaman's ignition plugged in, I was able to get it running and idling!  Thank you so much to everyone who posted on this thread; you guys helped tremendously.

[Patrick]

Now plug the Hondaman ignition back in, set the dwell and run time it. Then turn it off. You still have wiring to do.

You could tune up the carbs now, but then you will ride it. I guarantee it. You want everything to work before you take it out on the road. How do you plan to synch it?

Patrick

[c.tran]

Yeah I'll probably end up tackling the wiring tomorrow.  Is static timing enough, or would you recommend dynamic timing?  To my understanding, dynamic timing also allows you to set up the advanced timing when the engine is at 2500-3000rpm?

I don't have a tool to sync my carbs, so I'll probably have to enlist the services of someone who has the correct equipment to do so.

[Patrick]

You need to do a dynamic timing. Static timing is only to get it started. The nice thing about tuning up that ignition is you set the dwell and you can forget what your points look like. You won't have to look at them for years. After you get the timing and dwell just right, tuning the carbs is much easier.

[seanbarney41]

dynamic timing allows you to check that the advancer is functioning correctly.  The advancer was not designed to be easily adjustable, although it can be done by modifying springs and stops

accurately bench synced carbs are often very close when checked with vacuum.  If your bike rides okay, the lack of a vacuum sync is not gonna hurt anything.

[c.tran]

Ah so while checking my dynamic timing, if the index mark didn't line up in between the two tick marks clockwise of the TF marks I would have to adjust the advancer plate--not the timing plate--correct?

[seanbarney41]

that is pretty much right...the advance can be graphed as a curve.  So, note advance curve specs such as advance starts at say 1500rpm and ends between the two tics at 2500rpm, hook up timing light, start bike, make sure that F mark lines up at idle speed and that your idle speed is set below the start of the curve, gradually increase rpm and watch the mark move until you get to 2500rpm where it should stop between the two tics.  I don't know the advance specs.  They should be in the manual somewhere.
     Really, the timing is more important at 2500 rpm, so many will dynamically time the bike to line up with the two tics at 2500rpm and not worry about if the f lines up at idle.  I have found the advancers work pretty good on these bikes as long as the mechanism isn't stuck.  I have always found that static timing will match dynamic as far as the f mark at idle and that full advance will match the two tics, as long as the advance mechanism is not gunked up and sticking.

[c.tran]

Awesome, thank you seanbarney for the insight.  It makes a lot more sense to me now.

Now to find speedo and tach cables...

[alacrity]

... and ran it all the way back to the battery negative terminal.  This ensures a perfect ground to the batt which we know has a perfect ground to the chassis.

There is no guarantee whatsoever that the battery NEG has a perfect ground to the chasis. In fact, it would be far more prudent NOT to ground to the NEG terminal and instead ground to the frame directly if the additional ground is required/desired. It's shorter to the frame, it's direct, and it does not involve removing this wire when swapping a battery.

All too often improper grounds to the frame are in fact responsible for poor charging. Nearly everyone who has their frame powder coated needs to go back and grind the frame clean to bare metal for this very purpose.

yep- all true.
I scrapes to bare metal at the negative batt line to frame location as well as the cool grounds and a couple other key spots. I got the dedicated ground wire to the points plate instruction directly from Hondaman himself


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