Topic: Trouble starting '75 CB550 - FIXED

[c.tran]

Hello,

I'm sorry in advance for the lengthy post.

I'm relatively new to the forums; this is my first real post despite my having read dozens of posts before.  I have a 1975 CB550K1 and am having trouble starting the engine.  Here is most of what I've done and some specs:

1.  Tappet adjustment - 0.05mm inlet, 0.08mm exhaust.
2.  New points plate assembly - I gapped the points to 0.35mm and also did the timing with a 12v test light.  I made sure that when the F mark aligns with the index, the test light comes on; I did so for the 1-4 points and the 2-3 points, respectively.  I also tried to set timing in the same way, but using the T mark.
3.  Dyna 3 ohm ignition coils - Tested voltage to coils; they receive approximately 10.80v.
4.  Dyna 7mm copper core spark wires
5.  NGK 5 ohm plug caps
6.  NGK D7EA spark plugs - gapped all plugs to either 0.025" or 0.03", I believe; all spark plugs receive a strong blue spark when tested.
7.  Cleaned carbs - Cleaned with carb spray and an ultrasonic cleaner; set float heights to 22mm; set air mix screw to 1.5 turns outward (counter-clockwise) from lightly seated; replaced fuel bowl gaskets with new ones; bench synched carbs with a 1/8" drill bit.
8.  Replaced air box boots with new ones
9.  Replaced stock air cleaner element - Replaced with Stilltime's adaptor and K&N RD-0710 air filter.
10.  Installed Hondaman's Transistorized Ignition
11.  Installed Hondaman's 2 ohm resistor pack
12.  Replaced engine oil with 10-40W synthetic oil
13.  Reset cam chain tension adjuster - Loosened lock nut so screw can reset, then tightened lock nut.
14.  New battery - 12v 14a (using a friend's new CB750 battery until I get my own).
15.  Compression test - Tested with a Harbor Freights compression tester measuring 0.45mm outer diameter (fixed hose) with an adaptor hose for the spark plug hole (0.60mm outer diameter), totalling 40" in length.  Cylinders tested as: #1 (80psi), #2 (70psi), #3 (75psi), #4 (80psi); adding oil did not significantly improve the psi in any cylinders.
16.  Checked grounds and wires on main wiring harness

The conditions under which I try to start my engine are as such:

1.  I live in central Texas - currently the weather is in the mid 60s.
2.  Fully charged battery - measured voltage is usually between 12v-12.4v.
3.  Approximately 0.5-1.0 gal fuel in tank.
4.  Air box and filter are installed.
5.  Exhaust is not installed.  I have a MAC 4-1 sitting in the garage.
6.  Tried the choke at different positions and modulating the throttle at different positions.

When I attempt to start my engine using the start button on the right-hand control pod, it sputters and combusts, but will not start and stay on.  I am sure the spark is strong and fuel is going through; I was actually running pretty rich for a while.  I then set the air screws to stock settings (not yet sure if this fixed the A/F ratio though).  I am slightly concerned with the compression of my cylinders, though a motorcycle mechanic told me that he thought it was enough to start the engine.

I have tried pretty much everything I can think of and am at a loss.  Any suggestions or help would be greatly appreciated!

[DaveBarbier]

Compression seems pretty low. Since they're all around the same, though, that seems strange to me. Did you use the kick start or electric starter to test compression? Have the throttle wide open? Let it go for about 4 revolutions per cylinder? If oil didn't help then it's probably the valves aren't sealing well.

Any reason you haven't installed the exhaust? I think you should have it on when you're trying to diagnose a non-running issue.

So this was once running? Did it all of a sudden stop?

I also don't know what you mean by, "I tried to set timing in the same way, but using the T mark." Maybe this would make sense to someone with more experience but I don't think you'd ever set timing with the T mark.

Hopefully someone who has more knowledge can help, I really got nothing.


---
1978 Honda CB550K

[Gene]

Points should be gapped at .14 (Between .12 and .16).  All else fails, use a matchbook cover.

That should be all it is.  Your points are too wide.

[DaveBarbier]

Points should be gapped at .14 (Between .12 and .16).  All else fails, use a matchbook cover.

That should be all it is.  Your points are too wide.

He used a metric measurement. .3 - .4mm is correct. The .012 - .016 is in inches.


---
1978 Honda CB550K

[Gene]

dang metrics - I'm still behind - tho I know everything's metric . . .

[mrfish2]

Compression seems pretty low.

That's probably because the gauge he used had a 40 inch hose. A longer hose will give lower compression numbers.

[DaveBarbier]

Compression seems pretty low.

That's probably because the gauge he used had a 40 inch hose. A longer hose will give lower compression numbers.

Oh, I see that now. But 40 inches! Longest compression test hose I've heard of.


---
1978 Honda CB550K

[c.tran]

Thanks for all of the replies guys.

The PO told me that this bike was running before it had sat for a number of years.  My coils are routed correctly; one is for cylinders 1 and 4 and the other is for 2 and 3.  I suppose I can try with the exhaust on.  It could be that there isn't enough back pressure..but I kind of doubt it.  My friend's CB750 idled just fine without an exhaust.

I used the kick starter to test compression.  Yeah I figured the low compression could be due to the length of the hose.  The valves appear to be seated correctly.  I recently discovered that my timing and gaps keeps changing...I'm almost positive that is the culprit.  However, I just purchased the Daiichi points plate assembly from 4into1 just recently.  The plate doesn't seem to move at all when I'm trying to start the engine.  The adjustment plates for the gaps don't seem to move either.  I have no idea what could be causing the timing and gaps to change.

Also, whenever I use the test light to check my points timing (though I can actually hear the sound of the spark from the plugs), The test lamp turns on in correspondence with the spark, but it is very dim.  It barely glows and is slow to come on.  I thought it might be a drop in voltage to the points, but when I checked with a multimeter it read ~10v.  The test lamp seems to work well with all other aspects of the wiring.  Not sure if this may have anything to do with my engine troubles.

[70CB750]

Don't worry about the compression, often it improves once you get the bike running and put some miles on it.

The way I understand it, piston rings are supposed to be loose and on longer parked bike they can be stuck, held in place by carbon deposit. 

Good, hard, long run will get those rings to float again and compression will improve.

[Deltarider]

Don't worry about the compression

Calj is right. Besides, it is difficult to do a proper compression test. I myself never managed.

[c.tran]

Yes, my blue wire is going to cylinders 1 and 4.  Since I've been fouling up my plugs I don't think it's a fuel problem.  There is a strong smell of fuel coming out of my exhaust too in my attempts to start it.

Hm...so do you think I should just try to clean up all of my grounds calj?  I cleaned up the ground for the coils and the grounds for the points are brand new.  Even if there is some resistance in the harness, shouldn't the engine still start?

[c.tran]

I may have used the wrong description here.  By fouled spark plugs I meant that when I pull them out, the threads are covered in blackened gasoline.  When I clean them off, they look brand new.  I can't get a picture right now, but I can post one later if necessary.

Is it just the points that can be a problem or could the plate also be a problem?  Since I bought the whole assembly, it came with the plate, points, and condensers.  Would I be able to just swap out the points with TEC points?

I'll do that.  So I should test every connection I see for 12v (i.e. all the bullet connectors, ring connectors, and the plastic pinned connectors)?

[c.tran]

Thanks calj, I'm cleanin up my OEM points plate and points right now.  I'll try out different combinations of the TEC and Daiichi ignition parts and see if I make any progress.'

I'll post when I have updates.

[Mooshie]

Yes, despite a low voltage, the bike should start. How fouled are the plugs now? If they're badly fouled, it won't start. Post a picture perhaps?

The Daichi points are branded as a poor quality part. I've got a stock TEC brand you're welcome to if you'd like to try swapping it? Or grab a better quality TEC set locally if can find it.

I'd encourage you (after resolving the no-start issue) to go thru the harness and switches to locate your voltage loss. Use a multimeter and test for 12v at each junction, cleaning as you go when it drops. A 1-1.5v drop is too much as you get to the coils.

+1 to that.  And it is not just the points but the plate (and how it rests/sits--whatever the term is) as well as the points themselves.  You can get a good TEC on ebay if you search (that is where I got mine--reasonable price and no problems with needed constant adjustment).  I also use HondaMans electronic ignition though as well (set it once and done).

[alacrity]

yes.  No matter what else you do, go, right now, before taking another breath, and order Hondaman's magic ignition box.

Trust me here.  It makes a world of difference. The spark is so good and consistent that the bike is basically already running a split second after I thumb the starter -- like before I even have time to remove my thumb. Of course, everything else is set up correctly as well, but I did a test - simply disconnected the box and ran a half day with out it.... the starter would spin a few times before firing this way (straight from the points).  Plugged it back in and voila. Perfect.

You may well have OTHER issues, but if you have your static timing set correctly/perfectly...if you have good coils (you tested them right?) ...  if you have your points set and gapped perfectly, If your dwell is correct,  if you have your ignition wire connections correct, if you have a good ground from the points plate to the case and back to the battery (I ran an EXTRA ground all the way back to the batt from the points plate per Hondaman's recommendation), and if you have new spark plugs with proper gaps, and IF you THEN install hondaman's transistorized ignition box, then IF your bike doesn't start and run, your problem isn't with the ignition system.

[c.tran]

yes.  No matter what else you do, go, right now, before taking another breath, and order Hondaman's magic ignition box.

Trust me here.  It makes a world of difference. The spark is so good and consistent that the bike is basically already running a split second after I thumb the starter -- like before I even have time to remove my thumb. Of course, everything else is set up correctly as well, but I did a test - simply disconnected the box and ran a half day with out it.... the starter would spin a few times before firing this way (straight from the points).  Plugged it back in and voila. Perfect.

You may well have OTHER issues, but if you have your static timing set correctly/perfectly...if you have good coils (you tested them right?) ...  if you have your points set and gapped perfectly, If your dwell is correct,  if you have your ignition wire connections correct, if you have a good ground from the points plate to the case and back to the battery (I ran an EXTRA ground all the way back to the batt from the points plate per Hondaman's recommendation), and if you have new spark plugs with proper gaps, and IF you THEN install hondaman's transistorized ignition box, then IF your bike doesn't start and run, your problem isn't with the ignition system.

I have Hondaman's transistorized ignition, though I suspect my Daiichi points assembly to be a probable issue of my woes.  I'm sure my coils are good, my ignition wires are set correctly, and my sparks are gapped correctly.  As calj pointed out, my grounds/connections may not be up to par based on my low (10. voltage to my coils.

Is the points plate just grounded by its contact with the adjustment screws and the engine casing?  You said you also grounded the plate directly to the battery?  How so?

Hopefully I can make some headway with my TEC points/plate and isolate the issue.

[Patrick]

You say you set the carb synch with an 1/8 drill bit. Which side of the slides did you gap the slides? Do the slides only close to a 1/8 inch gap? They have to close all the way or you are trying to start the bike with the throttle half full open. If it has a gap like that and it catches it is going to shoot up to an idle of about 5000 rpm.

How did you test the spark plugs? Did you ground each spark plug wire to the block and turn it, or did you check all the plugs on one wire?

Where in Central Texas are you? Here in Austin it is 73.

Patrick

[c.tran]

You say you set the carb synch with an 1/8 drill bit. Which side of the slides did you gap the slides? Do the slides only close to a 1/8 inch gap? They have to close all the way or you are trying to start the bike with the throttle half full open. If it has a gap like that and it catches it is going to shoot up to an idle of about 5000 rpm.

How did you test the spark plugs? Did you ground each spark plug wire to the block and turn it, or did you check all the plugs on one wire?

Where in Central Texas are you? Here in Austin it is 73.

Patrick

I synched the carbs from the engine side of the carbs.  Hm..actually, the slides may only close to 1/8".  Can I correct this by turning the idle screw clockwise?

I tested the spark plugs by grounding them to the engine case and testing each one on their respective wire.

I'm actually in Austin as well--North Austin to be specific.  It was in the 60s when I was writing the original post.

[Patrick]

I'm actually just north of P'ville out in the county.

If you left your slides with a 1/8 gap you just set your minimum idle with the slides. That is not good. The slides have to close all the way. You set the final gap with the throttle screw. I bet you are shooting a firehose of gasoline into each cylinder. I did that the first time I bench synched my carbs. 

The cure? The carbs have to go back on the bench, Sorry. You use the drill bit just to make sure the slides are all closing at the same time. Screw the throttle screw in a bit before you bench synch, so that when you take the pressure off the throttle screw the slides close completely.

Do that and I bet your next starting experience go a lot better.

BTW, if you already have Hondaman ignition those daiichi points will work just fine. With his box the points don't fire, so don't burn. The springs suck, but if you have an old set of points you can double spring the daiichis or just use the spring from the older, better set. Make sure you lube the cam well, though. I have a bunch of old 750 points. Don't know if they are the same.

Patrick

[c.tran]

Ah I'm about a mile south of Pflugerville.

Hmm...That would make sense and explain why my sparks are always drenched in gas.  I have space on both sides of the throttle screw to adjust--is there any possible way I can back out the screw to lower the slides instead of taking them off?  Sorry, just trying anything I can to avoid trying to take off the air box and carbs and put them back on again...Makes me wish I had gone with pods.

What do I lube the cam with?  Sorry about all the questions..I'm pretty new to motorcycles and I had the great idea of trying to bring a 40 year old bike back to life as my first project and bike...

[Patrick]

If what you have told me about leaving a 1/8 gap when you bench synched your carbs is accurate your throttle screw will not lower the slide below that. I don't know how you can have threads on both sides of the throttle screw if you've never had it running. It means you would have had to start with a 1/8 gap and then screwed the throttle screw in creating a larger gap. If you try to start your bike again before doing anything with your carbs, please, please, please first make sure the bike is in neutral and also that there in nothing of value directly in front of the bike. Then start your GoPro and go for it.

Air boxes on these old fours are usually a pain in the ass, mostly because all the rubber parts are hard and inflexible. There are cures for that, but not to worry about with a not yet running bike.

Patrick

[alacrity]

I made a dedicated green ground wire and connected it to the points base plate, fed it through the woven sleeve that contains the other ignition wires there (blue, yellow, green) 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.

[c.tran]

Okay, not to get too far off topic here, but I just want to be clear.  I know there are tons of threads on bench syncing, as I've read dozens of them and watched tons of videos.  Is this the correct process?

1. Take off carbs
2. Back out main idle screw all the way (so the screw is not putting any pressure on anything)
3. Screw in the main idle screw until one of the slides seats at the bore (meaning no gap between the slide and the bore, looking in from the engine side)
4. Adjust all of the other carbs using drill bit, light method, etc to match the master slide (by looking through the air box side)
5. At this point, all the slides should be seated at the bottom of the bore (looking from the engine side).  Is this the final position for bench syncing?  Or do I have to back out the main idle screw a bit to let more air in for the idle?

[seanbarney41]

Ah I'm about a mile south of Pflugerville.

Hmm...That would make sense and explain why my sparks are always drenched in gas.  I have space on both sides of the throttle screw to adjust--is there any possible way I can back out the screw to lower the slides instead of taking them off?  Sorry, just trying anything I can to avoid trying to take off the air box and carbs and put them back on again...Makes me wish I had gone with pods.

What do I lube the cam with?  Sorry about all the questions..I'm pretty new to motorcycles and I had the great idea of trying to bring a 40 year old bike back to life as my first project and bike...

theoretically, it is possible to devise a way to lower all 4 slides roughly the same amount via the sync screws, but an accurate bench sync is important and it's gonna be real difficult to know what is really going on without pulling the carbs and having a good look see.  Dealing with the airbox seems like a #$%* at first but it just takes practice.

[Patrick]

Synch the carbs so that the engine side - the flat side without any scoop taken out - is as absolutely even as you can get them. Back off the throttle screw completely, then screw it in enough to give you some play so that after you synch the slides you can back off the throttle screw to make sure the slides close completely.  The whole point of the synch is to get all the slides moving exactly the same, not set the minimum gap.