Topic: 75 CB550F SS Dies after 10 min but starts right back up!?!? Battery is fine!

[Smudgemo]

I don't have anything useful to add.  I just wanted to say I dig the look of your bike.

[seanbarney41]

Have you tried turning up the idle speed screw after the bike is warmed up.?

[DaveBarbier]

Another test I’d do is as it’s sputtering and dying put your timing strobe on and see if the ignition is cutting out. Do this at home obviously not out on the road. Put the strobe on, fire it up and keep the revs up so it runs and see if the flashing light is consistent. Then let the revs drop and watch to see if the light goes erratic on you. Do this for cylinders 3&4.

I did the timing light for cylinder 4 and it was fine but when I did cylinder 1 it was erratic/ not consistent. Going in direction from left to right sitting on the bike.


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You did this for cylinder 3 also? So as the engine was sputtering the light kept on flashing consistently?

[BenelliSEI]

Yes, fuel level in the bowl is too low.

[Maraakate]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

[CarbasaurusRex]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Well before I get to that, I put on all the old coils and points. It now only runs on two cylinders, but all the wires get spark... two pipes are hot and two are cold. only other thing I notice is occasionally the very far left and far right carbs pour out fuel from the bowl nipples but cylinders 1 and 4 are running fine. Tried switching points from old to new and combo of both and still the same issue. Not to much when doing a static light test, the light comes on for the 1-4 T’F but no light whatsoever for the 2-3 T-F. Moving the plates and adjusting points do nothing. Now I’m confused more than ever...


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[CarbasaurusRex]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Also, it’s most likely not the idle screw because it would run pretty well until it warms up. Then the idle is high. Above 1500 or so. I have done a bench sync and a carb sync before all of this.


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[Maraakate]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Also, it’s most likely not the idle screw because it would run pretty well until it warms up. Then the idle is high. Above 1500 or so. I have done a bench sync and a carb sync before all of this.


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Then you do need to adjust it.  My CB550K the idle will drift higher if it's warmed up like that, you need to adjust probably a small quarter turn (maybe not even that much) after 10 minutes of actual riding.  I don't mean sitting at stop lights.  Drive it 35-50mph around some backroads.  Come to a stop sign, adjust that idle.  If it's too high that may be part of your problem.

Not sure how much you ride, but if this is your first bike it may be hard to tell what a good idle RPM sounds like for these bikes.  The tach is probably inaccurate, so it might be worth it to get an external tach that allows you to see the 500-2000 range in 100 RPM marks.  I've found a used one from the 70s on ebay for like $20.  I set the idle RPM by ear, since I know what it typically sounds like.  Even though my tach is reading about 1700 RPM which I know is not right.  When I put the external tach on it it was reading about 1100-1200RPM which is what you want.  So don't take that tach on the bike as gospel.

[Maraakate]

Just for the record, the portable tach I got for cheap was an old Suntune CP 7602 Inductive Dwell/Tach meter.  Pretty easy to find and cheap.  Probably worth getting one for your toolbox if you dont have a portable tach already.

[Maraakate]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Well before I get to that, I put on all the old coils and points. It now only runs on two cylinders, but all the wires get spark... two pipes are hot and two are cold. only other thing I notice is occasionally the very far left and far right carbs pour out fuel from the bowl nipples but cylinders 1 and 4 are running fine. Tried switching points from old to new and combo of both and still the same issue. Not to much when doing a static light test, the light comes on for the 1-4 T’F but no light whatsoever for the 2-3 T-F. Moving the plates and adjusting points do nothing. Now I’m confused more than ever...


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You're saying with the aftermarket points plate you still can not get 2-3 to fire or get the test lamp to come on when trying to adjust it?  If yes, then you probably pinched or broke a wire somewhere.

[CarbasaurusRex]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Well before I get to that, I put on all the old coils and points. It now only runs on two cylinders, but all the wires get spark... two pipes are hot and two are cold. only other thing I notice is occasionally the very far left and far right carbs pour out fuel from the bowl nipples but cylinders 1 and 4 are running fine. Tried switching points from old to new and combo of both and still the same issue. Not to much when doing a static light test, the light comes on for the 1-4 T’F but no light whatsoever for the 2-3 T-F. Moving the plates and adjusting points do nothing. Now I’m confused more than ever...


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You're saying with the aftermarket points plate you still can not get 2-3 to fire or get the test lamp to come on when trying to adjust it?  If yes, then you probably pinched or broke a wire somewhere.

I don’t have an aftermarket points plate. Only points themselfs and condensers. The points plate is the one that came with the bike.


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[CarbasaurusRex]

Have you tried turning up the idle speed screw after the bike is warmed up.?

Didn't even think to mention that.  Yeah, a good 10 minutes of riding is enough to consider the bike properly warmed up and this is when you should adjust the idle.  This is also when it is proper to do any kind of vacuum sync and adjusting pilot/air screws (gonna get the terminology on this wrong, I know it's different between years and if it points to intake or airbox, etc).

If you just started the bike then did your adjustments they will be wrong and drift as the bike warms up.  If you really can't wait, let it sit idling for 10 minutes with a box fan pointed at the engine to prevent overheating.  Even if it doesn't overheat, after sitting for a few minutes the idle WILL drift and getting this all dialed in will be difficult.

Well before I get to that, I put on all the old coils and points. It now only runs on two cylinders, but all the wires get spark... two pipes are hot and two are cold. only other thing I notice is occasionally the very far left and far right carbs pour out fuel from the bowl nipples but cylinders 1 and 4 are running fine. Tried switching points from old to new and combo of both and still the same issue. Not to much when doing a static light test, the light comes on for the 1-4 T’F but no light whatsoever for the 2-3 T-F. Moving the plates and adjusting points do nothing. Now I’m confused more than ever...


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You're saying with the aftermarket points plate you still can not get 2-3 to fire or get the test lamp to come on when trying to adjust it?  If yes, then you probably pinched or broke a wire somewhere.

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[Maraakate]

I can't remember the colour coding off-hand, but another potential issue is the insulating washer for points 2-3.

[Maraakate]

And by a pinched wire I'm referring to the where it exits the points plate to the harness.  Check with a multimeter.

[CarbasaurusRex]

And by a pinched wire I'm referring to the where it exits the points plate to the harness.  Check with a multimeter.

Ok got it running on all fours again. Started it up with idle screw a ways in. And of course it idles high. Waited ten minutes then readjusted it to a normal, true 1100 rpms. It has been about 35 min and it hasn’t died yet. So far so good!!! But question. Do I have to start it like this every time before I ride??? Is this what people back in the 70s had to go through before riding these Honda’s?


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[Maraakate]

You said waited 10 minutes.  Did you just let the bike sit there idling for 10 minutes?  If yes, this is wrong.  Ride the bike for 10 minutes, then set the idle.

You don't have to do this every time you ride.  Once it is set (with choke knob DOWN, i.e. off) it should stay at 1100 RPM.  Your starting procedure may change slightly for you now, depending on how off it was:

* Start the bike with the choke knob all the way UP.  Sometimes, depending on the temperature you may have to give it a slight touch of throttle like 1/8 or so.
* Hold the revs steady at about 2000RPM or so for a few seconds.
* Push the choke knob slightly DOWN until you feel the "detent".
* If the bike starts to stall out, give it a bit more throttle for a few more seconds until the idle stabilizes.
* Go for a ride, slowly start pushing the choke knob DOWN as time goes on.  You will know how long it takes for your bike to warm up depending on the route you take and the idle speed.  If I leave my choke up too long on that first detent the idle does start to go up.  When the bike is warmed up and the choke is DOWN/off then it stays at that nice 1100 RPM idle.  When it's not warmed up enough, say choke lever is mid way and you try to turn it off the bike may hesitate a bit or the idle may get too low and possibly stall out.  You'll get a feel for it.

Once you have the idle set this way, leave it alone.  Shouldn't have to readjust it again except when doing a vacuum sync, new air filter, or having to change out the air/pilot screws due to o-ring's causing an air leak.  Sometimes, if the valve clearances have drifted an awful lot or even your points timing or points spacing it may change your idle as well.

[DaveBarbier]

Good to hear that so far it’s not stalling. Idle speed adjustment is a set and forget. As it has been said, ride around (for my 650 it’s a little more than 10 minutes) until it is completely warmed up and you can totally disengage the choke. Set the idle. The next time you start it up when it’s cold you’ll need to apply the choke and slight throttle to keep it running. But just go riding. No need to wait for it to warm up in your driveway. In the later models Honda added a “fast idle cam” on the carbs where you pull the choke and it would ever so slightly open the throttle. That would be a more “hands free” approach. All internal combustion engines have to have a richer fuel mixture (ie choke) and a higher idle to run when cold. That’s why your car idles higher for about 30 seconds or so in the winter mornings. You just have to do it manually with your wrist for the old bike.

[Maraakate]

Yeah Dave is right.  I don't believe the 75 has the fast idle cam, or if it does perhaps it needs adjusting.  And yes, for some bikes could be more than 10 minutes.  Sometimes, depending on how I'm driving it may take a bit more than 10 minutes.  If that's the case, after 10 minutes just readjust that idle, but keep driving, and check it again at 15 minutes and 20 minutes when at a stop.  After it's dialed in you should be good.

If this was the only problem, then good call to seanbarney41.  Sometimes it's very easy to overlook the most obvious things.

Once you've confirmed that, personally, I would swap back to the original points and condensor and coil if you have not already, just for reliability sake and keep the new parts on hand in case of emergency.  However, you can do it either way you like.  Just from the grapevine it sounds like the aftermarket electrical components are real hit or miss on their reliability so it's a call you will have to make.  Just be sure you carry spares for a couple of months so you don't get stranded.

[CarbasaurusRex]

So the only issues is when the choke is all the way up, the bike won’t start at all. It starts without the choke having to be used. When the bike runs and the choke is engaged all the way, the bike dies.


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[Maraakate]

Depending on the temperature and how often you ride it and the condition of your air filter, carb tuning, etc. yes you may not need the choke fully engaged.  Some days, I only need to get it to that first "detent"  when pulling up on the choke and it will start with a bit of throttle.

You can always check the condition of your plugs.  If the bike is riding okay, you're getting proper MPG and it's not smelling like fuel then you're probably within spec, though maybe a touch on the richer side.  Just don't want to be too rich that you foul plugs or foul your oil.

But, if it really bothers you and is affecting performance you may just need to adjust the pilot/air idle screws to get the colour you want.  I've never really messed with those, someone else can chime in, but basically from what I understand is you set them all at specific starting point (I believe 1 and 1/4 turn) and then do small increments while listening to the idle.  As you chase that idle around you also need to readjust the idle speed screw as well.

[CarbasaurusRex]

Depending on the temperature and how often you ride it and the condition of your air filter, carb tuning, etc. yes you may not need the choke fully engaged.  Some days, I only need to get it to that first "detent"  when pulling up on the choke and it will start with a bit of throttle.

You can always check the condition of your plugs.  If the bike is riding okay, you're getting proper MPG and it's not smelling like fuel then you're probably within spec, though maybe a touch on the richer side.  Just don't want to be too rich that you foul plugs or foul your oil.

But, if it really bothers you and is affecting performance you may just need to adjust the pilot/air idle screws to get the colour you want.  I've never really messed with those, someone else can chime in, but basically from what I understand is you set them all at specific starting point (I believe 1 and 1/4 turn) and then do small increments while listening to the idle.  As you chase that idle around you also need to readjust the idle speed screw as well.

Great! That info helps. Another point to mention. People have said that these 550s are really quick. I’ve had a Gs500 before and they seem to be very similar in performance. I haven’t ridden a properly tuned, in spec Cb550 so I’m not sure if it’s normal. Also clutch is slipping so that could be a factor as well.


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[seanbarney41]

Gs500 is probably a fair bit faster than the cb.  The cb wont make good power below 6000rpm, so if it does not rev out to 9000 its gonna be slow.