stalls when hot

[jasper]

OK - I've been hanging out in the electrical section so far, but now that my ignition issues are sorted it's time to start tuning up the fuel.

1) Carbs dipped, stripped, rebuilt with new o- rings and bench synched.

2) 1980 Canada only petcock, two positions ON and RES. Using a hand pump to actuate the valve (zip strepped to handle bars). Plugged off the vacuum line from carb #2

3) Mix screws turned out 3 full turns from lightly seated.

4) Full tank of gas.

5) Dyna-S ignition. New battery, nice strong spark visible when a plug is pulled and grounded.

6) I set the valve lash to 0.003"...but just when I was buttoning up I checked a few and they were tight......hold this thought.

Long story short, the bike starts cold on the button, with no choke. Runs nice and strong up to redline. Idles ok at the first one or two sets of lights.

Hit some traffic, gets a bit hot...bog then stall. Third time this happens - no restart possible. Come back and hour later when it's cooled down and it starts on the button with no choke.

So I'm going to turn the mix screws in a half turn before my ride homw. When I get home I'm going to pull the valve cover and check my clearances for real (maybe tomorrow...gotta be cold).

Any other ideas gents??

Thanks

[Gonzo]

I don't have much more to say than you SHOULD need to choke from cold. Once the engine warms, it will take less fuel to combust so you can back the choke off. I'm thinking it's too rich from the start and once it gets warm there isn't enough air to keep things going. My bike is running VM's so I don't know about your carbs, but 3 turns sounds a bit much to me. But like I said, different carbs.

[niclpnut]

Yeah sounds like its rich, and you're seeing it get worse as it warms up.

Let it idle a few min after start and pull the plugs...

Will tell you for sure. Then use highest idle method for the mixture screws.

Of course checking the valve clearances cant hurt

Nic

[mike_of_bbg]

My bike ran better with the screws out to only 2.5 turns. I think they went in from there when I did the highest idle method. Yes, check the plugs. It could be that you're fouling the plugs, in which case you would see blackening of the insulator. What plugs? B8ES? You could try going to B7ES (1 range hotter) to prevent fouling. Make sure your filter isn't over-oiled. You also need to do a real sync of your carbs. A bench sync is a good start but you might have a cylinder or two, too closed, drawing too much fuel and fouling.

I can't remember from your Dyna thread: do you have a coil relay installed? Have you checked the volts at the coils?

[Flyboy]

Sounds like you may be getting a rich cut, plugs will have to come out to varify it, maybe blocked tank breather, check it is clear and you not getting a vacum in the tank as fuel is used, and stopping fuel flow.
I don't know where this story comes from that the bike HAS to have the choke to start and that it shouldn't start without it?
My bike has never needed the choke for start, even on the first start of the day, unless it has really been cold, then yes. Pfhaa, I say.
And yes, check your clearances, they may be borderline and then tightning up once the motor warms up, preventing the valves from sealing, leading to a loss of compression.
Are they not supposed to be at least .004??? not .003, dunno, just asking.

Or it may be totaly unrelated, you mentioned ignition issues, are you sure you are not loosing spark as yur CDI or something warms up, maybe not sorted yet?

[Gonzo]

I only say it should be choked because if it doesn't need a choke, then it's a bit rich. Perhaps your bike is just "rich enough" to not need it but lean enough to run fine after warming up. But that doesn't sound like the case here. Imo the choke was invented for a reason.

[Flyboy]

Gonzo, not arguing with you, I have seen most people say the same, and that is cool, I agree, choke is there for a reason, for you poor buggers who live three feet under snow in winter, here it seldom drops below 55 degrees even in the middle of winter.
In fact, white you poor lot are melting away in a heat wave, we are in the middle of winter now and it is going to be 70 today............Damn, I love Africa.
It may also have something to do with the fact that my bike still has standard factory jetting as it came, and I live at 5500ft above sea level, tweaking it slightly to the rich side.

[jasper]

All good stuff guys.

1) losing spark - considering this but I have a brand spanking new Dyna-S setup and I'm running without the cover over the signal coils to keep things cool. I just checked the spark at #4 as the bike is currently hot and bothered and the spark is very strong. No relay mod yet....I've checked the voltage at the coils 856 times now and it's always 12 volts +/- 0.5. I'm ruling out sparking issues.

2) Just tried to adjust the mix screws. Lots of people talking about the fastest idle method but not really easy to find a written procedure. Back in my Weber days (dual triples on a flat six air cooled car) I used to get the motor idling and then screw in the mixture screws one by one until the engine started to stumble a bit, then I backed off a half turn. So that's what I'm doing here.

In this case, turning in the mix screw on the #1 carb doesn't change the idle speed at all...not even if I turn it in all the way. The others start to stumble at about 1.5 turns out, so they are set at about 2 turns out now.

3) I rode home today with each screw 2.5 turns out. Before I adjusted them as described above I pulled the plugs and found #1 black. The others are black around the edges but the electrodes are tan.

4) The bike always sounds like it's missing a bit...like an uneven idle. I'm guessing something funny is going on with #1....but what.

5) Some weeks ago I did a compression check and if I recall correctly.

#1 - 90
#2 - 120
#3 - 120
#4 - 100

No really funny smoke that I'm aware of...black and sooty exhaust maybe but remember I've only just sorted the ignition out so who knows how badly carboned up everything is.

6) Brand new B8ES plugs.

I'm thinking that checking the valve lash is my priority right now....look for valves that aren't closing especially at #1. Spec is 0.001" to 0.003" but you know what ...I'm ok with 0.004".

Once that's done then another compression check...then try the mixture adjustment again. You know I never checked the float heights when I did the carbs. Gotta figure out the best way to do that. I saw a procedure where you hook a hose up to the drain and then hold the hose up higher than the top of the bowl. The fuel in the hose rises to the same level as the fuel in the bowl right.

Also...synchronising. Yah I have to get that sh*t together. Man oh man.

[Flyboy]

Jasper, sounds like you have something going on there with that number one cylinder all right, but one cylinder should not be enough to stall it once it gets hot and prevent a restart.
But you sound like you on the right track to getting it sorted out.
Please don't adjust your valves on my say so, I was not sure what your clearences should be, it just sounded tight to me, but if the book says 001 to 003 then that is what it is, and you seem to have erred on the open side, so that is good.

[azr]

If #1 isn't changing the idle when you adjust the mixture screw there's probably something wrong inside the carb but since you haven't done a synch yet you could try doing that first then see if the mixture screw effects the idle, if not you're going to have to pull that carb apart again. The best way to set your floats is with the hose method, it's really the only way to get it exact. If you can find the right size hose, just shave a bit of the end so it crams into the drain hole tight, that or buy a "float bowl height adjuster thingy" from Z1. I'm no expert on the 550's but 90 sounds too low, I always thought 100 was about as low as you could go with compression? hopefully that will be better when you take it now, valve adjustment always bring up the compression.

[hjfisk]

Sounds like you may be getting a rich cut, plugs will have to come out to varify it, maybe blocked tank breather, check it is clear and you not getting a vacum in the tank as fuel is used, and stopping fuel flow.
I don't know where this story comes from that the bike HAS to have the choke to start and that it shouldn't start without it?
My bike has never needed the choke for start, even on the first start of the day, unless it has really been cold, then yes. Pfhaa, I say.
And yes, check your clearances, they may be borderline and then tightning up once the motor warms up, preventing the valves from sealing, leading to a loss of compression.
Are they not supposed to be at least .004??? not .003, dunno, just asking.

Or it may be totaly unrelated, you mentioned ignition issues, are you sure you are not loosing spark as yur CDI or something warms up, maybe not sorted yet?

I agree check your clearances again you are running on tight side when the bike warms up. I also very seldom need a choke on my bike , and I'm getting 50 miles to the gallon on a 1000G .

[mike_of_bbg]

Let's get this clear on the valve adjustment - you're talking inches, correct? You didn't say that specifically but the number of zeros in the numbers you're giving says so. The spec is .001-.003 in inches. The spec is .03 to .08 in millimeters. If you're using inches, .004 is a little loose but should be OK.

Clearly #1 is running rich or not burning. At idle losing even one cylinder could certainly cause the bike to stall. It may be too closed. You need to clean that plug (soak overnight in vinegar) or get a new one (your chance to grab a B7ES too and see if that improves things). In addition to the idle screw, float height plays a huge part in the mixture. If that float's too high you'll run rich; it will just be throughout the throttle range. At higher speeds though the plugs self-clean better. Also make sure none of your choke plungers are sticking open when the choke is off.

I take it in your ignition travails you also checked the secondary impedances of the coils and verified that the plug caps were good?

[jasper]

Thanks gents...this is all helpful.

1) Mike - the little double hash mark after 0.001" and 0.003" means inches...at least that's what we do here. A single has mark is feet as in my dad was 6'6" tall instead of 6 ft 6 inches tall.

We're a metric country but we used to be imperial so we still use pounds and thousandth and even miles sometimes. My feeler gauges are in thou and I have a 0.0015, 0.002", 0.003", 0.004" and 0.005" to work with. That's why I'm working in inches.

2) Good to hear that the choke isn't always necessary, but it should still be a little harder to start the bike cold without one....I'd like to think.

3) I doubt there's anything physically wrong inside that carb. It went back together by the book. I should not have ignored the float heights though. The problems that are happening now are the same as before I rebuilt the carbs and that's the only thing I didn't do.

4) My ignition travails were very thorough indeed. My coils, wires, caps and plugs check out fine. The caps and plugs are new in fact. This is no longer a spark issue. Timing though is still up for grabs. When I first got the bike running I took a guess at the timing based on a vague recollection of a thread here and the bike ran the best that I've seen it. The next day I used a timing light and found that I was actually very advanced. I set it up according to the manual and the bike popped and idled lumpy as hell. I moved the timing back to the far advanced position and that's how rode yesterday. It simply runs better there.

5) Thanks for the tip on using the hose only for the fuel level test.

I'll report back.

[Gonzo]

4) My ignition travails were very thorough indeed. My coils, wires, caps and plugs check out fine. The caps and plugs are new in fact. This is no longer a spark issue. Timing though is still up for grabs. When I first got the bike running I took a guess at the timing based on a vague recollection of a thread here and the bike ran the best that I've seen it. The next day I used a timing light and found that I was actually very advanced. I set it up according to the manual and the bike popped and idled lumpy as hell. I moved the timing back to the far advanced position and that's how rode yesterday. It simply runs better there.

I'll report back.

Is it just me, or does it seem like the low compression would have an impact on this? In my mind with it's baseless logic it seems that this might be rectified once the compression and perhaps the rich mixture issues are fixed.

My reasoning is that with a higher compression and proper mixture it is going to require less burn time and get your timing back in spec. I could be off, as I said it's conjecture really, but it makes sense to me based on the little I know about engines.

[jasper]

UPDATE

1) First I checked the compression on #1 and it was 110 this time. May have been dry the last time I checked it.

2) Unplugged #1 spark plug lead and it didn't change the sound of the engine at all. Clearly I've been missing on #1 the whole time. Maybe just at idle, hard to tell.

3) Tried my damndest to get a hose in the drain plug to check the fuel level but very limited success. From what I can tell though the fuel level is on the low side. Can anyone tell me clearly where this level is supposed to be? I think it should be 6 mm from the mating surface between the bowl and the carb body. I appear to be a good centimetre below this seam.

4) I let it run for a bit and pulled #1 plug. It's black and wet. You'd think spark would be the problem then wouldn't you - wrong. I ran the bike with the plug out and grounded and the spark is very strong indeed.

5) I also switched my coils (easy to do with the DynaS ) and switched the plug wires. Unplugging #1 still makes no difference in idle speed or tone. So it isn't getting fuel.

6) While I was trying to measure the fuel level I also verified the constant flow of fuel into carb #1, so it's not going dry.

So it looks like my next move is to remove carb #1 and take it apart and check everything again.


Please ....any other thoughts are welcome.