Struggling to keep a low idle

I think the clip position I had the needle at originally was stock (4th position down counting from the top). Currently it is at the 3rd position.

I was going to try a 140 main, but I will need to order it. I have everything from 142.5 to 160, but I am missing a lot of the smaller sizes...

I just adjusted the float needles to open a bit more when the floats fall. I reset the float height to 26 mm. I will give this a try tomorrow to see if it has any effect.
 
Can anyone give me some suggestions in regard to what else could be causing one cylinder to run hotter than the other?
 
The way these bikes work one will run about 10 or so degrees hotter stock. What I use is a IR temp gun and adjust the carbs to get them as close as I can:) I would check your head temps at the exhaust side of the plugs and go from there.
 
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I am starting over with the basics. Last night I did a compression test; 150 psi on both sides after only 4 kicks.

I'm headed out to grab some supplies for making a better manometer. If the synch turns out to be fine I am going to re-check the valves and timing.
 
Hey bc hows it going
I.. like you, changed the condensers because of the arcing at the points.
My points are chronically pitting and my bike will not hold timing. When I take the points cover off and watch, the arcing coincides with the surge/hiccup/stall... and at the battery the volts drop.
Thats why I suspect it may be electrical.The new condensers didnt fix it.

Fuel starvation may cause similar symptoms? missfires?
I went through the carbs,jets,idle circuit,floats ect. petcock is good.
Did the basic tune up
carbs,valves,points, timing
Still stalling
I think my battery is bad. Talk about basics.
Maybe charging system is bad?
initially @ idle=12.70v holds idle
gradually drops to 12.35v and begins the intermitten fade/miss/ stall
Hope you make some head way. Let us know if the synch helps.
Later mang.
 
The new manometer worked great; I used much longer tubing and the heaviest weight gear oil I could find. The carbs are as close to perfectly balanced as this kind of tool will allow.

I started the bike cold with choke on full, after a minute I turned choke off, and let it idle for several minutes.

During the synching process the bike held an idle for 10 solid minutes. After each adjustment of the synch screw I revved the engine to a few thousand rpms. Performance was essentially perfect; no intermittent miss and no diving idle.

After I was done I took it for a test ride. After about a mile of 40+ mph riding I hit the first traffic light and the symptoms returned. The idle dives when I come to a stop.

After several more miles of 50+ mph riding I arrived in town and the symptoms continued to get worse. Every time I came to a stop the idle would dive below normal and I had to actively rev the engine to prevent it from dying.

The time was 9:30 pm (no sunlight) and the ambient temperature was only about 71 F or 22 C. These conditions are certainly close to ideal as far as engine cooling goes.

The bike runs beautifully otherwise and pulls very hard through the entire range.

Unless someone else has some ideas I am going to replace the plug caps (the only thing left) and re-check the valves and timing.

142.5 mains
50 pilot

Left side:

bp7es (looks totally normal)
1.25 turns out

Right side:

bp8es (white at bottom/base of ground strap, but the rest looks normal)
3 turns out

If I throw a bp7es on the right side the entire plug is white, not just the base of the ground strap.
 
Previously I had not bothered to look, but upon searching a little it seems as though using a steel insert in an aluminum head CAN cause a plug to run too hot.

There are companies that sell anodized aluminum inserts and they have a lot to say about this sort of thing. Granted they are selling something, but it seems logical enough to me.

I think the diving at idle may be due to the rich idle mixture (3 turns out right versus 1.25 left). I simply turned the mixture screw out farther and farther on the right until the plug started to take on some darker color. Apparently this is a poor way to compensate. Rather than crank up the idle mixture on one side I should simply go even colder on the plug.

Rather than tear everything apart, since it was done recently, I am going to return the right side mixture screw to 1.25 (the same as the left) and order some bp9es and bp10es plugs.

I have quite a pile of used plugs in my garage :laugh:
 
Hey, bc, sorry if I missed this earlier, but have you tried a #45 pilot jet? It seems like you wouldn't need to be so big on the pilot and maybe it's flooding out after riding hard? Just kicking some ideas around. Hopefully you get this sorted soon!
 
New spark plug caps (old ones tested 4.3 to 4.8 k ohms, new ones are just over 5 k)
Bp7es on the left w/ 1.25 turns out
Bp9es on the right w/ 1.5 turns out

Test results tomorrow afternoon. I will likely drop the pilot down at least one size. The 50s are excessive for my setup.
 
I am crossing my fingers on those caps. I just read in the service manual,

(pg 24....'Breaker point Ignition-Trouble shooting-section 3)

...Caps are fitted with resistors to prevent radio interference while operating and through heat or vibration those resistor value can increase considerably,even to becoming an open circuit.
A check is to switch caps and see if misfire switches too. Replace as a set

Caps will have a resistance of 9000ohms when caps exceed they will no longer fire.


I kinda paraphrased but thats what the service manual says.
Good luck and I have a feeling this is it!
 
I am running a bp9es on the right now.

I am placing a lot less emphasis on plug color, because mine look brown half the time and light gray the other half of the time. Perhaps these changes are due to the fact that I get gas from dozens of different sources.

I replaced the caps with the NGK LB05EP type; it didn't seem to make any noticeable difference.

Next I reduced the pilot to a 45 and set the mixture to 4 turns out.

The bike ran a little better, but it was lean at the 3,000 rpm transition and didn't want to do much more than 70 mph. When I stopped in my garage she promptly died at idle after only 10 seconds of sitting. Womp womp...

"Enough is enough" I said. I cracked open the carbs and raised the needle a notch (4th clip position) and bumped the mains up to 145. After this was done I checked the timing and I found a boo boo.

I noticed something funny; when the points were fully open the gap was less than 0.1mm... Hm! So I gapped the points properly (0.3 - 0.4mm) and reset the timing.

Once I slapped everything back together she started easier than normal and even sounded a little peppier at idle. Once I got out of the neighborhood I let it rip and was very surprised; I definitely howled out loud a few times. She felt, easily, 20 - 25% faster. I was literally being thrown back in the saddle in every gear.

After terrorizing the city for about an hour and a half I pulled into the garage and left it idling. She sounded just as strong as when I first started it; no drama.

So, this may be fixed, but I am still going to wait until a relatively hot day before I call it case closed.
 
I don't know what I was thinking at the time. I recently put in new points and set the timing correctly, but apparently completely ignored the gap when they open. There really wasn't much of a gap at all; the right side was particularly bad.

Does anyone else feel like this bike is pretty fast when it's been lightened and jetted? I am actually quite impressed with the mid range. I need to take it to the dyno and weigh it.
 
Mine gets up pretty fast now. I'm always surprised when I'm already doing 50 in third gear.
 
Correctly gapped this bike is torquey. Even without moving the needles up or down. It's just really rare that it's timed correctly.

it's a 400 twin. The power to weight ratio is insane.
 
My tracker has much more pep and power than my stock 79 but is also weighs 40 pounds less and has a tci a 2-1 and better carbs:laugh:
 

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