Lean despite efforts

[Torchard]

There are many threads on this theme …. I’ve got pods and a two-into-one exhaust set up with baffles. I have 30 pilots and 140 mains. It runs lean, and despite the common advice to drop the needle one position I feel I need to raise at least one position to enrichen otherwise the mix screws will be turn out too far. Why might it be this lean? I can find no leaks by the carbs or vacuum? Also once it warms it starts to buck/stumble around 30kph. I’m stumped as to where to look next.

 

[Torchard]

I’ll add the the bike is pretty much unridable at slow city speeds because of the constant shifting/clutching/throttling required to keep it out of the rough.

 

[650Skull]

Put your bike model in your signature so people can point you in the right direction without having to do research on your old posts

 

[Torchard]

Put your bike model in your signature so people can point you in the right direction without having to do research on your old posts

Done. Thanks.

 

[Torchard]

There are many threads on this theme …. I’ve got pods and a two-into-one exhaust set up with baffles. I have 30 pilots and 140 mains. It runs lean, and despite the common advice to drop the needle one position I feel I need to raise at least one position to enrichen otherwise the mix screws will be turn out too far. Why might it be this lean? I can find no leaks by the carbs or vacuum? Also once it warms it starts to buck/stumble around 30kph. I’m stumped as to where to look next.

The floats are set to 25mm.

 

[5twins]

If you have the '78 carbs then float setting is 24mm. That would make things a little richer than your current 25mm setting. Also, the '78-'79 carb set often needs two up on the pilots, to a 32.5.

 

[Torchard]

If you have the '78 carbs then float setting is 24mm. That would make things a little richer than your current 25mm setting. Also, the '78-'79 carb set often needs two up on the pilots, to a 32.5.

I’ll go back and double check the measure on the float and set to 24. And I’m not disputing your point about two sizes up on the pilot, but I swear it ran better previously w the stock pilot and main. Anyhoo, a
float adjustment and another move on the pilots are easy enough to explore. Thanks.

 

[Torchard]

I’ll go back and double check the measure on the float and set to 24. And I’m not disputing your point about two sizes up on the pilot, but I swear it ran better previously w the stock pilot and main. Anyhoo, a
float adjustment and another move on the pilots are easy enough to explore. Thanks.

So, set the carbs to 24. Put in 35 pilots because I had them handy. Leaned the needle because of the big jump in pilot. No difference. Once warm it runs rough and jerky off idle, at say 30kmph. If you give it throttle it responds well - no flat spots. But it’s awful at slight throttle on city streets.

 

[Torchard]

Here’s what I’ve discovered: regardless of whether the bike runs rich or lean (and the related manifestations of those conditions), the bike runs fine in the first 5-10 minutes. Once it warms, I’ll hear a miss. Not a backfire but a miss, like a slight hiccup. And from that point onwards it will start with the stumbling and lurching and generally running rough until I park and let it cool. Is this electrics perhaps? I know it’s not the coil, but regulator or e-advance?

 

[Jan_P]

OK firstly I tell everyone this as a first
Because it is easy to Do measure the charging Voltage across the battery when the bike is warm.

Then there can be a Voltage drop to coils and ignition box or parts please measure actual voltage there.

 

[Torchard]

Yes, now that I’m down to considering if this is somewhere in the electrics chain will test for voltage drops as you recommend. Maybe the regulator is faulty.

Also what are the signs of a faulty e-advance? Thanks.

 

[RC4MAN]

As a note here, back in the late 70's when I first finished building my tracker, I too used K&N filters and at the time a Hooker 2-1 pipe.
With my 73 model I anticipated it to run lean so I upped the main jet one size and fires the bike up. It ran ok so I took it around the block, let it cool and read the plugs. They were white, I went up another size on the main and repeated the process. Again the plugs were white and again I repeated the effort till it finally wouldn't run.
Spoke with some buddies who said that I was washing the plugs clean till it was finally so rich it wouldn't run correctly, suggested I take it back to the stock jets and settings and check it out. I did that and the bike ran fine, and got color back into the plugs. Never messed with it again till I later changed to half mile pipes with Super Trapps and went up one main size and left it.

 

[gggGary]

What are your valves set at?
a tight valve will act like you describe................

 

[gggGary]

I’ve got pods

Try a set of properly sized, oiled UNI foam filters. See how it acts then.
Many cheap pods block the slot above the intake that controls slide rising, raising havoc.

 

[Torchard]

I’ve got a guy coming over tonight and we’re going to begin at the beginning. Chain tension, valves, timing and then see what we can confirm via a multimeter. I wondered about something more mechanical like a valve or clutch. Thanks. T.

 

[Torchard]

Try a set of properly sized, oiled UNI foam filters. See how it acts then.
Many cheap pods block the slot above the intake that controls slide rising, raising havoc.

I’ve got uni pods and am careful about how they are mounted at I see this issue is common with the cheaper pleated pods. Thanks.

 

[Torchard]

As a note here, back in the late 70's when I first finished building my tracker, I too used K&N filters and at the time a Hooker 2-1 pipe.
With my 73 model I anticipated it to run lean so I upped the main jet one size and fires the bike up. It ran ok so I took it around the block, let it cool and read the plugs. They were white, I went up another size on the main and repeated the process. Again the plugs were white and again I repeated the effort till it finally wouldn't run.
Spoke with some buddies who said that I was washing the plugs clean till it was finally so rich it wouldn't run correctly, suggested I take it back to the stock jets and settings and check it out. I did that and the bike ran fine, and got color back into the plugs. Never messed with it again till I later changed to half mile pipes with Super Trapps and went up one main size and left it.

I hear you. But after this last pilot change and float adjustment, I did run with the mix screws 3 turns out just to see if I could get an obvious effect and managed to fully foul the plugs. Swapped them out and dialled in the mix screws and following a short run all looks pretty normal.

 

[Torchard]

I’ve got a guy coming over tonight and we’re going to begin at the beginning. Chain tension, valves, timing and then see what we can confirm via a multimeter. I wondered about something more mechanical like a valve or clutch. Thanks. T.

One more detail … I can throttle out of the stutter or under load (uphill) it will abate?

 

[Torchard]

Resolved: (fingers crossed) So, I was back-and-forth with Sam from Mike’s XS quite a bit in the last couple days because I started to question if the ignition module was defective and the source of my problems. They sent me an array of resistance specs, and I found that a couple were not met. They concluded that perhaps there was a grounding issue. I haven’t had any obvious ground problems to date and wiring is pretty solid and simple. But I added a dedicated wire from motor to frame, and went for a ride and the problem seemed resolved! I also did a few other wee things along the way but will re-introduce those to see if I can attribute solely to the ground. Shout-out to Sam. Now back to other perplexing issues like, “why so rich?” Heh. It’s the journey, yes?


QUOTE="Torchard, post: 743919, member: 37169"]
One more detail … I can throttle out of the stutter or under load (uphill) it will abate?
[/QUOTE]