Why does it sound like it is running out of gas?

[Incubus]

I have made some serious progress with Succubus, my problem child. But now, for the first time in years, I have a brand new problem.

I regapped the valves yesterday. I don;t know what I was thinking when I gapped them the last time, but they were mostly significantly off. Too wide.

So now, the bike runs much better. Better than it ever has, since I have owned it. Except... I was addressing a low rpm stumble when I regapped the valves. It was a bad stumble. Now. right off the line, when I first give it gas, the bike sounds and acts like it is running out of gas. If I twist the thrttole a couple (or a few) times to rev it up a little it runs just fine.

The bike has fuel. Not a lot, but it does have enough to run fine after I get past the initial issues. The carbs are clean. The bike idles OK. It's pretty rough, but I haven't resynched the carbs yet, so I expect a rough idle. The fact that it idles at all, however, makes me rule out the slow jets as the problem. The fact that it runs just fine once I get it going makes me rule out the fuel delivery, since higher revs are where it would run out of gas quickest if fuel were the issue, methinks. Spark also does not seem to be an issue since it runs very well once it is moving.

Can a bad synch cause the issue I describe? Could the air filter (a freshly oiled UNI foam) be choking off too much air at the low end? Is there something else I need to consider?

This bike is so close to being a sweet runner I can taste it. I am open to suggestions.

Patrick

[natemoen]

Sync could cause the problem. I would do it just to rule it out if nothing else. I doubt the air filter would be the problem cause that filter is going to flow more than the paper one would.

[cywelchjr]

Sync if it includes setting idle mixture would likely be the ticket. Your probably either too lean or too rich at idle, and fixing that and getting it right should make it take right off. The fact that it idles doesn't really tell much, because if other adjustments were made to compensate, even a fairly lean or rich idle mixture can idle decently.

[dbeardslee]

Have you tested your ignition coils? The alternator doesn't throw it's full voltage until it gets over 2200 rpms, and sometimes coil problems will cleverly disguise themselves as low rpm stumbles. JAT

[Cobia]

I'm with dbeardslee on that. I had a similar problem with my G and solved it simply by raising the idle from 850/900 rpm to the required 1K/1.1K. These bikes just don't produce enough juice to keep the plugs firing clean at those low rpm's.

[Incubus]

I'll take a look at that. I'm pretty sure I can find a pair somewhere in my pile of coils that will work if I need them. Probably only 3-ohm, but I can always take the resistor out of line.

Patrick

[Ken Talbot]

The fact that it idles at all, however, makes me rule out the slow jets as the problem.

But, you could be maintaining idle with only one cylinder working and the other three not. It really doesn't take much to keep it turning over at slow speed.

JAT.

[Incubus]

Not this bike, Ken. That's a lot of the reason it's mostly been parked for the last couple years. It would not fire on No. 1 at idle speed and wouldn't idle on the other three at less than 1800. Idling now is a huge step. It feels like I came home and found Salma Hayek stretched across my bed staring at me with pure animal desire in her eyes holding an affidavit from SWMBO swearing that nothing that happened that evening would ever be held against me.

All four pipes get hot at idle now. Two and three are hotter at the headpipe than 1 and 4, according to my laser thermometer, so the mixtures definitely need to be looked at. But it seems like they're all getting gas, anyway.

Patrick

[petejw]

Hi Patrick,
If the mixture screw adj and syncing doesnt help,
check your float levels, if there to lean the bike will
lag and if there set to rich it will bog down, and if there
uneven that could give you, your different heat readings
on the headers..