Am I Running Lean?

[JDS]

Most of the time when I slow down for an intersection (or for almost any reason) I use engine braking. When I down-shift and let off the throttle I get lots of crackling and some popping as the engine slows down. Does this mean I'm running lean? Any other time the engine/exhaust sounds great. I've got a D&D slip-on, and as far as I know nothing was changed on the carbs after the fact.. I bought the bike used.

I looked at the manual that was posted here and when I found fuel/air mixture it talks about adjusting the pilot screws - will this adjust the mixture, or is it something else?

[The CyberPoet]

Yes, it means your mixture is going lean off-throttle as the RPM's drop and the carb vacuum is already down at idle. Richening up the pilot screws should be able to compensate.

Cheers
=-= The CyberPoet

[xbubbax]

ive got a D&D full exhaust, and i run really lean. my exhaust is really poppy, but here are the key facts that will make you know if you need jet kit.

1. hard time kicking bike down at redlight, no matter what you do, idol screw, and does not help.
2. if you ride the hard for more than an hour, than you stop for 20 min then try to start it back up, it wont start at all.
3 it runs like shit in the lows. (its a givin when adding HP but should not be jumpy/skippy around 2000-4000 rpm.

i also have a pre 98 might be a lil diffrent for 98+......lits hope cyber can help you EDITED: he did help you hahaha

[JDS]

Awesome..thanks! I should have some time tomorrow afternoon to tinker with it.

[HS2020]

Bubba mines does that at times. I need to clean and rejet my bike and sync the carbs. I do not hav the tools to do it and I suck at doing carbs. So I guess I will let my local guys do it to save me heart ache.

[md86]

Rejet ? I thought your bike was running great , Jimmy ? WTF ? Come up one weekend and I'LL do it for ya ! You're buying dinner , though !

[HS2020]

Rejet ? I thought your bike was running great , Jimmy ? WTF ? Come up one weekend and I'LL do it for ya ! You're buying dinner , though !

It is running fine but it could use the carbs cleaned out and rejetted and synced up. I just need to get the jet kit but do not have the money for a jet kit right now. If I could I would come up since you are not that far away.

[mystahagy]

Yes, it means your mixture is going lean off-throttle as the RPM's drop and the carb vacuum is already down at idle. Richening up the pilot screws should be able to compensate.

Cheers
=-= The CyberPoet

Cyber I've got that same problem, but by how much would you suggest to richen them? What increments would you make the adjustments in? 1/4 turn 1/2 turn that kinda stuff. Just curious...

[katrider]

Another reliable sign of running lean is surging, either at steady throttle or small throttle openings. Also, look at your plugs. They will tell you tons about how the bike is running.

[The CyberPoet]

Yes, it means your mixture is going lean off-throttle as the RPM's drop and the carb vacuum is already down at idle. Richening up the pilot screws should be able to compensate.

Cheers
=-= The CyberPoet

Cyber I've got that same problem, but by how much would you suggest to richen them? What increments would you make the adjustments in? 1/4 turn 1/2 turn that kinda stuff. Just curious...

I'd go 3/8th turn at a time, but then again, I also am the type to run down to the shop and have it done on a dyno to make sure it's right... If you can find a small shop and already have the jetting very close, getting them to give you a fuel-air measurement/dyno run can be cheap -- especially mid-week, call-ahead and be leisurely about when they can fit you in.

Cheers
=-= The CyberPoet

[SUPA-FLY-KAT]

GUYS, I WAS JUST WANDERING...I KNOW TO JET YOUR CARBS , YOU HAVE TO CHANGE THE NEEDLES....BUT WHAT ACTUALLY HAPPENS MECHANICALLY WHEN YOU HAVE TO "REJET" ?

[The CyberPoet]

GUYS, I WAS JUST WANDERING...I KNOW TO JET YOUR CARBS , YOU HAVE TO CHANGE THE NEEDLES....BUT WHAT ACTUALLY HAPPENS MECHANICALLY WHEN YOU HAVE TO "REJET" ?

What happens at the combustion end of things:

The fueling goes either too lean or too rich, depending on the mod.

If it goes too lean, the combustion temps climb very high and everything runs way too hot, plus you can get after-fires in your exhaust from fuel-air mix that didn't burn in the cylinder. Plugs pit themselves and glaze over, or even melt their electrodes (from running too hot). Bike runs weak and then runs unreliably as the plugs foul (and finally doesn't run at all).

If it goes too rich, the combustion temps drop very low, combustion stops happening reliably, and the unburned fuel can burn in the exhaust instead (not normally as an after-fire, but as just a burn). Plugs foul super-fast (wet or dry fouling). Bike runs like crap and then refuses to start.

Bad jetting, dirty carbs or mismatched jetting (to mods) can result in one or even both of the above conditions (such as going rich on one end of the RPM range and lean on the other end).

Hope that answers your questions.
Here's a spark plug chart to help you understand the effects at the plugs:
NGK - FAQ - how to read spark plugs

Cheers
=-= The CyberPoet

[SweetLou]

Rejet ? I thought your bike was running great , Jimmy ? WTF ? Come up one weekend and I'LL do it for ya ! You're buying dinner , though !

It is running fine but it could use the carbs cleaned out and rejetted and synced up. I just need to get the jet kit but do not have the money for a jet kit right now. If I could I would come up since you are not that far away.

You can get a set of jet's (Just jets, not needles) from Dennis Kirk for like 12 bucks for 4 of them. They come in packs of 2. That would help get you started. Let me know if you need help finding the stock number. I have a catalog at home. Corey and I just went and got jets from them a coupla weeks ago. A lot of times when you go to get a jet kit installed at a dealer, all they do is the jets, and leave the needles stock. Learned that from Chris.

[md86]

I got a bunch from K , actually.

[KatanaMan]

while were on the subject. I have a full Vance and Hines exhaust, K&N filter, and a jet kit. We just jetted it and it still is popping when slowing down. Also, since the jet kit went on when I am under 4k if I crack the throttle it has a nasty stutter to it but once it hits around 4500 its perfectly fine. I normally don't have the RPMs that low but it happens and when it does it really sucks.

any suggestions on that one?