What are all possible causes of a lean condition?

[Jethro]

Which bike is it? You running pods and a V & H 4 into 1? The plugs for my 83 1100 are NGKD9EA.

It's the 83, I'm running pod filters and one of the last MAC true 4-2-1 performance exhausts. The book calls for NGKBR8ES plugs, so that's what I got. Maybe I need to try a colder plug?

Have you tried running the bike with the petcock in the prime position? Any difference?

I did try the bike in the prime position too with no difference. I am now convinced it isn't a fuel supply problem with either the petcock or the floats, because once it stumbles past the 6-7k rpm mark for a few moments, the power kicks in again and it pulls hard to redline.

but are you sure the top end of the motor is sound?

I'm as sure as I can be. I just finished a valve adjustment a few weeks ago, and a compression test recently showed a consistant 180 for all four cyls. I haven't done a leak down test, but I don't think I need to with those numbers. While I was in the head I pulled a few of the cam seats for inspection. Everything looks real healthy. The motor has 16k miles on it.

Is there something other than a lean condition that could be causing your plugs to come out white? After all, I think that if your engine is running better with the smaller jets, and any size jet gives you white plugs, there is something we're not thinking of.

That's what I am trying to figure out. I agree, it must be something I am not thinking about.

The bike runs nice. I have no hesitation off the line and it pulls hard with no flat spots until I hit around 6 or 7k rpms. Then I have a major flat spot that almost feels like fuel starvation, but it kicks back in hard after it stumbles for 5 seconds or so. That tells me that fuel is fine, becasue once I get to redline, it's pulling hard again. There is no popping anymore on deceleration. Basically runs nice, but plugs read way lean.

I'm mostly scared about burning a piston. I can live with a flat spot up top, but it sucks. After all, before I hit that flat spot at 6k I can be going 90.

[tfb]

Well Jethro, it looks like you and the others have covered everything I could ever think to check, and then some!

The only thing I would suggest is that you make sure it's running lean, because from what you say it doesn't sound like it's running lean. Are you running unleaded fuel? (Here in Oz we can't get leaded any more.) The reason I ask is because I've always found that 'reading' plugs with unleaded fuel is a lot more ambiguous. So it just might be that things aren't as dire as you fear.

Sooo... I'd suggest getting some exhaust gas analysis done, maybe at a dyno centre to check what's happening to your air-fuel ratio at different RPM and engine loads, etc. That way you will KNOW whether it's actually running lean or not, and if it is, then exactly how lean.

All the best,
Mike.

[Jethro]

That's good advice, tfb. I have an appointment for some dyno time at a local shop. He can't fit me in for a few weeks though, and I can't stand not riding my bike until then, but really don't want to burn a piston. Maybe I'm not really running lean? I am using unleaded, can't get the leaded stuff over here any more.

[scotty]

Did you try riding with the choke partially oin and then reading your plugs???

[snowbeard]

once you're at, say a third throttle, does pulling the choke still affect anything or will the open throttle plates just ignore it?

I'm following this as closely as I can because I think mine is lean on idle, but not at running speeds. if I pull the choke while running I get no extra push... but that may mean nothing?


y'know, I don't think I've hit WOT on my bike yet...

[earlfor]

I just finished a test run of about 100 miles on my 1100 after rejetting.
Stock intake/airbox/filter and exhaust. 1197 kit. I'm buring medium brown on NGKD9EA plugs using #130 mains and the needles raised 3mm. Gas milage is about 40 mpg and oil temp guage on an 80 deg day reads 170F.

Before I rejetted and raised the needles, when I would get home and shut down the bike, It would heat/expansion crackle. It doesnt do that now.
Does yours have the expansion/.heat crackling sound after you shut it off?

On the float bowl vent T's between the 1,2 and the 3,4 carbs, I have shortened those hoses to 1" and they vent straight up to atomsphere.

The only thing I can think of at this point Jethro is that your boots may have cracks you cant see or find. I would remove the carbs and take some electrical tape and wrap each boot with a couple of layers of tape. If the boots are old enough to be porous, the electrical tape will temporarily seal the surface and you will at least know what the problem is.

With #160's in that sucker, you have to be getting too much air.

Do the throttle plates fully close in your carbs when the throttle is fully closed?

Earl

[Jethro]

once you're at, say a third throttle, does pulling the choke still affect anything or will the open throttle plates just ignore it?

I tried that. No change in pull or feel when I'm on the throttle.

Does yours have the expansion/.heat crackling sound after you shut it off?

Nope. No crackle or pinging or anything. And the block is only slightly too hot to touch, although I haven't seen anything warmer than 50F here. Oil temp gauge reads 160 most all the time.

The only thing I can think of at this point Jethro is that your boots may have cracks you cant see or find.

Boots and clamps are brandy new OEM units. Pretty sure there isn't a single intake leak as I doused the boots with the most flammable fluid I had in the garage- crab cleaner.

With #160's in that sucker, you have to be getting too much air.

The 160's make the bike run like crap, but the plugs don't get any darker...

Could it be possible that my bike is so efficient that I get a perfect burn? I've ridden 300 miles on the bike and the plugs look like they just came out of the box, except for an off-white glaze on the very tip of the plug.

[snowbeard]

sorry Jethro, mine was a theoretical question of should pulling the choke at a third throttle make any difference? earl? still there?

[AOD]

Could it be possible that my bike is so efficient that I get a perfect burn? I've ridden 300 miles on the bike and the plugs look like they just came out of the box, except for an off-white glaze on the very tip of the plug.

Obviously not if you have a flat spot at 6000 RPM. At 6K you're running off the needle and main (main if WOT).

Have you done a plug check at 6000 RPM where it flattens out, to see wha the plugs read vs. say 9000 RPM where you say it pulls fine?

Earl, why are you running a '9' plug? I believe that's the hotter heat range plug...

~Adam

[Jethro]

sorry Jethro, mine was a theoretical question of should pulling the choke at a third throttle make any difference? earl? still there?

Ahh, yes. If you find that applying a little choke under hard throttle makes the bike pull harder then you may have an intake leak. What happens is that the choke cuts off some air and enrichens the fuel mix. It brings the mix back to where you should be if you didn't have an intake leak. Theoretically.

[snowbeard]

well at least your post helps someone, eh? good to know that if I still had an intake leak I could tell by pulling the choke.

now what does it mean that with throttle it does nothing from a choke, but at idle it revs up and then dies off unless I let go...?? I'm thinking there maybe something blocked up in my idle. I see in the carb cleaning guide that there is a choke circuit, but what holes/jets are responsible for the idle?

thanks for letting me horn in some on your thread J!!

[Anonymous]

...I doused the boots with the most flammable fluid I had in the garage- crab cleaner.

Gee, where I come from we usually just call crab cleaner "beer."

I'm not normally one to make a joke at people's typos, but I got a kick out of that.

Well man, I'll be interested to hear what the dyno testing tells you. As far as holing a piston, I think plug readings alone shouldn't inspire that fear in you. Your engine is running nice and cool, and so far you haven't mentioned pinging. I'd say happy riding man.

[earlfor]

In NGK, a 9 is a colder plug than an 8. In Champion or AC, I beleive it is the opposite. Dont know for sure though, I dont use those two "off brands" LOL

Stock plug for an 1150 is a D9EA, so why not the same plug for an 1197? :-)

Earl

Earl, why are you running a '9' plug? I believe that's the hotter heat range plug...

~Adam

[Clone]

My yamaha runs a little lean and the bike warms up really fast. I've never checked the plug. I take it to a shop and have them sniff the exhuast twice a year. The report tells me the proper range. The mechanic tells me it's ok so I leave it. It passes the epa inspection this way without any problems.
I think you should have the exhaust analyzed.
like the other guys said, I don't think your bike runs lean.

[pano]

Jethro,

If the weather and all else works out for the 9th I will arrive early and as I said in another post we can take a look with my newly aquired colortune We could also do a quick carb swap if that is something you want to try. I wonder there is something whacked with you needle set-up.

Have you tried the carbs from your 81? I forgot you had that.