Help me Leon! (and everybody) RESOLVED!!!

[Jethro]

Wow, by this page on the NGK site, I can honestly say that the nearest match is the first pic stating normal condition!

http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp?nav=31200&country=US

What seems wrong to me is that the very tip of the plug, the part you bend to gap, is totally coated in white, almost glossy. It in no way could be called tan or even grey as the NGK page says.

I'll take a pic of my plugs tonight for general comment!

[Mr. Jiggles]

Am I right in thinking that when I'm on the needle circuit, the size of the main makes no difference whatsoever? That would make sense, as I have a huge main jet in there now, and it runs like crap at WOT.

Over the past couple of weeks I've also been tuning my carbs, which is why I've taken such an interest in your dilemma. I've got KN pods with an aftermarket pipe of unknown origin. I had been running DJ132's with the needle in its highest position and I was getting surging (lean) at about 1/3 throttle which would be the needle circuit. I changed up to the DJ138 that comes with the kit and the 1/3 throttle surging that I had seen before went away. I don't know how correct this is but my thinking now is that the needle/needle jet meters whatever is coming through the main (afterall, the needle jet gets its fuel through the main, correct?). So, for a given needle position you'll get x% of whatever the main jet can deliver. However, like so many other things I'd bet that this relationship (if true) is linear only over a limited range of main jet sizes.

Jeff

[KEITH KRAUSE]

Let me put this jet needle/needle jet and main jet thing in different words.
Fuel enters through the main jet, goes up through the space between the needle jet and jet needle, and enters the carb throat.
Fuel flow will be regulated by the smallest opening along this passage. The smallest opening will be around the widest part of the tapered needle and the needle jet. The jet needle gets slimmer and slimmer towards its end.
As the tapered jet needle rises with throttle opening, much of it completely leaves the needle jet. The remaining portion, now much slimmer, allows more fuel to pass through the needle jet. The higher the needle rises, the wider the opening around the jet needle and the needle jet becomes. At about 3/4 throttle position, this opening becomes larger than the main jet opening. Since the smallest opening regulates fuel flow, the main jet now regulates the fuel flow.

[KEITH KRAUSE]

Jethro, I asked at your other topic about the possibility you could have jet needle spacer(s) missing or installed in the wrong order? Any spacer(s) that were used with the stock jet needle are to be re-used with a DJ needle. If a spacer is left out that goes under the e-clip, or on some carbs, the order of spacer install is incorrect, the needle can be "lean".
I gotta say the "noises" you're hearing do not sound good. Could be something beyond jetting. I hope not. I've heard "pinging" before, caused by either lean jetting and/or incorrect ignition timing. Usually, in severe cases, you'll see the plugs electrode start melting first. Pre-ignition.

[Jethro]

Nice. That explains it well.

Anyway, I've made some really good progress tonight. I came home and pulled the carbs to go back to the DJ138 main and put in the 170 air jet to richen up the pilot circuit. Got the carbs out and re-jetted and back in the bike in under 45 minutes. I'm getting too good at this. I left the needles at the lowest notch. Took it for a rip and this is what I have for plug reads now:


#3 cyl is still a little lean, but I'm pretty happy with the rest. A synch will probably do wonders after all this carb fiddleing. Bike rode smooth with no flat spot at all right up to 100mph. No hesitation at all off the line. Starts perfect with a little choke, nice and warmed up, ready to ride in 45 seconds to a minute. Sweet.

I still had wicked surging and cutting out at WOT though. For the first time I rigged up a clear fuel tube to the bowl drain like the shop manual shows. My freakin' float heights are way too low. I bench set them exactly like the book said, but it didn't cut it. The tube tells the tale clear as day. I'm resetting the floats now. How much you wanna bet that this fixes the problem?

Thanks everyone for the help, I may have it figured out now, I'll give you a ride report when I can (gonna snow tonight).

"And remember kids, don't trust your float heights to what you set on the bench!"

[Jethro]

I gotta say the "noises" you're hearing do not sound good. Could be something beyond jetting. I hope not.

Yeah, I think those noises were a loose exhaust manifold. That can make a hell of a racket at WOT for a moment. Luckly I didn't push it. I was convinced that my exhaust install was perfect, but the new gaskets probably crushed a little more after some miles. Gotta check everything. The noise wasn't there at all with the smaller mains on my test ride, and that was even before re-torquing the exhaust. But they were definitely a little loose.

I think I'm good!!!! This site rules. It's definitely therapy for me.

[Hoomgar]

Jethro, rock on buddy!

WooHoo!

I don't know my butt from a hole in my head when it comes to this stuff but after following this I knew there was no way the jets were the issue.

So glad you found it man

[KEITH KRAUSE]

I think your carb uses those "odd" shaped floats. Which part of the float did you use to make your measurements? I assume you removed the bowl gasket too before measuring. Fuel starvation would certainly cause your problems. I didn't see how it could be related to lean jetting. The jet kits usually work.

[Jethro]

Yeah, my floats look like two flat teardrops on either side of the float valve.
I thought I had to bend the tangs a little too much, but the book said 20.4mm from the mating surface to the bottom of the float bulb. I set it so it was just touching the pin on the vavle needle. I guess you can't trust that too much, so I'll make sure to check with the tube gauge from now on. Still haven't gotten to test ride after the adjustments, but everything else runs so sweet now. It's flawless unless I am over 7k on the tach. I'm sure it is the float heights.

How much will changing the float heights change the richness of the pilot and needle circuits? I'm scared I made it too rich now for higher float values- it is burning nice and tan as shown in the photo above, but when I raise the floats, will it richen all the carb circuits?

I hope it's not back to the drawing board for me.

[Jethro]

Well, the higher float heights didn't help. Still feels fuel starved at the top end. Gonna have to throw my Pingle valve in and see if that makes a difference. Guess I'll re-clean the carbs too.

Can an electrical problem only show up at the top end? It pulls hard until I really let the motor spin, then it stumbles. I don't get it.

[Hoomgar]

Gonna have to throw my Pingle valve in and see if that makes a difference.

As much as I hate them, I am putting my money on this one now.

[focus frenzy]

Can an electrical problem only show up at the top end? It pulls hard until I really let the motor spin, then it stumbles. I don't get it.

check your ignition advance, make sure it turns freely and is not gummy or frozen, it should snap right back when turned and released.
also if you have a voltage drop to the coils they will not be able to keep up under high load and high RPM.

[Jethro]

if you have a voltage drop to the coils they will not be able to keep up under high load and high RPM.

I'm assuming that I can check this by simply testing the voltage at the battery under different RPM's?

I'll check the advancer tonight as well.

Gonna really try and get this sorted out tomorrow. It will be warm enough to be able to road test it well and get plug readings at WOT.

[isaac]

Yes, weak ignition or messed up advance can definitely have a great effect on top end power. If your advance isn't advancing up there, power will trail off dramatically until it's just not there. Just ask my dyno numbers.243rwtq and only 165hp will tell you a thing or two in a hurry. Those are from my Volvo btw.

[focus frenzy]

if you have a voltage drop to the coils they will not be able to keep up under high load and high RPM.

I'm assuming that I can check this by simply testing the voltage at the battery under different RPM's?

I'll check the advancer tonight as well.

Gonna really try and get this sorted out tomorrow. It will be warm enough to be able to road test it well and get plug readings at WOT.

no, you have to check voltage at coils, power has to go from the battery to the fuse box (main fuse) to the ignition switch, back to the fuse box, back up to the kill switch before eventualy reaching the coils.
if you have the side stand kill switch add that into the equation.
lots of connectors and wire that can cause a healthy drop in voltage from what is at the battery.
what you need to do is measure voltage at battery with bike idling, then at the coils with the engine idling.
you will get false readings at the coils with the engine off.
also watch the voltage at the coils while reving the engine up.