Topic: Does Carbon Fouled Plugs Eliminate rejetting as a possible solution?

[ron.cieri.313]

Argh...Mark, did I just f*ck up the process...I was putting everything back together and forgot to turn the air pilot screws to 7/8's prior to syncing.  I sync'd the carbs at about 1/8 turn out for all four...at least there abouts...should I re-sync before wot plug chop test?...thanks.

[Johnny5]

Hey Ron,

If your bike is happier with the pilot screw set at an 1/8th of a turn out, then it sounds like you may need to go up a size on the slow jet.

But you'll be chasing your tail if you dont get the readings from WOT to make sure your main jet is good. Then proceed to the needle adjustment and plug chop, then the pilot screw.

If you're systematic, you'll be successful.

[mlinder]

Naw, you'll be fine, just set em to 7/8ths out and go give it a run.

[ron.cieri.313]

cool...thanks guys...should accomplish wot test this weekend.

[Otto]

I never really understood why the plug chop meethod was the way to go. It does tell you how the bike runs at full power, but, who runs at full power in 5th gear.

Not to sound old, but, wouldn't it be safe to run say in 3rd gear at say 4500 rpm for 1/4 mile, shut it down and take your reading? Enocouraging someone to run wide open in 5th gear and telling them to be careful is kinda well, missing a piece.

I guess what I am saying is, we all want to have our bikes run their best, given that, shouldn't we try to simulate real driving conditions? 

If a motor isn't happy within its normal operating range, why does it matter if it's perfect at 8000rpm in 5th gear. (Yes, I understand about the metering needles).

Like Ricky said to Lucy, "Please splain" ...

bc

[ron.cieri.313]

I'm sure Mark, TooTired, John, etc., can explain alot better than me, but the goal is to isolate a channel within the carb and analyze the fuel mixture being fed to the engine through that channel...and if you read Mark's note carefully, no fifth gear is needed...cuz you're right, I'm not riding WOT in 5th...at least I don't plan to.

By isolating each channel, you can adjust the carb part (main jet size - wot; needle position - mid; pilot screw - low) most influencal on the air/fuel mixture in that position...take the time to read TooTired's note to me above, cuz its a wonderful explanation...thx.

[333]

There is no difference between WOT in 5th or 1st gears.  And these bikes seem to like the upper RPM ranges, at least mine does.

One thing missing in your first post is valves.  Did you adjust them?

[ron.cieri.313]

Yep...valves, timing, sync'd...all that good stuff.

She does run like a bat outa hell but just not all the time...hopefully the plug chops will isolate when exactly she is not and what to adjust.

[mlinder]

I never really understood why the plug chop meethod was the way to go. It does tell you how the bike runs at full power, but, who runs at full power in 5th gear.

Not to sound old, but, wouldn't it be safe to run say in 3rd gear at say 4500 rpm for 1/4 mile, shut it down and take your reading? Enocouraging someone to run wide open in 5th gear and telling them to be careful is kinda well, missing a piece.

I guess what I am saying is, we all want to have our bikes run their best, given that, shouldn't we try to simulate real driving conditions? 

If a motor isn't happy within its normal operating range, why does it matter if it's perfect at 8000rpm in 5th gear. (Yes, I understand about the metering needles).

Like Ricky said to Lucy, "Please splain" ...

bc

Actually, he sid "Lucy, you got some esplainin to do!"

The way to get your bike running it's best is to make sure your AF mixture is as close to optimal as you can. You read AF mixture by the color of deposits on your plugs.
You do this by working from the largest circuit down. In order to do this, you need to run with basically, with the main jet being completely unblocked by the needle. Only way to achieve this is at WOT.
NBow, there actually IS a difference between WOT in 3rd and WOT in 5th, The way your engine uses fuel actually changes between full load and partial load. The load at WOT in 3rd is different than the load at wot in 5th once you've achieved maximum RPM in those gears. Why? Because you can redline in 3rd. You can more thnan redline in 3rd. The load is much lighter in 3rd than in 5th. These bikes cannot redline in 5th, not enough power, meaning that the bike is at 100% load at WOT in 5th.

After you've determined what the optimal jet size is for your bike at WOT, narrowing down other throttle position settings is greatly simplified. You just do a plug chop at half throttle, and adjust the needle up or down depending on plug deposits. Don't have to worry about main jet size anymore, only needle position, and the stock honda needle profile is designed for these bikes air fuel needs between 1/4 and (just under) full throttle.

Once this is done, the air screws can be set by plug chopping at idle to 1/4 throttle.

This method, outside of an actual oxygen sensor (assuming you understand that a truly stoichiometric ratio does NOT work and is NOT safe on these old aircooled/less than perfect combustion chamber bikes) is the only way to get a propper tune on these bikes.

[Otto]

Thanks Lucy.

I understand better.

bc

[Johnny5]

Find a large hill and run the bike WOT up it. It'll add load and help you get a decent reading. Plus, it feels like you're shooting to the moon!

[TwoTired]

Hopefully in support of Mark, as I agree with what he said...

At any given RPM, there is an ideal A/F ratio to simply sustain RPM (overcoming internal friction losses) and another A/F ratio that provides maximum power output.
So, what your really want is to place the engine under maximum load conditions for whatever throttle position you select, suddenly halt engine operations, and read the spark plug deposits that existed under those conditions.

WOT is the easiest condition to create for home brew users, and max power is needed for max acceleration, and the wind resistance requires the most HP to overcome at high speed.

For midrange, you actually need a hill that requires more HP to climb than simply straight and level cruise.    You only need about 5 HP to maintain a 50MPH cruise.  You normally adjust the throttle position so the engine provides just the amount of power needed for cruise.  However, when you jet/adjust carbs, you are actually trying to set each throttle position for best A/F ratio, when the engine is producing the max power at that throttle setting.  This is where a dyno is far superior for carb tuning.  You can set the throttle position and apply wheel resistancet so that the engine is making maximum power at that setting. If you can reproduce those conditions on the street such as with a hill climb (and sustain it long enough to make significant plug deposits), THAT"S when you'd do the  "plug chop" for midrange.  Usually a dyno setup can sniff the exhaust and indicate what the A/F ratio is at any power setting/throttle position, making the adjustment process far easier.

Cheers,

[mlinder]

Yep, what Lloyd said. That being said, it's difficult to find a long enough uphill climb that will load the engine at half throttle. So I usually just make her a tad rich at half throttle in "normal" riding and hope it's enough to compensate for the changes that occur when applying actual load at half throttle.

[ron.cieri.313]

Ah good...cuz Detroit is flat.

[Johnny5]

The thing is the more you ride, the easier it gets to know how the bike is running and responding. Running lean and rich has unique qualities.

For the most part, if the bike pulls nice, cold and warmed up in each throttle range, without surging and the burbles, then you're good to go. Of course, the only positive way to know is by checking the plugs.

[ron.cieri.313]

Yeah!...WOT test complete...I drove onto one our highways and then pulled offed and put on brand new spark plugs...I rode "wot" as best I could up through to 4th going over 6000 rpm's and even into 5th...I must admit it was pretty fun and she was quite steady...the engine sounded greated...I went about 3-5 miles and pulled over into a rest stop and cut the engine...pulled the plugs after allowing her to cool a few minutes...on 3 of the 4 plugs, there was a nice (I think its nice?) off-white buildup on only the tip...no sign of carbon fouling...on plug 3, the buildup was barely noticeable but similar.  I put them back in and ran back at wot pull off at about 4 miles and cut the engine...yeah, a bar right at the exit...had a beer as the bike cooled and checked the plugs...exact same condition will a little more buildup on 3.  They look like the tips had been painted white or off-white and the deposits cleaned right off with the wipe of rag...I'm so excited...please tell me what you think!?...thanks...ron.

[TwoTired]

Compare the plugs to this chart.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

White generally indicates "too lean".

Were there any deposits on the center electrode insulator?  There should be, the deeper you go into the recess of the plug.

[ron.cieri.313]

I don't think so with regards to additional deposits on the center electrode...if there were, the were similar to what was on the tip.

So, do you think I need to up the jet size then???...and run the test again.  Per Mark, I have 125 on now with needle set at middle position, pilot screw only about 1/8 out.

...thanks.

[Johnny5]

Go 130's.

....wait, was that my recommendation a month ago???

 

[mlinder]

Sounds like they may be a tad lean. as per TT said. there are 128's (127.5's, actually), that you could try but may as well try the 130's

[ron.cieri.313]

  Okay, let the rejetting begin...

...maybe I'll be able to fit another wot test inbetween the rain tomorrow...thanks all...ron.

[ron.cieri.313]

K...rejetted last night with 130 mains and just got back from WOT test...I think things have gotten at least a little better.  I ran the bike on several 8-10 miles legs on a freeway like before only slightly longer stretches...most of the time I was riding in 4th at about 5800 - 6000 rpms.  I would drop into 3rd and really rev her or move up into 5th and give her some throttle as best i could within reason.

...the results in a nutshell are less white more grey to tan residue.  Only on cylinder 1 did i really get brown with dark grey to black residue on the rim of the plug and center electrode.

2 & 3 were very similar to each other...not much buildup...light grey on the tip and some brown deposits on the plastic or ceramic underneath the center electrode.  3 had a gold deposit on the rim also.

4 was light grey to tan on the tip and not much of anything else.

So what do u guys think?...still too lean?...should i go up one more main size?

Do i need to re=sync cuz of the different deposits on getting on the plugs?

Also, new issue (maybe I should start  a new thread?) or probaby is one...I'm having trouble shifing up or down between gears 1 and 2, I have to double or triple click?...this no a regular issue.

...thanks again...ron.

[mlinder]

I would try 132.7's or 135's.

Is your clutch adjusted properly?

[Johnny5]

Hey Ron,

Dont confuse WOT to high rpms. You may be seeing more of your needle readings than your mains. The throttle's gotta be pinned and the engine killed simultaneously. It's the toughest reading to get, cause the bike is moving like a bat outta hell.

[mlinder]

Hey Ron,

Dont confuse WOT to high rpms. You may be seeing more of your needle readings than your mains. The throttle's gotta be pinned and the engine killed simultaneously. It's the toughest reading to get, cause the bike is moving like a bat outta hell.

This