Topic: Carb help please

[flybox1]

With popping on decel, or at idle, your mixture is still wrong.
What plugs are those? 
Were they new for the plug chop done above?
What were the parameters of your plug chop? 
(You didnt give any of these details for the plug chop, so we cant give you detailed suggestions)

[Loctite77]

With popping on decel, or at idle, your mixture is still wrong.
What plugs are those? 
Were they new for the plug chop done above?
What were the parameters of your plug chop? 
(You didnt give any of these details for the plug chop, so we cant give you detailed suggestions)

Yes they were new plugs. They are NGK DR8EIX Iridium plugs at .28 gap. I did the chop on an exit ramp from the highway. Hit the kill at about 3/4 throttle in 5th gear about 70mph.


Yeah Son!

[flybox1]

great.  did you ride with these plugs in all the way to the exit ramp?  How far?
and how long had you been holding that throttle position when you killed it?

[Loctite77]

great.  did you ride with these plugs in all the way to the exit ramp?  How far?
and how long had you been holding that throttle position when you killed it?

I rode about 15 miles before the chop, about 8-10 at highway speed 65ish. I only rolled up to that throttle position for about 15 seconds before I hit the kill.


Yeah Son!

[flybox1]

great.  did you ride with these plugs in all the way to the exit ramp?  How far?
and how long had you been holding that throttle position when you killed it?

I rode about 15 miles before the chop, about 8-10 at highway speed 65ish. I only rolled up to that throttle position for about 15 seconds before I hit the kill.


Yeah Son!

^^^ this information is what i'm looking for, and it invalidates your plug chop.
A plug chop needs to be done on NEW plugs, with the throttle position to be chopped held for several minutes for adequate deposits to form on the insulators.  Riding around before you do your chop places deposits on the insulators. 
Sorry.  The test shows deposits for all the throttle positions from the time you put the plugs in until the time you shopped it.  Its meaningless.
Ride to your test area.  Put new plugs in...Ride only at your desired throttle position (3-5min) until you 'chop it'...coast and pull the plugs.

[flybox1]

I would suggest starting with an idle plug chop.
Its the easiest to do, and will help with the popping on decel/idle after the throttle is abruptly closed.
Get the engine hot.
Put in a new set of plugs.  Start it and let it idle 3-5 min under a fan. 
Pull the plugs and adjust your IMS as needed to achieve light tan insulators from each cylinder.

[Deltarider]

I don't know where the idea came from, but new plugs are not essential to do a plug chop. As long as your plugs are good, they can serve. It's about the colour and old deposits will either burn of or take the colour for that rpm. Also 1 minute of maintained constant speed is enough. What you could do in a test, is first run the bike hotter (burn of) and then let the rpm drop to the rpm you want to investigate and maintain this speed for about a minute. Apply the clutch and kill switch at the same time. Tip: Todays gasolines do not show much on sparkplug noses. A spoonful of castor oil added to the fuel tank can help.

[flybox1]

I disagree, Delta.  We tested this on a friends 79CB750
He was soot fouling plugs at 1/2+ throttle position.
We did an idle plug chop with these same dark plugs and there was no change in insulator color.
Performed the same idle plug chop with NEW plugs showed barely any color.
Same hot engine.  Same 4+/- minutes.  Same box fan.

[Loctite77]

Seems like a lot of work and expense for new plugs... Not that I'm lazy, but I just want to ride. I was kind of hoping to confirm that "generally speaking" popping and an occasional backfire at closed throttle deceleration is a sign of extra in burnt fuel so I would lean out the mixture with the idle screw.... Was hoping for an easy fix


Yeah Son!

[PeWe]

Try new NGK D8EA.
My engine did not like the iridium plugs. They behaved as a colder plug than D8EA.

[Loctite77]

Try new NGK D8EA.
My engine did not like the iridium plugs. They behaved as a colder plug than D8EA.

I've seen you say that in other threads. What do you have the gap set at?


Yeah Son!

[flybox1]

Try new NGK D8EA.
My engine did not like the iridium plugs. They behaved as a colder plug than D8EA.

I've seen you say that in other threads. What do you have the gap set at?


Yeah Son!

I only use D8EA's also...same gap
IMO, iridiums are wasted $$

[Loctite77]

Try new NGK D8EA.
My engine did not like the iridium plugs. They behaved as a colder plug than D8EA.

I've seen you say that in other threads. What do you have the gap set at?


Yeah Son!

I only use D8EA's also...same gap
IMO, iridiums are wasted $$

For sale.... Lightly used Iridium plugs....


Yeah Son!

[PeWe]

0.7mm

[PeWe]

My conclusion was maybe OK for racing. Not country road crusing mixed with some WOT up to 100-120mph then back to 50....my plugs did not burn clean despite lean carbs. I stepped up pilots and mains later on with D8EA.
I have ordered a bunch of Denso std plugs recommended by Hondaman. I tried them earlier but with my floading VM29 carbs so they did not live long.

[Loctite77]

0.7mm

This is the biggest gap I've seen? Why do large? Usually only see numbers from .25-.32


Yeah Son!

[flybox1]

My conclusion was maybe OK for racing. Not country road crusing mixed with some WOT up to 100-120mph then back to 50....my plugs did not burn clean despite lean carbs. I stepped up pilots and mains later on with D8EA.
I have ordered a bunch of Denso std plugs recommended by Hondaman. I tried them earlier but with my floading VM29 carbs so they did not live long.

I tried the X24ES-U's and still, went back to the D8EA's 
Denso's made cold starts harder 

[Deltarider]

I disagree, Delta.  We tested this on a friends 79CB750
He was soot fouling plugs at 1/2+ throttle position.
We did an idle plug chop with these same dark plugs and there was no change in insulator color.
Performed the same idle plug chop with NEW plugs showed barely any color.
Same hot engine.  Same 4+/- minutes.  Same box fan.

You forgot to start with a 'burn-of period'. To me plug chops at idle is a waste of time, in particular for the CB500/550, but this has been discussed before. Owners of an original 4-4 Four can simply have a peek in the exhausts exits. You can also ask your partner 4 tampons and insert them temporarily (at idle only). Pro's sniff. Don't you love these simple machines? 

[jonda500]

.28 inches is way wrong it should be written .028" or 28 thou(sanths or an inch) which is .7mm.
John

[scottly]

The instructions for my Gerex ignition call for a plug gap of .063-.065", but I've never gone wider than about .045", as it's difficult to bend the ground-strap that far.

[Deltarider]

The instructions for my Gerex ignition call for a plug gap of .063-.065", but I've never gone wider than about .045",

Even with .045" your plugs will erode and as a consequence won't live long.

[alacrity]

My bike seems to run a bit better with NipponDenso plugs instead of NGK. I got the idea from Hondaman.

[Loctite77]

So I recently decided to try some velocity stacks thinking it would lean things out (more air). However I was dread wrong and the carbs are now running richer. Way rich. Plugs are black, yesterday on a ride when I opened it up at 100mph, A friend riding behind me said black smoke poured out the exhaust. Others have commented that it sounds rich. I'm puzzled. This is what I have.

76 CB750f.
Stock Motor
Open 4/1 exhaust.
Clips in the lowest position on needle.
115 Main Jets.
42 slow jets.
Screw .5 turn out.

I'm confused because everyone tells me 115 is too lean and my buddy with virtually the same engine/exhaust/velocity stacks is running 125's and running well. I was advised to put the clip in the last position but that seems like the reason for running rich. Should I try the second from the last?

Does the mixture screw effect anything other than at idle?


Yeah Son!

[calj737]

If the clip is in the lowest (nearest the tip) then it's the most amount of fuel. The higher the needle clip, the less fuel. Raise it 2 notches.

[Loctite77]

If the clip is in the lowest (nearest the tip) then it's the most amount of fuel. The higher the needle clip, the less fuel. Raise it 2 notches.

Yes it is in the lowest (richest) position. I previously had it two notches up and it was too lean and stumbling. I guess I'll try it one notch up.


Yeah Son!