Topic: decel popping

[Paintedseat]

Hondaman suggested 38 to 40 pilot jets and 115 main. It made a huge difference in my bike.

[M.Henry]

now those will richen up the A/F form the stock lean set-up.

What engine characteristics would I expect from setting the jets to 38 and 115 away from that stock 35 and 1XX?

What engine characteristics would I expect from setting teh idle air mixture screw different? A healthier idle?

Granted I know I'm asking a big question of how does somewhat smaller A/F changes affect an engine, I know engine performance is a big balance of a ton of variables.

[TwoTired]

Sid enote: I ran a compression checker on the two outside cylinders this weekend and got 150 PSI and 180 PSI. That is more then a 10% increase  so do I need to look into that?

Have you read the FAQ about compression testing?

[M.Henry]

Sid enote: I ran a compression checker on the two outside cylinders this weekend and got 150 PSI and 180 PSI. That is more then a 10% increase  so do I need to look into that?

Have you read the FAQ about compression testing?

I'm about to now.   

[M.Henry]

OK, So I cleaned the plugs with a torch then wiped them off and reinstalled them. I then tried to start the bike and it appears I am still not running on all cylinders. Guess it is time  troubleshoot that. Then get to seeing what the spark plugs look like after thats resolved.

[M.Henry]

oh and the exhaust looks like it might have had some smoke (black ish) coming out.

[TwoTired]

Black "Smoke" is usually unburned hydrocarbons or soot suspended in a gaseous atmosphere.

Often indicates too rich a mixture.  But, if you have soot deposits lining the exhaust pipes, those deposits can dislodge and get suspended, too.

Check the float levels/ fuel bowl levels yet?


When you torched the spark plugs, did you get the porcelain white again?

[M.Henry]

I do have some soot deposits in the pipes, but this did appear to be actual smoke consistently enough and I havent had that problem before so I doubt it is consistently dislodging soot on every exhaust puff on each pipe.

which means I am probably running rich still.

Yeah I will check the float levels (clear tube method).

Yeah I did get them white. I might see if my buddy will let me hit them in his sandblast chamber. that would really get them all clean right?
The flame certainly didn't want to burn off the carbon too easily though.

[TwoTired]

Black smoke means it has dark particulates floating within it.

Sand blast is good.  Just make sure no sand gets lodged in the plug to fall into the combustion chamber.

The plugs will self clean when the combustion chamber attains the proper heat  ~1300 degrees F.  Rich mixtures won't allow that.  Lean mixtures will and with even higher temps.

The maximum adiabatic flame temperature a propane torch can achieve with air is 1,995 °C (3,623 °F)

When steel is a brown red color, its about 1100 F

http://www.smex.net.au/reference/SteelColours02.php

Cheers,

[PeWe]

About sooty plugs...Any good way to clean them?
I have several setups of sooty plugs after some carb problems I have had.  All of them almost new.
A friend talked about carb cleaning possibilities on gas stations available decades ago. Put plug in a hole and press a button. Must have been a sand blaster or similar.

In a case like this it would be fine to clean plugs after each jetting riding session ending up in black and try again.

[M.Henry]

Yeah I have 3 levels of cleaning plugs.

The crappy quick way is a brass wire brush or sandpaper and hitting it lightly to get the smchmoo off.
my new usual way is hold the plug tip in the flame of a propane torch directing the flame tip around to focus on different parts of the plug head.
The best way is to hit the end of the plug with a sandblaster. Unfortunately not all of us have access to sand blasters at home.

Though you should take this all with a grain of salt when you consider that some of the fancier plugs on the market have coatings on them such as iridium. sandblasting or sandpapering can remove this coating and essentially remove the reason you paid more for those plugs.
I feel its more worth it to use regular steel plugs and have the ability to extend their lifecycle much longer by being able to clean them.

[PeWe]

The black velvet sooty ceramic part need to be white again. I have seen sooty plugs where the arc goes everywhere.

[M.Henry]

Ok so I worked on the bike again last evening.

I changed the carbs back to the 4th needle position, nearly back to the stock position now. I changed the field coil cover with the one from my original K7 engine. and I cleaned all the sot off of the plugs.

I then started the bike up again, and no real improvements. It still has small bits of black soot coming out that is barely visible in the exhaust puffs. she also feels like all the cylinders are firing, but it does not feel like they are all firing at full power. She has a very weak idle when the choke is fully on (closing the carb position). When reved she has no accel stall but when she comes back down in RPM to idle she comes down to far and will die if not given a touch of throttle.

any ideas on what may be causing this weak idle and weak power feeling?

[RJ CB450]

Just side note.  When you got a bit of heat, do revs pick up a little when you choke on?

[M.Henry]

yes, but not much, with the idle set screw not quite making contact it sits at 900 - 1000, in the past the same un-engaged set screw setting would leave me at 1100 or so.

This 1000 rpm with a weaker feel from the engine means that this is barely above the biking dying. I think this may be why it dies when the rpm is coming down, it comes down just past the idle and drops into the rpm area were the bike wants to die.

[TwoTired]

Check the float levels/ fuel bowl levels yet?

See reply #56.

How old is your air filter?  What type?


Note that brass is conductive and porcelain is abrasive.  Cleaning the center insulator with a brass brush can leave "tracks" of brass on the porcelain surface and the spark energy can travel upon that bypassing the spark gap.

Have you tried new spark plugs yet?

Applying choke blocks inlet air.  That's part of why it enriches the mixture.  Why do you expect it to idle well when the air supply is restricted?  With choke on, you will need to open the throttle some due to poor atomization on a cold engine.  The carbs are properly tuned for an engine at normal operating temperature.

Cheers,

[TwoTired]

yes, but not much, with the idle set screw not quite making contact it sits at 900 - 1000, in the past the same un-engaged set screw setting would leave me at 1100 or so.

This 1000 rpm with a weaker feel from the engine means that this is barely above the biking dying. I think this may be why it dies when the rpm is coming down, it comes down just past the idle and drops into the rpm area were the bike wants to die.

Seems like you tweaked all the individual slide adjusters enough to prevent them from allowing full slide travel to the carb bore floor.  That's why your idle adjuster loses control.  You likely did this during carb sync, chasing balance.   You need to change an adjuster with the idle knob backed out so that the slide can reach bottom of mechanical travel.  The re vacuum sync so that the other carbs match that one as a "master carb".

Cheers,

[Paintedseat]

Are you still running the 40 pilot?

[M.Henry]

no it is still the stock pilots for a k7. Is that a 35 or is that a 40?

I will check the float fluid level tonight and get back to you.

I had bench synched the needles to the immovable arm and they all seamed good. Can you explain more what you mean with no hitting the carb floor part? Like they are not all closing?

Also the problem seams to be sooty spark plugs, is it the richness that would be causing the sootiness?
I'll have to dig around, I think I do have a few fresh spark plugs. no brand new ones though.

[TwoTired]

I had bench synched the needles to the immovable arm and they all seamed good. Can you explain more what you mean with no hitting the carb floor part? Like they are not all closing?

Yes, the slides need to be allowed full travel via the actuating arm.  Fully closed to fully open.  The individual slide adjusters used for vacuum sync can be ill adjusted to prevent full slide closure.  Then the idle knob cannot control how closed they can get for a proper and solid idle adjustment.

Also the problem seams to be sooty spark plugs, is it the richness that would be causing the sootiness?

Almost certainly.  Can be caused by clogged air filters.  Fuel leakage from too high fuel level in the carbs, etc.  But, also shunted spark from contaminated electrode insulators.  This is a chicken and egg scenario.  Too rich contaminates plug, contaminated plugs don't do a complete burn and leave soot on the plugs.  Root cause is mixture, fouled plugs blinds user to root cause.

Cheers,

[Paintedseat]

Check your pilot jet size and your plug gaps.

[M.Henry]

I had bench synched the needles to the immovable arm and they all seamed good. Can you explain more what you mean with no hitting the carb floor part? Like they are not all closing?

Yes, the slides need to be allowed full travel via the actuating arm.  Fully closed to fully open.  The individual slide adjusters used for vacuum sync can be ill adjusted to prevent full slide closure.  Then the idle knob cannot control how closed they can get for a proper and solid idle adjustment.

Also the problem seams to be sooty spark plugs, is it the richness that would be causing the sootiness?

Almost certainly.  Can be caused by clogged air filters.  Fuel leakage from too high fuel level in the carbs, etc.  But, also shunted spark from contaminated electrode insulators.  This is a chicken and egg scenario.  Too rich contaminates plug, contaminated plugs don't do a complete burn and leave soot on the plugs.  Root cause is mixture, fouled plugs blinds user to root cause.

Cheers,

Ok so I'm back at it again. Gonna clean the plugs real well, check the float level, and let it idle out for a bit then try riding and see how she feels or if she is ridable

So with these pd carbs, what float level am I aiming for? And it is measured down from the top of the bowl level (gasket surface essentially)

[M.Henry]

Oh ha  I just noticed there is a thread active right now on setting the pd42 carbs back to stock properly. Nevermind.

[M.Henry]

So with the bowl level corrected to roughly 14 mm (why go 12.5 mm or 14.5 mm? Can anyone answer me that?). She still sounds and feels (exhaust puff strength) like cyl 1 is not firing too well.

With how much I've been playing with the spark plugs I've noticed my plug wires are atrocious. I think I'm gonna get them replaced with the kit linked below.

Oh and I looked at my jet sizes. The carb currently has a 115 and a 35 installed and she is set at the 2nd notch from the top (4th notch from the sound of the usual convention)

[dave500]

float height isn't critical,its like a washing machine inside the bowls when your riding the bike,imagine inside the fuel bowls on a dirt bike?