I know this will be hard to believe, but...

[TOOLS1]

I have a running problem I can't figure out. Toolbabes Bobber is not running right. It idles, but will not rev up. It starts running rough, and popping. It has new points, and condenser. I just replaced the ignition advancer, and went through the new carb. I am at a loss The only thing left is the coil, but it works while idling?
TOOLS  

[rrgunslinger]

Do a compression check ? Valve adjustment? Intake leak? 

Harvey

On May 2, 2012 6:01 PM, "TOOLS1 [via Honda CB750'S]" <[hidden email]> wrote:

I have a running problem I can't figure out. Toolbabes Bobber is not running right. It idles, but will not rev up. It starts running rough, and popping. It has new points, and condenser. I just replaced the ignition advancer, and went through the new carb. I am at a loss The only thing left is the coil, but it works while idling?
TOOLS  

Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
1976 CB 750-A X 2
1977 CB 750-A X 2
1981 CB 750
1995 KZ 1000 P-14
1981 KZ 750 LTD X 2
1973 CB 350
1979 CM 185 Twinstar
1987 Honda TLR 200
1982 Honda XL 80
2005 Yamaha PW 50
South of Edan (Kansas City MO)

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[TOOLS1]

I forgot to mention it is a 1979 Honda CM 185 Twinstar.
It has compression. The intake has a new gasket on one end, and a new O-ring on the other. Also I did check the valves not long ago, but I might go, and check them again.
TOOLS

[MarkPBG]

If it were a 350 chevy, I'd say the timing is off, it's got ALL the symptoms. Bikes, dunno yet, still learning those. Good Luck...
p.s. when I read the title, I thought for sure you were going to announce you either bought another bike, or sold one, either way, I wouldn't have believed it. lol

[Hellbilly429]

Mine will do that when the plugs are fouled, although I am sure you checked that already Tools

[rrgunslinger]

You said new carb.  Where's the old one? Just saying...

[Piute]

MarkPBG wrote

If it were a 350 chevy, I'd say the timing is off, it's got ALL the symptoms. Bikes, dunno yet, still learning those. Good Luck...
p.s. when I read the title, I thought for sure you were going to announce you either bought another bike, or sold one, either way, I wouldn't have believed it. lol

        My 1st thought also Mark
                                                    Don't hurt the Lil guy,Hows TOOL Babe doing

[shinyribs]

I agree with Mark that it could be timing related.

An ignition coil is just a big capacitor. It could "work " but still be bad. Like it will idle but it cannot store enough energy to support higher rpms.

But, everytime I was ever stumped by an ignition problem that I just could not solve...it ended up being fuel delivery. They can mimic one another pretty well.

[TOOLS1]

I have checked the entire fuel system. I am really suspecting the coil. I have looked on ebay, for them, and there are none to be found.
TOOLS

[shinyribs]

Hire a professional. Sounds like your over your head Just kidding bud. Good luck with it,hope you get it sorted out.

[Lucky 1]

QUOTE..."It idles, but will not rev up."

Lean condition symtoms.

Are the idle jets clean? Can you take them out and see daylight through them???

"New carb" How long ago???

[TOOLS1]

The carb is about a year old. I took the whole carb apart, and cleaned all the jets.
TOOLS

[sgtslag]

Actually, coils are not capacitive, rather, they are inductive.  

The coils could possibly be failing at higher RPM's, which translates to higher frequencies.  I cannot, however, say that is the case, but it is possible.  Do you have another set of coils to try (anything that might work)?  It would be a good idea if you could swap them out, temporarily. to eliminate them from the list of possibilities.  Any coil that generates enough voltage to jump the gap, will work, as long as the input impedance is similar.  Cheers!

[TOOLS1]

I wish I had another coil to test it with. It is a 6 volt system that uses one set of points, and one coil with two leads. Not very common.
TOOLS

[shinyribs]

Ewww. Yeah,I dont think Napa is gonna shelf that one

[LukeM]

Any way to convert it to a 12v system?  That would open up a whole lot more parts availability.  We're starting to run into parts availability problems with these 30+ year old bikes.

If a fuel problem (aside from jets and stuff):
Fuel flow/delivery?  Clogged fuel line?  Dirty petcock filter? Clogged vent in the tank? Dirty fuel line filter?

Good luck.
Luke M

[Re-run]

Well 4 possible issues come to mind.
A lean condition
A rich condition
timing
ignition

I dont remember if you checked the plug, see if it is white or black. This would rule out lean or rich.
Timing could be off. It is easy to forget about it when checking things. It is one of those "how did I miss that" things.
Something in the ignition. I would rule out the wire as you would have missing at any rpm.
A simple ohm test of the cap would take a few seconds. I would assume 5k - 10k ohms would be ok.
Change the sparkplug with a new one.
After that, the coil.

[rrgunslinger]

Could just be the crapy gas we are forced to use.  But my bet is still on the carb.  It starts, it idles, Timming advance? but even if, it should rev...spark plug gap...a weak spark requires closer setting.

Throw enough SH#$ against the wall your bound to hit something.

[Hellbilly429]

Hey tools, is that XL80 you said you got for the grandbrats a 6v system? I know my XR75 is.
Honda XR75 Coil

[Lucky 1]

Coils almost NEVER fail.
Sounds like it is running lean.


Just take an DC clamp on timing light and clamp onto any plug wire one at a time.
You will have your answer.

To diagnose this problem I would need:

Year of bike.
Engine size.
Intake type.
Exhaust type.
idle jet size.
main jet size.
needle position.
Mixture screws.