Topic: Ignition Coil Mystery: Tests GOOD but could it be BAD?

[Honda3]

On my 73 Honda CB500F:

Bike hesitates and surges at low RPM, often when moving from a stop.

Gas mileage is atrocious. On a little bike like this, Im putting in $6 every time I got 12 miles

Plugs 2 and 3 are a bit fouled, carbon fouled, not oil fouled or anything else

Plugs 1 and 4 are normal but sometimes go black too, esp plug 1 on cyl 1

Carbs were newly rebuilt and there is absolutely nothing in the carbs or jetting or the rebuilding process that could be causing this.

took the coils off and tested them last night.

reading 5 ohms on the primary side of each and about 14,000 on the secondary.

Ive heard coils can test good, but still be crap.

Any advice? Im putting on dynacoils tomorrow to match the Dyna S ignition system already on the bike.

[Duke McDukiedook]

When they heat up to temp, yes, they can be bad.
If they are the original coils one of them may be bad and still test well when cold.
If you are going the dynacoil route be sure to get the 5 ohm version to match what you originally had.

[Scott S]

Welcome back, JWilde. How many usernames is this now?

[Honda3]

When they heat up to temp, yes, they can be bad.
If they are the original coils one of them may be bad and still test well when cold.
If you are going the dynacoil route be sure to get the 5 ohm version to match what you originally had.

Im not sure what you mean. The previous owner put a dyna s ignition system on to replace the points system.

I have no idea what coil is on there but it looks super old and is 5 ohnms. I got the green Dyna coil DC1-1. I called dynatek and they said thats the correct coil for my setup.

[Honda3]

Welcome back, JWilde. How many usernames is this now?

Hi Scott

Hope you are well.

It is not my intent to cause any distruption of any kind in the forum. Ive calmed down quite a bit since I first started riding and was hot-headed.

Should I be allowed to remain, you'll get no trouble from me.

J

[Greaser Greg]

Once upon a time I was a real nad-buster. Any little thing set me off at times.  Finally figured out that I have issues with processing certain foods, like nightshades and most grains that aren't produced without glyphosate.  My stress level was always right at the limit, and I'd wonder, "this is no big deal, why am I flipping out?"  Stopped eating wheat altogether, and other stuff unless certified gmo-free.  I'm m a whole new me.

Did you try testing the coils when hot?

[TwoTired]

Your coils measure fine. 

If it's not sparking you'll feel a cylinder miss,  or the head pipes won't get evenly heated.  Fouled plugs can cause misfires.  Fouled carbon soot plugs indicate fuel delivery unbalance with air inlet.

Nothing in the spark circuit will make the engine draw more fuel.   You are looking in the wrong place.  It's the carbs that deliver fuel to the motor.

Good luck!

[Tracksnblades1]

Welcome back, JWilde. How many usernames is this now?

Hi Honda 3,

Without exception, I just noticed 👀 you don't have any Yelp complaints.
With exceptions, I have read and understand the Forum rules 1-6.
Sometimes one can be tracked through your IP, as only a member, I don't have access to it.

Hoping you get your ride sorted out.
👍

[Duke McDukiedook]

Lloyd is probably right in this instance, it probably is not your coil being bad.
I would take a better look at your crabs.

[Scott S]

 When were the carbs rebuilt?

 What brass did they use?
 
 When's the last time it had a tune up  (valve adjustment,  etc)?

[Don R]

 No coil can make the bike get mileage that bad.

[Honda3]

No coil can make the bike get mileage that bad.

What could it be then? Compression is good. Air filter?

[Honda3]

When were the carbs rebuilt?

 What brass did they use?
 
 When's the last time it had a tune up  (valve adjustment,  etc)?

It had a tune up about a month ago. It has dyna s ignition. The compression is good. Not sure about the valves.

[TwoTired]

Stock sprockets, wheels and tires?  Clutch slipping?

But, most likely is a carb issue, imo.

[Honda3]

Stock sprockets, wheels and tires?  Clutch slipping?

But, most likely is a carb issue, imo.

The carbs are brand new, rebuilt. AND this happened with the old carbs as well so Im inclined to think its something else.

Hoping its the airfilter which did look kinda cruddy

[Scott S]

 What brass did they use when they rebuilt the carbs? Genuine Keihin or aftermarket. If you have aftermarket emulsion tubes and needles, then all bets are off. You can probably work around aftermarket pilot and main jets, but the emulsion tubes/needles are crap in the "kits".
 Did they pull the emulsion tubes when they rebuilt the carbs?

[Honda3]

What brass did they use when they rebuilt the carbs? Genuine Keihin or aftermarket. If you have aftermarket emulsion tubes and needles, then all bets are off. You can probably work around aftermarket pilot and main jets, but the emulsion tubes/needles are crap in the "kits".
 Did they pull the emulsion tubes when they rebuilt the carbs?

Not sure but uggggh  with this. Ive spent $580 on carbs during this process, not to mention installation because I was too busy to do it. I knew I should have gone ahead and got the CR carbs from Dynoman, like I did when I had carb problems on my 1982 CB900F.

If the air filter doesnt solve this problem, Im taking the carb rack out and buying CR carbs and calling it a day.

I feel like an idiot. Ive spent SOOOO much on this. But I will survive.

[Scott S]

 CR carbs will be WAYYYYY over carbed for a 500 engine. Way, way too much for a basically stock engine.

[Honda3]

CR carbs w

Yep. Thats what Buzz at Dynoman told me yesterday when I emailed him.

[Duke McDukiedook]

Yeah, if it is stock you would be better off just having Harisluv rebuild your current set and pay to have it put on and tuned.

[Honda3]

What brass did they use when they rebuilt the carbs? Genuine Keihin or aftermarket. If you have aftermarket emulsion tubes and needles, then all bets are off. You can probably work around aftermarket pilot and main jets, but the emulsion tubes/needles are crap in the "kits".
 Did they pull the emulsion tubes when they rebuilt the carbs?

It was the airfilter. I put in a new one and the bike runs as good as new.

[Duke McDukiedook]

Good to hear that is what the problem was. That must have been one janky filter.

[Honda3]

Good to hear that is what the problem was. That must have been one janky filter.

Held it up to the light, couldnt see a thing so I guess it was dirty!