Logo
FULL SITE MENU

New question, BF100 coil reading too high or too low?

M

mroman59

Member
Hi guys, I just decided to test my ignition coil's primary and secondary resistance values. I have a BF100 with the serial no. that shows my coil is 30500-881-004. I emailed Honda and they sent me a document stating that the primary is 0.56 ohms +/- 10% and secondary is 8k +/- 20%.

I took my reading with 3 different meters to compare. My primary came out to be 1.5 ohms and the secondary is 33.1 k ohms. As you can see, these values do not match and are too high. When I read about and talk to people concerning these values they talk about getting readings that are too low and how this can affect the running of the engine. However, no one mentioned anything about getting values that are too high.

Does anyone know why I would get too high of a reading, short of using the meter wrong? As you can see, they are about 3x as high. Since the meter changes by a factor of 10 when you turn the knob, then the 1.5 could really be 0.15 ohms and the 33.1 could be 3.1K ohms meaning that my values are way to low and perhaps part of my problem. However I can not seem to register those values on any of the settings.

Thoughts are welcomed,
Mike
 
The motor is running good, idles good and runs good until you get full throttle and then it just dies. I am not sure how long it takes to die after I hit full throttle, but it sees to vary, but lets say less than a minute. Then it starts up easy after that. I first thought it was the fuel pump and then the carburetor. I got new parts for the fuel pump except the diaphragm because the diaphragm is obsolete. The diaphragm looked really good and no pin holes see while holding it up to light. Next I moved onto the carburetor and cleaned out. It was very clean and could not find anything that looked bad, i.e. float. I cleaned and checked the points. After that I read how a lot of people were experiencing what I am and it turned out to be either the coil or the condenser. I changed the condenser, but have not had a chance to take it out for a test drive. I was looking for a replacement coil when I decided I would take it out and check the resistance values.
 
Tegweni said:
The readings should be taken at ambient temp +/-20 degrees and not after the motor has been running .
Click to expand...

The resistance between the 2 plug wires should between 6.4K & 9.6K measure the resistance between the primary wire & earth should be between 0.46 & o.66 ohms
 
Tegweni, thanks for the information. The test was taken when the engine was cold. Your resistance values are in line what my book says. Therefore, if my readings are correct, both the primary and secondary are out of specifications. But I am not sure why the engine is running good with a bad coil. In any case, I will explore getting a coil that has the correct readings. Since I think that my coil readings are too high, rather than low ... the question is why and how should that affect how my engine is running.
 
Accurately reading small values of resistance can be tricky unless you have a top of line digital multi-meter and good leads - Fluke, Extech, Klein are all good ones and typically have an error rate of under +/- 1%. There are probably others out there. See if you can beg, borrow, or otherwise get your hands on one of those, re-test.
 
Thanks, I was planning and calling around today to see if any of my friends have one. I was thinking of taking it into the boat shop and asking them to do it for me. I would hope they would not charge me. LOL
 
Don't know where you live, but a good auto parts store should have a good digital meter that you could use to test on site. Some even offer loaners. At least they used to.
 
Back
Top