bf100 ignition parts identification? and a few more questions..

thanks for reading. Think I picked up a bf100. its a b100l cdi ser# 17xxx.

Think that it was monkeyed with and parts swapped out from other motors..

not finding spark but will try again in the dark.

specifically any way to identify the coil? I see different specs for cdi vs points system on the resistance check.. and the primary resistance checks seem closer to what is listed for the points system...anyone know if the part number is printed on there somewhere? have not pulled it yet.

question 2.. the parts schematic shows the plug boots as removable.. I am not getting a tight fit on one of them and see some corrosion. anybody take these off.. they are a hard plastic.. unscrew like an old vw??

and lastly...if its the wrong coil, would it blow the cdi unit? All I see on testing that is the thru eliminating the other components..

thanks in advance for the help..

Hi rocknroj,

It's been quite a while and several damaged brain cells ago but I used to tinker with these from time to time. Can't pick one up to work on em anymore but I'll share what notes I have in my old shop manual.

First off, make sure your running NGK DR-5HS spark plugs gapped at 0.024" to 0.028". These old girls don't do well on other plugs for some reason.

I do seem to recall that the coil high tension wire caps were replaceable but I can't remember how they were attached. That is, if I EVER knew in the first place! I was thinking that they had a set screw type attachment but I don't remember ever replacing any. So, proceed with caution there. Sorry for the low information on this point.

These outboards don't make "bright blue spark" at pull start speeds because of the relatively low voltage coming from the exciter coil. So, yes, look for spark in a dark/nighttime setting or throw a blanket over your head and the outboard and recheck for spark.

Make sure that the coil primary isn't grounded by a shorted wire or defective stop switch.

I have two notes in my shop manual about ignition coil resistance:
First, the resistance in the secondary is the same for either breaker point or CDI. You measure by probing the high tension leads with your meter leads inserted in each plug cap. I have crossed out the specification in the shop manual and wrote in 31.5k ohms for BOTH breaker point AND CDI fired engines.

I have also crossed out the resistance specifications in the manual and wrote in:
Breaker point ignition primary resistance = 1.5 ohms

CDI coil primary resistance = 0.8 ohms

I remember that there was much discussion and confusion about the specs at the time and I took those readings from running outboards with a Fluke 87 multimeter at room temperature. I didn't write down the temperature so that is as close as I can get.

I don't think if someone installed a HIGHER resistance coil (breaker point coil) that it would damage the CDI. The higher resistance might, though, not allow for adequate spark because of low primary "saturation" during low rpms. Just my opinion.

In a low/no spark situation, don't forget to check the pulsar coil and it's connections to the CDI. It's always a good idea to look in on it under the cam sprocket cover to ensure that water or debris hasn't interfered with it's placement and that it is secure.

Well, I hope this helps you and,

Good luck!

One other thought about a no spark condition on these.

Many of them were equipped with a neutral safety "contraption" that consists of a reed switch, magnet and a Y shaped plate that would rotate between the switch and magnetic field to prevent the engine from starting when in gear.

Since it's a "make connection" to start set up, all you need to do to see if it's good or not is to jumper the reed switch terminals and check if spark returns. Of course this comes with additional wiring and connections to go bad so that would be a consideration too.

Good luck.

thanks jgmo! Really appreciate you taking the time to look that stuff up.

I could not get a reading on the secondary circuit (between the 2 tension leads) but might have had the wrong scale on my cheap meter.

I have a runner of the same style so i could do a coil swap and see if that does it. The honda parts schematic shows a 2 different connectors for the plugs depending on cdi vs points style. Think my runner with cdi had soft rubber boots and these are hard plastic.

Is there any way to ruin a coil if its not hooked up correct? they are kind of spendy to replace.

D

First thing I did was disconnect the kill switch. Was gonna try and locate the neutral contraptio

The trigger coil (under the cam) checked within spec at the plug. Haven't checked the exciter coil yet.

Well, being a bit of an idiot myself I'm confident that I could ruin a coil but, since they are basically just step-up transformers, they aren't really polarity sensitive. These coils are powered by ac volts from the exciter coil so polarity is constantly "switching" anyway.

As a matter of fact, 12 volt, battery powered, automotive coils are considered polarity "dependant" NOT "sensitive" only because the polarity of the current through the spark plug is important to the relation of the heat differences of the electrodes. I'm not an electrical engineer and don't profess to understand it all but I did read that somewhere. Might explain why NGK plugs seem to work so much better in Honda outboards.

However, it will be important to connect the coil to the pulsar correctly because of the way it interrupts current flow in the coil. Not sure about what damage could take place there but, at a minimum, it could disable spark.

If you have ac volts at coil positive when pulling over the engine, then the exciter isn't open or grounded and is likely ok. If no ac volts during cranking you will need to check exciter coil continuity and resistance value. My manual states 330 ohms +/- 10%.

Let us know how you're doing and

Good luck!

Got my points and CDI system's mixed up!

There SHOULD be positive dc volts at YOUR ignition coil because it is rectified inside the CDI.
Sorry if I caused (myself) any confusion!

LIke I said, it's been awhile and I'm a bit of...well...you know.

Good luck!

I am confused about checking the exciter. It has 1 brown lead. The honda shop manual shows testing between the body and the core. Also says it can be tested without flywheel removal. So with my mirror i tried to connect my leads. Seems I am testing case ground to brown wire. What is meant by the 'core'. Do i need to pull the part to test it? Any part I could reach with my probes seems to be grounded via the mounting bolts.

The coil and trigger seemed ok to spec. could not see the spark in the dark but my vision is poor and yanking the rope at the same time is tough. Bench tests are easier on my shoulder.

No, you should not need to remove the exciter coil to do testing. The term "core" is probably a missed translation from Japanese to English. It's just a simple copper coil winding around an iron core or "pole shoe" to create induction into the wire when a magnet passes by and sets up a field.

You are simply looking at the continuity of the coil windings by probing the wire end and case (chassis) ground. If you're using a digital voltmeter, polarity isn't even a consideration.

If the resistance is too high it's an open or partial open coil and if it's too low the coil is shunted to ground.

Another way to check is to see if it produces ac volts when the engine is pulled over by probing the same points...wire end and ground....with your meter set to the ac volts scale. I don't have the specific voltage written down anywhere and can't remember what minimum should be. It's just a guess but I think more than 20vac is required at start speeds to fire the coil but I may be completely wrong about that.

If you do find that you need to pull the flywheel to check magnets it's not that difficult if you have a good wheel puller.

Good luck.

One thing to remember about working on these old girls is that it's more than likely that someone, possibly more than some-one, has been in there before ya....
.... futzing around with things.
This can present you with some fairly wild curve balls to try n hit.

Just sayin'.

thanks again jgmo
I Rechecked the exciter and seems in spec. So everything seems to check out on the ignition side with simple resistance tests, timing coil, ignition coil, exciter coil. Have the stop switch disconnected. Did not check the rectifier or the charge coil but I don't think those don't have any affect on the unit starting or running the 2 visible problems are the lack of the plastic cap on the cam wheel (think I can order that) and a loose spark plug boot.

Still trying to find an answer on how those spark plug boots come off. specifically, there is a small metal spring thing that bites the tip of the plug to make a firm connection. Thats gone or broken, not sure. Wonder if the people that sell the replacement piece may shed some insight into the replacement. It appears the coil and wire are a single assembly so need to be careful and not cut the wire short. The coil is about $80 +.

Maybe I can get it to hold tight with some duct tape just for testing. If the thing run then look into a longer term fix.

They honda parts show 2 different boots depending on cdi vs points. I am guessing there's a different resistance reading in the cap..

I believe the major difference in the spark plug wire caps is that the later issue for CDI were noise suppression while the points ignition ones were not.

I thought you stated that you couldn't get a resistance measurement through the secondary portion of that coil....?
If the secondary is open then there's no need to worry about replacing anything on the wires.

Did you try the coil from your "runner" yet to see if you can get spark?

Had an injury so it was time-out on the motor repairs..

Finally got the coil off. Needed to remove the charging outlet to get to the coil bolts and the charging outlet mounting screws were wobbled out and rusted up tight. A lot of patience and an impact driver to get 'em to budge. Checked my runner and it also has rusty screws on the charge port.. Left that one alone..

So I answered my own questions regarding the spark plug boots/connectors and the coil markings.

The spark plug boots on the BF100 CDI coil do unscrew. The coil tests perfectly at 7.6 K between the wires.(per clymer) Plug boots or connectors had no continuity on either as I suspected. The big clue was the lack of the rubber boot on the wires and the apparent corrosion that was visible. So some new connectors are on order. They have an acute angle to fit inside the cowling so have to get the part from honda.

The coil is also stamped on the back with big letters CDI so one can tell if its from the correct engine. Its on the motor side so you cannot see it without removal.