Honda B100 CDI connection question

Working on an older 70's/80's Honda B100 short shaft that was a basket case I found on marketplace, (I love a challenge lol) This one appears to have been converted to the later CDI ignition, with the CDI box, exciter and pickup coil on a points engine of sorts, the Model is a B100-10021x , The CDI box was missing so I ordered one for a later serial number that seems to match up on the color wires, with 2 exceptions. The exciter and the coil are both new, and check out fine with my multi-meter for ohm checks. I don't have the tool to measure the pulse/exciter coil signals though.

There is no neutral safety switch on this motor, so wondering if I need to short the blue and black/white wires together? Also the pickup coil has a SAE style male/female plug, and the replacement CDI has 2 male bullets, green and white, the pickup wires are brown/black, so I have a pigtail to change the polarity and see if this one will do the job, has the same resistance range (120ohms going from memory) as what the later serial number - apparently they must have changed the style connectors, or this one is the wrong year, I believe the CDI is for a 1997 BF100, as this was the only option from Honda that I found on boats.net that matched the other components that came with the motor in a box. Sort of a 'rubiix cube' of boat ignition when I got it.

Will I short anything out if I short the blue/black wires for the neutral safety circuit?

Thanks, I have found many helpful posts on here, really hoping to get this one on the water soon. Seems like a solid setup, just need to sort out the wiring one of these days!

Update: I decided to just connect the neutral safety sw wires, and it fired right up. Feel like an idiot now for asking ha! So now I have spark taken care of, I have moved onto the carb. It acts as if there is no low speed circuit in the carb. If I spray a little carb spray in the intake it fires up and runs, as long as I am giving it some throttle input, won't idle and dies. When I go to restart won't fire off, have to spray a shot in the carb and same routine, no idle. Just throttle above 'part throttle' where the motor is racing. So I pulled the carb a couple times, replaced the body gasket and pilot screw O-ring, tried the pilot screw at 2 turns out, 1 turn, and blew out the tiny orfices in the carb wall just where the throttle shuts.

This carb is getting the best of me, geez, I thought the ignition was the only thing wrong with it too lol I think I will pull the carb off one more time (4th time?) and check the float level, book calls for .400" from the gasket surface. Not sure what else to clean on it, all passages seem to flow liquid, pulled the small screw and blew everything out, from the main jet to the low speed holes. Scratching my head on this, don't want to spring for a new carb if I can avoid it. Will update when I get the carb sorted, otherwise she should be a great little motor. So Close!! Could be something stupid like a vacuum leak I guess. I decided to warm it up a few minutes just before taking a break and checked the compression, got 140 on both cylinders, so I gather I put the timing belt on correct.

Hi,
Are you sure the fuel pump is working properly? I mean, is it filling the float chamber as it should?

Carbs that have been sitting can have problems with the float chamber air vents being plugged up by dirt or bug/spider activity. There are two vents on the top of the main body. Check them when you have the float bowl removed.

I agree with you about checking the float setting and movement.

Remove the main jet and emulsion tube and make sure that the holes in the tube are all clear and that the tube isn't cracked.

There are air jets that can get clogged just like the vents. Look for the drilled passages at the top edge of the carb throat on the choke plate end. Hose those passages out real well while you have the float bowl off and the slow jet plug and emulsion tube removed. That way, if you do dislodge anything in there it can find it's way out and not make a clog in another spot.

It's a good idea to flush and backflush these passages where you see the cleaner escaping to get a thorough cleaning. I always backflush the idle, transition and high speed orifices too. Those are the tiny holes located at the top of the carb throat at the throttle plate end.

These BC carbs are as simple as it gets and shouldn't give you any trouble if you just perform these steps to get one clean.

Hope this helps and good luck.

jgmo said:

Hi,
Are you sure the fuel pump is working properly? I mean, is it filling the float chamber as it should?

Click to expand...

Thanks jgmo!

Far as I can tell, when I gave it a couple pulls with the fuel line disconnected, it was shooting fuel out in small spurts, and the bowl never seemed to run dry while it was running, since that was my first suspect. The fuel feed fitting that plugs onto the motor was leaking bad, so I ended up stacking two O-rings to get it to seal while priming with the bulb. So I know I am getting fuel to the carb fine, just not flowing into engine to my liking at idle.

I did notice 2 vents for the float bowl, both blew air through ok. The carb was surprisingly clean for how old it is.

Going to go back over the carb again following your advice, I did not pull the emulsion tube out, just the main jet. It's as if there is a feed channel from the main circuit that may feed the low-speed idle circuit that has a clog. I was able to pull the screw plug and pilot screw and shoot carb cleaner through the idle/transition holes. Did not find a pilot jet or see how the idle circuit is fed with fuel. Since there was a tiny amount of ethanol jelly looking crap in the bottom of the bowl I suspect a clogged circuit somewhere. Same symptoms as when one of the bikes sits too long with ethanol mixed fuel in it. I could let the carb soak in chem-dip I use for most carbs, but was afraid that would wash off the corrosion protection coating as well. So I am just using carb spray.

My other suspect is the intake gaskets, I pulled the intake off to check the thermostat (new one is on order) since I noticed it was running hot (no water from the pee hole either, so once I sort out the carb issues I will pull the L/U and replace the impeller) and the intake gaskets are pretty dicey, crusty and brittle so it's possible I am fighting a vacuum leak which could cause the same symptoms perhaps. Just no idle fuel flow. Will give it one more cleaning, and button up the intake with new gaskets, carb gasket and a new thermostat.

Thanks for the carb tips!! Much appreciated.

Update #2:


So I took the carb apart one more time. Had to do a bit of reverse engineering to figure out the low speed circuit was clogged. Tried to document what was causing it to run so bad, this orifice appeared to be a brass plug is was blocked so well, so I took my smallest number drill (a .024") and ran it down to see if I could at least get it to poke through whatever was blocking it, must have been some really old gook from ethanol. Once I drilled it I could get light to pass down to the main well, and air would finally move from the jet to the idle orifices. I was worried for a bit I was drilling into a plug that needed to be there it was so clogged. After this and checking the float was at .390" I slapped it back on one more time and it fires up first pull! Idles like a champ, so this had to be the culprit for my no idle. Almost ready for the water! Waiting on a couple parts, and the lower unit will come off for that stuff.

Thanks for the help jgmo!!

Should add, I don't know what size that brass orifice in the idle well/low-speed jet is supposed to be or if it will cause a part throttle stumble just leaving it at .025, my hope is any other crud in the hole will just loosen and have enough fuel flow for when it is under load. Just running it on a bucket stand it idles and revs fine though. It's actually a great runner, just can't run it too long till I get the water flow situation addressed next. She is almost there!

Well, I can't tell from the photos but it sounds like you have (had?) an obstruction in the slow jet. If that orifice you drilled was under the "cap", then that's it.

But it should unscrew from the carb body so that you can thoroughly clean it. It should have a slot for a screwdriver but if someone has been in there afore ya, they may have broken the "ears" off. Carelessness ruins many of these "never were available" parts. It's just the way it is with this old stuff.

It sounds like mission accomplished though since she runs and you seem happy.

Good luck with the pump and dialing her in for HAVING FUN!

jgmo said:

But it should unscrew from the carb body so that you can thoroughly clean it.

Click to expand...

I tried my best to remove it, but it seems pressed into the body of the carb. Just wasn't getting any airflow from the main well (where the emulsion tube sits) up to the idle circuit/well under the screw cap. I figured fuel HAD to flow through there as there was no other path for fuel to make it up from the bowl to the idle circuit. Fortunately my guess must have been correct lol

Here is a photo showing the fuel feed path from the main well to the low speed jet that then feeds the transition/idle orifices near the throttle plate. It is running like a top, so I will leave it be, very happy with how easy it is to start now.



I pulled the lower unit last night, and realized it has a cracked impeller housing and I ordered the wrong impeller, but the gaskets are correct. Now just waiting on the thermostat, new impeller and a new impeller housing then I can button it all back up and head for the lake.

Thanks again for all the info. Been reading lots of posts and it has been a HUGE help with this project.