'84 200ES Big Red Fouling plugs

[RadRacer203]

Working on my new to me '84 200es and overall it seems to be mechanically sound. Runs, shifts, no metal in the oil, etc but I'm kinda stumped on this.

Has stock everything, carburetor gone through, and it runs alright most of the time but fouls plugs like you wouldn't believe. There's no smoke so I know the rings and valve seals are fine, and it's not running rich as far as I can tell but after about an hour of use it fouls the plug.

I know it's not an air leak or carburetor issue, I went through the carb completely and set it to factory settings, and I used a bit of rtv on the intake where it meets the motor. I also adjusted the valves. No matter what I try it always runs the exact same, kind of inconsistent on the idle, breaks up at the top end, and fouls plugs constantly. Any ideas? I don't know what else to try. Maybe it's a spark issue?

[ZacH_GrifF]

If you remove the airbox lid and it runs better its prolly rich. If it runs worse you might have a spark issue. Just something you can try

[RadRacer203]

It runs about the same with the airbox lid off, and also with the muffler off too. I did some investigation into the spark, I know the coil is good cause it came off a running machine, but everything else is an unknown. I did check the magnetic pickup behind that cover on the side of the head, and it appears to be rotated all the way clockwise in its adjustment and turning it counterclockwise it runs worse. I haven't checked the timing yet but i'm thinking that could be my issue?

[shortline10]

Low compression , improperly tuned carburetor or weak spark are usually the cause of fouling plugs .

[RadRacer203]

Low compression , improperly tuned carburetor or weak spark are usually the cause of fouling plugs .

I think we can rule out low compression, I nearly tore my shoulder out of its socket pulling it over lol. The carburetor I just cleaned and set to factory settings with factory jets, I think it may need a bigger jet cause it breaks up at the top end, but that could also be spark. Is there a walkthrough of how to test all the parts of the ignition system? The only ones I can rule out are the spark plug and coil so far

[MrConcdid]

You could still have low compression, if the timing is off, and it fires to early, that can rip your arm off.
I would start with setting the timing, then set the valves, then install a new plug.
run it, and read the plug, your carb could be rich, but I'm betting on no advance springs, valves to tight., carb out of adjustment.
This guy is a real ass, but he can fix a 3 wheeler.

https://www.youtube.com/watch?v=IiihbGQXUsw

https://www.youtube.com/watch?v=by3ySKWbw8k

good luck

[RadRacer203]

Got the service manual and did some more digging in the ignition system. I did find a problem with the magnetic pickup/pulse generator or whatever you want to call it. The manual says it should have 20 ohms +/- 10 resistance with the magnet in front of it, mine is 90 ohms. I don't know it's THE problem but it's certainly a problem

[350for350]

It's certainly a good place to start.

[RadRacer203]

Got the new pulse generator installed along with a new muffler and I know the timing isn't perfect, but it seems to rev great now and doesn't break up at the top end like it did before, but as soon as I try to start idling it down, it just cuts out and I have a hard time restarting it. CDI box?

[RadRacer203]

I'll be running it longer today to see if my plug fouling issue is gone, it certainly seems to run much better now aside from not wanting to idle

[RadRacer203]

So I've been doing more digging, it's definitely a spark issue, the spark is quite weak. I can rule out the plug, 90% sure the stator isn't the issue, and a brand new pulse generator made a weaker spark than original. I've been trying to get a cdi box to swap out for testing, but seems my cdi box has a different pinout that the 2 I've tried. The replacements look identical but when I plug them in I get no spark and the reverse light sticks on even with the reverse switch disconnected

[ATC King]

Try a new spark plug cap.

There's a resistor built into them that can go bad.

[kb0nly]

How is your timing? The pulse gen should be right at the top if the cam and crank are timed correctly, if you got it turned off to the left or right of center your timing is probably off a bit, could be the cam timing is off, i would check the crank/cam timing, its easy enough for the cam chain to get sloppy and skip if it wasn't maintained. From my experience the cam usually ends up being off clockwise when this happens because the resistance of turning the cam counterclockwise with a loose chain causes the chain to just skip a few links. Then someone comes along and tightens up the chain or replaces it and the tensioner and they don't get it timed right. Also check the springs on the advancer, the magnet that spins on the cam, there is two small springs on the centrifugal weights, they rust and fall apart quite often, or just get weak with age and the advancer won't spring back, this allows the magnet to rotate clockwise without much effort, the result is you have to clock the pulse coil clockwise to match it, this would also account for not wanting to idle because the timing is off with this condition as well.

As for the CDI modules... If you bought one of those knockoff aftermarket ones with the round connector that the original plug will fit you will either find that removing the gray wire which is the reverse wire will restore spark or it just won't work at all, i bought a few of them to test, they didn't work on either a 200ES or on my bench tester, they appeared to be wrong internally for the AC ignition system on these. But its worth pulling the gray wire from the plug, you can unpin the contact and pull it out of the connector if you don't want to cut it and then try it again. The other option is to get a cheaper square connector 5 pin CDI and replace the stock round plug for the square plug and make it compatible with more common CDI modules like you find on the other years. That's what i have always done to them. I documented that here on the forum and the dratv.com website has the wiring info and a cheap CDI that works as well.

My 200ES was fouling plugs as well, no matter how much tuning and carb tweaking i did, even replaced the exhaust.. In the end i put a new CDI module on after changing out the plug and it ran great from then on, the old CDI just wasn't producing a good enough spark for complete combustion. It would break up and stumble on acceleration, and it would pop and fart at full throttle. Replacing the CDI fixed that. But since your pulse coil is off from 12 o-clock i would look into timing and the advancer springs as well to rule that out.

[RadRacer203]

I'll try a new spark plug cap, just have to find one. I would use the one off the chinese coil I have but the part that clips onto the plug pulled out...

As for the cdi, unplugging the grey wire with the original box made no difference, and with the chinese box and with a used original box I got from ebay with the same connector, neither had spark with or without the grey wire. I'm wondering if they might be meant for a different model but with the same connector? Or Honda changed the pinout halfway through the production run? The keyswitch was awful on my XL70, they had like 4 or 5 variations all with the same connector but different pinouts between ct70 variations, sl70, and xl70

[kb0nly]

Did you rule out the kill switch and ignition switch? Easiest is to just pull the headlight and disconnect the kill wire from both switches and then see if you have spark, they go intermittent with age, the kill switches get rusty inside, the ignition switches get corroded from water going down in them as well.

If you are using a known good CDI and there is no spark then its time to start chasing other things, but you might be looking at a CDI swap with a newer style connector and getting away from the round connector. The gray reverse wire actually doesn't do a darn thing, on either the OEM or the aftermarket CDI's. I de-potted and reverse engineered the OEM CDI for these and found the gray wire wasn't even connected inside, the pin was soldered to the board but there was no trace from it. I think it was a change that Honda never fully implemented, the inhibitor relay takes care of the electric start safety, so i don't see how the gray wire ever influenced anything at the CDI, if it killed spark so it couldn't be started in reverse then it would also kill spark when it was already running and you put it into reverse, so this connection really never made sense to me and after looking at known OEM 200ES CDI modules and finding there was no connection to that wire internally the only result i could come up with is they intended to use it somehow but never did? As a matter of fact, look at the 200ES Honda service manual page 15-3, it doesn't even show or mention the gray reverse wire on the CDI.

The reason i say to remove that wire with the Chinese ones is they did make a connection to that pin inside, and its to the ground through a resistor, not sure what they were trying to accomplish, but its not correct, and sometimes just not connecting that pin they will work, but there is a mix of them on the market, i ordered four of them, and only one actually produced any spark on my bench tester. The other three did nothing. I suspect they are a DC powered CDI intended for another model, maybe a motorcycle or scooter and someone was like hey the connector is the same it must fit those too.... I haven't had one yet that worked on a 200ES, the one that i got that did create spark was after swapping wires around to find the right pinout combination to make it work while testing the pins with a multimeter and making educated guesses based on the readings.

I just don't even bother and swap the connector and move on. If you eliminate your kill switches by unplugging them and still no spark the start testing stuff with an ohm meter. The black/red wire from the exciter/stator coil to ground should be around 230 ohms, but anything above 200 usually works. The pulse coil should be around 20-30 ohms to work, i have seen aftermarket ones as high as 60-100 ohms, and they worked too, but check with your meter even if its a new one, unplug the blue and green wires and see what there is for a resistance across it. Ohm out the spark coil also, the primary side from the wire tab to frame ground should be 0.2-0.4 ohms, the secondary side from the spark plug cap to ground should be 3-5 kilo-ohms. I like to remove the plug wire from the coil and the plug cap cut off say a quarter inch of cable and then screw them back in to refresh the connection.

Now if those check out the next step is to check the exciter/stator voltage output, set your voltmeter for AC volts, put one lead on the black/red wire and the other to the engine or frame ground, pull it over with the recoil or spin it with the starter, you should see 10-30v depending on how fast its cranking, if your electric start is really healthy you might see even more.

If all these checks are good then its the CDI, that's where i put my money on it. I have replaced more CDI units then coils or stators. We are dealing with 40 year old capacitors inside them, so its no surprise they are starting to go leaky and fail and even if they do work their output is lower then it should be. I have put a high voltage probe on the ignition system points and checked voltages with an old CDI at the plug and a new CDI, and the output can nearly double with a new CDI installed.