hi guys. I love Evo's, simple and reliable, I had a 1994 FXDL that went on for ever with no problems! I have just bought (2 months ago) a 1992 FXDC with around 50,000 miles on it from England (I live in Spain). The bike has not been well looked after but she did run. She has drag pipes, dual fire, S&S Super E and everything else pretty standard. The previous owner has done some electrical DIY and some wires were all over the place but most are sorted now (by me).

I was driving back from a mechanic who had tidied up the head lamp wires and fixed a leak in the primary (due to an old lay down i think). He couldnt fix a problem with the left hand blinker but in the end I fixed it as it was a simple short from having connected two black wires in the front part of the harness - not sure where they led to but once I disconnected them the blinker worked. Anyway...Im heading back from this mechanic and she starts to misfire badly, the sound she's making is like a very short, harsh "blap, blap", almost like a baffle has fallen out. Worried Im on one cylinder but no Im on two but sounds like *****.

I get home, read up (trying to learn and misdiagnosing is very painful and time consuming!) and check the plugs, they are sparking, I decide it might be Ignition coil - I do the ohms test (but as it turns out later I misdiagnosed this) and think its broken so i order a new ignition coil. 2 weeks later it arrives (in spain everything takes time) and in the meantime I have gone over all the wires and fixed the blinker and rear brake light (I still have the oil light stays on but I think thats just a new oil gauge). She's all prepped up and i install the new coil, take her out and at first, the first 2 miles she's ok but then its back, blap blap, misfiring etc. She doesnt splutter particularly and I can get up to some speed but she sounds terrible, very short sharp sounding exhaust and it seems to be the front exhaust is much hotter than the back - I think the back cylinder might be ok but the front is making the blap blap sound and quite speeded up.

My diagnosis was obviously wrong and now i have a spare coil. OK, my next choice is
1. Take it to a proper mechanic and get it sorted, hopefully quickly, so i can relax about the engine and review other mods.
2. In the next day or so Im going to check the plug leads but I think these are ok.
3. Could it be a fuel problem? blockage or dirty carb? the spark plugs are pretty white hot so pretty sure its running lean.
4. Could it be the VOES...which i'm just finding out about! but might try and test, any input would be appreciated.
5. Could it be the Ignition Module? Haven't tested this, is this easy to test and how please.
6. I haven't done the air leak test by the intakes yet...probably worth a shot.
7. Any other thoughts from your guys also appreciated.

It certainly sounds like a misfiring problem, she does work but just sounds like poop.

I do have the Clymers manual which has been helpful so far with other small problems but this is getting into quite heavy mechanic area for me I think.

Finally....Opinions on whether can I ride her to a garage that is 45 minutes away or is it best not to ride her at all until I solve this...I'm terrified of reading about "detonation" and blown pistons! The problems of self diagnosing over the internet!!!!

Thanks for helping me re-ignite my faith in simple, tough Evo's! Monchidog

 

Testing the ignition module.

1. Take off the cover
2. Get a heat gun or hair dryer
3. Start the bike and using the heat gun or hair dryer on the ignition module see if the problem occurs again.
If the ignition module starts bubbling replace it.
If you can see where it has melted before (a goo leaks out of it) then replace it.

 

How are the plug wires? Are they the originals? Is it happening right off idle or only at higher throttle openings? Definatly pull the nose cone cover(rivets are original, screws mean it's been opened previously). I would also check voltage at the coil to make sure you're getting the same voltage the batt is showing. And be sure to get a good voltmeter. Yes I call them voltmeters, old habit.

 

Thanks Texashillcountry, gotta say I had to check where you were going with that but it makes perfect sense, she starts fine but when she heats up it she starts misfiring. I will have a go at the weekend as shes loud and the neighbours get pissy.

Yamaharley, the plug wires seem ok, tested them this evening and seem ok but cant find the ohms reading for the plug cables in my handbook so not 100% sure. She starts just fine and runs fine for a couple of miles and then she starts to "blap", she works ok but sounds like she's going to explode. I checked the ignition coil is that what you mean? Checked it for ohms but not when connected but hey I just put a new one on so shouldnt be the problem right?. I am still learning my way around a multimeter but a little knowledge is a dangerous thing!
Thanks guys.

 

Glad you figured it out as I meant cam sensor plate when I typed ignition module.

Sorry about that!!!

 

Check the VOES. Had a similar problem with the sporty. Tracked it down the the VOES vacuum line. The bike came with a hypercharger installed and the diaphragm on the hypercharger was not seated correctly.

 

Agree with all above posts for places to check...oh and being a fellow 92 FXDC owner I need pics!

 

 

I just went through a long, drawn-out 'mis-fire' episode, chasing my tail for some time. I read a lot of stuff on the matter, and got a lot of good advice here.

It sounds as if the problem occurs when the engine heats up. It's not the only cause, but as texashillcountry says this is a classic symptom of the ignition sensor (located behind the circular cover in the middle of the cam cover on the right side of the engine) having gone 'bad'. Works fine when cool. Causes a mis-fire when warmed up.

I concur with the advice to inspect this sensor, and if the 'goo' enclosing it has 'run', or bubbled up, replace it. (If it were me, on a bike this old, I'd replace it for good measure, anyway. Just to be done with the potential for problems. Eventually, from my reading it seems these will all fail. Just a matter of time).


Alan

 

Well guys, it seems like Texashillcountry gets the prize, a virtual beer coming over! First shot right on the (cone) nose! here's a photo, a little shaky but clearly a melt down. Damn I wish i'd asked this question before getting the new ignition coil!! Nothing beats experience and that comes at a cost! Thanks to all of you for your comments and I will be checking out the VOES as her rubber tubes are pretty worn anyway.
OK, so now my question is, is this an easy fix (looks like it) like a simple unscrew and replace (with some wiring connections) or does it need "mapping" or setting up? I think I'm going to go for a simple dual fire replacement and later on review whether to go for a single fire set up. The cost here is around €60/$65 from Zodiac or Custom Chrome...anyone got a specific brand which is good please let me know.
Apples402 and Wildbill, some fine looking 92 FXDC's....not sure how many were made but they aren't common! Can you help with choosing a seat as I can only find 4 options, the original (dont like it), Mustang have 1 option, Corbin have 1 option and LePera have Bare bone and silhouette...which is probably my first choice. Not a lot out there and if you look at my photos you'll see she came with a wrong fitting seat, huge gap above the fender! She's a bit of a mess (cables, wires and over 25 skulls!) but its only the beginning!

Final question to Apples402 and Wildbill...anything else I should be aware of that might need replacing?

Thanks again folks!