Misfiring AGAIN!!!! maybe it's a sign for me to get a car...

1981 XJ750 Seca

Just hit 50000km!

Two weeks ago I was having a hard time starting, and it eventually wouldn't run at all. I finally diagnosed it as an ignition coil and fixed the problem only to find out there is a second problem.

http://xjbikes.com/Forums/viewtopic/t=40968.html

At that point, I was having a steady misfire in cylinder 2 at idle to 1/4 throttle, then again at WOT.
I pulled the carbs and found out my main jet and pilot jet were mixed up during my carb cleaning.

http://xjbikes.com/Forums/viewtopic/t=41167.html



I've put on 200km on my bike since it's been fixed and it ran perfectly.
Until tonight when i was on my way home. It was raining, and I got on the highway after about 10 minutes. Another 10 minutes onto the highway, it started misfiring.

Now I have no clue if the rain is just a coincidence or if it's causing a short somewhere.

This time the misfire is sporadic. for a second it can be misfiring even at 10% throttle all the way to WOT from 3000rpm to 6000rpm. Then next thing you know I got power through the entire throttle and rpm range. And it'd sometimes just misfire a shot here and there. And sometimes it'd hunt a bit on idle.
I'm pretty sure I'm running on at least 3 cylinders, but I'm not sure if it is misfiring in only one cylinder.


I have a feeling this is going to be a big pain in the ass......

I don't think anyone here could blame me for sending my bike to the junk yard at this point...... I've had nothing but hell for the past month.

I've cleaned the carbs, replaced and gapped the plugs, checked and corrected valve shims, done compression test, vacuum sync'd.


Once again, thankyou to all those reading this and trying to chime in.

 

My money is on the rain and misfiring being more than coincidence. You had a coil that failed and even though it isn't fun to think about usually the other one isn't far behind. It's highly likely that you have microfractures in your coils body and it's letting in H2O-that will cause all kinds of havoc and misfiring. The symptoms are a dead giveaway, the heat from the engine evaporates some of the water that got in there and it comes back to life then more water and there you go again-of course I could be wrong but I'm betting that's the deal.

If that is the issue you could replace the coil, but you can also fix it by coating the whole outside body with rubberized undercoating, or not ride in the rain. So it's not as much a PIA as you might be thinking.

No offense but after all the work you've done, and the things you've learned, the success you've had-I would be surprised to hear you ditched the bike. Truthfully what you've been dealing with is pretty typical for a 32 year old moto, but the + side is each time you solve a problem (when it's done right) it isn't likely to come back anytime soon.

Don't give up yet.

 

Will seal up the coil bodies and shrink wrap the wires just to be extra cautious.... My guess is if this IS the problem then it's my newer coil as I did not have this problem before....

And as you and my friends pointed out, dealing with problems is pretty typical for a 32 year old bike......
I do agree with that point, but I had NEVER THOUGHT i'd have to spend 3 weeks working on it almost every night to keep it running.....

I was just telling my girlfriend (who paid for half of the bike as a gift) that I absolutely LOVE this bike and how I wish I had the patience, time, and money to redo the ENTIRE electrical system, customize a fuel injection system, rebuild the motor and transmission, replace almost every moving part, and custom build a turbo kit. That is how much i love this bike. I just wish I can make it run perfect and reliable for years and years to come, as well as rediculously powerful and fun.

But the truth is I'm SO FED UP WITH ALL THESE PROBLEMS and knowing that I'm just going to stumbling into problem after problem...... makes me want to fix it up and sell it before another problem comes up so I could recuperate some costs and perhaps look into a newer bike....

I do also agree that once I fix something, it should be good for the next little while.... But the problem with old bikes is that anything can break, even things that are not supposed to.... And my BIGGEST WORRY of all time is that one of dozens of wire is just aged to the point where the insulation cracks and shorting out when it's humid out...... I would NEVER be able to solve that mystery.......

 

Ahh, but they're not "problems" they're merely symptoms...

You need to read this: http://xjbikes.com/Forums/viewtopic/t=24010.html

An XJ can be very reliable, but you have to bring it back to that point.

 

I'd still lean towards the rain causing wet coils.

Now, if you KNOW the coils are NOT cracked at all (look at the bottom between the humpes where the wiires come out), then I'd open the headlight bucket and take a close look in there.....any wires gettin bare, crossed, or shorting against the bucket, or headlight? That's common............

Dave F

 

Is one header cooler than the other? Could the garden hose be used to simulate rain to test the water theory?

 

arg..... makes me wanna shoot myself in the head

I'm going to check my coil thoroughly tonite and seal it up if possible.
Then check my headlight bucket. But last time I was in there, things looked fine


And I ran it for about 20 seconds and all the headers seem approximately the same temperature (spraying water test)

 

RD, don't let yourself get that way. We've all been there, and it won't help. You WILL eventually get if straightened out. We've all (well, most of us) have gotten through it, too. LOL

Dave

 

I felt so relieved and happy a few days ago when my bike was finally running right.....
but then it's just throwing another problem at me.....
i'm sick of it running like crap every other day

 

I had some misfiring in HARD rain before. The spray bottle trick might work for bad cracks, but doesn't do anything on my bike's coils. It's hard to stimulate a really good downpour. Have you tried coating the whole coil in RTV black? I wouldn't bother "looking" for cracks, just coat the whole thing, if there are minute cracks, that should seal them.

 

The more effort you put into it BEFOREHAND, the more reliable it will be. Your only "problem" is trying to hurry the process and skipping over things as a result.

It really IS about frame of mind as much as anything else.

You'll get there.

 

Re: Misfiring AGAIN!!!! maybe it's a sign for me to get a ca

My XJ had the same symptoms as you describe.
I put a set of new aftermarket coils in it and never had any trouble since.

Maz

 

K my friend also agree on the coil theory.

I did clean out my carb bowls again and saw some crap in there. Went to buy an inline filter. Dude at the shop said it's the rust from the tank. I may or maynot end up doing something about that. It looks real clean from the filler, so my guess is it's not too rusted and it will sort itself out over time especially now that theres an inline filter.


I had to ride 45 minutes to work and 45 minutes back today. Misty and foggy in the morning, and misty/showers at night. Not a single misfire.

I still decided to go NUTS on my coils and wires with a spray bottle and what do you know......... it starts misfiring...................

I feel like going back to the junk yard and getting him to replace it assuming he has a second one laying around (1&4 has long leads so it HAS to come from a 1&4)

Or just call it a day and insulate it with one thing or another.

I'm going to try and see if any local stores carry "plastic dip". I think it'd do a nice clean job of sealing everything i want without any open edges or anything. I don't think RTV Sealant would hang on there very well.....
My second option from plastic dip or plastidip would be undercoat.

My buddy also mentioned giant shrink wrap tubing. Might consider that ON TOP of plastic dip or undercoat just to help keep things on there.

When i fix something, I like to go the extra mile to make sure I won't have to fix it again.

 

Re: Misfiring AGAIN!!!! maybe it's a sign for me to get a ca

rd,

You ride in the rain a lot. Replace the coil.

Gary

 

" back to the junk yard and getting him to replace it assuming he has a second one laying around "

junk yard parts are not new parts. thats a corner that doesn't need to be cut.

 

ARG...... Junk yard part is $40. Replacement part is $250 plus 2 weeks to ship in..... if I can insulate a cracked coil and make it work, I could really use an extra $200 right now....

 

Last time I bought new Dyna coils was from Z1 entreprises. Very good service, and good prices. I just checked on their website, the Dc-1 3.0 ohm dual output coils are 130$ a pair, 67$ for one.

 

I'm pretty sure that if I go with dyna coils then I should replace both of them.
I checked on ebay. Still going to end up around $200.
I will look into automotive coil packs.... see if I run into some luck

But what's wrong with an old coil if it's resealed and working great?

 

I think nothing's wrong with a good old coil properly sealed. Make sure it is bone dry before you seal it, though.

I also remember some XJ-X bikes put a homemade black plastic deflector in front of their coils to stop most of the rain and the water splashed by the front wheel.

 

if you can find car coils listed by primary resistance, please share

 

go to junk yard with a DVOM was my plan....

 

seal them. then if they still fail you can still get new ones down the track

 

They work great in the dry. Only makes sense that sealing them would work.
Will do that tonite/tomorrow

 

If you coat them in epoxy you'll have coils that are as waterproof as they were when new.

 

Have you checked with chacal yet? For OE replacements, Dynas, or good pre-owned?

Yes, if you "seal" coils that are fine unless wet, they should be OK. I'd rather find an original coil that is fine, though (that's what I'd do, personally.) Or start trolling for NOS.

Are you absolutely 100% sure it's the coil itself, and not associated wiring/connections reacting to moisture?

 

pulled the coils out again. Looked closely..... if only I knew what to look for.
Yup I've got a crack.
JB Weld and rubberized undercoat!

 

Hair dryer first or.......?

 

oh yea, rinsed it down with some rubbing alcohol, also helped clean it up so the epoxy and stuff would stick better

Then blew dry with a hair dryer.