Sputtering, please tell me how to diagnose

[MattA]

I have been having problems with the bike "coughing."  Every once and a while it will lose power in one cylander, so it drives with no power.  I thought it was my carb, so i took it apart and fixed a broken part, but it has gone back to doing this.  I will soon take apart my carb so see whether my fix held, i do not see why not.  If it is ok, what kinds of things should I check for, in order of what I should do?  I have run some B12 through it too, but no change has been seen really.  Please comment.

---Matt

[sdinino]

You didn't say if your carb fix solved the problem for an extended period of time, so I'd start checking for an electrical problem. Look at the plugs - is one fouled worse than the other? Might be a coil, or a TCI problem.

I'd tend to think it's not mechanical if its intermittent.

[QBS]

One cylinder cutting out is often caused by corroded spark coil connections. They're under the steering head brace area.  Clean them to bright and shiney and add a thin film of non metalic grease to keep new corrosion away for a long time.  Cheers.

[Lucky]

I tend to agree, it sounds like ignition.
 i'd start by first determining which cyl it is, if poss, then swaping coils, wires and yes plugs (if the porcilin cracks way down in the plug it can look ok but still short to ground.) to see if the problem stays with the same cyl.

also you may have moisture in the TCI, try soaking it in WD-40 with the back cover off, but don't try to take it out of the case, you'll break it.

--Lucky

[MattA]

Good news, and bad news.  The good news is I checked the fix I did to the carberator and it is still in good condition, working just fine.  Even the epoxy is still on, which means it indead is gas resistant.  

The bad news is I took off the spark plugs (which I will say is quite a task... very fruistrating trying to get into the front one).  Anyway, when I took them off, they don't look too bad.  They are definately not silver and shiny, but no corrosion.  The front one was dark reddish, and the back one was just brownish.

I am pretty sure it was the front cyllander that has gone out.  When it dies, the tach drops completely, showing 0 rpm's and i hear the one cyllander firing fine.  The reason I still think it's some kind of fuel problem is it usually happens at around 4000-5000 rpm's.  When it happened the other night, i shifted from 5th to 4th, which was a higher rpm, and it did not die out anymore.

Any suggestion on what to do would again be appreciated.  If I should soak the TCI unit in WD-40, I can do this, but how do I soak it while it's still on the bike?  Thanks.

---Matt

[Lucky]

Take it out of the bike, it's easy.
there are several things to check at this point,

Plug Wire bad: swap to test

bad Rev Limiter:  cut Yellow/Black wire at TCI 6-prong plug
(this is very common)

Front Pickup bad: swap with a good one to test (hard to do)

Front coil bad:  swap to test

TCI bad-> swap to test

--Lucky

[MattA]

Tommorow I will be doing a couple of the things suggested.  I plan to cut the Yellow/Black rev limiter wire and see if this fixes my problem.  It would make sense if this was the problem, as it usually doesn't lose power in the front cylander until I have been riding for a few minutes.  After doing this, if the problem does not go away, I will switch the plug wire.  I do not think this is the problem because it always messes up after I have been riding for a few minutes, its never done it right after I started up.  I would think if it's a bad wire, it would be completely random.  This seems more "patterned randomness" if you can say that...  If this still doesnt change it, I wil lremove my TCI and soak it to remove any moisture.  

Hopefully one of these things will fix my problem.  I really want to take a good trip on my bike, but obviously can't if it's unreliable.  I guess if none of these work, I'll need some more detailed help on checking the coil and pick ups.  Thanks, I will post an update tommorow afternoon.

---Matt

[MattA]

Its me with an update.  I cut the wire on the TCI and taped it up, ran my bike for about 5 minutes (driving it), and it acted up again.  I took the TCI unit off and soaked it in WD-40, but do not think this will do anything either (I havnt yet put it back on the bike) cause there was no water in it and no signs of water either.

I still am not convinced this is an electrical problem.  It always does it after riding for a short period of time, typically happens about at 4000 RPM's, and if I run it higher/faster, it doesnt typically sputter.  I can be sure that it is the front cylander, because when it sputters, I lose half my power and the tach goes to zero, correct?  

I dont know if it just needs a good cleaning (the carb), or what.  I have filled it with premium fuel and mixed that with the B-12 stuff, but still havnt found any difference.  Sometimes it seems the B-12 changes it some, but that is probably my imagination.  

Anyway, its frustrating having this messed up, as I would like to ride it, and I don't have tons of extra time to fix stuff, but wouldn't mind fixing stuff if it actually improved the bike.  Once again I ask for things to check, or how to check and see that the jet is not clogged.  What is hard is it is not a consistant problem, so when I check the bike, the carb may not appear clogged, but actually might be.

Anyway, suggestions, please.

---Matt

[Jim]

HAd similar problem on my vision, it was the spark plug cap, kept coming off after a few miles, ordered new ones, the rubber that helps hold them where in poor repair, imagine that on a twenty year old bike, with my vision it has been the little things that are big, dirty carbs, seal on starter and now spark plug caps.  Good luck

[MattA]

I soaked the TCI in WD-40 and then let it sit for a few days to dry out, then made sure it was completely dry with a blow dryer.  I put it back on the bike, and rode for over 30 minutes with it riding rine, no problem at all.  The difference was I was riding at 60+ MPH, and other times it messed up when I was going 40 MPH, so lower RPM's.  I will ride it again and see what it does after riding for a while at low speed/rpm's.  If it does still mess up, what could be causing it to mess up only when running it at lower RPM's?  Thanks.

---Matt

[Lucky]

if the ign checks out then check the spray pattern on the acc pump nozzles, make sure it's not hitting the throttle plate or side of the carb.

if their ok, might be time for a dip.

--Lucky