Weak Spark, Hard Starting

[shutchis]

I ride an '82 XJ1100 Maxim. It has dyna coils, soild core spark plug wires, new 5k ohm spark plug caps. and a new battery; turns the engine over pretty quick.

This MC will NOT start when it's cold (below 50 degrees F.) With a few words of encouragement, some starting fluid, and lots of cranking, It might start. I checked the fire on cylinders 1, 2, and 4 by using an old spark plug layng on the engine block, it was blue, but lacked the real snap I'm use to hearing. The spark was the same on all the cylinders.

When the weather is warm, it starts, I guess the fuel vaporizes better and ignites easier.

When it starts, it purrs.

Any ideas. Thanks

[LoserShoes]

The XS has a transistor ignition, not a CDI. The transistor just replaces the points. So no snap like a CDI. Sounds like it's time to clean the carbs out good, and check that the enriching ciruit works ok.

When you shoot in the starting fluid, it runs for bit and then quits, right? That a sign of not a rich enough mixture for starting cold.

Steve

[fxrer]

It might be your float bowl enricher jets are clogged - that was the problem on my SG. Do a "search", Ken Talbot posted some very clear pictures awhile back on the culprit jets. Clean them, and the problem disappears!

[randy]

Stan,

I have to agree with Steve and Rick. I've been working on these TCI units for quite a few years and haven't seen one yet that will give a hot blue spark like you might see in a car or on a CDI ignition. The XS spark is almost impossible to see in daylight, but it sure is enough to light the fires!

It probably wouldn't hurt, though, to clean the connectors in the ignition system as well as doing the carbs!

[shutchis]

hmmm, the carbs are clean; I've gone through them several times, including the enrichment circuit, but I could have missed something.

Here's something new; when I let go of the starter pushbutton, I can tell it wants to start. I wonder if the starter is dragging the voltage down...causing a weak spark?

When I spray in ether starting fluid, it may or may NOT start. It seems to be random. If I fires, it keeps running.

I would think the Dyna coils would produce a hotter fire, I know the stock Yamaha coils are marginal. Thanks for the response.(s) If you think of anything else, I value your comments. I guess I'll ride the Hoda CB900F Super Sport tomorrow.... I love those warm Houston winters!

[randy]

It probably wouldn't hurt, though, to clean the connectors in the ignition system as well

What he said.

[Ken Talbot]

Originally posted by shutchis
hmmm, the carbs are clean; I've gone through them several times, including the enrichment circuit, but I could have missed something.

Once again, here's a spot that often gets overlooked because it at the bottom of the float bowl, not in the body of the carb:

If this orifice is plugged, fuel won't get to the enricher circuit....

[fxrer]

Stan,

That’s the picture of the jet I referred to (Thanks again, Ken!). It’s easy to overlook, but it’s the first to get clogged if gasoline sat in the bowl for a long time.

When my bike had cold start problems, Ken pointed it out to me. I tried spraying carb cleaner through those jet passages. Two carbs were so-so, but nothing flowed through the other two. So, I carefully reamed those tiny little jets out with guitar string wire, then sprayed again, and ….. voila...… fluid spurted out. After re-install, the bike started from cold like new again.

But Randy, chip in here, does his bike have the ballast resistor in the starter circuit which might have failed? Just another thought.

[randy]

does his bike have the ballast resistor in the starter circuit which might have failed?

Rick,

If the ballast resistor is blown, it wouldn't run at all, yet he says it runs in warm weather.

Here's another thought - what about low compression? Have you adjusted your valves and cam chain latley (or ever)?

[LoserShoes]

Yep, that sounds electrical, how about taking out the plugs, put it in gear and rotate the engine past the firing point with the back wheel, and seeing what the spark looks like then? If it's better, then probably something in the starter circuit. The cold will make things worse by making the engine harder to turn over.

By the way, when its cold, is it damp also?

Steve

[shutchis]

Okay, I need a round TUIT.

I spent the whole weekend replacing a water pump in my 70HP Evinrude outboard motor; instead of working on my XJ1100. Priorities...My wife wants the boat off the driveway, something about Christmas and no place to park! Okay, that's done; now the MC.

I picked up a compression guage from my brother. I'll check this tonight, and then I'll use another battery to turn the starter motor. I hope it starts.

Here are some questions for Randy and others ...

Is it possible the timing has "slipped (i.e. advanced)"?

You work on TCI's; I know that the XJ has an electrical advance. Do you have any circuit schematics, electrical diagrams, or engineering data on the TCI?

What function does the vacuum switch perform? (The one located under the gas tank) Does this have something to do with advancing the timing under load?

When should the switch contacts be open or close, i.e. with the engine off, during the starting (cranking) process, and running?

I know this is a lot of questions; but I'm sure I have a timing/ignition problem. Thanks again for everyone's comments.

P.S. The water pump needed replacing; Age broke one impeller blade and plugged the water port causing the engine to run "hot". I love springtime...motorcycles, golf, and fishing! Merry Christmas to all.

[BLUEJEEPLAB]

My two cents worth, since you mentioned that it wants to fire momentarily when you back off the starter button and it's a clod weather problem. When I was having trouble with the Beast (my Ford F250), i ended replacing the carb for a similar problem (didn't want to start at all unless choked down real hard, then didn't run worth a crap). After the carb replacement, it would do exactly what your described, as I let off the switch it would catch, but didn't have enough spin to keep running yet. I bought a new battery and he fired right up. (Sad story ending - Turns out I didn't need to replace the carb, same problem occured a few weeks later and turned out the Huge vacuum hose that runs to the Charcoal Cannister was cracked at the cannister, I just jiggled it right when I initially put the carb back on)

Anyhow, I digress, if you can, put a booster charger on it when it is cold and see if the additional juice helps. Don't put it on boost for more than 10 or twenty seconds though.

[TopCatGr58]

Hey there Shutchis,

When you say timing, do you mean electrical vs. mechanical like valve? Hope not the latter! You can take a timing light and remove the left side cover and check to see when the #1 cylinder is firing! The timing plate is fixed, and ALL timing variations are controlled by the TCI. The centrifugal curve is built into the chips on the TCI, the vacuum is controlled by signals from that little black box under the tank, but are sent to the TCI for adjustment! I think that vacuum sensor is a potentiometer type device, not just ON and OFF, but sends a variable amount of power/signal depending on how much vacuum pressure is sensed!? A simple test would be to just unplug the vacuum hose to it if you think you're getting false signals to see if that helps in starting!?

Are you sure you have the right/correct DYNA Coils, they made both 1.5ohm and 3.0 ohm varieties!? You can check the model # on the coil for this! On the older XS's, the TCI would bypass the ballast resistor circuit to send full 12volts to the coils for stronger starting , and then to the resistor circuit once it started, but the XJ and later XS's don't have this problem, so you should be getting full 12 volts to the primaries. Have you checked to see how much voltage you're measuring at the primaries?

Okay, just reviewed the XJ wiring diagram, the starter relay ONLY controls power to the starter, there is a separate parallel tap from the (+) battery going to the MAIN fuse and the rest of the circuits. There are 5 points/switches that can interfere with starting: the sidestand switch...oh, there's a sidestand RELAY as well, the clutch, the handlebar ON/Off, the Emergency/tipover switch, and the Tranny Neutral switch, and they all seemed to be wired into the "Starting circuit cutoff relay switch!

I'll let an XJ or electrical GURU comment further on testing these! Did you ever try to test your TCI per Randy's web page tips!?
T.C.

[JWSanders]

I've ran my battery down several times in the process of getting my bike running. I would experience the same thing when letting off the starter button when the battery would start getting weak....a quick gurgle then no more. Like it wanted to run.

Charging the battery would make all well again.

Never hurts to have a fully charged battery when troubleshooting, I imagine. One less problem you know you have. Or don't have, as it were

[prometheus578]

"Oh Geez, here comes 'know it all' again."

I would experience the same thing when letting off the starter button when the battery would start getting weak....a quick gurgle then no more. Like it wanted to run.

"Interesting question." I say to myself, as no one else is around, "I shall ponder this."
Engine idles nicely around 1100 RPMs. Start going lower and she starts to falter. Probably dies at around 700 or 800 RPM. (guessing) "Why is this?", I ask. Hhhmmmmm...
Piston moves downward creating a vacuum that is filled by air moving through the carb, which in turn siphons up fuel, mixes with the air and fills the cylinder. (Actually, the movement of the piston creates a low pressure area which the outside atmosphere flows in to fill, but let's not split hairs here) We commonly call this vacuum.
Anyway... it takes a certain amount of "suction" force to draw fuel up from the carb bowl. This is determined by the speed at which the air flows through the carb body. This speed is determined by how quickly the piston moves downward, creating the low pressure zone. At a good idle speed, the piston speed is sufficient to produce a decent vacuum and a good fuel mixture. Lower the idle speed and you've reduced the vacuum, resulting in a weak fuel mixture, and the engine starts to stumble.
"Yes, you magnificent blowhard, but what does this all mean?"
To start the bike, the starter must turn at a sufficient speed to make the pistons draw enough vacuum to get a viable fuel mixture. If the battery is low, the pistons are slow, the bike no go.
The "Gurgle": With the slow starter, the engine is technically running, (getting a little fuel and spark), but it's the starter thats keeping momentum. When you release the starter button and get that "I wanna start" gurgle, it's just the last cylinder doing it's dying firing.
I may not have answered this thread's main question, but the time taken to cook up this theory was time enough to cook up my frozen pizza.
"We dine in style tonight", he says to no one in particular.