Not-So Fat & Blue Spark

[Moki of Rancho]

Hi all, I have a DNS (Does Not Start) situation here- battery's all charged up and she's TRYING to start, but no result. Usually I just crank until the battery dies again. I went through the troubleshooting procedures in my Clymer manual, and it mentions the spark should be 'fat and blue'. I checked, and it looks like the plugs are all giving off a VERY weak spark (as viewed in a fairly dark garage). However, as a former welder I'm worried that my basis of comparison might be off.

Anyway, if my spark isn't where it needs to be, what parts should I start checking for replacement/repair? Thanks!

[bobthebiker88]

well, a strong spark should be a good bright blue spark, much like a welding arc, but condensed and much smaller.

if its yellow, or sporradic, you have a problem.

[duaneage]

Check the voltage on the orange leads of the coils, should be close to battery voltage. If not, clean the kill switch, connectors, everything in the path from the ign switch forward. Then check the bolts which ground the coils to the frame, clean and tighten if necessary.

[Nessism]

In my experience you don't need a "fat blue" spark, just spark. Particularly if judging in an area where there is lots of light.

Regarding the bike in question, how long has it been since it has been running and are you positive the carbs are clean?

[Moki of Rancho]

Regarding the bike in question, how long has it been since it has been running and are you positive the carbs are clean?

The bike hasn't run since 1995, as far as I can tell. The PO said it started the summer before I got it off him ('09) but I'm pretty sure he was full of it.

I cleaned the carbs myself, then took the bike in to my local mechanic and had him rip them apart and clean them again.

The bike has a new(er) wiring harness, everything plugged in correctly via wiring diagram. I'm not 100% sure about the ground wires, though, nor the condition of the plug cables.

I'll be buying yet another multimeter tomorrow night and checking over the things recommended by duaneage.

[Big T]

Some things to check

1. Voltage at coils as mentioned
2. Condensors - it does have points and condensors?
3. Plug caps

Get it 12V at coils, try to start it and see if there's sparking at the points (sparking at points is bad)

[Graham]

Some things to check

1. Voltage at coils as mentioned
2. Condensors - it does have points and condensors?
3. Plug caps

Get it 12V at coils, try to start it and see if there's sparking at the points (sparking at points is bad)

Since when?

Did anyone mention replacing the plug wires?

[Moki of Rancho]

Did anyone mention replacing the plug wires?

I'd be the happiest wannabe wrench monkey ever if that's all it was! I'm pretty sure the plug wires are original... meaning potentially in terrible condition. But that kind of applies to everything that I haven't already reconditioned or replaced.

[Datsa Noydb]

I am surprised that nobody has mentioned adjusting the valves.

It is on the list of many things to be done on BassCliff's site.

.

[Big T]

Since when?

Did anyone mention replacing the plug wires?

Always - spark at points lessens the signal to the coils

That's what the condensors are for

[Dogma]

I am surprised that nobody has mentioned adjusting the valves.

It is on the list of many things to be done on BassCliff's site.

.

Valve adjusting for sure. I'm with Nessism on the spark too. My 850 started easily and ran fine for years on a yellow spark.

Work the process... make sure what needs to be good is good. Valves adjusted, carbs dipped and idle mix set, some kinda spark.

[Moki of Rancho]

I forgot to mention my 850 is an '80... manual says it's too new for points/breakers. And yes, I had to check the manual because I pulled off the cover and was staring for several minutes going "Where the eff are my contact points?"

Anyway, I checked the ignition coils. Looks like one of them isn't getting any power to it at all, and the other is sitting around 9-10 volts (with the battery is at a good 12v). I guess this means I should check those wires all the way back to the 'ignitor unit' -wherever the heck that thing is, and try to figure out where the problem is. Any tips in this area?

Also, I got the valve cover off... definitely need some new shims (some clearances too tight), lucky me I found a guy who sells them in here in town!

[BassCliff]

Hi,

Yes, clean the entire wiring harness, every connection, every connector, fuse box, ground, light bulb sockets, everything from headlight bucket to tail light. You'll find tips for that in the electrical section of my little website.

If you still don't get 12v at the coils, the coil relay mod is quite popular. Guess where you'll find information about that?


Thank you for your indulgence,

BassCliff

[Moki of Rancho]

Bass, I just realized the 850 in your sig is what mine is supposed to look like when it's finally de-gunked. I spent most of this year trying to decide whether the Mokicycle was actually blue or green...

Anyway, I'll be taking apart the wiring harness fairly soon. It's in better shape than the original harness, but it's definitely not perfect, I tell you what.

[BassCliff]

Hi Moki,

My bike was repainted after my wreck. That is not the stock 1980 color for my bike. My bike used to look like this...



Now it looks like this...



Notice the differences?

Jessie is looking kind of grimy lately. I think I'll give her a bath tomorrow.


Thank you for your indulgence,

BassCliff