Author Topic: Electrical Problems that defy all logic! (Read 1859 times)

chadbenson · « **on:** March 29, 2010, 05:40:01 pm »

So I finally got my '76 550 to fire up after a carb rebuild and all the typical tune up items. Having got that done I went to work on the clutch and got it all worked out (hopefully) But after buttoning everything back up it won't fire anymore!

So I went to trouble shooting.......

1st: I checked the kill switch was in the "run" position and that the battery was charged and the ignition was on. CHECK!

2nd: I pulled spark plug number 4 to check for spark. First few kicks it showed a spark so I moved on to number 1. No spark on number 1, so I went to plug number 3 and it was sparking ok. On to number 2 and no spark there......totally doesn't make sense.

3rd: Went back to plug number 4 and now it wasn't sparking anymore. So I plugged it back in and then opened up the points cover. I took a screwdriver and stuck it to the points to see if they were getting spark. Point 1-4 was showing a decent spark and point 2-3 was showing an ok spark. Though it was inconsistent with each time i would try to arc them. Sometimes the 1-4 would spark great and smoothly with me opening and closing it. Then sometimes it wouldn't, same with points 2-3.

4th: I took out spark plug number 4 and laid it against the motor and kicked it a few times to see if would spark again. It didn't, so I took a screwdriver and touched the points for 1-4 and the plug was showing a strong spark consistently with each time I touched the point. Number 2 showed no spark when kicked or when the point was arced. I did the same test with 2-3 where number 3 showed a spark with kick but not by arcing the point. Once I made my way around back to number 4 it didn't show spark by either method (and I made sure the battery had enough charge the whole time also)

So I don't even know where to begin now. I'm guessing maybe a good first step would be to check all connections are cleaned and secure. I've been told the coils rarely go bad but then again it's a 30+ year old bike and you just don't know.....
I know it's a really simple system so it shouldn't be to hard to fix I wouldn't think.

I'm clueless, any similar situations or help would be super appreciated!

Thanks!

bucky katt · « **Reply #1 on:** March 29, 2010, 05:49:29 pm »

clean all conections with contact cleaner and make sure theyre all secure enough.

bistromath · « **Reply #2 on:** March 29, 2010, 05:50:30 pm »

Sounds like you probably have spark. If you had intermittent spark, it should fire SOME. If it's not firing at all, you probably have fuel issues. Crank it a bunch, pull the plugs, verify that they're wet with gas.

chadbenson · « **Reply #3 on:** March 29, 2010, 05:58:26 pm »

It would hit a few cylinders when I was kicking it over. But wouldn't start probably due to only like two pistons hitting. When I checked all the plugs they were definitely showing signs of fuel. I was thinking timing might be an issue but, that wouldn't explain the intermittent spark when I would arc the points and it would visibly fire sometimes

bryanj · « **Reply #4 on:** March 29, 2010, 09:28:14 pm »

Renew the plug caps and trim the HT lead 1/4 inch

chadbenson · « **Reply #5 on:** March 30, 2010, 06:57:41 am »

Is there anyone that offers the wires and boots to change out these old ones? I've checked bikebandit and partsnmore. Partsnmore shows some boots for 750s. Wouldn't those work for 550s as well?

Sporkfly · « **Reply #6 on:** March 30, 2010, 07:21:43 am »

550 stock coils require some... Modifications... To replace the wires. They're a "single" component and you need to cut them up a bit to get the wires out. I believe there is a thread in Tips and Tricks section or the FAQ.

Aside from that, have you replaced your points? Cleaned all connections?

Gregorymoto · « **Reply #7 on:** March 30, 2010, 07:27:55 am »

Did you say rebuilt carbs? If you have power and spark i would start there.

chadbenson · « **Reply #8 on:** March 30, 2010, 07:32:02 am »

haha! yeah I've noticed that the wires are straight into the coils. Sorta a silly design I think considering they might go bad and need to be replaced. Anywho! I've cleaned them yes, replaced no.

I know that when I was opening the points by hand I could sorta hear a tiny electrical click I think coming from the coils. Could have been the battery though....not sure. It's just doesn't make sense that with the plug out and me looking at it and opening the point it sparks. But when I kick it over it doesn't! IDK...... I'm going to go lurk the FAQ like you said.

Thanks!

p.s. gregorymoto, I have intermittent spark....it comes and goes. No rhyme or reason.

Gregorymoto · « **Reply #9 on:** March 30, 2010, 07:36:30 am »

How many V are you getting at the coil.

chadbenson · « **Reply #10 on:** March 30, 2010, 07:38:44 am »

Not sure, looks like I need to break down and buy a voltmeter though.

bryanj · « **Reply #11 on:** March 30, 2010, 09:01:08 am »

Still say new plug caps, NGK are about the best. Not change the leads just trim 1/4 inch from the cap end

Spanner 1 · « **Reply #12 on:** March 30, 2010, 10:07:48 am »

If, like you report, you can produce spark with a screwdriver across the points but no spark from the points then they are not opening or more likely they need ( badly!) to be cleaned....... might open and close o.k., but corrosion on points= no spark.

chadbenson · « **Reply #13 on:** March 30, 2010, 11:15:49 am »

I've cleaned them once already but they now have some white oxidation on them. I'm guessing to buy a points file and see if that will do the trick?

Freaky1 · « **Reply #14 on:** March 30, 2010, 01:16:05 pm »

I have built wiring harnesses with my dad for years and dealt with more electrical issues on different cars, trucks, and bikes from mine to my friends. The A1 thing to do is stop running around from this to that and start by checking the ground wires. I can't tell you the absolutely nutty unexplainable things that a bad ground can cause. My '77 750F had the harness grounded between the coil and the frame (two different metals BTW), and the battery is grounded to the frame at the rear motor mount on the right side by the rear foot brake. I'd bet you unknowingly loosened up the ground somewhere and it's not getting good contact. Between the clutch and the carbs, thats right in the area where mine is grounded, that's where I'd begin.

chadbenson · « **Reply #15 on:** March 30, 2010, 04:15:42 pm »

thanks! i'll definitely be sure to do that. I had planned on buying some contact spray and going to town on all the connections anyways.

dusterdude · « **Reply #16 on:** March 30, 2010, 04:36:28 pm »

condensor(s)?

chadbenson · « **Reply #17 on:** March 30, 2010, 04:40:14 pm »

that's definitely a possibility. they hold charge right? if they are not sending correctly it could explain the on and off character of the spark? idk...

mick750F · « **Reply #18 on:** March 30, 2010, 06:32:49 pm »

Something to consider is that sometimes 2 separate problems can pop up at the same time. A couple of years ago my ignition switch crapped out and after replacing it with a known good one I was still having intermittent problems. After much head scratching and probing I finally discovered a slightly loose ground connection. All I'm saying is that when dealing with electrical issues on an old bike don't confine yourself to one area. That and do yourself a favor and check/clean every connection you can find. As has been mentioned I'd also look into replacing plug caps along with trimming the leads too. They are over 30 years old after all.

Mike

steamnjn23 · « **Reply #19 on:** March 30, 2010, 09:44:01 pm »

make sure that the colored wire from the 1-4 points go to the 1-4 coils, and the colored wire for the 2-3 points goes to the 2-3 coils (mine was switched by PO)

chadbenson · « **Reply #20 on:** March 31, 2010, 05:24:40 am »

Well last night I did a typical spark test by the way of laying the plugs up against the head and all plugs show spark now!!!! crazy.....but plug three was a little weak looking but sparking nonetheless. So I hooked up the gas tank again and made sure all the typical stuff was on (killswitch, ignitiion, petcock, etc.) but sadly still not running. I pulled the plugs and they were showing to be wet with fuel.....I don't know.........still haven't been able to go over the whole bike with contact cleaner yet. hopefully tonight. I would like to be able to get this thing to fire up again on my own without having to pay a mechanic.

Gregorymoto · « **Reply #21 on:** March 31, 2010, 07:18:53 am »

When you rebuilt the carbs what did you do to them.

chadbenson · « **Reply #22 on:** March 31, 2010, 08:33:09 am »

new: main jets, idle jets, needles, float valve and seat, and air/fuel screws. The needles were set to factory and the air/screw mixture is out 1 turn from bottom (per the clymer manual). And also the carbs were completely cleaned out, emulsion tubes including. The bike was running pretty good before I opened up the clutch cover. It was probably at least a week and a half in between while I was inspecting the clutch though.

Any suggestions?

What's a way to make sure that the carbs are functioning other than checking to see if the plugs are wet with fuel? Possible open up the bowl drains to make sure they are getting fuel?

chadbenson · « **Reply #23 on:** April 01, 2010, 12:12:18 pm »

Guys (girls) it's running now!! and the clutch seems to be working properly as well. I don't know what happened but this morning when i went to check spark all we're hitting. So I buttoned down the tank and she fired up! Thanks for all the advice

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Author Topic: Electrical Problems that defy all logic! (Read 1859 times)