Topic: Got Spark, but no fire!

[Zeke]

Hey All,

My old engine thread is stale and too long, so I want to focus here...

My bike is running on #2 and 3, doesn't appear to run on 1 and 4.  That is, after a minute of running I can't touch the exhaust of 2,3 but 1,4 are cold.

If I remove sparks and ground them, crank over I get spark on all cylinders.  Maybe not the brightest spark I've ever seen, but it's blue.  Plugs are gapped correctly.

I tested the coils with a multimeter as described -- on both between the + and - terms I get 2.2 ohms, between the spark plug wires I get 12.2K ohms (I believe that's without the boots)  I don't know what this tells me.  Someone said that the primarys should have around 3.x ohms and the secondary around 12.5K or something -- seems like I'm close.  I also checked the "pulsers" (E-points) and they are within spec.

OK OK, by now you're all blaming it on gas.  Well, the carbs were never dirty in the first place and have been disassembled and cleaned 3 times now, floats set, everything.  All bowls have gas.  I'm telling you, they are CLEAN!

I'm going to try a new set of plugs tonight this was suggested by Steve.

What else can I try to troubleshoot this?  By all rights I should be wheelieing down the alley by now!

I have an appointment with a bike tuner on the 23rd (he comes friend recommended) if all else fails.

HELP!

Zeke

[Patrick]

Zeke, try switching the plug wires between cylinders #1 and #2. If the bike will fire on #1 and #3 after that, then your problem likely isn't fuel and it could be the spark. If you have points, check to make sure the points are clean and properly gapped. If the points are OK, check the compression on cylinders 1 and 4. If the spark, fuel and compression are correct, check the timing for the 1 and 4 cylinders. Your manual will tell you how to do that. It only takes fuel, compression and spark delivered at the right time to make the engine run. Eliminate one potential problem at a time. Whatever is left is the answer....

Hope that helps.

Patrick

[kghost]

Ref. Patricks post.

He's on the right track but you cant put the 2+3 wires on 1+4. Timing will be off. What you can do is swap the coil wires than the caps. Thus 2+3 will now Fire 1+4.

[cben750f0]

just swap the blue and yellow wires at the coils, and then swap the leads, this just swaps the coils round... dont anyone else find 2.2 ohms for factory coils a little low?... if it was 2.2 ohms then you should have  mean mother of a spark!!!!... i read 3.2 with the VF1000 coils and you dont want to be holding onto those when the starter is hit!!!.(another story .)
  NEway, would try to find a  set of coils you know are good, and give them  run, this then can eliminate them as a problem... then the only other place is the points and condensers... was talking to my mechanic, and he has found over the year that sometimes condensers can mess up interminatly.... BTW just a though... have you checked you plug caps?..,. do they read open circuit, or do they have a value... i know when i was haveing trouble it turned out to be a stuffed spark cap.... it turned out that th system was throwing a spark from the end of the lead to the plug, but not using the cap ... when you looked at it you had a spark, but as soon as you loaded it up, the reistance was to high, and the bike would play up like a pork chop... i am running out of things that could be a problem... B4 i say pill the carbs again....will have a think... peace

[Salem350F]

Just my 2 cents worth.  I just got my project '72 CB-350F running that was having me pull my hair out all last week.  Similar to your description #3 would be cold.  If I juggled the 3# wire it would cut in and out.  I put new points in checked and rechecked the timing, adjusted valves, everything.  I kicked and kicked.  First I found that one of the coil power (black) wires had come loose, with all the tank on and offs.  I thought for sure I had it but now it would not start at all.  I laid the plugs on the engine connected to see a spark, no spark.  I removed all the spark plug ends and trimmed them back about ¼ inch and watched for a spark, a great nice blue spark from all four.  I then reinstalled the terminal ends after polishing up the conductor; I left a little wire out to make sure the screw got plenty of metal to metal contact.  I connected the plugs and watched for the spark, great spark at all 4 gaps.  Installed the plugs and started kicking- nothing except two putt putts and then fuel soaked plugs again!!  What to do?  A trip to get four new plugs, off I went and returned home with the plugs crossing my fingers while I gapped them to .028. Installed them. Switched on the ignition and said a little prayer before I kicked.  Fired up ON THE FIRST KICK!!.  Warmed up a few minutes the  idle a little high, I then took my first spin!!  Ran great.  Set the idle, I had rebuilt the carbs over the winter, my bench sync must be dead on because it ran great all the way to red line.  Not only that but the clacking and marble sounds were gone!!  Now a trip to the DMV to get the thing registered   

Check the wires and terminations- and 4 plugs might help

[CTCStrela]

If you're getting spark on all four cyls, pull the airbox off, and try spraying starting fluid into the "dead" cyl's.  If the rpm's pick up, i.e. the cylinders fire, then it's GOT to be a fuel delivery problem...

if not,  maybe a burnt valve? 

How is your compression?

[Zeke]

Guys:

Thanks to all for the help.  I put in the new plugs and again in the air, great spark.  Ran it for 30 secs, and it seems only 2 and 3 are running -- that is, they were hot, 1 and 4 were not.  So I got out the alligator clip wires, and swapped the coils around as described above -- same deal -- 2 and 3 running, 1 and 4 were not.

I'll tell you now, that this here bike is one of the elusive 650s with CDI ignition.  I swapped around the "spark units" and same thing. That's when I saw a potential problem.  The 4 wires that go to the pulsers (i.e. electronic points) had been cut at some point and spliced using automotive blade connectors -- and they aren soldered, just crimped.  It looks like the PO might have had a short or who knows?

After fooling around with the wires a bit I started it once more and this time I got intermittent sputtering from #4 exhaust.  That is, it popped once in a while, but the pipe was still cold. 

I definately don't like the looks of the splice job -- I'll try to pick up some wire, heatshrink, and a 4 pin molex connector and put it back together right.

I had an intermittent issue like this years ago with a CDI ignition -- that's the only problem with them.  They work awesome until you get a partial short or a bad ground or whatever -- then it's an expensive part swap game to find out what's wrong.

Oh, and for those of you that asked compression questions, etc.  This is a fresh rebuild and I've done everything by the book to this point.  Compression is good, new rings, valve job, valves adjusted, torque wrench, bench sync, you name it, I've done it.

I do know now that the coils are good.  I checked the pulsers(points) per the manual and they both checked out.  So it's got to be one of four things:

bad wiring
bad spark unit
plug wire issue (doubtful, they are new OEM wires, and I checked the boots tonight)
carbies?

Zeke

[Patrick]

Hi again, Zeke, I've already contributed my two cents worth, but I found another penny lying around....

First, of course Kghost is right. Switching the spark plug wires alone would throw off the time. That's why I spend a whole lot more time pondering than torqueing when I work on my bikes. I didn't ponder enough before my last reply. But, if you've switched the coil wires and caps and it still fires only on #2 and #3, and if you've checked the compression and found it good across all four cylinders, I really think you're chasing your tail concentrating on spark delivery alone for this problem.

Now, to put his reply in perspective, I work on these old bikes strictly as a hobby because I enjoy it. I love these old bikes and really enjoy bringing a badly abused machine back to life. A lot of these other guys are pros. I spend days, weeks or months doing what some of them can do in an afternoon. I've had some success, but this could never be anything but an avocation for me. If I tried to do it for a living my long-suffering and impatient customers likely would put out a number of contracts on my life.

Based on what you've posted, however, if this were my bike I would already have begun pondering the mysteries of fuel delivery and air/fuel mixture by now. Since you say you've thoroughly cleaned the carbs, have you double checked your air screw? Are the intake boots in good shape and properly seated? Did you bench sync the carbs before you mounted them? What do the spakr plugs on #1 and #1 look like after the bike runs? Do they have fuel on  them or are they clean?

Also, if you haven't actually put a compression tested on the cylinders, I would do that too, if it were me. Sometimes I think I've nailed the specs only to find out I forgot something or assumed something. That's why I rebuild these amazing old beasts so slowly.

At the end, the wait and the work are always worth it. Good luck.

Patrick

[Robert]

If you have some starter spray or break cleaner handy, disconnect the ruber tubes (airbox side) and spray that in carb#1 or #4 while the engine (or half of it  ) is running. If there's something happening you have a carb problem. If not it's likely to be ignition related.

Side note. When rewiring the pulsers, give attention to polarity, it does matter. Pulser generators produce AC but ignition is triggered by the negative half wave of that AC.

[Zeke]

Hey Guys:

Compression is 140+ on all cyls, and it's a fresh build so I didn't expect to get 170 yet.  Pilot screws are preset at 2-1/8 turns out per the 1980 addendum in my shop manual.  Carb boots are brand new OEM.  (had to cut the old ones to get the carbs off.....

I didn't check the plugs after yesterday's run but when I took out the old ones yesterday the 2 and 3 were a nice brown color and I smelled #1 -- it stank of stale gas.

Robert I will pay attention to polarity but it'll be a pain in the ass.  the wires were cut near the harness at the downtube so they are hard to see and even harder to handle.  I hope to god I don't have to remove the airbox to solder the wires.

In fact, since the 4 wire plug for the pulsers was chopped off, it's possible that the polarity is switched right now.  If not, then I have to assume that the PO's wiring is faulty.

I haven't tried the carb clean thing yet, but I'll do that tonight hopefully before I tear into the wiring.  But with the intermittent sputtering I got last night from #4 it sounds more like a wiring problem to me.

Thakns

Zeke

[Zeke]

U P D A T E

OK so tonight I disconnected the AirBox and tied it back out of the way.

Ran the engine for 1 minute.  Stopped it, then removed #1 and #4 plugs -- they were stinky with gas.

Hmm.  Just for kicks I disconnected 2.3 and turn her over -- I had spark.

Put the plugs back in and hooked up the new OEM wires -- started again.

Sprayed carb clean in #1 and nothing happened.  Sprayed in #4 nothing happened.  Sprayed in #3 and the bike sputtered and stalled.  Same with #2.

Restarted and wiggled the wires where they are spliced and #4 sputtered -- seems like an intermittent electrical problem.

I'm gonna redo this horse#$%* wiring before I do anything else -- practically on principle.  Unfortunately I will have to undo all the wires at the battery box and pull out the harness to accomplish this -- there simply is not enough room to fix the wires in there, not to mention using a butane powered soldering iron near the battery is a bad idea.

Won't get to this until Saturday as I'm going to see Phil Lesh tomorrow night (if there's any deadheads out here in SOHC land).

I will report back, as usual.

When this FXXXer is finally running again I plan to do a "case study" for the FAQs of all my efforts -- hopefully they'll be of help.

And, as usual, thanks to all for the help you've saved me from torching this bike.

Zeke

[cben750f0]

mate some times its hard not setting the old girls on fire ... trust me i had a dicky plug cap... and do you think i would check it..noooo... i had to do everything else first!!!.... sometimes the simple things are the first things we dont do... and when we actually decide to do it.... want to smash stuff cos it was the problem... so you aren t the only one who has wanted to cremate to old dears, but be happy in the knoledge that you wont be the last either... ..peace

[kghost]

Aahhhh, You mean that Redrum,Redrum Redrum moment!

[Zeke]

mate some times its hard not setting the old girls on fire ... trust me i had a dicky plug cap... and do you think i would check it..noooo... i had to do everything else first!!!.... sometimes the simple things are the first things we dont do... and when we actually decide to do it.... want to smash stuff cos it was the problem... so you aren t the only one who has wanted to cremate to old dears, but be happy in the knoledge that you wont be the last either... ..peace

Morning, Ben....

I did check the plug caps -- getting something like 5.5K ohms -- or was it 5.5ohm?  Good Point though, I'll swap those buggers around as well just to be sure.
Zeke

[cben750f0]

5.5k is right... so they are alright... my one that didnt work... showed nothing!!!...if in doubt.. change them out... ..peace

[Zeke]

Hey Guys:

I fixed up the wiring to practically military specs with solder, heatshrink, and a new connector for the "points".

I'm running on 4 cyls now!!  Yippee!  Now if I can just get the f'ing carbs tuned!!

If it wasn't for the help of you all regarding the firing checks I'd have gone crazy.

Again, it's very interesting that I saw spark when testing the spark in air, but when the system was called upon to give a consistent spark to run the engine it wouldn't fire.

Bottom line is, if you need to replace a piece of wire on your bike, DON'T do a #$%*ty job!!  If I was to get my hands around the neck of the jerk who fixed this bike I'd tear it off -- I've wasted over 40 hours in the garage cleaning the carbs three times and checking compression and blah blah blah because of a substandard repair. 

I don't use crimp connectors on critical parts or things exposed to the weather -- My boat trailer's wiring has been bomber for over 10 years because I soldered every wire as opposed to using those connectors.  Something to think (and rant) about.

Zeke

[kghost]

I hate to rain on the solder repair/upgrade crowd but.........

In Aviation (this means the airplanes flying over your house) crimp connections are prefered over solder. What? What the F@ck?

The reason is simple. Done correctlt crimp joints are less prone to failure than Solder.

Lead Solder is prone to fatigue cracking. Also damages the insulation on the wires.

I Sh%t you not.

Go ahead and solder if it makes you feel better thought

[Zeke]

Well, I suppose I'd believe that -- if your connectors and crimp tool are matched and of good quality -- and done correctly...
I'm aware that aviation standards are the highest out there and if there is a best way to do something that's how its done.

I used to work as an electrician in college for a while and we had these nice connectors for repairing commercial wiring -- the fittings were sealed with silicone and heat shrink, and also used an expensive crimp tool to do the job right.

But these #$%*ty ones that you get at the hardware store with the $2.00 crimp tool are absolute horse#$%*, and I've seen the result as a failure more than a success.

When I took apart the wiring I gave it a good yank and it pulled right apart.

I think for the ordinary SOHC repair man who typically runs to the hardware or mass auto parts store will have better luck with some slobber and heatshrink over the crappy crimp conns.

I also don't think you'll have a too much of a problem with a solderd connection as long as the wire isn't stressed against the joint.

Anyway thanks for the help.

Zeke

[kghost]

Will agree with the sh@tty butt splices and tools

[Dennis]

The quality level of approved materials for aviation repairs is on a whole different level than discount hardware or autoparts stores for sure!!

[kghost]

That must be why I keep throwing those in my tool box!

[cben750f0]

thanx for that man... some of us have to live with mediocre(?).. parts ... though i did solder all my conections for the coil upgrade, and also for the relay to coil power upgrade... but the terminals were also crimped, then silicon sealed, then heat shrink... so i am hopeing mine will be all good, another thing i found was i went through the hole electrical system with a pin file and cleaned all the terminals... havent had a flat battery since, and thats with using the 3.2 ohm coils...peace

[dusterdude]

hey guys,i need confirmation on this.i checked my coils yesterday(72 k1)and got 4.6 ohms on both,is that good.thanks

[cben750f0]

yeah thats ok, they are reading... if they dont work they dont show a reading... and the fact that both of them are showing the same... means they are ok, it is very rare to see two stuffed coils, usually it only one...peace

[dusterdude]

cool,thanks