Diagnosing #4 cylinder not firing

[mcompton1973]

I am starting a new thread because my first one was primarily about the carbs...and this is electrical...

 

Problem: Bike seems to be running good, but getting 24mpg on average at 65mph(ish)

 

Diagnosis: I thought this was a carb issue because the previous owner had issues. I got carbs sync'd and runs good, but MPG was bad. Someone said look at making sure all 4 were running right. I assumed that because carbs sync'd they had to be right. That was wrong. #4 cylinder did not boil the water off like the other 3 did. Pull the plug wire, and no change in how it runs etc. Pull #2 , and bike dies. This leaves me to think it HAS to be running on 3 cyl's.

 

Steps I have taken so far: Not much. I did pull a plug wire off my parts bike and trimmed the end and attached it to my bike with zero change.

 

Questions: Is there a way to test things to isolate which part of the spark is the issue? I was planing to pull the plug and swap it out. I was thinking there is a little tool I can plug into the wire to check if spark is coming through the wire, but I am certain it is not. A brief search makes me think to swap the coils from my parts bike or something will be a huge pain...I will do it, but wondering if there is a better way than just swapping parts around. Also, this is not my area of expertise. I dont know how to really use a volt meter etc.

 

Lastly, I saw a little mention of a COP modification or something....Does this have value for me?

[Yammer Dan]

Swap the plug. These things are very picky about their plugs. Before that since it will run start it and put a screwdriver in that plug cap and hold it close to the block to see if it is firing. It will jump fire a short distance just don't get bit!! It won't hurt much. I'm used to it.

[CaseyJ955]

I like COPs, I have them on my Venture and Vmax. Before doing this we should find out what is wrong the current setup.

 

Are you 100% sure there is no spark? You can pull the plug wire and slip an extra plug into it and hold the plug body against a ground and should see some spark, try it on a live cyl and you will see. It might even zap ya, most of us have been zapped many times haha. there is a tool sold at parts stores in liu of a plug So once you know you have no spark at the plug and do have spark on the other 3, I would start at the beginning of the chain. First make sure you have 12v going too the coil at the low voltage side with key on/engine off, then if yes you would measure ohms resistance across the coils low voltage side, and HT side with coils unplugged and key off. This just to make sure the coil is getting power in and the windings arent shot. A coil can ohm out ok and still be bad but thats improbable. I suggest using a decent multimeter and check not only cyl #4 but all and record your findings, were looking for consistent findings across all cyl. I realize you said you were not familiar with the function of a multimeter but it might be a good idea to surf youtube and check out some basic instructions, its really not bad once you see how it works. A digital one will be much easier to use, all you need to be concerned with is reading DC volts and resistance in ohms. Knowing how to use a multimeter for these two things will be very handy in the future. You can get a fairly decent one for probably $25-30.

 

Im assuming you got a good look into the nose of the coil where the HT lead (spark plug wire) plugs in, you could have a nice layer of that gnarly green corrosion inside there and that will keep it from firing, it has to be clean bare metal. Im not sure if a faulty TCI can prevent spark to only one cyl but it would make sense. Lucky the TCI and coils are in the same area, and also lucky you have spares, but not all TCIs are the same.

 

My first idea was to put a photo of one of my old coils up with direction of where to test but im at work for several more days. Feel free to call me and I'll see if I can walk you through it, its really not that bad. Really nice to have a parts bike, yes?

[bongobobny]

Once you have eliminated plugs and wires and are positive there is no spark to the number 4 plug (also look inside the cap of the coil for the dreaded green crud) you can always switch the wiring plugs from the primary of two of the coils AND the corresponding plug wires and see if the issue stays with the same cylinder or moves to the other cylinder...

[videoarizona]

Great advice guys but he says he's challenged by electrical issues.

Anyone near him to help with learning how to do this?

 

Regardless.... Think you need to find a way to throw in a new plug on#4.

[BlueSky]

Remove the plug. Put it back into the spark plug cap and ground the body of the plug against the engine with the engine running. You should see a spark at the spark plug gap.

 

If you have spark, it might be worthwhile to do a compression test on the engine. To do so, remove all plugs and hold the throttle open when checking the compression. A good compression test number will assure you that there is no mechanical problem.

[mcompton1973]

OK...

Had a chance to run to parts store. I got 1 new plug. Was going to get 4 but they didnt have the NKG and I read enough to know to only use them. They had the Champion equivalent. I got one to use temporarily for diagnosing mostly. I also grabbed a tool that will show me spark at the end of the wire.

 

I plugged the tool into the end of the wire and the other end onto the plug still in the engine. It showed sparks in the chamber to say it IS getting spark. So I got excited and figured that it had to just be the plug. Pulled the old plug off. Didnt look horrible, but some black on the electrode etc. Not wet black though...almost looks powdery. Put in the champion plug (note: I did not grab a spark plug gap tool....) and started it. Did not seem to make any difference. Let it warm up (in the garage, gravel is muddy outside) and put water in the area where the spark plug goes in #3 cyl. It starts hissing and boiling. Put it in the same place on the #4 that was giving me issues. Nothing. Now...its hot...just not hot like it should be.

 

When I swapped the wire the other day, I just took the false gas tank cover off, and finagled it with my fingers...trimmed the end of a different wire from the parts bike and put it on the bike. I did NOT get into look at the coil at that time or anything at all.

 

So it would seem there is SOME spark....maybe not ENOUGH spark....is that possible?

[snyper316]

Great advice guys but he says he's challenged by electrical issues.

Anyone near him to help with learning how to do this?

 

Regardless.... Think you need to find a way to throw in a new plug on#4.

 

I am near him and have offered help up, I Have spark gap tester that comes in pretty handy, for checking spark.Also got another neat little plug that will tell how hot/cold that plug is firing.

[Yammer Dan]

Auto Lite 1163's work great in these things when working on them. Cheap and if you screw them up no big deal. Gapping them helps. What color is the fire??

[mcompton1973]

I am near him and have offered help up, I Have spark gap tester that comes in pretty handy, for checking spark.Also got another neat little plug that will tell how hot/cold that plug is firing.

 

 

I might have to take you up on it. I was thinking once I realized it was 1 cyl short it was going to be an easy fix...lol. not so much. haha.

 

I might run it up to Joplin one of the next couple weekends if I cant solve it before that.

 

 

 

The tool that I had was a little $5 deal. The spark in it was yellow...but I dont know if it shows any variances. I am going to try it on one of the other cyl's tomorrow to see if they look the same or not.

[rbig1]

well plug cap comes apart probably green here is pic

[snyper316]

I might have to take you up on it. I was thinking once I realized it was 1 cyl short it was going to be an easy fix...lol. not so much. haha.

 

I might run it up to Joplin one of the next couple weekends if I cant solve it before that.

 

 

 

The tool that I had was a little $5 deal. The spark in it was yellow...but I dont know if it shows any variances. I am going to try it on one of the other cyl's tomorrow to see if they look the same or not.

I have the Morgan carbtune colortune plug so it could be issue of running rich.. Or your rear one could be running to lean..

 

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[bongobobny]

I almost hate to say it, but a compression test may be in order. There could also be a possibility that your intake valve is not opening enough, but I am thinking in the vein that Snyper is, misadjusted or malfunctioning carburetor.

 

Yes, there is also a possibility that your spark is not strong enough. With a spark gap tester, you should be able to pull a spark slightly longer than 0.100". Your plug should be gapped around 0.035" give or take a little...

[CaseyJ955]

If #4 is consistent with the other cylinders in regards to spark than a comp test is the next quick test. With good compression we're back to carbs. Just curious but how often do we find actual engine problems beyond misadjusted valves? I sure haven't heard of to many cases.

 

Snypers offer of help is a very fortunate thing. Helluva nice guy!

[snyper316]

I do know our bikes can be cantankerous. I haven't heard of many of our motors really being out of whack. I am wanting to say that compression can be affected by carbs not seated properly too. But if there seated and synced properly I would see if AutoZone has a compression tool to run that test first I have rented them in the past, its been 20 yrs but I would assume they still rent them.

 

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[CaseyJ955]

I do know our bikes can be cantankerous. I haven't heard of many of our motors really being out of whack. I am wanting to say that compression can be affected by carbs not seated properly too. But if there seated and synced properly I would see if AutoZone has a compression tool to run that test first I have rented them in the past, its been 20 yrs but I would assume they still rent them.

 

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I think Autozome loans them with deposit, or used to. A basic one can be had on the cheap although I wouldnt expect great accuracy with a cheap-o. It will, however, let you know if you have a problem or not, it will also let you see how it compares to the other cylinders, so even a cheap one is worth having. Im going to go ahead and 3rd a carb issue as the culprit. When you get the right NGKs and are ready to install, this is a perfect time to do a comp test on all cyl. Also we'll see how each plug looks compared to #4 . This should tell us a good deal about the engine and fuel management.

[snyper316]

I think Autozome loans them with deposit, or used to. A basic one can be had on the cheap although I wouldnt expect great accuracy with a cheap-o. It will, however, let you know if you have a problem or not, it will also let you see how it compares to the other cylinders, so even a cheap one is worth having. Im going to go ahead and 3rd a carb issue as the culprit. When you get the right NGKs and are ready to install, this is a perfect time to do a comp test on all cyl. Also we'll see how each plug looks compared to #4 . This should tell us a good deal about the engine and fuel management.

Don't know what your cheap is but I do remember the one they loaned out in Washington mo was $165.00 basically you paid for the tool and when you brought it back in one piece they gave you your money back. So guess that is deposit. Only reason I remember it I thought it would be a by the day thing.

 

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[BlueSky]

I do know our bikes can be cantankerous. I haven't heard of many of our motors really being out of whack. I am wanting to say that compression can be affected by carbs not seated properly too. But if there seated and synced properly I would see if AutoZone has a compression tool to run that test first I have rented them in the past, its been 20 yrs but I would assume they still rent them.

 

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Compression will not be affected by the carbs not seated properly. To get a good compression reading, the throttle has to be open when checked. If the carbs are off the bike, the compression can be tested accurately.

 

http://www.ebay.com/itm/NEW-8Pc-Spark-Plug-Cylinder-Compression-Tester-Test-Kit-Professional-Gas-Engine-/332155770002?_trksid=p2385738.m2548.l4275

[CaseyJ955]

Don't know what your cheap is but I do remember the one they loaned out in Washington mo was $165.00 basically you paid for the tool and when you brought it back in one piece they gave you your money back. So guess that is deposit. Only reason I remember it I thought it would be a by the day thing.

 

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I dont even remember what I paid for my Snap-on comp gauge set but $165 would have been nice. I have one for diesels that was upwards of $250. Those are locked up in my box, at home I have a K&D (i think) with a bunch of adaptors and a nice case, gave $35 IIRC. For a basic crappy Chinese screw in quick disconnect in a bubble pack on a hook at Autozone or Harbor Freight I'd be surprised if you spend more than $20. It would be fine for occasional use and backyard mechanical andentures. I do all my own work and I couldnt live without one. Its one of my favorite troubleshooting and pre-purchase tools.

[snyper316]

Compression will not be affected by the carbs not seated properly. To get a good compression reading, the throttle has to be open when checked. If the carbs are off the bike, the compression can be tested accurately.

 

http://www.ebay.com/itm/NEW-8Pc-Spark-Plug-Cylinder-Compression-Tester-Test-Kit-Professional-Gas-Engine-/332155770002?_trksid=p2385738.m2548.l4275

That's good to know it was a youtuber that's said that while checking compression, it was low he said he didn't have carb in place..... Lol compression was still a little low then he did a seafoam thru air intake then shut off for 15 minutes for soak... I believe ya trust me but you know if you seen it on internet it has to be true, btw we will have 15 days of darkness starting on November 14th..... Saw it on internet...

 

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[CaseyJ955]

He probably meant combustion instead of compression. Intake obstruction might skew a comp test by giving a false low r/t intake vacuum while cranking, which is why a comp test is normally done with ign disabled and WOT, preferable at op temp. Youtube is generally good for instruction, cocky adolescents taking a compound fracture after trying to skateboard off a barn, a small person lifted off their feet after shooting a 10g and people dusting cops with R1s. So yea, I like youtube!

[ddoggma]

I had kinda the same problem, I got a set of the caps and wires off ebay. Problems solved. Had the green rot on one coil, had to clean the spike where the wire goes in. Best thing I ever did to the bike. She really goes now and I'm getting 45-50 miles per gallon.

[mcompton1973]

Yeah, caps/wired might be next step. I still can not decide if it is really carb or something else.

 

Today I rode it to MO and met up with Snyper.

 

We put his colortune in the #4 . there is clearly spark....but pretty much no actual combustion. We were seeing white sparks...every once in a while we would get an orange flash when we reved it....but that is only a flash and not consistent. Still no sound difference in the engine with plug wire attached to the #4 or not. We closed the pilot screw all the way....no change. Open it 3 turns....no change. We took out the screw, sprayed carb cleaner in there, let it sit, repeat a couple times.....closed it all up....no change.

 

Another interesting thing. The spark plug has only 200 miles on it...black, dry tip...smells like gas.

[videoarizona]

Suggestion: Pull your TCI out. Various threads show how to get it out and move it to top of air cleaner.

Take it apart and check the diodes that are connected to the output for each cylinder.

Also check the connectors for corrosion.

Lots of pics and info on this... On the site.

Spark issues can only be bad wires, coils, plugs or TCI issues... That includes corrosion on wires to coils and TCI.

Simple to trace down... And a visual inspection of each stage is usually all that's necessary to find the problem. Corrosion kills ignitions.

[mcompton1973]

I did pull the TCI out of my parts bike. I have not done anything with it... But thought about Cleaning it up and seeing there was a difference. I looked and have not found directions on removing the coils.... Unless the only way is to remove the whole fairing. I was told to try and switch the plugs and wires from the 2 and 4 and see if the dead cylinder moves or not... So might try that.