Fuel, Spark and Compression - But No Start!

[Dr. Frankenstein]

This kind of ties in with my Dial/Tuning question I posted in here, but is a little different. I started the bike today, and it's running on cylinders 1 and 3 (the right side), but not 2 and 4. I have spark visible on all four plugs, it's getting gas and will run, so I have compression, but 2 and 4 are not lighting.

Cylinder 1 and 3 run off of the two coils, as do 2 and 4. Again, I have fuel, spark and compression, but 2 and 4 won't light...electrical connection, maybe...? I need to get it running right before I try to re-time the engine, but I'm puzzled as to why, if both coils are firing and I have fuel, spark and compression, why won't cylinders 2 and 4 light? I DO have spark on those wires...Again, electrical connection somewhere? I just don't understand why if I have fuel in all four cylinders - you can smell it coming out of 2 and 4 when the engine turns over - compression and spark, why it won't fire. The plugs were a bit sooty when I took then out - could be because before I reset the mixture to 1 3/8 turns out they were at, like 2 1/2 - but I'll try cleaning them and replacing them, but beyond that I have no idea why 2 and 4 aren't lighting.

[Dr. Frankenstein]

Okay, so I took out the air filter and dug down into the wiring - using the wiring diagram, I looked at what blue and yellow wires were coming off the coils and where they went. I thought I maybe I had wired it up backwards so I switched the blue and yellow wire connectors where they plug into the wiring harness 'just to see', and sure enough now 2 and 4 light, but 1 and 3 are cold - bad coil?...but that doesn't make sense, because if 1 and 3 were firing and 2 and 4 weren't until I switched them around, that shows me that both coils are working....so what is preventing them from firing at the same time? A wiring harness connector?

Using the KISS principle ("Keep It Simple, Stupid') I'm going to go through all the connectors, see if there's any corrosion and check back here before I change out the coils to see what you guys have to say. I currently have new OEM type-looking coils in there as well as the electronic ignition installed, but really thinking about switching over to 5-ohm coils.

[Dr. Frankenstein]

I think I found the problem....I'm pretty sure that blue wire isn't supposed to look like that...
DSCN2749 by Dr. Frankenstein1, on Flickr
DSCN2748 by Dr. Frankenstein1, on Flickr

What would cause them to melt like that...? It's only melted on this one coil, the other one's fine...Cedric, any input...? Anybody...?

FWIW I was running this bike with electronic ignition and the ballast resistor in place...could that be a factor? Or just a bad coil?

[redglbx]

Dr, probably an internal short that got things really hot if I was a betting man.

Does that plug wire next to the blue wire go to your offending cylinder by chance?

[Dr. Frankenstein]

You would be correct, Sir! I was looking at them on the bike and tracing it back to which cylinders fired off that coil when I noticed that mess at the bottom. I need to go back and take a look at how Cedric has the 5-ohm coils wired up. What's a good size wire for those? It looks like 16-gauge, but I'm thinking 14 would be a bit beefier to handle the voltage. But what would cause the short?

[Sagebrush]

AGE

[Dr. Frankenstein]

Yah, but I bought the coils new two years ago and only put 60 miles on them...I'll just replace them with the 5-ohms I have, see what happens. But will 16-gauge wire be sufficient?

[gltriker]

Yah, but I bought the coils new two years ago and only put 60 miles on them...I'll just replace them with the 5-ohms I have, see what happens. But will 16-gauge wire be sufficient?

Based upon this Google search result, I would say yes 16 gauge is sufficient Delete the ballast resistor in your new coils installation, too.

"16 gauge wire is a type of electrical wire that can handle different amounts of current depending on the temperature and voltage. The amp rating of 16 gauge wire is 17 amps at 75°C, 18 amps at 90°C, and 13 amps at 120V or 240V123. The wattage of 16 gauge wire may vary between 50W and 120W at 12 volts. 16 gauge wire is used for some vehicles and extension cords."

[gltriker]

Yah, but I bought the coils new two years ago and only put 60 miles on them...I'll just replace them with the 5-ohms I have, see what happens. But will 16-gauge wire be sufficient?

https://ngwclub.com/forum/viewtopic.php?t=77232

Dr. John - I use a lot of those original type connectors when I restore wiring harnesses. You can order them from several places but I got this last batch from eBay. The wire is rated for this type of application.

Here are the links:
Connectors:
https://www.ebay.com/itm/283601470211
https://www.ebay.com/itm/224898601743?var=523767174391

Wire: https://www.ebay.com/itm/113148282074?var=413453603076

Screws:
https://www.ebay.com/itm/111998058244?var=410940302698
https://www.ebay.com/itm/174811165268?var=474299991251

[redglbx]

Dr, are you looking at the 5ohm Dyna type coils ? If so you should see a significant bump in coil output ! Remove the ballast resistor if you have an electronic ignition and this should boost your coil output from the 7k volts of the oe coils to around 35k volts. You should see improved starting and an improved low speed throttle response.

It’s not going to be a night & day difference but the better starting should be noticeable, check the plug caps while you at it, they should measure less than 5k across them. Use solid core wires. Let us know !

[gltriker]

This kind of ties in with my Dial/Tuning question I posted in here, but is a little different. I started the bike today, and it's running on cylinders 1 and 3 (the right side), but not 2 and 4. I have spark visible on all four plugs, it's getting gas and will run, so I have compression, but 2 and 4 are not lighting.

Cylinder 1 and 3 run off of the two coils, as do 2 and 4. Again, I have fuel, spark and compression, but 2 and 4 won't light...electrical connection, maybe...? I need to get it running right before I try to re-time the engine, but I'm puzzled as to why, if both coils are firing and I have fuel, spark and compression, why won't cylinders 2 and 4 light? I DO have spark on those wires...Again, electrical connection somewhere? I just don't understand why if I have fuel in all four cylinders - you can smell it coming out of 2 and 4 when the engine turns over - compression and spark, why it won't fire. The plugs were a bit sooty when I took then out - could be because before I reset the mixture to 1 3/8 turns out they were at, like 2 1/2 - but I'll try cleaning them and replacing them, but beyond that I have no idea why 2 and 4 aren't lighting.

Dr. John -
* 2 and 4 are wet with gasoline but 'not firing' * takes me back to a discovery by one of our fellow members.

Check that the choke cable has some slack when the choke knob is pushed back fully into the off position.
Also make sure the fine wire torsion spring choke mechanism located under the #4 and #2 carburetors' choke shaft rubber cap is allowing their respective choke shutters to open completely.

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20230723_113042 (2).jpg (56.72 KiB) Viewed 329 times

[Dr. Frankenstein]

Hi Red - yes, those are the ones. It was something I was meaning to do anyway, but this latest problem made me focus and actually DO it, so I'm just going to change the whole coil system out.

Hi Cliff - I'm just going to change them out and see where I'm at; I believe the choke is fine, it was working last week...but I'll check again! (And thanks for including that coil How-To, I was going to go looking for that!)

I'm looking forward to doing it, but kind of bummed that I may have to cut an inch or two off the OEM air filter housing. It's a very tight squeeze without it.

[gltriker]

snip Hi Cliff - I'm just going to change them out and see where I'm at; I believe the choke is fine, it was working last week...but I'll check again! (And thanks for including that coil How-To, I was going to go looking for that!)

I'm looking forward to doing it, but kind of bummed that I may have to cut an inch or two off the OEM air filter housing. It's a very tight squeeze without it.

nope

my method OEM Air Filter Housing intake snorkle trim link:
https://ngwclub.com/forum/viewtopic.php ... 56#p819956

[Dr. Frankenstein]

"I'm just going to change them out" means I'm going to get rid of the OEM-style I had and put in the 2-pole 5-ohm ones.

"I will find the photo/s of how I sliced just a little bit off the lower part of the OEM air filter housing's intake 'snorkle'" - that's what I mean - you had to modify the OEM air filter housing. Not really a big deal - I mean, who's going to see the air filter anyway, but still...

[gltriker]

"I'm just going to change them out" means I'm going to get rid of the OEM-style I had and put in the 2-pole 5-ohm ones.

"I will find the photo/s of how I sliced just a little bit off the lower part of the OEM air filter housing's intake 'snorkle'" - that's what I mean - you had to modify the OEM air filter housing. Not really a big deal - I mean, who's going to see the air filter anyway, but still...

here's the solution
https://ngwclub.com/forum/viewtopic.php ... 56#p819956