Right cylinder firing less than left

[m in sc]

yeah. I can't remember who used to always say 'doesn't mean it's firing under compression' might have been quencher or aylor

[Dvsrd]

Chainsaw dealers/ repair shops often have handy ignition testers. Basically a large spark gap inside a transparent housing, with a Crocodile clip for ground connection and a spark plug like thingy that the spark plug cap fits on. These will easily detect a weak spark caused by bad coils, bad points, bad capacitor. Or my absolute favorite. Low voltage on the coil +terminal, caused by voltage drop through the rather convoluted path from battery + to coil +. An easy check would be a direct "jumper" from battery to coil ,with a 10 A fuse just in case.

[Super Dave]

Perhaps I should be more exacting when describing what the bike is doing when it is running. Instead of calling it a misfire, I'll opt out for a description. When RPMs are applied, one side would cut out. It would not fire at all, or just sometimes on one side. (Seems to mostly idle with both cylinders working) There is no backfire, or popping. It simply would stumble a little bit when applying RPMs, then quit firing. Occasionally when RPMs were applied you would hear the cylinder sometimes fire back up, then stop. It would also switch sides, and exhibit the same symptoms on the other cylinder, but only after restarting.

[m in sc]

is it better with the headlight off vs on? have you tried that? im being serious. if its worse w headlight on, electrical. low running voltage to be exact.

[Super Dave]

I have had the motorcycle running with the headlight on, and with it off. Have not noticed any changes. It has been missing mostly on the left side, I left the gas on, and let it sit for a few minutes. There was gas coming out the Overflow tube of the left carburetor. I have the valve needle seats on order from Mike's XS. Hopefully I'll be able to install them in a few days.

[Super Dave]

I replaced the left coil. It had 4.4 ohms before I installed it. After installation, I rechecked it. The coil showed showed only 2.8 ohms. I checked the other side, 4.4 Ohms on the right side. Then I unhooked the orange wire on the left side coil, it showed 4.4 ohms. I then turned the ignition on, and checked the left side coil again. This time it showed -1. The coil was getting voltage from the battery on the left side. The right side was fine, it showed 4.4 ohms. I was checking the connections by the battery, and happened to put my hand on the left coil. It was noticeably warm! The left coil is getting voltage from the battery, and going through the system and heating up the coil. I'm surprised it occasionally fired at all on the left side. Has anyone ever experienced anything like this? The problem must lie with the rectifier, the voltage regulator, or somehow the generator.

[m in sc]

they get power from the same single wire lead, so no, none of those things. it should be a 2 pin female bullet connector that basically sits on the frame tube. 

if the ignition is left on, one will heat up if the points on that side are closed... or the condensor is shorted. it can even do it on a dyna system but will eventually burn out the pickup.

the orange coil wire is the points lead, the brown wire is the power lead.  check coil resistance completely unplugged. anything else is a crap shoot. it IS a good idea to check them after being run and warmed up though, but still unplugged.  0.02

[teazer]

Did you try a new condensor and while you are in there, double check for frayed wires or wires rubbing on the frame or engine cases.

[Super Dave]

The condensers are new. With no wires connected, the left coil reads 4.4 ohms. Fully connected, for some reason it jumps down to 2.8 ohms. That reading is with the key off. The right coil, reads 4.4 ohms connected or not

[RDDave]

I recently fought a similar gremlin. I can make 2 points on this:

First, once the engine is 'loaded up', it needs to be run warmed up under load long enough to clean it out. No amount of run time without load will clear it out. Getting there may take multiple plug changes till it gets warm and pulled through a few gears, but is the only way.

Second thing I learned is that the NGKs won't take being fouled and cleaned more than a time or two. After a lot of experimenting, I ended up with the NGK Iridiums. Not much more money on Amazon, but they resisted fouling much better than the standard plugs. AND I could clean them many more times as I was trying to figure out what was going on. They ran longer allowing me more time to try different things.

Often I had to put a clean set in, run till one fouled, change it, run some more until anther one fouled. And kept doing that until I was able to get it warm enough to pull through a few gears.

During that time, I checked and rechecked pretty much everything. Eventually, it stopped fouling the plugs. It may have just been so 'loaded up' from the previous owner's mistakes that it took a while to get fully cleared out. Lots of adjustments weren't quite right, but I never found any one thing that I can say was 'it'. 

[irk_miller]

The condensers are new. With no wires connected, the left coil reads 4.4 ohms. Fully connected, for some reason it jumps down to 2.8 ohms. That reading is with the key off. The right coil, reads 4.4 ohms connected or not

If a coil reads low resistance with power on, than there is a short present in the primary winding.

[m in sc]

new condesors arent nec good ones.

try new coils.

these are suspiciously cheap but work awesome on rds, and the bolt holes line up. just need a spacer, and a bullet to blade adapter to be made, easy stuff. IF it still does it with these, its not the coils.

as far as ngks... ive run sets for years w out fouling them. the ones in the 70 r5 are i -know- 5 years old. 0.02

[RDDave]

Right now, the recommended Suzuki coils are available on ebag for less that $14 a pair including shipping. There is a 10% discount code available for a short time.

www.ebay.com/itm/291264625288

[m in sc]

i forgot to ad the link. lol. ^ thanks for that.   https://www.ebay.com/itm/275850575096?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=5r9H0_TZSJq&sssrc=2047675&ssuid=9DXeqLNdSLW&widget_ver=artemis&media=COPY

[1976RD400C]

I think the 2.8 ohm reading is caused by, when having the wires all connected, you are actually getting a reading of 2 coils, that are connected in parallel, due to the +12 leads on the coils being connected together.