Spark plug fouling

[mewherman]

So my r5 engine works great until it fouls it's plugs, the thing has eaten four sets of plugs now. Once they're fouled they're garbage and no amount of cleaning will bring them back to life for more than a few minutes. I rode the bike on the highway at 60-70 mph this evening with no issues. Got home, looked at the plugs, and they're kinda oily and have a black electrode but not the plugs isn't totally black or anything. I put them back in, this is after a test ride where it didn't foul a plug and was still running fine, and it fouled the right side again, it seems to foul the right side over the left, it also will backfire through the carb and out the exhaust if it's beginning to fail.

Would this just be down to me needing to shotgun a new everything on the ignition system? I double-checked the timing and points gap and it's normal. I'm getting pretty tired of working on this bike, I thought I would finish the restoration and it would be fine with minor issues, not have 1000 problems. Everything in the ignition system is old/original. I was going to replace the points and condenser when I did the engine rebuild but economy cycle said they were out of stock on the parts and would send them when they were in stock, well that was three months ago, so I guess I need to buy points somewhere else.

With fresh plugs it starts up and runs strong and then seems to degrade quickly, it usually loses the right cylinder if you shut it off and then try and start it back up again after cooling down a bit. Although I have lost the left side as well and I have also lost while riding.

It's a little odd since I never had any ignition issues with the bike when it was on the road two years ago with its original engine. I've also only fouled one plug ever on one of these bikes prior to this. 

[85RZwade]

Hmm, oily plugs and right side fouls first? Is your transmission oil level changing over time? Sounds like your clutch side crank seal may be passing oil. Leakdown test time!

[m in sc]

lean the needle a clip. usually if the ignition is weak it will start dropping one or the other cylinder. also, verify oil pump settings.

[Milan]

Disconnect the oil pump.
Try running with a 40 : 1 good premix, and see if it still happens.
That will tell you if its over-oiling, or a leak

Also, the leaning out thing above.

M

[AAAltered]

I've been through several "fouling plugs" issues.  For me it was:
- weak battery.
- failing coil
- once I had a Dyna pickup fail

At least for me, it's always been ignition related.

[Yamaha 179]

All these responses are good but I'll bet AAAltered's is correct.  I have several old YMC Tech Bulletins addressing plug fouling, mainly on RDs but other bikes also, that spoke about weak coils and bad bullet connections.  They recommended removing the bullet connectors and soldering the ignition harness wires together to ensure a good
connection and replacing the RD 250/350 coils with XS 500 B coils.  (They have the same mounting studs and just bolt in place.)  Another bulletin spoke to replacing the high-tension leads even though the current leads appear to be in good shape.  Apparently, voltage could be lost through radiation or conduction as resistance through the tested leads was normal.
Lyn Garland

[dgorms]

Unscrew the plug caps from the plug wires, trim a 1/4" reinsert. These corrode over time and cause fits.           

[Striker1423]

You would lose the coil completely if it were dead once its good and hot. Mine ran awesome for around 10 minutes then it turned into a one lunger I had to limp home. Once the coils were replaced it ran fine.

I also had points arcing under the insulator before. Found that at night in the garage... it also backfired a LOT (de-cel, idling, you name it) that was fixed after finding the insulator was so old it was broken in half.

I also had as Dennis described. Trim the wires and replace the plug caps. All cheap to do. File the points if they're burnt.

Moral of the story? Old ignition parts typically mean a loss of reliability.

[m in sc]

I agree, old ignition parts are time bombs. However, if BOTH are fouling plugs, its either a supply voltage issue or a carb setup issue in my experience.  If its  afailing ignition component, it will almost always rear its head on one cylinder before the other.

by chance.. did you rebuild the carbs with a carb kit and use the kit needles in the kit? if so, thats a problem as well. they are -always- wrong.

[2t Fan]

can we really check the health of the ignition system by one of Motion Pro Ignition System Testers ? 

[m in sc]

the issue is that on these types of systems, the problem is when they are hot (usually). spark strength is important cold, but hot is where these systems tend to have issues. 

[RustyRD]

Resistance in the wiring will reduce current available  for proper operation. Correct voltage can still be present , however the current available to operate correctly will not if the resistance of the circuit Is high.

[m in sc]

Resistance in the wiring will reduce current available  for proper operation. Correct voltage can still be present , however the current available to operate correctly will not if the resistance of the circuit Is high.

I agree here. friend of mine with an r5/rd hybrid is dealing with this right now. we need to go thru the wiring to see where hes losing amperage. voltage is good, charging is excellent, but he has a loss somewhere and we need to just dig into it. By removing the headlight it was 'cured' he thought, but , its really not. this is  points bike with stock everything except oregon vrr.  My guess is he has dirty terminals or a slight short in the gauge bulbs.  this affects the whole system. But, even on this, it always loses the left cyl 1st, even with new coils, replaced coils, wires, caps, etc.

[RustyRD]

Ohm's law will give you the answer. Voltage divided by resistance equals current. It does not take much with all the bullet connectors to add up . Poor ground at the battery and at the coil ,a little rust here some corrosion there and next thing you have a circuit that may have 50 to 200 ohms resistance    12v/50ohms=.24 milli amps of current.. nothing near what an ignition at full song would need. A thorough check of the entire circuit is needed. Try one of the online ohms law calculator to see the dramatic effect resistance will have of current available.

[m in sc]

agreed. however a lot of people are terrified of doing that. (for no good reason)