Consistent fouling of plug

[cmyoch]

I see that this is a common issue but I'm not finding a solution. As the title states, I consistently foul my left plug. My carbs were cleaned recently and everything is set to factory spec. My left slide was adjusted differently than the left and I corrected that along with a carb sync. I have new coils and new wires. Valves and timing were set late last season before parking the bike for the winter. My motor has 65,xxx miles on it and the head gasket is leaking. Maybe that's the issue but I've been riding like this for a couple years with minimal issues. I tried the dead cylinder method last night and the best I could get it to run was 1 1/2 turns out which I know isn't right. Plus, the bike died a few times no matter how if I set the screw at 1 or 2 1/2.

Did I miss a step here somewhere?

 

[5twins]

I would check float level on that left carb. Measure both "bulbs", in other words measure twice, once from each side. The floats can get twisted or tweaked on the mount bracket and be sitting at different levels.

I would also check the points gap and timing on that side. The thing about points is as soon as you start running the bike, they start wearing and the timing begins to change. Also observe the points while the bike idles. Is the left set sparking a lot, more so than the right? That would indicate a condenser gone bad.

 

[JP50515]

sounds like what my bike was doing. I pulled the engine to find that I had oil making its way into the cylinders at both multiple spots. Hate to say it but at 65XXX it might be time for a rebuild.

 

[mouser]

I fouled one plug consistently on the same cylinder and it turned out my throttle flap on that cylinder was not seating properly. I adjusted the flaps and the problem disappeared.

 

[cmyoch]

This last cleaning I also set the float heights the same using a caliper. I'm thinking the head leak is probably contributing to the majority of the problem. I've torqued the bolts a little bit more a couple of times with no success. I think it's time for the rebuilt motor to go back in. I just need to get it assembled and installed.

 

[cmyoch]

I went through everything again yesterday and it hit me while I was cleaning the motor again due to my consistent head leak. I wonder if oil found it's way down into the plug cap? I pulled the cap and snipped 1/8th off the coil wire and cleaned the inside screw of the cap with contact cleaner so it had a nice clean connection. I put 40 miles on her last night with no problems. I only had a couple stumbles but that can be contributed to a dirty plug from before and maybe a mild carb tune.

Regardless, I'm waiting for some gaskets from MMM to start my assembly of the other engine, it's time to get it done and in there. At least I can ride a little in the mean time!

 

[angus67]

wtf is a throttle flap? should i worry my flaps arent flappy enuf?

 

[gggGary]

The flaps get fluffy.

CMYOCH as a desparation measure to keep it going before you get the overhaul done you can go hotter on the plug, a BPES6 will keep oil burned off for a while longer but won't stop the cloud following you. What is the compression?

 

[cmyoch]

gggGary, last year my compression test was around 120 on both sides if I remember correctly. I can double check later today. I run Autolite 63's gapped at around .035. My riding style is never over 60mph. I ride the back roads at about 50 mph 98% of the time with short stints on the highway. I wonder if the constant lower speeds contribute some of the issue as well?

Standby for a report back on my compression. Also, do you suggest a narrower plug gap?

 

[DogBunny]

Ever since I bought my primary rider a couple of years ago, the left plug showed signs of oil. Like your bike, it had about 120 PSI on both sides. I would just periodically clean the plug, and all was fine.

About 500 miles ago, I finally had to switch from a BP7ES to a BP6ES on just the left side because the plug was fouling too quickly. Now, all is just as it was before. I expect to get at least a year more riding before I have to do a re-build. Who knows, maybe I will get several years.
At the time I did the plug heat range change, I did a little research, and idling and very low RPMs contribute to this type of fouling. When you are riding those back roads at 50, it might help keep the plug clean if you periodically do the 50 MPH in 4th gear.

 

[angus67]

the occasional high spirited stint on the highways prolly helps clear out that plug, should be good there.

 

[gggGary]

Thick oil, cheap bastard's friend for over 100 years...

 

[cmyoch]

I was going to ask if a different weight of oil would help