Broken Sparkplug

[camos]

A few days ago the engine on 89 VR started running like crap. Yesterday I found the left front plug cap was loose. The brass insert was elongated which meant there was not a good connection to the plug. Replaced it with one off the 90 VR and it seemed to run a bit better but not much. Today I replaced all the plugs and found the left front plug was not properly tightened and was actually broken.

 

Never seen anything like that before. Hopefully the missing bits will make their way out of the cylinder before they do any serious damage. Not going to hold my breath on this one.

 

[Marcarl]

Yep!! looks like they need some renewing. I would grab a stick magnet to see if I could maybe by chance find it in the cylinder. It would make me feel better. Not saying it is even in there anymore, but you just never know.

[M61A1MECH]

I am not sure the electrode is magnetic, you could also try one of those small OD bore scopes you hook up to a smart phone or laptap. Like this one; https://www.amazon.com/Endoscope-Depstech-Borescope-Inspection-Adjustable/dp/B0749BQG1B/ref=sr_1_14?ie=UTF8&qid=1536529717&sr=8-14&keywords=borescope+for+android+phone

 

Just make sure the OD is smaller than the spark plug hole.

[vzuden]

The borescopes work great. You will be able to the entire top of the piston. You may have to rotate the engine slightly (after scope is out!)

[camos]

I think you are all right, however, this happened three days ago and I've ridden the bike for about 6 hours since then so I decided not to worry about dark possibilities and just replaced all of the plugs. Just going to cross my fingers and hope that those two little bits will make their way safely out the exhaust. It seems to be running well so far at least.

 

I've owned this 89 VR for about 3 years and this is the first time I have needed to change the plugs. It's my guess that whoever put the plugs in did not get that one plug tight enough. It appears I should have checked them all right after I bought the bike but I didn't think of it and just changed all the fluids.

 

Live and learn.

[Patch]

This plug allowed for compression leakage as seen on the bottom surface of this spark plug nut. The resulting leakage would of course lower combustion temperatures increasing carbon buildup in that one jug and is evident on the plug threads .

 

The link below brings you to the NGK trouble shooting site with an explanation that fits this scenario.

 

http://www.ngk-sparkplugs.jp/english/techinfo/troubleshooting/10/index.html

[YamahaLarry]

Have seen similar happen in an automotive engine before. Was during my USCG days and happened to our crane car that had an old inline Chrysler engine.

 

Top of piston and bottom side of head/valves looked like someone pinged it 100s of times with a small pick. But, no metal in the cylinder. Our best guess was it simply disentigrated and exited the exhaust port. We discovered it during a regular maintenance of the engine and had to pull head to check for metal. Luckily we had nothing better to do at the time.

[M61A1MECH]

So here is my story from a long time ago, had a Datsun B210 hatchback, I monkeyed with the air cleaner so much I managed to strip out most of the threads where the stud went that held the air filter in place. Being young and stupid, I just took some all thread rod (probably not the right thread as metric all thread was scarce back in the day) and threaded it into the mount hole in the carb, secured it with a nut and lock washer, good to go, stayed like that for a number of years. One morning after my commute from work the night before, the car ran terrible, like it was running on 3 cylinders. Well it was, I pulled the air cleaner and found the rod out of the hole in the carb, the nut was in place, but the lock washer was gone, pulled head and found the lock washer neatly trapped under both the intake and exhaust valves, what are the chances? Like above the top of the piston and inside the head were all dinged up. Fixed it and she ran like a top for many thousands of miles after that.

 

Sorry did not mean to hijack the thread, but I had not thought about that adventure in a long time.

[YamahaLarry]

So here is my story from a long time ago, had a Datsun B210 hatchback, I monkeyed with the air cleaner so much I managed to strip out most of the threads where the stud went that held the air filter in place. Being young and stupid, I just took some all thread rod (probably not the right thread as metric all thread was scarce back in the day) and threaded it into the mount hole in the carb, secured it with a nut and lock washer, good to go, stayed like that for a number of years. One morning after my commute from work the night before, the car ran terrible, like it was running on 3 cylinders. Well it was, I pulled the air cleaner and found the rod out of the hole in the carb, the nut was in place, but the lock washer was gone, pulled head and found the lock washer neatly trapped under both the intake and exhaust valves, what are the chances? Like above the top of the piston and inside the head were all dinged up. Fixed it and she ran like a top for many thousands of miles after that.

 

Sorry did not mean to hijack the thread, but I had not thought about that adventure in a long time.

 

Nice story. You will have to throw more than a washer in a Datsun's engine cylinder to put it out of commission. The little truck they had back in teh 70s and early 80s was the toughest little vehicle on the road.

[Patch]

So here is my story from a long time ago, had a Datsun B210 hatchback, I monkeyed with the air cleaner so much I managed to strip out most of the threads where the stud went that held the air filter in place. Being young and stupid, I just took some all thread rod (probably not the right thread as metric all thread was scarce back in the day) and threaded it into the mount hole in the carb, secured it with a nut and lock washer, good to go, stayed like that for a number of years. One morning after my commute from work the night before, the car ran terrible, like it was running on 3 cylinders. Well it was, I pulled the air cleaner and found the rod out of the hole in the carb, the nut was in place, but the lock washer was gone, pulled head and found the lock washer neatly trapped under both the intake and exhaust valves, what are the chances? Like above the top of the piston and inside the head were all dinged up. Fixed it and she ran like a top for many thousands of miles after that.

 

Sorry did not mean to hijack the thread, but I had not thought about that adventure in a long time.

 

Certainly fluky that it nearly made it out;) This would have happen during the most turbulent moment and during the valve overlap, which is a very brief segment in crank timing.

[camos]

This plug allowed for compression leakage as seen on the bottom surface of this spark plug nut. The resulting leakage would of course lower combustion temperatures increasing carbon buildup in that one jug and is evident on the plug threads .

I think the carbon buildup on the threads would most likely be from leakage around the threads. Even the resistor had a coating of carbon. I mentioned in the original post about the brass insert in the cap being ovaled. My guess is the wear was from the plug flopping from side to side by combustion pressures.

 

Also, as I have previously mentioned in a couple of posts, I thought there was a bit of a valve tick coming from the front left of the engine. Turns out that tick was probably the plug flopping back and forth because the sound is now gone.

 

So far so good, the engine is running very well at this time.