Is there an engine condition that cause plug failure?

[38racing]

Not fouling. Some may remember my saga on the fire damaged zturn which i restored. Has tecumseh vtwin. Cut with it once this season. Ran fine. Got it out today and noticed a miss. Did a balance test and found it faltered more when right was grounded with little change when left was grounded. I swapped plugs side to side. Now little change on grounding right and engine stops when grounding left. My conclusion is now bad right plug. I pulled it and it was the e3.18. Other side happens to be br6es. I had another e3.18 in my plug tray so I installed it and it ran fine again and did all my cutting. The reason the plugs did not match was from previous time when I was sure I had a bad brand new br6es. Both plugs are shown as crosses to the rn4c spec for this engine. I expect to stick with ngk . would too hot a range plug lead to failure. Should I try slightly colder plug. Br 7 or 8?

[KE4AVB]

Plugs can fail at any time for no apparent reason here. NGK are not known for failures but they do fail. The NGK that fails here regularly is the CMR6H(7H) 10mm plugs. But some reason this year I have seen a lot plug failure here. No brand in particular

I just got in a Kohler SV590-3220 (2013) with no start condition and was running fine until near the end of the cut when the engine went into run away. He shut it down and later went to move it when it would not start.

What I found so far is something I haven't seen in 20 yrs. Both throttle plate screws went AWOL and crushed the plug gap saving the engine in one sense. I still got the pull the head to see what other damage was done and if I can find both screws. It is a shame that Kohler don't want to sell the carburetor parts if you go by the IPL but I do have the carburetor tech manual and it appears I can still get the parts I am looking for. I just not paying $4 apiece for the screws so sourcing the M3-0.5 brass screws otherwise. Now of course I need a couple bushings made to repair the throttle shaft holes after I ream then round again. Either the customer is getting a new carburetor as he is in rush.

[38racing]

A friend brought his rider that i repowered a couple years agi. Briggs ohv is well used. It's using oil. My daughter's did that due to start of head gasket failure. He then mentioned that it doesn't idle down. Quick check show linkage and governor ok. I'm hoping it's not governor internals. I also thought of throttle plate screws.

[KE4AVB]

A friend brought his rider that i repowered a couple years agi. Briggs ohv is well used. It's using oil. My daughter's did that due to start of head gasket failure. He then mentioned that it doesn't idle down. Quick check show linkage and governor ok. I'm hoping it's not governor internals. I also thought of throttle plate screws.

Yes oil usage can be the head gasket if it is 21, 28, 31, or 33 CI OHV Intek engine.

Just a couple weeks ago I had to replace the governor and camshaft then the head gasket on a Briggs 310000 series. The ACR failed bending the governor which proceeded to wear the nylon teeth down to nubs. Of course the governor failure afterwards. The head was the second time it blew. This time the cylinder was warped .005" in the area of the blown area.

Side here you might need to Heli coil one or more of oil pan screw holes. The above engine I had to do two more of them as they pull through at the new torque specs. Last year I did one of the same engine so I have Heli Coil tools and coils already on hand. You will the near 1/2" ones or better yet the 5/8" long coils.

Another customer is having a really bad time with his mowers. First take the NZTR steering out, 3 day after I got that fixed he runs over a tree stump. Well I got that damage fixed and return the mower Saturday. Then pickup his other where he took out the NZTR steering Saturday. Well he showed back up this morning with again deck problems (I haven't went to look at it yet). But he is also describing that engine is trying to lockup so he probably the ACR failure on that mower and the mower I got Saturday also has the ACR failure.

Boy I wish this month of Mondays will end soon or I will lose my last nerve. I only got one nerve left and this week might just break it. I wish the customer this morning would have waited until I at least had finished my first pot coffee.

[Arkie]

Yep, bad spark plug. Champion is usually to ones that quit me all at once, especially the little ones used in chainsaws and 3.5-5 Hp engine.

About spark plugs.

I have a old briggs l-head 20 hp twin. Really a nice looking clean engine on a MTD tractor mower. I knew if I killed the engine after it had been setting for awhile when hot it would most likely not re-start. Choke, no choke, did not appear to be gas related.

Engine would start up fast cold and could operate the engine for about 30 min to hour, kill engine and no re-start, fast cranking. Long story short could install new spark plugs of the correct type and gap and it would be ok for awhile and require NEW plugs again after these had run for few days, then back to square one, new set again. Just replacing one would not get a go.
I could install the removed plugs into another engine and get a good run and start.
Could see what appeared to be a good spark when cranking the engine.

I finally decided that I was going to fix that engine or scrape it for parts. It would not start right when I needed it to go back to work. Kinda acted like it wanted to be on unemployment or disability social security and I do not allow slackers hanging out close to me.
I check the valve lash as right on, did a cylinder balance test as good, engine would idle really good at slow rpms and ok at fast rpms,
I installed a new clone coil, type coil that has both high tension leads out of the same coil body and the engine has been ok ever since. Will now even run and start ok with the type of plugs I do not like, CHAMPION.

Sometimes a guy has too just start swapping parts, especially when electronic magnetos are in the loop.

[38racing]

Way way back when I was a teenager the family had a 1961 Mercury comet 6 cylinder. It would start to miss. I would take it to my cousin in law who was a Dodge mechanic. He'd narrow it down to which plug had failed, replace it, and I was good until the next failure.

[wristpin]

What I found so far is something I haven't seen in 20 yrs. Both throttle plate screws went AWOL and crushed the plug

I had a customer who’s business was repointing old brickwork ( grinding out the mortar between the bricks and applying new mortar). He ran six Generac generators powering angle grinders to grind out the mortar. Those machines took a pasting with minimum maintenance. In one week we had one in not responding to the throttle/ governor. Throttle plate screw AWOL and the plate propped up in the Venturi. No sign of the screw and no engine damage. A week later one with no compression - throttle plate screw jammed under the inlet valve; no other engine damage. A recall of the remaining machines found no more loose screws but we found a method of inserting a punch into the venturi to support the screw head with another to peen over the end of the screw protruding from the spindle. End of issue !