Spark plug insulator around electrode broke off in the motor

[TGM_OFFROAD]

Twice now in a short amount of time I have had the porcelain insulator break off and wreck my top end. Both times were with an NGK iridium plug. Any idea what is causing this? Or has anyone heard of this happening to them? Both instances were with different heads. First the s3 with the high high compression head and second time with an RK tek head. Squish is right around 1.2 on both.

https://youtu.be/_I4NOqaBD_g

[hannesd]

if you've had it before, why didn't you check this time instead of keep riding (back home)? maybe you could have changed spark plug and if you have some tools, quick take the exhaust off and take the bits out?

[Gasser Nate]

Possibly a shitty spark plug socket.

[Doc Brown]

Originally Posted by Gasser Nate

Possibly a shitty spark plug socket.

I can imagine that a socket brakes the insulator above the hexagon, but his porcelain was broken around the electrode.

My personal opinion is, that the engine suffers from detonation. He has several riding videos on YT and I always have the impression that something sounds weird. Detonation can kill spark plugs...
The engine sounds strange in this video too. Long before the plug failed....

[hannesd]

Originally Posted by Doc Brown

I can imagine that a socket brakes the insulator above the hexagon, but his porcelain was broken around the electrode.

My personal opinion is, that the engine suffers from detonation. He has several riding videos on YT and I always have the impression that something sounds weird. Detonation can kill spark plugs...
The engine sounds strange in this video too. Long before the plug failed....

i thought the same... first i was thinking big end or cranck bearings ...

[TGM_OFFROAD]

I am not sure why I am getting detonation. The RK tek head should not be raising the compression ratio that much. I am already running 101 octane fuel. The jetting did seem to have a little lean spot around 1/3 throttle. I will do a pressure test once it is rebuilt to search for a potential air leak.

The jetting I was running at the time was

48 pilot

A/S 1.0

NECH needle on the 5th position ( I bought two needles that are richer on the suzuki chart in hopes I can richen the mixture but keep the same power delivery, I really liked the smoothness of the NECH)

170 main, the main doesnt seem to be an issue since when I go wide open it is fine, the issue seems to be 1/3 to 3/4 throttle at high rpm where I get the lean spot.

Engine mods are
RK Tek head 13.5 to 1 is the supposed ratio per the stamp on the head insert / S3 racing cylinder / House of horsepower exhaust

timing is not adjustable so I don't know how that could be a factor

When I rebuild I am going to back to the GP head that came on the bike when I bought it.

[Gasser Nate]

Originally Posted by Doc Brown

I can imagine that a socket brakes the insulator above the hexagon, but his porcelain was broken around the electrode.

My personal opinion is, that the engine suffers from detonation. He has several riding videos on YT and I always have the impression that something sounds weird. Detonation can kill spark plugs...
The engine sounds strange in this video too. Long before the plug failed....

I have seen them fracture the porcelain all the way through. To be honest I didn?t even watch the video yet, just a quick comment before I went to sleep! 😆

[Doc Brown]

Originally Posted by Gasser Nate

I have seen them fracture the porcelain all the way through. To be honest I didn?t even watch the video yet, just a quick comment before I went to sleep! 😆

Yeah, this can happen, I just have never seen that to be honest.

If it were my bike I'd get rid of the RK head and use the OEM head. Then I'd use the OEM needle, jets and slide plus the exhaust (if available) and the OEM spark plug. During rebuild I'd check:

reeds
rubber flange the carb sits in
flywheel and especially the woodruff key
ignition pick up and if it sits tight
power valve (ease of movement)

Then go for a test ride and see if the engine sounds normal. For me the engine sounds strange in all your videos. You may remember that I asked you on Thumper Talk which camera you use because all other vids I have seen the 300 GG's sound way different. I really admire you for being so patient and not giving up.

Sorry for bending your ears and writing so much, but I need to mention that I don't like it if a needle is used in its lowest or top position. You mentioned that you have your NECH in fifth(!) position and the AS only open 1 turn. For me that indicates that something isn't right. I have jetted quite a few 300 Gasser's and at standard temperature (18 C or 65F) and with either a 40 or 42 pilot jet I never had it at less than 1.5 turns out, most of the time between 1.75 and 2 turns.

Maybe someone can borrow you an identical carb for testing. Unfortunately the US is so far away otherwise I had sent you mine. I can't ride anyway, we are all under quarantine due to Covid virus.

If all the things mentioned above are good and there are no air leaks you can start to play with the carb. Maybe a JD kit (worked for me very well on 3 Gassers) would be worth a try.

Good luck!

Doc

[TGM_OFFROAD]

Originally Posted by hannesd

if you've had it before, why didn't you check this time instead of keep riding (back home)? maybe you could have changed spark plug and if you have some tools, quick take the exhaust off and take the bits out?

Yes I was just riding it back to my truck. I carry tools with me but nothing to take the springs off my expansion chamber

[swazi_matt]

Originally Posted by TGM_OFFROAD

Yes I was just riding it back to my truck. I carry tools with me but nothing to take the springs off my expansion chamber

not going to add to the sparkplug issues, but an easy way to remove the springs is to use a zip tie, just make a big loop and use it as a pull