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]

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....

 

[TGM_OFFROAD]

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

 

[hannesd]

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.

 

[SS109]

Yeah, the engine doesn't sound right in that video. Sounds lean to me. I would definitely be checking for air leaks. Make sure the exhaust pipe is sealed up well to the cylinder as air can be introduced there as well.

 

[Gasser Nate]

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!

 

[gg3]

Bit of a mystery?
48 pilot- Rich
A/S 1.0-Rich
NECH needle on the 5th position- Rich
170 main-ok
Sounds real lean.It should have eaten that hill climb with ease.
Agree with ss109,air leak or really low float level?
Sorry no help really.

 

[Doc Brown]

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

 

[Jakobi]

Even at 44 seconds on the downhill she sounds likes shes lean with erratic idle. Like others said.. check your engine for air leaks.

Also take the time to cc the trapped volume.. especially if you've had a failure. Double check timing.. and I wouldn't bother with iridium plugs in a 2 banger.

 

[TGM_OFFROAD]

I got my cylinder and piston today so I am going to start the rebuild process and then pressure test.

I pulled the flywheel and everything looks good visually.

I think part of my problem is I don't know what it is "supposed to sound like" other than what I hear on videos and that is always hard to judge. This is my first 300 and first 2 stroke since my rm125 in 1999.

Should have pressure test done in about 2 hours or so.

 

[Anders]

I got my cylinder and piston today so I am going to start the rebuild process and then pressure test.

...

Should have pressure test done in about 2 hours or so.

We will watch this space...

 

[swazi_matt]

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

 

[gg3]

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

So you don't need to take the skin off your knuckles,scratch your pipe or hit yourself in the face with pliers to remove them?

 

[TGM_OFFROAD]

Put it back together and it dropped from 7 psi to 5psi in 3 minutes. I found bubbles at the base gasket which is weird because it is brand new. Its a paper gasket, would you recommend using a sealant on it?

 

[TGM_OFFROAD]

I used some ultra copper sealant on the base gasket and now it is holding 6 psi for 16 min now.

 

[Zman]

Yeah, the engine doesn't sound right in that video. Sounds lean to me. I would definitely be checking for air leaks. Make sure the exhaust pipe is sealed up well to the cylinder as air can be introduced there as well.

It sounds lean to me as well at high rpms. That can be a problem even with 100 octane fuel.

Sorry I responded to page one of this thread.

 

[TGM_OFFROAD]

It sounds lean to me as well at high rpms. That can be a problem even with 100 octane fuel.

Sorry I responded to page one of this thread.

The weird thing was with a 170 it would get on the pipe. A 172 would cause it to sputter like it was too rich. I think my base gasket was the air leak, I have it sealed up now it would seem. I am going to test it again in the morning and hopefully take it out to the local park to do a test ride.