Spark plug insulator around electrode broke off in the motor
 

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

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?

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....

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

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

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.

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.

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! 😆

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.

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

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.

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.

We will watch this space... :)

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?

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?

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

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.

The leaking base gasket could have been the reason. At least I really hope that.

If you are not sure about the sound due to the fact its your first two stroke I recommend you to do what I did. I asked a two stroke nerd to listen how my bike sounded and he gave me good advice how to detect possible errors in jetting.
Though this was many years ago I am still grateful.

I really keep my fingers crossed for you.

Ok so rebulid is done. Pressure test is good now after some gasket sealer with the base gasket. It held 6psi solid for 10 minutes. Sprayed water all around the base of the cylinder and left side crank seal since I already had the flywheel off and no bubbles.

I reinstalled the stock pipe and my turbine core 2.1 silencer.

I am using the stock head which in my case is the gp head since that was what came on my bike when I bought it used.

Reset my jetting back to stock
42p
A/S 1.5
N1EF needle at #3
175 main jet

Rode around in my parking lot since I was jot able to get to the OHV park today. Had to take my dog to the vet :(

First impressions, pilot is too rich but the needle is slightly lean around 1/3 to 1/2 throttle and main is too rich. It will sputter at WOT.

Here is two videos of cruising around, let me know if that sounds right to you

https://youtu.be/cfMVjM9BCQw

https://youtu.be/vi1GraiXyZY

How do I check timing on this bike? The timing is fixed also so I am not sure how it would get out of adjustment. Even at stock everything it does sound off compared to other bikes I have heard in videos. Could the CDI cause this.

Where was the base gasket leaking? I always use some sealant at the front and back where the cases meet. Did the cases show any signs of leaking on disassembly?

By timing, I was suggesting that the flywheel was retained properly and woodruf key not sheared, etc.

Gotcha, the flywheel and everything looks good. I did have an issue with the woodruff key shearing when I first got the bike due to the flywheel not being properly torqued but I replaced the key, luckily the ktm key is the same dimensions because the gas gas one was not available at the time.

When I pulled the jug the base gasket was damp and torn at the rear. After the rebuild the rear was where the leak was coming from until I reassembled with some sealant.

Went to 1.75 on the a/s and raised the needle 1 position to richen it up. It feels better but still doesnt sound right to me.

https://youtu.be/A-OFq-ObXPk

sounds very rich, but your engine should be warm before judging your jetting.
in the clip it says you have needle at clip #4? why so high/rich?
this is not standard setting.

What temp and altitude are you running at?

So rich.. moister than a wet fart at the moment.

As per my last post, what temps, altitude and humidity are you running at?

Where I live is 15 feet above sea level, where I ride 80% of the time is 500 to 2500 feet. Temp was about 60 F with 70% humidity.

I admit I am puzzled now. It's to rich at WOT and you raise the needle further? Doesn't make sense to me.
Whatever!

Whats wrong with your dog. Hope its not serious :(

Just a urinary tract infection, she is ok.

I raised the needle because it had a lean spot round 1/3 throttle and bogged with quick throttle input and still had some detonation. I put the nech needle on #4 and it felt 100% better than the stock needle but seemed to lean still due to detonation when trying to purposely lug up the little hills I have here. I am getting a hold of a new cdi box to plug in next week just to cross that off the list.

I listened to the videos again.

First two it blubbers down low as they all do. Thats caused by the NE1F which is very rich down low. It sounds much better through the rev range but I am not sure if that hesitation at WOT is caused by an overly rich mixture. I dont know the sound that good....

I don't want to be a pita and sorry if I annoy you but I think you change too many things at a time. From video 2 I had opened the air screw to 2 turns just to see if the blubber down low gets better. If it does not get much better, DROPPING the needle to clip 2 had been my next step. I am pretty sure that could have cured the blubber down low and the hesitation at WOT (if caused by richness).

Cheers
Doc

PS: your idle seems to be too high. Set it as low as possible, accept that it may stall from time to time. I cant judge the third video....

Glad she'll be fine soon. That's good news. I had dogs myself and I know how hard it can be when they suffer.

Could not hear detonation but I trust your words, no doubt. Its very strange that it detonates with the OEM set up. That really puzzles me as this set up is known to be rich. Maybe the problem is ignition related but if the woodruff key is ok and the flywheel hasn't moved on the crank....and the pick up isn't loose.... I have no idea. Has your CDI been updated. I can remember that we had to bring ours to the dealer who updated them. No clue what has changed...

edit: missed that you used the NECH instead of the NE1F. Is the NECH richer than the NECW? Cant find my notes at the mo.

All the videos after the rebuild were still the stock N1EF. I might take it out tomorrow depending on the weather to actually do some testing. The parking lot test is very limiting. I dont feel like jetting in the rain.

I may be over sensitive due to recent events and think I am hearing detonation when I am not. But the times I heard it were off camera I think.

I dont know if the CDI was ever updated, I tried to find out when I got the bike but the closest dealer was 200 miles away and were not helpful. They also have dropped the Gas Gas line at this point. The guy I bought the bike from had a couple 19 CDI left over from the race team and he is going to give me one to see if it helps.

Took another crack at it today and it looks like the morning is going to be clear tomorrow so I am gonna go out for a quick trail ride. I put my jd jetting blue needle back in and it feels pretty good, a little rich still but will know for sure tomorrow when I can actually open her up and clear it out.

Here is how it sounds. Opinions?

https://youtu.be/ec07rdf4-10

Sounds good to me. I'd try the other CDI without changing anything. Swap them a few times and do a short lap if possible. I am really curious if that will change anything.

Its the first time I can say it sounds perfect. At least at all throttle openings you tried. The engine was not fully warmed, I can hear that it slightly hesitates down low but this is absolutely normal and nothing to worry about. It will disappear when engine and exhaust are hot.

When the bike is ridden with cold or not fully warmed engine the pipe stays cool and gets wet from fuel residue. As long as the pipe is wet and oily you'll hear it splutter a bit but that will go away once it is hot and has been revved.

Yes, riding it hard in shorts on wet tarmac isn't a good idea. Hope your neighbours wont be too upset when you ride around their houses numerous times ;) Good Luck!

Once you get the jetting correct you may want to give yourself a little detonation safety margin. You can retard the ignition timing by rotating the stator plate in the same direction that the engine spins. You will get about 1 degree of ignition timing for each 1mm of rotation measured on the circumference (outer diameter) of the stator plate.

That being said, I do not remember if the new bikes allow for ignition timing adjustment.

The 18+ bikes are not adjustable unfortunately