Gday Nsrworld.
I'm new to the forum world in general. I'm from Sydney, Australia.
I can ususally look at other peoples problems to generally fix mine.
I own a NC30 as my daily ride and I acquired a Mc21 Dry clutch at the beginning of the year that was out of rego and hadn't been run for 6 months. So i thought I would "attempt" to turn it into a track bike.
So I got a couple of Top end rebuilds. Having never done one i gave it a go anyway. Pulled out the engine for good measure and went ahead and did them. Cleaned the Carbs and did the airbox mod also rejetted.
Took it for a spin around the block a few times seemed like everything was goood.
Got my track day sorted put on some fresh tyres as the others looked a bit crumbly.
I think it was first flying lap going down the main straight it Seized with a puff of smoke and a locking up back wheel, pretty sketchy.
Was it over heating you ask?
Honestly I have no idea I was like an excitable school boy I didn't even look at the gauge. Yeah I learn from my mistakes and now thats all i will look at.
I pulled out the spark plug and it was bad. I mean i'm far from any sort of expert but the sparking tip was non-existent Matt@tyga said its detonating.
So i'm now in the process of fixing it.
I pulled out the engine again and it looks like the cylinder has a couple of scratches down it only one that i can feel with my fingernail I got all the piston melt off with Hydro chloric acid.
I have taken photos of the damaged cylinder, piston and cylinder head. Also I took a photo of what I assumed to be bluing but I don't know what that is.
I'm waiting to purchase the appropriate tools to use the guide on here to open the engine up to look for debris.
I'm not 100 percent certain of how to upload photos.
I usually annoy Matt with my problems.
So I thought I'll try this forum thing.
Sorry for the whole non- technical language and my first post being a problem.
http://imgur.com/N8sTD,ye9CE,fMN5z,7WtqP,SDOt4
If this isn't the right way to add pics can someone let me know the best way to do it.
Cheers everyone
Chris

Welcome and sorry we are meeting you under these circumstances. What modifications or non standard components have you got on your bike? Forum rules state we can't talk about.jetting but a stock standard bike would not normally result in that much damage.


Was this out at eastern creek?

I only saw the image of the head, I would agree with the diagnosis of detonation. What fuel and plugs were you running?

Gday mate,
Thanks for the reply.
Yeah I was at Eastern creek.
Its pretty much stock.
I cut open the airbox, and re wired the pgm for those extra ponies and jetted to suit from a very reliable source.
Whatever the standard plugs are the br9s and 95 unleaded petrol.
So i'm not sure what the pre seizure cause was.
I'm going to junk the oil pump when i put it back together.
Do the rest of the photos work?
Cheers

Get yourself a exhaust gas temperature sensor . It will show you if your jetting is out and help prevent damage . The pitting I see looks more like damage from a piece of ring , hard luck mate

Having had a long break from two strokes and forgetting everything before doing my own NSR rebuild, I thoroughly recommend you become a member here.

from my own build (you can look it up here on this forum once you are a member) I would recommend removing the oil pump and going for premix - especially for a track only bike.

Then when you have it all together again, print the tuning guide - I got my bike pretty well spot on for jetting before getting to the track just following the guide on the back deck (I left it a touch rich).

So after all that I guess I want to know is the cylinder and cylinder head useable or do i have to look into other options???
My first bike was an NSR150sp but it was very reliable. So i didnt really need to do any top-end rebuilds or real maintenace just fill oil and go.
I'm just learning about all this stuff. I would rather do it all myself as when i go into some of the local bike shops they correct me when I say its a nsr250 as they arent that common over here. Another shop doesnt work on import bikes. And i like fixing it.
So any info on anything will go into my increasing knowledge.
I have taken a couple of photos of NSR's and other bikes on my site. My Mc21 is the colourful garage shot. Also the smokey Nsr150sp was my old bike and the Repsol is my Nc30 i painted although the right side is now destroyed as I came off the same day I seized the MC21. Yeah was a great day.
anywho
www.dixonandmoore.com

Cheers

I can't tell about the cylinder but the cylinder head can be reused. Not perfect but not vary bad either.

It looks like you have a major air leak in there.
Considering the bike being sitting for a while, the crank may need new seals.
_________________
2t-racelab.com

It doesn't look like detonation to me. Detonation looks like sandblasting with coarse sand. The only thing I see is some hammering, from some kind of object. A piece of ring or piece of spark plug.
Below is a picture of a head with detonation. Its difficult to see on the photo but some material is actually missing. Its been corroded away by the explosions. In the marked area there is a groove as if it was etched out by acid.


_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

Certainly an object caused the marks on the cylinder head right in front of the spark plug.

But I reckon all started from detonation judging from the rest of the cylinder head and also the melted piston (looks like there is almost a hole in there).
_________________
2t-racelab.com

Thanks for all the reply's.
From what I can gather from all this info.
Seems that it was detonating to the point that the spark plug tip came off and got smashed into the cylinder head.
And melted and all bad things happened from there.
I'm unsure about the cylinder condition I've emailed Matt for his expert photo judging skills.
Then I gotta get all the tools to open it up. (a first time for me).
Before I do the rebuild i'll definately become a supporter of the site.
Just gotta purchase all the bits and bobs.
Hopefully I can have some more success.
But I definately learn from my mistakes.
I'll keep you al updated with how its all going.
Thanks again
Chris

Do you have a list of tools that you need ?
Torque wrench
Feeler gauges
Micrometer
300mmx300mm plate glass
12MM ring spanner

I didn't see the piston picture but it confirms that it wasn't detonation but probably preignition. See below what Wikipedia says.
Detonation will happen along the outer rim of the piston/head whereas preignition happens under f.ex. a too hot sparkplug.
The sparkplug melting also confirms this.
Which sparkplug and which type of fuel did you use ?

You can draw your own conclusions, but if you rebuild the engine and put in a wrong sparkplug, don't say I didn't tell you

Detonation
When unburned fuel/air mixture beyond the boundary of the flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur. Detonation is characterized by an instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front. A local shockwave is created around each pocket and the cylinder pressure may rise sharply beyond its design limits.
Preignition
Pre-ignition (or preignition) in a spark-ignition engine is a technically different phenomenon from engine knocking, and describes the event wherein the air/fuel mixture in the cylinder ignites before the spark plug fires. Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chamber, a spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events....................pre-ignition can quickly melt or burn pistons since the power generated by other still functioning pistons will force the overheated ones along no matter how early the mix pre-ignites.

_________________
Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

What wires do you splice ? Stock nsr's should not break that easily unless something major is out of sync .
If you did the gear splice onto the wrong wire it will advance the timing too much and contribute to the damage .\
Any chance you can load more pics as all i see is a head ?

Gday
Neal: tool wise I need the
Clutch Holding Tool Flywheel Holder / Pin Tool TYGA Flywheel Puller/RC Valve Remover Combo Tool.
Also I did wire splice not to the gear just the power one if that makes sense.
(as in there was two ways one to the gear or one to the main power)
I think with the pictures, when you open that link it should say first picture second pictue and so on but i will try attatch them too.

pbekkerh: I'm just running standard 95 fuel and the reccomended br9's. I will take a picture of the spark plug tommorow for you. It doesnt look melted it looks corroded. There were different plugs in there when I got the bike I'll have to double check what was in there. But I just replaced them with the recommended ones.

[img]http://imgur.com/ye9CE[/img]

[img]http://imgur.com/fMN5z[/img]

[img]http://imgur.com/7WtqP[/img]

http://imgur.com/a/zzMD0


Last edited by knoxy_7 on Sat Oct 06, 2012 11:42 am; edited 2 times in total

2Tracelab wrote:Certainly an object caused the marks on the cylinder head right in front of the spark plug.

But I reckon all started from detonation judging from the rest of the cylinder head and also the melted piston (looks like there is almost a hole in there).

Yeah I was sooo shocked when I took off the cylinder and saw this:

http://imgur.com/a/zzMD0