KTM uses nikasil coating for the cylinder (hard wearing). No need to add the cross pattern for the cylinder.

 

Its interesting that your piston has almost no carbon on the surface. This tells me the previous owner had recently replaced the piston. Do you have the oem service manual ? If not you need to get one. The s/m calls out the piston and cylinder working limits. I suggest you take your cylinder to a shop and have them precision measure the bore. Your best course of action should be to buy a new oem piston (Wossners are also very good quality) and send both the new piston and cylinder to be re-plated. Then you know for fact you have in spec piston to cylinder clearence.

 

Yes this is the dream scenario. However impossible in the country I live in, Indonesia. I cannot even find a place to measure the bore, let alone plate the cylinder.

If the cylinder needs plating, my only option would be to buy a new cylinder (about $1800 here)

I can buy the tools myself to measure it. But as for plating. I want to fully assess the condition of the cylinder first.

The marks inside the cylinder are aluminium transfer and can be scrubed off with scotch brite. I have already got 90% off with just a few mins of rubbing. There is some questionable areas where I cannot tell if it has penetrated the nikasil.

My main concern at this stage is: was this piston to big from the beginning.

Its a size D 71.955

You can be assured the person that installed this piston did not measure the bore with a dial bore guage and mikrometer.

And I wonder if that is why we see a fair amount of transfer here.

Will share cylinder pics once I got it scrubed as well as I can.

 

PV & exhaust cleaned up a bit
Will send to ice blast

 

Piston's definitely got a bit scoring on it. Big question is what about the jug?
Can't really tell how bad it is by the pictures above.
What does the cylinder look like around the exhuast port?

 

Found the piston be be size D : 71.955 which is the largest

I wonder if it was too big for the cylinder at the time of installation. And that is possibly why the piston skirt has there marks.

Exhaust pics too. PV still in place for now. Will disassemble and clean up later

 

Current conditions

 

double post, ignore

 

So after reading your other "blink code" thread and this one my strong suggestion is to STOP any further replacing parts are your just running around in circles guessing and wasting money. To answer your question in this thread 90 psi is absolutely a blown top end. Most all the 300's are up around 175 psi with a healthy top end. You FIRST need to disassemble your top end for a close inspection. Also more facts and history on the bike, did you buy this bike new or used ? If used previous owner history ? Did the engine ever run well ?

 

Yes exactly what I'm thinking. Already sourcing new piston kit and a new S3 head.

The compression would explain the engine not running, but the blink codes seems like another problem altogether.

But your right, first step now is a new top end.

The history of the bike is a mystery. Im a New Zealander living in Bali, Indonesia. Bikes like this are hard to come by, and it was sold to me from a dealer.
It was deposit paid before delivery. Only after receiving it did I start to discover all the issues.

The bike worked fine on arrival besides the TPS code showing. I immediately dumped out the gear oil and found water in it. Changed the water pump seal and gasket.

On a ride the other day, it just died in me. Since then I have all the above problems.

Only yesterday did u finally get a compression tester and got that identified. So thanks for confirming that for me. I will immediately proceed with top end.

I will measure the bore and get the appropriate piston size within tolerance. While it's open I'm thinking to add the AA S3 head too. And then add the GET ECU. This should help with trouble shooting anymore errors too.

 

Most shop manuals show 150psi as a cutoff for rebuild.
Honda: 153 - 187
Ducati: 150 - ???
Kawi: 150 - 228

So to read the abstract in the book, the duc shows in caps POOR next to 150. Therefore under 150 says to rebuild top end. Add the high and low, divide by 2 and this shows the blueprinted running number of say 170 is the ideal compression.

So 90 is well off the running comp.

 

I'm thinking 90 PSI would hardly start and run.
You can use select fit base gaskets to adjust squish and compression slightly or simply pop for high compression cylinder head. PV adjustment would be required for best result. See Slavens Racing video for correct adjustment instructions.