Detonation probs.

[Lozza]

There appears to be no hints of detonation there.

[Moto]

 What model + size KTM is it?  We can then tell you what dimension " X " you should have.Once you have measured this is and know it is correct it can be eliminated from being your problem. 

[evo550]

'09 250 2t.

There appears to be no hints of detonation there.

Yeah,
I was suprised at how clean it was, considering it's up to 50 odd hrs running Castrol R30, which has a bit of a reputation for excessive carbon build up.
I think I will raise the needle a clip or two and replace the base gasket with a genuine item as a first step.
Thanks for your help guys, will keep you posted, racing next w/end.

[Lozza]

'09 250 2t.

There appears to be no hints of detonation there.

Yeah,
I was suprised at how clean it was, considering it's up to 50 odd hrs running Castrol R30, which has a bit of a reputation for excessive carbon build up.
I think I will raise the needle a clip or two and replace the base gasket with a genuine item as a first step.
Thanks for your help guys, will keep you posted, racing next w/end.

I think the 'reputation' is a load of shite

[oz555ktm]

  That Looks Like a wisco Piston?

   Mahle (KTM ) Piston are  flater on the top of the piston .
   Wisco  seam to be allways Higher .
 
   I have found that some time the Crown could be .4 of a mm Higher ..

    So you need to all way check the X factor .

[evo550]

Piston is Vertex, OEM.

[Slakewell]

If all you have done is changed the rings and replaced the base casket and it was running fine before. You have raised the compression.
You need to measure the thickness of the old casket and replace with one the same.
You could try BP 100 fuel and see if that stops it.

[Lozza]

..............but where is the deto? Plug looks fine (even the burnback looks good)and there is no evidence on the head and piston??? There is  something at around 8 o'clock on the head but it does not look like detonation.

p.s. You have bad 'pie cut' which means the head/cylinder mating is not straight.

[evo550]

What are the signs of Deto?
What's a pie cut ?

[Lozza]

What are the signs of Deto?
What's a pie cut ?

On the head at about 8 o'clock there are some marks without looking at it closely .I can't make it out from the pic. 'Pie Cut'.........I dunno either I just said that to make myself seem intelligent/scientific    But study the burn pattern closely

[evo550]

Bit of a difference in thickness, the genuine one being the thicker of the two.
Although KTM list 4 different sizes, the thinnest being .25mm
Is it possible to run higher compression and jet to suit.




There is something very Ji about this thread

[CamP]

The thinner cometic gasket has raised your compression enough to ping on your current fuel. It will probably run well on better gas, but if you don't want to switch fuels just reinstall a 0.8mm base gasket.     

[Lozza]

My calculation says you have `1cc less due to the gasket, I still can't see that causing problems. But I'll go back to the piston again and I still don't see any evidence of deto on the crown or the head. Here's a pic of some good deto, you can see the difference in the colour of the crown and the pitting under the plug.

[vmx42]

Hey Lozza,
It might be a giant coincidence [with the ring change] but what about some kind of ignition problem?

Could some high rpm misfire be mistaken for pinging [or pinking for the US members]? A dodgy plug cap or high tension wire?

Thanks
VMX42

[Lozza]

Ignition timing looks perfect according to the plug.