New Head Needed?

[frenchie]

After the right hand cylinder tried to burn a hole in the piston which was probably down to the main jets being too small and starting on the rebuild. On looking at the head I am also a bit concerned to it's condition.

There is evidence of a previous event on the same side with marks to the head as shown in the picture, but also, I'm not sure if the head has been skimmed at some point.

Should there be a "lip" in the casting between the gasket face and the concave part where detonation occurs.

Would a head in this condition (skimmed) produce higher compression, as I am told it would, and therefore increase the chances of this happening again?

Or should I start looking for as new head??

[47x]

a skimmed head will make higher compression,you could have them detonation marks machined out,i have seen worse,get a engineer to look at it first before you throw it.check the surface of the barrels to,see if there warped.hth.

[bigal1]

a bit of filla be as good as new ........new head req.. u can get that fixed but by the time you have paid out for that it would be cheaper to get a new one ..or used

[arrow]

Thats not detonation marks, those marks are from a previous blow up. It will run just fine if left like that, providing there are no high spots, the low spots will not cause a problem.

[cb250g5]

They look like big end rollers to me. I'd live with it.

[flames]

i have a head with a dome a hole lot worse than that dude.it has also been skimmed.if i were you,i would fit that back on the engine with the used gaskets in place for time being,torque it down then use the bent bit of sloder technique to measure the squish.if less than 0.8mm,tho i would prefer to sit at not much less than 1mm,you could try 2 base gaskets,if this wont bring the gap up high enough,try 2 base gaskets with a thin spacer between them.this is how i run mine and it goes like stonk!!! well,it did,still building rest of bike round it at mo,but still puts front in air on the powerband.

[Norbo]

The head has been skimmed but ive seen worse as far as marks in the dome is concerend.

[bryan]

get it off to someone like Bob Farnham or Mick Abbey, they should be able to machine it back to standard volume with narrower than the standard (over 2mm) squish for less than you can but another 350 head for. Look at about £60ish for the machining and about £85+ for another head.

[db8888]

Hi it would be worth checking the crank has not twisted on the centre shaft due to the problem being on the right hand cylinder the ignition timing is always ok on the left side due to the woodruff key and flywheel are on the left side..........