Head

[Calum]

@killersbeez Yes mate. Clean head.

What size is the piston on the 4FU?

[Killersbeez]

It's standart bore, it is in pristine condition, not oval just the scores.

[Darty]

Try and get the 4FU fixed, they are Nicasil plated bores, so yes it's expensive to repair the cylinder wall regardless, but I believe the transfer porting is better than a 3MB.

[Calum]

@darty I reckon they are too bud.

[declan]

@calum you mention head pitting what caused this and this leads to poor performance?

[Calum]

@declan Detonation can cause this, this happens when the fueling isn't set up properly, causing the fuel to ignite before the piston reaches TDC, in other words without the spark plug igniting. This causes masses of problems as the force of the piston going up is met with the force of the explosion. Destroys bearings and pits the head.

A piston failure or debris will also cause pitting. But for tuners it's usually detonation.

[Jens Eskildsen]

Are the barrels really plated? Which models is that? Could have sworn than mine was steel lined.

[Calum]

@jens-eskildsen The 4FU's are nikasil plated.

But it's possible someone fitted a steel liner to the bore, since they can be rebored. PJME offer this service.

[Jens Eskildsen]

Argh, roger, mine is a different model then, havent actually checked which one tho'

[Killersbeez]

Got this in the mail yesterday, pumped to get it on the bike when the domed piston comes. TBH it looks like it hasn't even been run lol