[Mustang508]

Hi wanting to know if anybody else with 748/916 etc has seen the type of crack in between the inlet valves as per the pic?

cheers
Clive

 

[belter]

no.

 

[Namor]

No, and was work performed on those heads? Porting, valve seats replaced, etc?

 

[ducvet]

Not common. I bet they have a history to break there.

 

[xracer]

Loo

No, and was work performed on those heads? Porting, valve seats replaced, etc?

Look at the machined surfaces in the combustion bowl Johnathan. All the voids where they have been welded showing. And the squish area, even though it looks to ya e been surfaced has what looks like to be a debris field.
OP, give us some history. And no, don’t run it.

 

[Namor]

I agree, but asked anyway b/c the ports look smoother than my memory tells me.

 

[xracer]

I agree, but asked anyway b/c the ports look smoother than my memory tells me.

Your memory is correct. Also notice the blast media between the guides.

 

[Mustang508]

Hi Guys
thanks for responses. I bought the bike at 6k miles, off a guy who brought it with from UK. I have never ridden it on the road, only raced it. Completely standard and as far as I'm aware motor has never been touched, till I opened it up to go the 853 route. But my rebuild has stalled as once I had the heads vapor blasted, saw that both heads had cracks as per pic almost identical, hence me asking if anyone else had seen this kind of crack.
I have had two different opinions from engine repair guys 1. its fine, seats are lipped so wont fall out, put it back together and carry on racing 2. get it repaired or replace the heads as at some point the seats could come out and.......
So about to have both heads repaired as I would prefer my heads than some unknown 2nd hand heads of the web somewhere.
cheers
Clive