Holy Exhaust Port

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brxpb

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I was about to put my header pipe back on this afternoon, I had a quick look inside with a torch and this is what I saw,
I had the head off at easter so I know it wasn't there then, and it hasn't had a massive amount of use this summer, have any of you seen this before?
My first thought is that an ambitous amount of the port floor may have been removed in the past, and it's suddenly given in, or perhaps a bubble during the casting process has worn through, I don't think ports should wear, should they?
I thought of pretending I hadn't seen it, (this is my default thought when my Norton is involved).
Would you carry on using it until winter is here?
Would it be repairable by ally welding and grinding back?
I couldn't tell anything on it's last outing, no smoke leaks or likewise, and I think the hole would have a long way to go before it showed on the other side.
Forgive the images, I was an image virgin untill today.




Holy Exhaust Port


Holy Exhaust Port
 
I think I see a hole.....its difficult to be sure what is going on.....

If you poke a piece of wire in there, does it appear somewhere else?

If it was running recently and that hole is open, you would have known......
 
brxpb said:
I was about to put my header pipe back on this afternoon, I had a quick look inside with a torch and this is what I saw,
I had the head off at easter so I know it wasn't there then, and it hasn't had a massive amount of use this summer, have any of you seen this before?
My first thought is that an ambitous amount of the port floor may have been removed in the past, and it's suddenly given in, or perhaps a bubble during the casting process has worn through, I don't think ports should wear, should they?
I thought of pretending I hadn't seen it, (this is my default thought when my Norton is involved).
Would you carry on using it until winter is here?
Would it be repairable by ally welding and grinding back?
I couldn't tell anything on it's last outing, no smoke leaks or likewise, and I think the hole would have a long way to go before it showed on the other side.
Forgive the images, I was an image virgin untill today.
Click to expand...

As you are in the North Wales, check out this outfit: http://www.camcoat.com/main/

They apply a thermal barrier coating to the inside of exhaust ports designed to stop the head soaking up excess heat. The coating is quite thick and applied by brush I think (looking at the jo they did on mine). It may well be that their process could seal that hole and prevent any further similar issue. It is not expensive, but it does require the head removal.
 
Its a blow hole...the same as whales have..proberbly the crater is just a crater...no passage way. porus cratrus Nortunus :lol:
 
John, why do you think it would have just appeared this summer, I've had the head off plenty in the past and it's been fine, do you think BP could be putting sand in their petrol?? :)
 
Could have been a sand ball ,thats got losse and blown out..whales suffer badly..then a good blow on bingo! its out. prob in there for many seasons :?:
Unless you think is a mini sink hole :lol:



brxpb said:
John, why do you think it would have just appeared this summer, I've had the head off plenty in the past and it's been fine, do you think BP could be putting sand in their petrol?? :)
Click to expand...
 
Yes, the head studs were helicoiled, and also by N***IL so probability is they would have drilled too deep, but that was 20 years ago.
This wasn't there at Easter, and I know it looks round with clean edges like a pilot hole but that was me poking around with wire this afternoon that has made it look like that. Is it a possibility that all those years ago they've drilled so deep and left a spot on the port floor of almost tin foil thickness that has eventually give up. Ludwig, is that roughly where the head stud hole would appear if you were to drill right through, what would be the best way to fill it?
 
No, it's a combat head.

Fast Eddie, thanks for that pointer, I looked them up and it now looks like I'll be several hundred quid lighter by next riding season!!
 
Thank the Lord! had it been the start of a sink hole the whole head may have fell into it...sorry for my zane :oops: if it just a pilot hole ..no problems..i bet some one saw the break though and filled it..then the filler shrunk and got blown out?
 
brxpb said:
Yes, the head studs were helicoiled, and also by N***IL so probability is they would have drilled too deep, but that was 20 years ago.
This wasn't there at Easter, and I know it looks round with clean edges like a pilot hole but that was me poking around with wire this afternoon that has made it look like that. Is it a possibility that all those years ago they've drilled so deep and left a spot on the port floor of almost tin foil thickness that has eventually give up. Ludwig, is that roughly where the head stud hole would appear if you were to drill right through, what would be the best way to fill it?
Click to expand...

Perhaps the accidental break through was filled with some Liquid Steel or the like..., or maybe a tiny plug pressed in which, after many years disintegrated/ejected?
 
I measured that head stud hole (on a 750) at 18.8 mm deep.
That is getting quite close to the exhaust port floor.
 
Fast Eddie, yes £20 both ports, and then there's my other bikes then there's the piston coatings then the headers etc. :D Tis an illness, spending money on motorbikes.
Anyone remember the movie Brewster's Millions, all he needed to do was buy a Norton Commando!!
 
brxpb said:
Fast Eddie, yes £20 both ports, and then there's my other bikes then there's the piston coatings then the headers etc. :D Tis an illness, spending money on motorbikes.
Anyone remember the movie Brewster's Millions, all he needed to do was buy a Norton Commando!!
Click to expand...
Yeah fair point! Tis good stuff though, I started using them on racers that had a propensity for seizing! On my Commando I had the piston crowns, valve faces and exhaust ports thermal barrier coated. And the piston skirts and valve stems anti friction coated.
But this stuff was cheap compared to everything else... You don't have to tell me about spending money on bloody motorbikes !!
 
Boats are the same way, right :) a hole in the water where all your money goes. The happiest days are the day you bought it and the day you sold it :D
 
Without removing the head at the moment, the best filler in this environment would be what?
 
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