paulincayman
Hero member
- Location
- Cayman Islands
My head hurts
- Thread starter paulincayman
- Start date
Andy
Hero member
- Location
- Auckland, roughly
Interesting. I never really understood how much renovation could be done on a head until I joined this forum
paulincayman
Hero member
- Location
- Cayman Islands
Yes, And I never realized how many things could need renovating one just one bike..
Paul's head just one of a few all alloy 1977-78 heads we are doing at the moment, all cracked everywhere
3 are going to be the new diesel versions
10th August PL, IM, CB, one other
3 are going to be the new diesel versions
10th August PL, IM, CB, one other
Laverda SF
Hero member
Shit - A load of bad fuel mix's ;o(
piranha-bro2
Hero member
- Location
- Melbourne
So are cast skull heads a better option? Or did they also suffer from some sort of weakness in triples? 750 heads seem to fare a lot better - thank fuk!!
motoddrob
Hero member
- Location
- S/W Australia
I have a cast skull head that after spending over 2k on its now only good as a door stop
So it's not only ally heads that have problems.
So it's not only ally heads that have problems.
piranha-bro2
Hero member
- Location
- Melbourne
Is there a known reason why this is such a prob with triple heads? How did the factory resolve the issue in later models? Or didn't they?
paulincayman
Hero member
- Location
- Cayman Islands
Not mine ..more than enough as it is..
Although the skulled heads have a few issues, most problems arise from over-enthusiastic porting.
The early skulls without seat inserts generally hold up well, it's the later type that had factory seat inserts that are most likely to crack, usually from insert to plug hole. Many heads with retro-fitted inserts show cracks, possibly from too much overlap when fitting, usually from insert to combustion chamber edge. As the later (120°) skulls with factory inserts have a shallower combustion chamber, I tend to think these were also reinforced around the insert area, I have yet to see one of these cracked between insert and plug. But, there's no way of confirming without cutting up a couple of heads to compare skull thicknesses.
Amateur porters often go to town and remove far too much metal from all the wrong places, leaving not enough material to support an insert, should this need to be retro-fitted.
No problem with fitting a second plug to skulled heads, just not much point in it... maybe if you increase the bore to 90+mm you might find an advantage. As it is, an 80mm bore is small enough for a quick burn of the intake charge with a single plug, no significant shift of ignition timing would be possible.
piet
The early skulls without seat inserts generally hold up well, it's the later type that had factory seat inserts that are most likely to crack, usually from insert to plug hole. Many heads with retro-fitted inserts show cracks, possibly from too much overlap when fitting, usually from insert to combustion chamber edge. As the later (120°) skulls with factory inserts have a shallower combustion chamber, I tend to think these were also reinforced around the insert area, I have yet to see one of these cracked between insert and plug. But, there's no way of confirming without cutting up a couple of heads to compare skull thicknesses.
Amateur porters often go to town and remove far too much metal from all the wrong places, leaving not enough material to support an insert, should this need to be retro-fitted.
No problem with fitting a second plug to skulled heads, just not much point in it... maybe if you increase the bore to 90+mm you might find an advantage. As it is, an 80mm bore is small enough for a quick burn of the intake charge with a single plug, no significant shift of ignition timing would be possible.
piet