Very nice looking machine.
The article mentions that it is 1200cc. They have used the Terry Prince 92 mm top ends and a standard stroke crank. The output given is 115 HP with 11 to ones and 90 HP with 9 to ones that they are using.
A compression increase from 9 to one to 11 to one on its own wouldn't give that size of power increase, according to all that I have read on that subject. The effect of CR raises alone is well documented with dynomometer testing.
The Wallace Racing CR calculator says that a 90 HP nine to 1 engine will produce 91.95 HP at 11 to one, no other changes.
To obtain the 25 HP output increase mentioned, your Friday night changeover wouldn't be limited to changing the pistons. There would be a new cam going in, probably bigger carbs and a change in ignition timing.
If I was doing the work and really hurrying, the bike would be all ready to go by Monday morning when it was time to change back to the 9 to one setup! So I think that makes a great story but is unlikely to occur.
But I doubt the bike will get ever used in that way. It is likely more of what Terry P refers to as one of his " Coffee Shop Racers". This differs from a cafe racer.
He explained that a lot of his customers want a machine to cruise down to the local coffee shop with, then display to friends and admirers.
And it displays very well!
I think they are missing a lot of fun with the docile setup in there.
My Special is at 10.8 to one with the MK5 cams, 41 mm Dellortos, Pazon racing ignition etc, and it's still really quite tractible when it needs to be.
On edit- I see the bike is e start. It could be that the lower Cr. was needed to allow the estart to work.
At 10.8 or 11 to one these TP engines with the large squish band are extremely difficult to roll over. On the other hand, at 9 to one it's doubtful that the squish is even in effect. At clearances above 60 thou it doesn't do it's job. I didn't really want 10.8 but had to go there to get the squish at 40 thou.
It all works, no ping.
Glen
The article mentions that it is 1200cc. They have used the Terry Prince 92 mm top ends and a standard stroke crank. The output given is 115 HP with 11 to ones and 90 HP with 9 to ones that they are using.
A compression increase from 9 to one to 11 to one on its own wouldn't give that size of power increase, according to all that I have read on that subject. The effect of CR raises alone is well documented with dynomometer testing.
The Wallace Racing CR calculator says that a 90 HP nine to 1 engine will produce 91.95 HP at 11 to one, no other changes.
To obtain the 25 HP output increase mentioned, your Friday night changeover wouldn't be limited to changing the pistons. There would be a new cam going in, probably bigger carbs and a change in ignition timing.
If I was doing the work and really hurrying, the bike would be all ready to go by Monday morning when it was time to change back to the 9 to one setup! So I think that makes a great story but is unlikely to occur.
But I doubt the bike will get ever used in that way. It is likely more of what Terry P refers to as one of his " Coffee Shop Racers". This differs from a cafe racer.
He explained that a lot of his customers want a machine to cruise down to the local coffee shop with, then display to friends and admirers.
And it displays very well!
I think they are missing a lot of fun with the docile setup in there.
My Special is at 10.8 to one with the MK5 cams, 41 mm Dellortos, Pazon racing ignition etc, and it's still really quite tractible when it needs to be.
On edit- I see the bike is e start. It could be that the lower Cr. was needed to allow the estart to work.
At 10.8 or 11 to one these TP engines with the large squish band are extremely difficult to roll over. On the other hand, at 9 to one it's doubtful that the squish is even in effect. At clearances above 60 thou it doesn't do it's job. I didn't really want 10.8 but had to go there to get the squish at 40 thou.
It all works, no ping.
Glen
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