| Author | Message | ||
     Stevel |
In the process of making an 1125 stroker crank, I measured the cylinder head and stock piston volumes. I did this several times. The measured volumes were: Head = 25cc Piston = 16cc I calculated the head gasket volume at 8cc. As you can see, there is no way the factory stated 12.3 to 1 CR is correct. It is more than a full point below advertised. I would like confirmation that these numbers are correct. I did not consider cylinder deck height in this, so the real CR would be even less. | ||
| Blownharley |
I noticed that there seems to be different styles of pistons, see attached photos. The pistons I got is quite flat with cut outs for the valves with the center just a little bit higher than the squish area. the pistons below that i found pictures of on Internet looks quite different.    | ||
| Blownharley |
BTW, i think the statement from Buell of the comp ratio of 12.3:1 is very close! look at my calculations below:  As you can see the volume should be 49.77cc to achieve 12.3:1 and if you add up your volumes I got 49cc which is darn close, at least in my world  Way closer than one point off! | ||
| Blownharley |
The other calculation in the picture is to achieve 9:1 comp ratio in my Buell 1125 RT under construction.. (Message edited by blownharley on January 07, 2014) (Message edited by blownharley on January 07, 2014) | ||
| Mcelhaney14 |
1125/2 = 562.5 cc 562.5 + 49 = 611.5 cc 611.5/49 = 12.48 CR Looks pretty close to me. | ||
| Stevel |
Blownharley, Thank you. You are correct. It was not my measurements that were incorrect, it was my arithmetic. I forgot to add the unswept volume to the cylinder volume before dividing the total volume by the unswept volume. Thank you also for the photos. I was not aware of the two piston styles. I am assuming the piston with the flattened center is the later model. The 2008 piston with the peak I believe contribute to erratic flame propagation and spark plug shrouding clearly evident in your photos with the carbon deposits. (Just one of several reasons for the low speed, high vacuum surging these bikes exhibit.) |
