Thanks for documenting you mods! I am thinking about doing some similar ones this winter. Had you considered doing a Bore up to 297cc with a JE Piston? HONDA - 2011-2012 CBR 250R - JE Pistons
I don't want to change the bore but If I knew JE made a higher compression piston I would have went that route. I emailed them a while back and they told me they wernt going to do anything with the 250. I wonder how much the piston kit is.
Not sure the price for the std bore piston with a slightly higher ratio but the 297cc Piston, 11.0:1 ratio is $205.52 (Piston, rings, piston pin and lock ring).
I think it's cool and trying to improve performance on the model. I know sometimes alot of motorcycle manufactures don't release the FULL amount of performance of the engine. They don't want an alot none mechanical people in there. But it seems you have tapped in and I want to see the end results as well! Please keep us posted of what you're doing! I'M very very interested!!
All right guys and gals. Since everything i have in the shop i'm waiting on parts for I had some time to work on my own bike!.
I started buy cleaning up the head. After I got everything cleaned up I decked the head for some higher compression. Then I cut the valve seats. The reason I had to cut the valve seats was because they were pitted pretty bad. The bike only has 5000 miles on it but this is another good reason to hate ethenol!. So now the valves will seal correctly.
Here are a few pictures. I still have a good 4-5 hours of porting to do on the head. As you can see in the pictures the castings are really rough thus slowing down air flow both into the engine and out. When I am done the exhaust side will look like a mirror. and the intake side will be cleaned up but have a bead blasted texture to help with the air/ fuel mix.
