I was just wondering why kawie lowered the compression ratio on the bf750 compaired to the prairie 700 and bf650i???? This is not a compare top speed and power question. From what I understand, the higher the compression = more power. So if that is true, then if kawie made their bf750 with a higher compression ratio, it would have no problem with the outy800????? If you truly know about compression ratios and motors, please reply. If you don't and want to bash or make up cr4p......please use another forum. I am trying to educate myself and see what my friends are telling me is true. Thanks for the honest replys.

 

I don't know if Kawasaki had problems with engine knock or (pinging) but by lowering the compression ratio it will work more effectively with unleaded fuel. Higher compression engines require the right fuel to make them operate properly and unleaded fuel really hurt the high compression cylinder heads than ran so long on leaded fuel. I use to race off road vehicles and when the supply for leaded fuel slowly became more scarce and more expensive I had to lower my compession ratio to accomodate for the unleaded fuels.

As I said, I do not know if Kawasaki had problems with this or not but it sounds like they did this to extend the life of the motors a little.

Hope this helps,
Mud

 

Thanks for the good information. But from what I've been told, the bf650i and the prairie 700 have higher compression ratios. If that is true, why not the bf750i? I had a 700prairie and I ran regular unleaded and it did fine.

 

I have been told that Kawi dropped the compression on the 750 to help with the cooling. A higher compression engine will run hotter than the same exact engine with lower compression. I don't know if kawi had trouble with the bf750 running warmer than they wanted during their r&d. To my knowledge none of the other kawi vtwins had a problem with cooling as long as the radiators are kept clean. With the irs and large displacement I would like to think kawi anticipated more people using them for mud bogging and other activites where the cooling system will be tested. Your bute will make more power with higher compression pistons. A better set of cams would be a good idea too giving your motor more air to compress. One draw back to higher compression is you may have to run a higher grade fuel to keep from getting predetonation. Predetonation is when the air/fuel mixture detonates early due to higher compression or a poor grade of fuel. As I understand you can go 1 compression point higher and still run pump gas ie 9:1 to 10:1 or 10:1 to 11:1 but any over that and your taking chances with predetonation and burning your motor down. With a set of high compression pistons, cams, and a little clutch work to help get the added power to the wheels you'll be leaving all but highly modified outi's in the dust.