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The Raptor 700 has been one of Yamaha's greatest successes, and there are a lot of options when it comes to motor performance. There have typically been two popular big bores for the 700, the 105.5mm 734cc and 108mm 770cc. The 734cc kit is more popular, mainly because it is a drop in cylinder. The 108mm big bore requires you to bore your crankcases for it to fit. This must be done because the cylinder skirt on a 108mm cylinder is much thicker with a larger OD than the 105.5mm. The cylinder needs to be this way to protect the skirt and the bore integrity. That 108mm piston is really big!
So most people just replacing a top end go with the 105.5mm set up. But if you are redoing the entire motor why not consider the 108? You are already splitting the cases and tearing down the whole motor, and boring the cases is an easy and quick mod for a qualified shop, so the hassle created from the 108mm kit is kind of neutralized. Because boring the cases is not a big job at all, it should only cost you around $100. If you are redoing the whole motor with big bore, stroker crank, cam, etc. you are likely spending $1500 to $2000 (at least), so another $100 does not increase the cost of the build by that much really. The 815cc stroker is very reliable, and our cylinders are designed to keep it that way. You can get 11:1 for pump gas or 13.5:1 for race gas.
We stock the replacement parts so you don't have to worry about tracking them down when it comes time to freshen up the motor. The 780cc big bore stroker is a great kit, but make no mistake, the 815cc makes more power. Just something to consider.
Disclaimer: What you read in these blogs are just individual opinions. This is for informational purposes only and is information gathered over several years working in the industry and hands on experience. We realize there will be people who disagree with some of the information posted as well as people who may have more insight. That is what this blog is all about and why we really appreciate your comments as well as formats like this. We all have the ability to learn from each other. So please, read on!