What kind of horsepower and torque numbers can I expect to see if I do an 88" upgrade to my 2004 XL1200R? Assuming I stick with the stock carb and stage 1 jetting that I have with my SE II's pipes and SE II A/C.

Here's an example of an 88 incher someone brought to me for a tune-up (we weren't involved in the build-up). This one had a set of STD heads, not sure how they had been prepared but even right out of the box STD's aren't bad, and it kept it's CV carb. Not sure what he had for cams but they weren't stock ...

http://www.nrhsperformance.com/pictures/88inchcv.gif

The pipe was reverting down low but otherwise OK. But just overall, it's a disappointing result. The thing ain't filling the cylinder very well anywhere.

The thing is, cylinder fill & velocity don't have a linear relationship, and cylinder fill (and thus power) falls rapidly when you get to a certain velocity due to an effect known as "inertia block". It starts taking more energy to pull additional charge through the restriction than you get from the additional charge.

This is one of the reasons I'm always talking about the theory of constraints. It only takes one constraint to hold back the whole system, and it doesn't matter how good everything else is, that constraint is going to define the result. I've seen that happen over and over.

So bottom line, 88 inchers with stock heads, cams, and/or carbs are often disappointing.

Don't mean to throw water on your plan, but at the same time, I gotta shoot straight with you, otherwise I just have an unhappy customer, and I want all customers to be happy.

Call us at the shop and discuss it, I'm sure we can put together a plan that'll work well for you and your goals. No obligation, if you want to chew on it for awhile that's fine, but at least you'll have the info.

thanks for the dyno.

I always learn alot from these posts.

Planning on doing 88" this fall and any info is good info!