So I work at a Dealership as a salesman. You end up learning or figuring out some stuff. Such as a 117 take of jugs and pistons will make your 107 a 114 big bore. I’m gonna make a few changes. Like I’m not gonna use the stock take off 117 piston which are 10.2:1 4.075” pistons instead I’m gonna order the Harley 11:1 4.075 pistons that where offered in the original 107 to 114 stage 3 kit. Not because I prefer Harley parts, they just end up being the cheapest after my discount and I know Harley brand parts fit Harley products better then any other brand. I’m going 11:1 because it will give me more potential for higher achievable hp and torque. I am gonna go after market with the cam though as I have never been impressed with SE cams, and I’m completely undecided on brand or grind. I know I wanna stay under .500 lift due to the size of the displacement. IMHO I don’t think you need to go high lift unless you running 120 or more displacement. So anything .460 to .490’s. The only head work I’ll do now it upgrading the spring for cheap insurance. Later I’ll try to get my hand on a set of stock take off heads and send them out to be port and polished and a valve job. Also I’ll be running a stock throttle body and manifold for now. Later I’ll upgrade to a 64mm TB and manifold. I’ll also be upgrading the cam plate and oil pump to SE plate and pump for cheap insurance and peace of mind and because of the discount. I will upgrade the lifters but reuse the stock push rods, mainly because I’ve seen them reused in M8 cam upgrade with no problems many times over. I’ll tune it on the Dyno using a power vision licensing. I’m not worried about my ESP due to the fact that I work at a large dealership and actually understand how the warranty works and personally know everyone in the service department. I really get a chuckle over how worried people get about their warranty. Just have a good relationship with the dealership you use and keep your stock take off parts.

please let me know your opinion or if you can think of something I’m not. Stock 117 parts are becoming more and more available due to people upgrading their ST models to 131’s at purchase. Just an idea how to get some cheap hp and torque instead of buying a HD stage III kit. Thank in advance.

 

think the 107 uses the 9 disc clutch pack and the SE and 114 and bigger engines use the 10 disc clutch pack..what exhaust system you planning on using, as you probably know, these M8s are finicky in that regard...that's a real Frankenstein monster parts build you got planned, good luck !

 

Good point. I talked about it briefly with my buddy who’s the tech who always works on my bike. I think I’m just gonna go with a SE clutch pack. Again discount and I only plan on getting less then 120hp and less then 130 on torque. As for as intake and exhaust I’m running a forward facing heavy air breather (like the ones on a ST) and a Bassani 2 into 1 ripper. Mainly because I’m running a 14 in shock in the rear and have to have a shorty exhaust. It should flow pretty well.

 

Since the stroke is different, what is advertised compression for the 117, won't be that in the 107, just keep that in mind up front.

 

Well you might want to get a different tech buddy, because if they told you using the stock 117" pistons was even an option, they don't know enough to be working on Harleys. The 107" has a shorter stroke than the 117", so the stock 117" pistons would give you really low compression, about 7.25:1. It might run, but not very well. If I were you and had the shop services available to me that you have, I would bore those cylinders and fit a set of 119" pistons to them, still Harley parts and available to you at a discount. There is plenty of meat on the 117" cylinders to do this. When you get down to it, the old adage that there no substitute for cubic inches still holds for naturally aspirated engines. If you're going to do the work, you only want to do it once and you'll come closer to making your projected horse power and torque figures with a 119" big bore.

 

Yup - factory engine specs tell you the 114 is bored and stroked from a 107.

 

Whether you have a 9 or 10 plate might be a year model thing. The 2017 107" M8's, my RGS included, mostly had 9 plate clutches. My 2021 Sport Glide had the 10 plate clutch in it from the factory. The SE clutch has the same plates as the 10 plate, so if you have a 10 plate clutch in your bike, you would just need to change the springs to the 1200 or 1275 N springs.

 

I don’t know where you’re getting your math for 7.25:1. But that’s incorrect. But it doesn’t even matter because like I stated I’m using 11:1 HC pistons from the original 107 to 114 kit Harley use to sale. If I was gonna go 119 I’d just go with Harleys 119 kit in the long run it would be cheaper. Now later on if I feel froggy I’ll bore those jugs to 4.250 and make it a 124. Like you said they have more than enough meat. Also yes the 117 the 114 and the 107 all have different compression ratios. I’ve done the math it checks out.

 

yes compression raitio for a 107 is 10:1 compression ratio for a 117 is 10.2:1. But as I stated I’m buying 11:1 high compression pistons so I won’t be using the stock pistons. I’ll keep those on the shelf if a buddy need them for a repair.

 

yeah it’s weird man and I’ve been trying to do the research on if it was a sub model thing, like a standard road glide to a road glide special or if it was because they went cable clutch to hydraulic back to cable. Cause I know the hydraulic and cable clutch baskets are different. I’ll figure it out today at work and I’ll update the thread on what I find.