I have an 18 slim with the M8. I'm looking at S&S's gear driven cam and their big bore kit. I currently can't afford the total power package which includes both. What would be the better option, pros/cons?

https://www.jpcycles.com/product/305...-pushrod-tubes <- Cams

or

https://www.jpcycles.com/product/280...k-big-bore-kit < - Bore kit

 

Does going to a bigger bore cause vibration in a solid mounted balanced M8?

 

Cams first.

 

Kinda, havta do cams first.

 

Or just wait a bit and save up until you can afford the power package and get both in one shot.

 

Here is your issue. If you do the cam first which one you going to do? The Big Bore kit can use a larger cam profile and run good, the stock bore engine may not like it as well. So you have to make your mind up what your willing to live with until you do the second half of what your wanting to do. I would also steer you away from the gear drive stuff as it's not necessary for a M8 and your crankshaft run out may not allow for it. That you will not know until you open it up, so just run the chain drive and you will be fine.

 

The main reason to do cams first is that you will get the biggest bang for the buck with cams.

Both the big bore kit and the cams will also need upgraded exhaust and air intake to get the real benefit, so assume those are part of the package of doing either just the cam or just the big bore.

Look at the dyno curves. The 107 motor in stock setup tests out about 80 HP. A well tuned 107 motor with cam, pipes and intake can get you easily to 110 HP and some combos over 120 HP. S&S shows a curve going to 120 HP for thie 550C cam (but the curve doesn't say if it's the107 or 114 motor used). So the cam/pipe/air combo nets you about a 50% gain in peak power. Huge!
https://www.sscycle.com/products/550...-19-m8-models/

The S&S 124" kit + the 550C cam (and of course pipes and air cleaner) gets to about 128 HP, or about a 60% gain in peak power, which is huger, but a lot more expense for not that much gain over the on the cam/pipes/air combo.
https://www.sscycle.com/feature/powe...wer-package-m8

The one place you'd really notice the difference with the big bore kit is the low end torque, and yes, you'd feel that all the time, and it would be wonderful. But your biggest bang for the buck is easily the cam, which also will give you a big bump in low end toque over stock, just not anything near the big bore kit.

 

These are good points, I'm planning a 107 Stage II, want to get as much as I can out of the 107.
I think by the time I get tired of that combo Harley will have the next or bigger engine to play with. I just don,t want to sink that much $$$ into a big bore then trade the bike in.

 

Thank you all for your input. I am pretty sure I'll go with the cams.