107" big bore build using 114" cylinders.

[Adam76]

Hey guys,

Looking at build options for 2017 M8 107" Road Glide. I have already bought a set of take off 114" cylinders for this build - which I understand can be bored out a little further than the 107's?

What do you advise when it comes to bore size on oem 114" cylinders and what pistons are recommended?

Thanks.

[stickman53]

I picked up a set of take off 114 jugs for my 2019 M8 107.  Had them bored to 4.125 and installed CP Carillo pistons BHM8117-FT.  Now it's a short stroke 117. 

[Adam76]

I picked up a set of take off 114 jugs for my 2019 M8 107.  Had them bored to 4.125 and installed CP Carillo pistons BHM8117-FT.  Now it's a short stroke 117.

Thanks Stickman. What compression did you end up with using those pistons and what cam did you run?

[stickman53]

I'm running the TTS-100 cam, with a .030 head gasket. I figured it was close enough to stock, so never calculated the compression.  It runs great.

[Deye76]

I picked up a set of take off 114 jugs for my 2019 M8 107.  Had them bored to 4.125 and installed CP Carillo pistons BHM8117-FT.  Now it's a short stroke 117.

  Bet it's pretty smooth too.

[stickman53]

It is pretty smooth.  Crank runout measured .0035, not perfect but not too bad either.  I plan on keeping this bike for awhile.  It'll haul the mail too !

[Coyote]

0.035 is not too bad? 

[Ohio HD]

Maybe it's in millimeters?     

[rigidthumper]

I'm betting he's missing a 0. (.0035" runout)

The 114 cylinders can go to 4.185". Suburban Speed sells Mahle pistons for that setup. Makes the 107 a 120.
HD sells 4.155" pistons.

[stickman53]

0.035 is not too bad? 

My bust....yeah forgot a zero, meant to say .0035 in crank runout.

[Adam76]

I'm betting he's missing a 0. (.0035" runout)

The 114 cylinders can go to 4.185". Suburban Speed sells Mahle pistons for that setup. Makes the 107 a 120.
HD sells 4.155" pistons.

Thanks Rigidthumper, what's your opinion on taking the 114 cylinders right out to 4.185"? No option for a rebuild down the track? Which piston / bore size would you recommend?
Thanks.

[rigidthumper]

The longevity seems to be good, so pick the compression you want.  The 4.125 gives you two more .030" clean up passes if you get a scuff--4.155, and then 4.185, if you're thinking rebuilds down the road. If you just want a bit more, the Daytona cylinders are 4.25", and seem to be holding up well. FM has 124 kits with Daytona cylinders for not much more $ than some shops charge for pistons

[JSD]

Before counter balancers the extra piston weight would require rebalancing the flywheels . Is the Balancers still keeping the engine smooth. Just a thing I think about.

[BigT]

I built a 117" from a 107" by boring 114" cylinders back in 2018 before the big bore cylinders were being sold. I never noticed any additional vibrations.

[Adam76]

I built a 117" from a 107" by boring 114" cylinders back in 2018 before the big bore cylinders were being sold. I never noticed any additional vibrations.

Hey BigT, what pistons did you use for this build? CP?