Best Compression Ratio for a TW-7H ?

[aalsalem]

Hi, am looking to upgrade my 2009 Harley 110Ci Road Glide CVO  FLTRSE3 so far the bike is stock as it came out the factory.

a friend of mine is going me his TW-7H for free  to install on my bike 

Am going to keep the heads and TB stock, only changing the cams to TW-7H and was wondering what's the best CR (Pistons) to go with ? that works  best with the TW-7H ?

bike has the 2:1 D&D pipes

thanks in advance for any help with the info

[Don D]

10.3-10.5:1 Depends on available octane, squish distance, and how the bike is tuned. By the way piston manufacturers advertised compression numbers are not always correct. The stock flat tops will work fine if the heads are milled ~.050 but that is a healthy cut that I personally would avoid, if possible. The next method would be to bore the barrels and hone and use a small dome piston. The SE domed pistons are too much of a dome. You need about a 6cc dome. The SE pistons dome can be trimmed, I have done it.

[aalsalem]

10.3-10.5:1 Depends on available octane, squish distance, and how the bike is tuned. By the way piston manufacturers advertised compression numbers are not always correct. The stock flat tops will work fine if the heads are milled ~.050 but that is a healthy cut that I personally would avoid, if possible. The next method would be to bore the barrels and hone and use a small dome piston. The SE domed pistons are too much of a dome. You need about a 6cc dome. The SE pistons dome can be trimmed, I have done it.

Well currently in Kuwait and don't trust the machine shops here to mill my heads perfect in Kuwait, I will be running octane anywhere between 95 to 98 octane, so if we go with a 10.5:1 piston and a 0.3 cosmetic gasket. do you think that's a good idea with the proper tune ? would I have any pinging issues?

[Don D]

Your 98 is rated by RON method VS our USA gas is rated using PON method. A swag is -5 points for the RON VS PON so it still would be ~93 octane compared to USA fuel. So if machine shops are a little sketchy how about dyno tuners in Kuwait?

I would not buy a standard piston, ball hone, and trust the rings to seal. If oversized pistons are used you are back to the lack of good machine work again.

If I was there I would order new pistons and cylinders from Harley. Calculate the dome trim and certainly there is somebody locally that can handle that.

[Hillside Motorcycle]

10.35 would be my recommendation.

[C-Cat]

Like Scott said 10.35, I ran it at 10.4 with a Fatcat and it was very strong right off the twist of the throttle, carried out well too. Lots of fun there!

[838]

I'd be looking on eBay, or asking one of the vendors on this site that's in the US, for a set of 110 inch barrels. Get them to one of the vendors on this site to be bored to 113 with a set of pistons, and then just have the whole kit shipped back to you in Kuwait.

By doing it this way you'll know the Pistons are bored Honed and precision fit to the cylinders, and the machinist in charge will make sure to get you within the appropriate compression range for the 7H. Then you can sell of your other pistons and cylinders to cover some of the costs, or keep them in case you want to redo the top end again someday.

[Don D]

I have both black and granite cores.