View Full Version : New Pistons for 65 FLH

06-15-2007, 11:15 AM
Short Story: I need new pistons, and I am looking for recommendations. I have heard of the advantages of KB, but I don't know anyone that has used them.

Long Story: After spending several hours cleaning carbon off of the old pistons, I found that one is stock, and the other is 0.020 over. I guess I should have checked the cylinder dimensions first.
The good news is...now I have a couple of real nice ash trays!

Thanks for any suggestions,

06-15-2007, 01:39 PM
Gary -

I like KB's. I can't say enough good about them. But, they are considerably lighter than OEM. I cannot say how your engine would run, if they were installed without doing a rebalance on the flywheel assembly. I really like them because of their low expansion and being able to run 0.0005" to 0.001" piston to cylinder wall clearances on a new build.

Now, to address what you found. Dealers/shops made a practice of changing only one piston, if there was only one offending cylinder. In some previous discussions of balancing flywheel assemblies, it has been stated (maybe on other forums) that if you stay within the bounds of standard to 0.070" OS on your piston(s) replacement, engine balance is unaffected to any great degree. I like the philosophy of old. If you need to clean up one cylinder with an OS piston, and just rings on the other, do just that.

Good news is that you don't need to make ashtrays. Clean them up. Check clearances. If you can get by with just rings, do just that.

As I like to quote/paraphrase Tom Cotten, our V-Twins are very forgiving in balance. They will take almost anything we want to do to them, and still run just fine.


T. Cotten
06-15-2007, 09:45 PM
Don't look now, but generic oriental pistons (Korean, I think) are just fine. Great quality control for many, many years.

And don't sweat the difference in bores.
The motor doesn't even know it has two cylinders.
Thats why, for a v-twin, balancing is a tuning technique, not the critical mechanical aspect it is for opposed motors.

Dinosaur durability is what made American V-twins into the icons they are.

The only thing bad about mismatched bores is that most distributors try to goon you for a set instead of individual pistons.

Please stay brand-name with rings, however.


06-16-2007, 12:35 PM
Thanks Guys!
I'll let you know how the story ends.

06-16-2007, 03:26 PM
I just returned from the machinist. The clearance is fine between the standard stock piston and the cylinder wall. He did weigh the two pistons, and found that they were within 2 grams of each other. I'll order stock rings, and I guess I can finally finish putting the top end together.

Thanks again, for your help.