A reminder, my old pistons were cleaned weeks ago and they are at the Indy with the heads and jugs, so I can't play with that at the moment. That was an older pic.
Have you read any of my rebuild thread ?

 

i have an 84-86 parts book and was looking at the diagram of the pistons, there are no reliefs shown on the pistons. the part # is 21940-83 for the "standard" piston. what's the part# for later years and does the parts book show reliefs?

 

They use the same P/Ns, only they call them "PISTON & RING KIT, STD, NOTCHED" (image link).

 

Thanks fellas, I will call the stealer to price out those pistons completed with rings and pins, stock size...

 

I'm now thinking that's why they put .060" head gaskets on it because no relief...

 

GW, how many miles are on the motor?

 

Just over40 k.

 

I think that makes sense, 60 thou plus another 10 or 20 on the cylinder.

Still, I'd really encourage you to measure it all up. Put the valves in the head without springs, put a metal ruler or straight edge over the face of it, fake a .500" lift, and measure the distance between it and the lip of the valves. You need to know.

John's right that valves can hit pistons but there are always other elements in the equation, e.g. someone's skimmed the head, used a thinner gasket, faster ramping/higher cam etc.

However, reducing that squish and increasing the compression (two separate efforts) will improve not just performance but also efficiency. Let's approximate at 75 thou. It is too much.

There's a guy on Ebay right now with a stock set he says only had 500 miles on them before upgrading. If you don't cut corners (or piston reliefs) somewhere, you're going to get caught in the, "only $50s more" trap until you've spent $100s of dollars more all over the place, e.g. you say "$75 for standard pistons" (plus rings etc?) ... but then "for $50s more", you're going to be able to buy better, higher comp, quality ones.

 

"Bolt In Cam" assumes everything is stock, that is why they usually suggest you clay the heads.


Old bikes with unknown history require more checks and effort which will save you a world of pain...

 

I had another look at those 500 mile old pistons and there's no scuffing on the skirts to suggest that they have done any miles at all. They would sort your problems and save $100 or $200 depending on which other way you were to go.

There's another set without rings currently at $25. New unbranded ones for $13 each (don't they are H-D, any one have any idea which make they are?), or what look like new OEM others with a set of cylinders current at $100. Given the choice of giveaway OEM ones or V-Twin Manufacturing's cheap alternatives for more, and you just want back on the road, I'd tend to go for OEM quality ones.

If I was going down the hole of spending money, I'd tend to want to do it properly with high quality name pistons at a higher compression, e.g the Wisecos etc, and really set the engine up. The difference is, say, $250 to 350 depending on how much machining you'd go for, e.g. first over-bore, setting the squish etc.

What would the ROI be? Probably only a 10 or 15% in comparison to the 85 to 90% of putting in the cam, but another 40,000+ miles before you needed to strip the engine again. Is that of any benefit? Folks here will tell you they can go 100,000 without needed stripped ever ... so probably not. It depends if the feeling of accomplishment is setting it *really* well is worth anything to you.

In real terms, if you're not going to do it again or for a living in the future, it's probably not.

Buy the used pistons, clean them up, stick them in, do a few 100 miles until you feel confident in at all, and then relax. You've gone through enough.

If you have another $350+ to spend; buy first size over 10:1 pistons, bore and hone and trim the cylinders to set the squish, level the face of the cylinder heads, run a dremel around below/behind the edges of the valve seats to make sure they're matched nicely, and re-cut 3 angles on the valve seats. Don't worry about the compression as it won't actually be at 10:1 but probably only 9:1 and the clearances will be fine.