Help! Frustrating piston gap fiasco

[shovelryder]

Per my earlier post I sent the flywheels out to T& the other guy and had them rebuilt (1976 FLH). I asked them to bore the cylinders 50 over and fit new pistons. They sent me some "superior" pistons and rings)
I have the bottom end together and went to do the cylinders.
I have .024 ring gap with the new rings.
 Me thinks thats way to high so I call T&0 and the guy says "well they should ok I'd run em"
I say " Thats not what I read or the manual says and this is a lot of work to find out they arent OK".

 I ask can I run 60 over rings on a 50 over piston and file the gaps myself. He says sure. He says "I have a 45, I run .060 rings on 080 pistons cause no one make .080 rings. He says it runs "okay" and he dosen't think it burns too much oil.

In my opinion, if I asked them and paid them to bore and fit pistons they should have checked the gap.

I go to my local INDY (Who has had my heads going on 8 weeks) and buy some Hastings 60 over rings. He mic's the bore and says they are .003 bigger than the pistons. Local Indy says they should be "okay". Geesh

I get home (40 miles round trip) unbox the rings and the set is missing one of the 2nd groove rings!!!
 I call them and they say "Oh..okay ...we'll order you another set ..be here maybe tues wednesday of next week.
So now I'm wondering should I run the 060 rings on .050 pistons.
I'm at the point I'm thinking of buying some rope and a short stool to stand on!!!

[easyricer]

.010-.020 is the ring gap and piston should fit in at .001-.002. So yeah you got some funky stuff going on. Don't make me feel really good right now about sending my bottom end up there?
 If I remember right these KB pistons I have are supposed to have a .0005 (loose) fit, but I have a good machinist who I can trust to get it right.
EASY

[shovelryder]

Eazy...you are corect ...book says 10-20 thou. and 001 -002 on the piston to bore.
The bottom end look fine tho when I got it back. They rebushed the ends / rebuilt the  rod bearings and only the rods had been beadblasted. I hope they did the rebalance correctly.
 
I am extremely disapointed about the pistons and rings. I asked for their best and this is what they sent. I think they just bored/ hone them from the old .040 to .050 like I asked them to, but just threw in the pistons and rings without checking.
Also they had my already disassembled flywheels for 5 weeks so be patient. You will not hear from them either. I just happen to call them at the moment the guy was boxing mine up to return them to me.


T&O are supposed to be the best and thats why I sent it there, but I quess the old masters have been replaced by younger guys doing the work.

Just tired of having to double check peoples work and pay for stuff thats not done right the first time.

[xlfan]

Are the bores straight and round within .0004''? What ''superior'' pistons did you receive?

If yuo've got forged pistons, .003'' might even be on the ''tight'' side.

Tight running KB's requires increased top ring gap about .0023'' for your bore, obviously not correct for your piston clearance though.

[easyricer]

XLFan may be right. If they sent you a set of forged pistons, the tolerances are different again and you may have a tight fit, as the denser material needs more room to swell. I've only seen one cast piston that failed in my life, we replaced it with a forged piston. That was on a Honda almost 30 years ago. The bike belonged to a buddy of mine and he rode that thing as hard it would go every time he fired it up, he actually cracked the top of the piston.
EASY

[Ajayrk]

Do the piston have steel expansion control struts?  If so they are cast.

Also .006 x the bore diameter will give a very close approximate ring gap dimension.

[shovelryder]

The pistons are cast with the steel expansion strut. They are "Superior" brand made in Taiwan. They are the same as "Dixie" and Eastern ect. They are all made in Tiawan by the same few manufacturers. The cylinders were bored and honed and mic  out to be striaght. The local indy says the cylinders are .003 bigger than the pistons. I think I will call Hasting in the AM and ask them about using the .060 over rings on .050 pistons. I find different opinions on-line about doing this. Some engine builders say they do it all the time for custom gaps and others say the pistons will be noisy.
LIke you'll ever hear that on a shovel with drag pipes!!

[dusty1]

Go ahead & use .060" o.s. rings on your .050" o.s. pistons.Set ring end gap .010"-.020".You should have no problem.Piston to bore running clearance is determined by piston manufacturer.Usually .002 to .0025.I called T&O and they told me they set their clearances up at .0025,which is ok.Yours being .003" is a tad loose,but ok,nothing to stress about.Forged pistons require more clearance than cast pistons.

I once did a top end & had piston to bore clearance setup at a tad less than .002".I rode it around the block after putting it together,lugged engine as i was goin around a corner.Bike stalled.Years later on another top end overhaul,i saw why it stalled.A piston had started to seize in its bore!!This tells me that you should never ever run tighter than .002 on a shovel with cast pistons.T&O said i had better be damn careful breaking it in with .002 clearance,thats why they set em up with .0025 clearance.EVOS on the other hand are setup with less than .002 clearance 

[shovelryder]

Dusty1,
I am confused...isn't .003 more clearance than .0025?

[dusty1]

Yes it is.A half ten thousandth of an inch more.(next to nothing)

[shovelryder]

UPDATE***
I contacted Hastings Rings and spoke to Dawn. She confirmed I could run .060 over rings on a .050 over piston and file the rings to obtain the gap I desire.

She did say to use the .050 over oil rings and scraper tho.

She even gave me individual part numbers. She is shipping them to me. They were only a few dollars.

[easyricer]

good news....
EASY

[HILLSIDECYCLE]

Thumb of Rule is .004-.005" per inch of bore, and that is as TIGHT as you would want.
Biggest fear in setting ring end gap too tight, is once the rings butt togather, they can break, and that ain't no fun.
Scott

[76shuvlinoff]

  Which is I believe why after about 4000 miles on hone and new set of rings I found broken rings in both cylinders, my usually on-the-mark Indy made it right. 

[69 harley]

Yes it is.A half ten thousandth of an inch more.(next to nothing)

Not being a smart ass but half a thousandth is actually 5 ten thousandths (.0005)

[HILLSIDECYCLE]

1/2 of a ten thousanths of an inch,(.00005) at that point is measured in 50 millionths.
Scott