I did a top end rebuild and cam change on my '06 Twin cam (88") a couple months back, and after running it for a while, I think the motor has a "cold piston slap". Pretty audible when cold, quiets down and goes away completely when warmed up.

This is something I am very attuned to, because my VW drag race motor does. But it is built intentionally loose with .006" skirt to wall clearance. It clatters pretty bad till it gets some heat into it.

I was "***-uming" the piston fitting job done on my barrels was done correctly with the right clearances, and this is where I think I have screwed up. I should have checked, and I didn't. I assumed it was right. No excuses. I have precision measuring tools, including a dial bore gage, but I just didn't do it. Right now, I don't know if it was done correctly or not. The only way to know is to get back into it.

Many on this board offered advice on going from my current 88" to 98". When it came down to decision time, I opted to go .010" and use KB oversize pistons.

I also had the heads freshened up with a SERDI valve job, and installed S&S 509G cams, lifters and adjustable pushrods. I did use that advice!

My goal was reliability and good fuel mileage. I don't push the limits on the bike.
The oil was clean after the first change at 100 miles, and that was 500 miles ago. I'm gonna dump it here again soon, just to see if there are any particulates. Cranking compression was 170psi on both holes.

Once warmed up, it runs really nice and is fairly quiet. However, it takes about 3-4 miles for the clatter to quiet down. And now, I'm wishing I would have taken the advice and just ordered a 95-98" kit.

Or perhaps I'm worrying too much.

At any rate, I've been looking at different vendors to go ahead and swap out the jug and pistons while the weather is still cold so as not to cut into riding season. And how would that work with the 509 cams if the compression ratio were kept low?

 

Wow! I know I am no mechanic and not the most mechanically inclined person, but this is what your post looked like to me:

Έκανα ένα άνω άκρο ανοικοδόμηση και το έκκεντρο αλλάξετε δυο μήνες πίσω, και πιστεύω ότι ο κινητήρας έχει ένα "χαστούκι κρύο έμβολο". Αυτό είναι κάτι που είμαι πολύ δεκτική στις, γιατί η VW με κινητήρα αγώνα drag μου κάνει. Αλλά είναι χτισμένο σκόπιμα χαλαρά με 0.006 "φούστα σε τοίχο κάθαρση.

Ι "***-uming" η τοποθέτηση δουλειά του εμβόλου γίνεται σε βαρέλια μου έγινε σωστά με τις σωστές αποστάσεις, και αυτό είναι που νομίζω ότι έχω μαντάρα. Θα έπρεπε να είχα ελέγξει. Έχω ακριβείας εργαλεία μέτρησης, συμπεριλαμβανομένου ενός διαμέτρημα οπής γραμμή, αλλά υπέθεσα ότι έγινε σωστά. Αυτή τη στιγμή, δεν ξέρω αν ήταν ή όχι. Ο μόνος τρόπος για να μάθετε είναι να πάρει πίσω σε αυτό.

Πολλοί σε αυτό το σύστημα προσφέρει συμβουλές για μετάβαση από το σημερινό μου 88 "έως 98". Όταν ήρθε κάτω με το χρόνο λήψης, επέλεξα να πάω 0,010 "και χρησιμοποιήστε KB υπερμεγέθη έμβολα.

Είχα, επίσης, τα κεφάλια ανανεωμένο με μια εργασία βαλβίδα SERDI, και να εγκατασταθεί S & S 509G έκκεντρα, ανυψωτικά και ρυθμιζόμενο ωστήρια. Έκανα χρησιμοποιήσετε αυτή τη συμβουλή!

Ο στόχος μου ήταν η αξιοπιστία και η καλή χιλιομετρική καυσίμων. Δεν ωθεί τα όρια για το ποδήλατο.
Το έλαιο ήταν καθαρό μετά την πρώτη αλλαγή στα 100 μίλια, και ότι ήταν 500 μίλια πριν. Πάω να πετάξει εδώ και πάλι σύντομα, ακριβώς για να δούμε αν υπάρχουν σωματίδια. Μανιβέλα συμπίεσης ήταν 170 psi και στις δύο τρύπες.

 

OK. I did a couple of edits to clarify.

 

Trust me - it wasn't you, it was me.

 

Is the slap really that bad? From what I know of the 509 it likes stock compression so going to a 95" shouldn't be too much compression with a .040 gasket but maybe add an offset key if you go 97" or 98". Ideally I'd think you would want more cam though to take advantage of getting more compression.

 

Jay, It's not very loud, but loud enough to hear over the pipes. Admittedly, I am a bit OCD about stuff like this


Sailmotion. No worries man. What you quoted from my post looks greek to me!

 

Going to 95"/98" is a smart move; bore/hone job and a set of pistons. The170ccp looks about right for the configuration but ccp in the 185-190 range would be better. You mentioned a SERDI valve job but not porting and, if that is the case, I see no reason to change cams. The 509 in a 95"/98" configuration is going to bump ccp up in the 190-195 range and the cam should respond well to the added compression; compression releases would be a good idea. Since you "don't push the limits" on the motor, a set of 3.875" SE cast flat top pistons for 95" are reasonably priced. Going to 98", as you surely know from this forum, puts you in the aftermarket for pistons which typically cost a bit more. Good luck with the project; let us know what you decide to do and how it turns out.

 

IMO if you hear slap like that on a new build,,, well it's not going to get any better... Even if you buy a Kit from somewhere you need to check that too...

Just out of curiosity, who fitted the pistons??

 

Hypereutectic pistons will rattle if set up a little loose.. I screwed up when I bored the cylinders for my 07 EGC to 103 SE cast.. About 1/2 thou too loose.. The rattled a little when cold since assembly.. Almost 65000 miles ago.. Bike is a little short of 80000 right now.. My condolences on your cam selection. Hope you are using something better than a DFO for a tuner. Mine will got to 107 after I finish the heads and cylinders.

 

you say you'er OCD about stuff like a little engine noise ...but didn't check the piston to cylinder clearance ...??? REALLY !!! what else did you assume was done correct ...ring gap ...valve glide clearance ...etc !!!???

but now you'er SURE it piston slap ...because of your past experience with this type of noise ...!!!
OK...IF YOU SAY SO !!!

you tried to cheap out w/ something off the net w/ the KB pistons which are about the cheapest you can get ....

now you have to "do it again" ...when you could have Done it right the first time ...
you should buy a honda and just ride it !!! when it starts making noise , throw it away and get another one !!!