rings snagging ports on a happy-time?

[OldPete]

I would most strongly suggest you search for Egor's post on cylinder porting. In it you will read where he states that the port edge should be champfered by using a smooth steel rod. Like the shank of a new drill bit. This folds the edge of the chrome plating into the port where the ring edge will not grab it. We are only talking a few .001" of an inch here, nothing major. A cast iron bore should be slightly beveled with a fine file however. Good hard chrome is not easy to file anyhoo.
Be sure to check the ring indexing pins inside the piston's ring lands. If one of these went missing the ring will rotate, its end will cover the port and catch the edge.
If upon tear-down you find no signs of the slightest scoring, like a slight polishing at the port edge, I would not suspect the rings catching the port.

 

[Scottm]

Any messing around in there could lead to trouble. But I guess either you know what you're doing, or someone else will.

I possibly posess the skill to preform this task, but admit I lack the confidence. I'd almost buy another cylinder before I started taking things apart.
I'm gonna try and sound smart here. Augi , had the damage you've seen like mine been on newer bikes with newer guys like me? Now after every ride, i get my 14mm socket onto those headbolts. I usually get just a fraction of a turn but I don't ****** down on it like He-Man. all this to ask, can a "loose cylinder" provide enough movement/vibration to allow the snagging, or have you seen it in bikes where the rings have already seated after break in?

 

[gone_fishin]

only if too loose, imOpinion...'cruzin's "70" was well-broken in with attention to detail when the damage occurred.

don't be trying to get more turns, try to maintain tightness. get a small torque wrench if you're not sure about tightness...someone please post the proper head-torque for 8mm studs??? it's here somewhere but i'm swamped this morning.

i don't believe it's a newness thing, it's more the luck of the draw...

my original "70" had extensive bushing damage but was otherwise just fine, it could/should have led to ring snagging too, but didn't. yours was fine in lower end but had ring/bore damage.

i think gap position may have something to do with it, but not enough "scientific" data yet to confirm...more data means more broken engines, so i'd rather not have more, yaknow?

the "65" i tested & blew up was showing a "slight polishing at the port edge" (thanks pete) on bottom of exhaust port:



to further this research: when rebuilding, i place the ring gaps towards the rear (intake) side of bore...any more input that would help?

 

[Scottm]

I understand I hope not to contribute any more physical data to that research.
I did search for "head torque" and "torque". And got these 3 links all fell between 22-27 ft/lbs or 90in/lbs. That seemed to be a standard for aluminum.
http://www.motoredbikes.com/showthread.php?t=4686&highlight=torque 27 ft/lbs

http://www.motoredbikes.com/showthread.php?t=4960&highlight=torque 25ft/lbs

http://www.motoredbikes.com/showthread.php?t=4146&highlight=torque 22-27 on aluminum or 90 inch/pounds