Tear er' down ---- AGAIN.

[joolstacho]

Well I don't see how that could work Alan. You've got me all fascinated now...
The gudgeon pin offset is front to back on the piston, no change to piston travel, surely it'd need a vertical offset to affect port timing (or have I finally lost ALL me marbles!!!?)

[tz375]

That's true hat piston pin offset does create slightly different timing on the way up versus down but not enough to worry about. The real reason is to reduce thrust against the bore.

[Vintageman]

All 3 jugs bored ,5 over and 3 new Suzuki .5 over pistons installed. And yes it's noisy. I believe the excess noise is due to sharp edges on the ports. The port edges were just better than razor sharp. i.e. just hit a quick lick with some emery cloth to remove the razor edge. No chamfers at all.

.

So you at least pulled the heads off so far?

Yes no chamfer bad. Do you see sign of fine scratch above/below the ports (from metal bits of cylinder wall or rings). If noisy due to that reason I would think you may have some.

If the upper ring snagged hard on the way up it can bend the piston metal down causing the lower ring to be pinched for example.

You'll need to pull those jugs and put a nice chamfer. If scratches on walls or skirt know of the high spots only

Also, make sure those key stone rings were put right side up. Now I never done that and more than once.

Check piston fit (measure ... large clearance? and or look for signs of high spots or early seizure spots) while jugs off

[Alan H]

http://www.torqsoft.net/piston-position.html" onclick="window.open(this.href);return false;

is a good read and provokes thought.

[Coyote]

Continued under the post "Head off".

[Suzukidave]

All 3 jugs bored ,5 over and 3 new Suzuki .5 over pistons installed. And yes it's noisy. I believe the excess noise is due to sharp edges on the ports. The port edges were just better than razor sharp. i.e. just hit a quick lick with some emery cloth to remove the razor edge. No chamfers at all.

It would be interesting to know for sure what the piston to bore clearance really is .