gt380 pistons

[smokingbanana90]

Hello, I am looking to replace the pistons in a gt380. The center piston has a melted hole in the middle. Would it be ok to replace the pistons with standard size and hone the cylinders or should I go oversize and get a bore job? Also has anyone bought the reproduction piston ring sets on ebay from Japan? Thanks a bunch!!

http://www.ebay.com/itm/72-77-Suzuki-GT ... 4c&vxp=mtr" onclick="window.open(this.href);return false;

[Coyote]

As far as the Japan pistons go, several forum members have / are using them and the consensus is they are fine. Would not be afraid to use them. The price is less than A third of what you would spend on Suzuki stuff.
Only careful inspection and accurate measuring will tell you if you need to go oversize If you see any deep scoring, the answer is already yes. That's when it gets expensive. The ebay seller does not sell oversize sets for the smaller triples, Only the 750. Believe me I have just been down that road with my 550. Had to go first oversize because of a trashed cylinder. I had to pay out the nose for all OEM stuff. Apart from that you also have the cost of boring. It becomes high dollar in a hurry. Different shops charge whatever they want for boring. My guy does it for $45 a hole. Simple math tells you that it cost me $135 for sizing alone. Hopefully your bores are OK and you can get by with a set of CrusinImage pistons.
None the less you need to tear it all the way down. The metal from that hole went somewhere. If you're lucky it was expelled out the exhaust..On the other hand it might be in the crankcase waiting to do further damage to your fresh top end.

[Vintageman]

I don't recommend these pistons. I bought a set and the wrist pin fit into piston was very loose if not sloppy and choose not to use them. I was concerned about long term reliability. He does over OS for the GT380 not for GT550. I would use original Suz piston for they have proven quality.

The correct way is to measure your bore for wear is with internal bore gages measuring device...
If you don't have access to such a tool, empirically look at the bore for deep score marks, scratches and wear - a few fine scratch are OK.

Look at the very top of cyl for the he ring does not get to travel all the way to the top. De-carbon the top area if need be to see the true cyl liner. If you detect a step/ridge between where the ring travels versus were it does not that is wear.

If only minor scratches/wear give it a very light hone to deglaze oil film so new rings will seat faster. If you have aluminum from the holed piston stuck to cyl. wall you will have to remove it carefully (google how to do that... for example Muriatic Acid). My experience, if you have "significant" Aluminum build up stuck to the cyl liner the cast got hot from friction, become molten soft, and vaporized away a significant amount.

Most people over hone with honing stones. It does not take long to peel away material unnecessarily and increase your piston to cyl clearance. There are special brushes that just deglaze for example if you can't control yourself. I have even use 320 grit sand paper for example by hand. There is no need to take out ever scratch or at least in trade for piston slap.

[Vintageman]

I don't recommend these pistons. I bought a set and the wrist pin fit into piston was very loose if not sloppy and choose not to use them. I was concerned about long term reliability. He does over OS for the GT380 not for GT550. I would use original Suz piston for they have proven quality.

The correct way is to measure your bore for wear is with internal bore gage measuring device...
If you don't have access to such a tool, empirically look at the bore for deep score marks, scratches and wear - a few fine scratch are OK.

Look at the very top of cyl for the ring does not get to travel all the way to the top. De-carbon the top area if need be to see the true cyl liner. If you detect a step/ridge between where the ring travels versus were it does not that is wear.

If only minor scratches/wear give it a very light hone to deglaze oil film so new rings will seat faster. If you have aluminum from the holed piston stuck to cyl. wall you will have to remove it carefully (google how to do that... for example Muriatic Acid). My experience, if you have "significant" Aluminum build up stuck to the cyl liner the cast got hot from friction, become molten soft, and vaporized away a significant amount.

Most people over hone with honing stones. It does not take long to peel away material unnecessarily and increase your piston to cyl clearance. There are special brushes that just deglaze for example if you can't control yourself. I have even use 320 grit sand paper for example by hand. There is no need to take out ever scratch or at least in trade for piston slap.

[Vintageman]

Check this out ->

GT550 1.0mm OS from cruzininage finally

http://www.ebay.com/itm/72-77-SUZUKI-GT ... 031wt_1069" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;" onclick="window.open(this.href);return false;.

[Pete O'Dell]

the rings are shite on cruising image pistons hence price.

[tz375]

Pete, in what way - material, thickness, tolerances or what? And what are the consequences of those deficiencies?

Do they just not last as long or do they cost performance? I used a set in the Phat Trakka and it made almost 80HP on the dyno when I first set it up. I will do a compression check and see how much it has lost. It doesn't have a lot of miles on the motor and they were all at 5000 to 8000 a quarter of a mile at a time

If mine has lost a lot of compression I may just put new rings in or upgrade to WISECos at a slight price premium.....

I should probably start building a spare motor for the day that it throws a rod or holes a piston.