OK so after doing some research i found out that the pistons needed for a 555 motor is no longer made by weisco. I found out that there is only a 541cc max available. Well then i thought long and hard and realized hey, slowboy racing can make custom forged pistons in any fashion you want. So if anyone need them made they say they can make any piston "...Motorcycles and even ATV's, we can have anything custom made." as per slowboy. Well i was wondering if there is any interest maybe we can get a group deal since we each really only need 2. the price is about 500 for a set of 4. Any way just letting yall know it is still possible to get that bore or even bigger. If your interested look em up at www.slowboyracing.com i went under the dsm category then engine, pistons and finally SBR custom pistons. They helped make my 408hp beast of an eclipse by providing great parts.

mark

They still list the GPZ1100 17mm pins in there catalog, where did you check?

Quote from: coll0412 on December 06, 2007, 09:23:34 AM
They still list the GPZ1100 17mm pins in there catalog, where did you check?

The GS uses 18mm pins.

i would be interested if I saw a succesful install with feedback on the "worth it" factor.

I built a 555 several years ago, along with a current 541 and a 569 being built now. Not sure what the performance gain would be with just the 79mm pistons since I had Megacycle cams as well. My 555 probably had 50-55hp with stock CV carbs. The racer who bought it podiumed it in all 3 races the first weekend.

The biggest problem with the 79's is that the sleeves have to be bored thin which risk cracking if run too lean, I have one which this has happened. The 569 I have uses 81mm pistons and have had the sleeves replaced so there is still plenty of material left.

Just dropping in high comp pistons should yield good but possibly disappointing results. There are other things that should be done as well to utilize their potential. Free flow exhaust & air filter, ignition advancer, 34mm carbs (best with flat slides or even better with CR Specials), high lift cams, heavy duty valve springs, necked valves, mild porting (exhaust mostly). Each mod may add only a little but all together there is a very noticable gain.

You and I, DG, are going to be talking soon ... I just paid off my GS, and it needs about 5 or 10 extra ponies more than the V&H pipe and K&N filter gave it ...

Quote from: dgyver on December 07, 2007, 09:41:36 PMThe 569 I have uses 81mm pistons and have had the sleeves replaced so there is still plenty of material left.

How did you manage that?

Any crankshaft problems on that monster?

Quote from: GeeP on December 08, 2007, 11:09:17 AM

Quote from: dgyver on December 07, 2007, 09:41:36 PMThe 569 I have uses 81mm pistons and have had the sleeves replaced so there is still plenty of material left.

How did you manage that?

Any crankshaft problems on that monster?

I bought them with the sleeves already swapped. Just needed to hone them for a proper piston fit. The cases need to be cleared a little for the larger diameter sleeves, no big deal.

Milling the head to increase the compression ratio will seriously reduce its life. With keeping the head stock mill, it should be ok. It is for my track bike. Only time will tell on its longevity.