Old Yoshimura 816cc Big Bore piston kit for GSX750ES has a ring missing

[Nessism]

Those are cast pistons. Wiseco didn't make them.

Yup, cast. Yoshimura has used a lot of cast pistons over the years.
GSX750, What made you think they were Wiseco?

As far as only having one compression ring goes, that was not unusual for high performance piston kits back in the day. Some companies use a dykes style single compression ring. Using pistons like this on the street will work but obviously, the pistons will develop blow by faster than if there were two compression rings.

[Billy Ricks]

Wiseco had an 816 kit for the 750. I kind of assumed Wiseco too without paying attention to the pictures.

[GSX750ES junky]

OK... I read all your replies and think I got the point.
I'll sum it as I understand it and I'll try to offer a (crazed) solution...

Rings should be installed as in the picture below.
The oil ring consists of 3 actual rings (the gold one sandwiched by the 2 thin black ones). The other 2 grooves should house 2 compression rings. Since I have only one I need to order another one.

[GSX750ES junky]

There is a very renowned workshop in my area that deals with pistons and cylinders of motorcycles.
They said they can add a third groove to the 3 P2 pistons which I have for 40$. As you can see in the picture below it is going to leave a safety margin of aluminum (A) which greater the safety margin of aluminum of the stock P3 (B).
On the other hand one could claim that A is located at a more critical area close to the combustion chamber...
After I do this I'll need to order a total of 4 thick rings.

What do you say ?
I can of course save the hassle and return the pistons to the eBay seller but adopting the solution detailed above means I'm paying a total of 230$ instead of buying a Wiseco kit which where I live sells for ~ a 1100$

[Nessism]

Those P2 pistons have the ring groove in a different location than P3. Since, as you say, there is a good shop in your area you might want to take the pistons in to them so they can examine them first to see if there is room for the extra groove without getting too close to the valve clearance cutouts on the piston crown. There isn't anything wrong with running them with the single ring though. And if you are using one ring on P3, use it in the groove nearest to the piston crown, not the one in that photo.

[GSX750ES junky]

After you mentioned valve clearance (see picture) there is no need for a shop to tell me that another groove cannot be added .
So the possible choices now for compression ring settings are:

1) All P2 will have 1 ring ; P3 will have 1 ring close to the crown.
2) All P2 will have 1 ring ; P3 will have 2 rings.
3) I return the package to the seller and spend 1100$.

I still do not understand what is the drawback of option 1 and why a setting of 2 compression valves is better for street use...

[Nessism]

Two compression rings are better for the street since compression gasses that get past the top ring should be sealed by the second ring. Also, as the top ring wears the second is there to take up the slack so to speak.

Using one compression ring reduces friction, which was once thought to be significant for high performance applications. Ultimately though since the second compression ring will only exert significant force on the cylinder wall when compression gasses force it too, there is no big deal having it there as a backup so to speak - in case of top ring leakage.

Send back or keep? If the seller didn't mention the difference between the different pistons I'd ask for a partial refund. If he balks, you could press the issue and ask for a refund then if you want. Personally, it wouldn't bother me to run with only one top ring as long as you aren't going to expect long term durability out of the engine - more than say 20k miles.

[rapidray]

Looks to me like you wasted 80 bucks. I would return them to the seller. You need a 3 ring piston for street use for it to seal well & live for very long. I can get you custom made CP Pistons, the BEST in the industry, with all the bells & whistles, made to YOUR specs, for 800 bucks. That includes pistons, pins, rings, & clips. Whoever told you 1100 is taking you for a ride! Let me know if I can help. Ray.

[GSX750ES junky]

Happy end !!!
The guy immediately returned me the 80$ + the expensive shipment.
Now I have the coolest and meanest 4 ash trays on the market.
If I had no Asthma I would start smoking ...

[GSX750ES junky]

Currently my engine has 0.5 pistons. The cylinders don't look good and compression tests yielded 115 PSI for outer cylinders and 105 for inner ones.
I wasn't able to find stock 1.0 pistons anywhere and Suziki doesn't make them anymore. Apparently I have 2 options now:

1. Paying ~800$ for a Wiseco 816cc kit (Taxes etc.) + 150$ for drilling the cylinders.
2. Paying 1000$ for a new cylinder block + 450$ for stock 0.0 pistons & rings.

So it's 1450$ for a totally new engine that can have additional 2 life cycles or 950$ for a 816cc Wiseco based engine.
For the short term option 1 seems more reasonable.
For the long term...A few years from now I might be facing a situation in which the cylinders cannot be drilled anymore and the cylinder block which I can buy now will not be available anymore...

Ideas ? Thoughts ?

[Nessism]

My advice...bore the cylinder you have and install those Yoshimura pistons. Use one ring on that P3 piston as already discussed - unless you can easily find that extra ring in which case use two. Monitor the compression to judge for wear and watch ebay at the same time for another set of 70mm pistons/rings. Those single ring pistons will be fine for a while, it's just hard to judge how long. You should be able to find some decent pistons/rings within the next couple of years which then should be an easy swap at that time.

[Billy Ricks]

My advice...bore the cylinder you have and install those Yoshimura pistons. Use one ring on that P3 piston as already discussed - unless you can easily find that extra ring in which case use two. Monitor the compression to judge for wear and watch ebay at the same time for another set of 70mm pistons/rings. Those single ring pistons will be fine for a while, it's just hard to judge how long. You should be able to find some decent pistons/rings within the next couple of years which then should be an easy swap at that time.

Probably the best thing for now. If you take your time on Ebay and the classifieds here you can pick up what you need to do it the way you want in a year or two. I think if you call Wiseco, even though they aren't their pistons, they can fix you up with rings. They have about a dozen different flavors in different bores. They have sets with different thicknesses and can probably hook you up. I think you can even buy them for just one piston.

I've found NOS heads, valves, decent cranks, and other stuff just taking my time. I had a couple of blocks with a liner missing in one and another with a chunk knocked off of the bottom of one liner. I made one good one out of the two and have a couple of good liners to spare. I have enough parts to do a couple of top end jobs when the time comes. I know buying a block over the internet could be a crap shoot, but in time you could run across a Wiseco set and punch out your block. If you're going to spend the money for a new Wiseco set I'd consider the custom pistons through Ray.

[GSX750ES junky]

I managed to find the wiseco K816 kit for 500$ including shipment. Listing it as "pistons for racing lawn mower" will make sure I pay very little taxes.

So the figures are
- WISECO based overhaul : 500$ wiseco (head gasket included) + 150$ drilling = 650$
- New cylinder block based overhaul (added 85$ for head gasket) : 1535$
- Yoshimura kit based overhaul : 150$ + 85$ (head gasket) = 235$

I guess the picture is different now.
For 415$ I get additional ~ 40,000 miles.
I also want to finish re-building my GSX and not going through the whole story again after 20,000 miles.

Wiseco ?

[rapidray]

As long as it doesn't spin a rod bearing after you complete the build, something this engine is NOTORIOUS for doing!!! Heck, for 1400, I can take one of my 1100 core engines apart, hone it, re-ring it, install all new gaskets, & you will have 110 hp that won't break! Ray.

[SVSooke]

Ray he has a 85 third gen motor,not the 80-83 second gen.Apparently not as prone to that.OP`s other thread http://www.thegsresources.com/_forum...d.php?t=171408