Riva Ss Flat Pistons Help.

G

geraban19

X
#.0 said:
Those Kawasaki pistons in the picture have the skirts trimmed way up. :bigeyes:

I think most people are using the Kawasaki flat tops for the stock stroke lamey engines. You would be wasting you money going with the Riva superstock pistons for that application.
Click to expand...

The only reason I got those RIVA/R&D pistons is because it is an OEM ported cyl instead of a Lamey wich has diferent ports that let U go with simple KAW's.

Gera
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
My Riva SS pistons weigh 348 grams and the wrist pins are 90 grams each.

You can save some weight by using the older style Wiseco wrist pins which are the same size and weigh about 58 grams each.

3rid said:
I also received 2 set of different pistons and weighted them.
So for your information here are the results.

new shape/design : 346g / 345g
old design : 319g /317g

all in grammes.
Click to expand...
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
Yep... you're right the Kawasaki pistons don't work too well on the 61x big bore sleeves because of the ring pin alignment issue on the auxiliary transfer ports.

geraban19 said:
The only reason I got those RIVA/R&D pistons is because it is an OEM ported cyl instead of a Lamey wich has diferent ports that let U go with simple KAW's.

Gera
Click to expand...
 
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No Square..No Round..FX-1
Location
South Jersey Shore
#.0 said:
My Riva SS pistons weigh 348 grams and the wrist pins are 90 grams each.

You can save some weight by using the older style Wiseco wrist pins which are the same size and weigh about 58 grams each.
Click to expand...

I was told to always use 'Blaster' wrist pins and bearings, and to NEVER use the Wiesco ones. Apparently the Weisco's fracture and break up. I don't know about the older ones though. The reason I was told to use these pistons is because of the ring end gap re-location/orientation.

Thanks guys.
 
masterblaster

masterblaster

X-H2
does the wear at the end of the ring clips really make that big of a diff? Ive talked with many people about big bore yami cylinders who use the kawi flatops and ive never heard a person say they snagged a ring? the cost of the pistons is double from riva for this very slight change in design
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
masterblaster said:
does the wear at the end of the ring clips really make that big of a diff? Ive talked with many people about big bore yami cylinders who use the kawi flatops and ive never heard a person say they snagged a ring? the cost of the pistons is double from riva for this very slight change in design
Click to expand...
When you expose one side of the ring to the auxiliary transfer port window and have the other side seated against the sleeve you're just asking for trouble. Also the skirts are quite different on the Kawi pistons and they have to be trimmed to clear the Yamaha crank webs. The 80 dollar difference in price between the Kawi pistons and Yamaha specific flat tops doesn't justify modifying the piston and risking internal engine damage IMHO.
 

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G

geraban19

X
#.0 said:
When you expose one side of the ring to the auxiliary transfer port window and have the other side seated against the sleeve you're just asking for trouble. Also the skirts are quite different on the Kawi pistons and they have to be trimmed to clear the Yamaha crank webs. The 80 dollar difference in price between the Kawi pistons and Yamaha specific flat tops doesn't justify modifying the piston and risking internal engine damage IMHO.
Click to expand...


I agree with U.
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
We can use the Kawasaki Wiseco pistons with 81-85.5mm bores in our 7 port cylinder (8mm stroker with the long 133mm rods) with no problems with the ring pin positions. The Wiseco 813 series pistons also use the KD rings instead of the TD rings on the Riva pistons. The KD rings are a better ring for longevity as they're a thicker ring, won't wear as much, and will not snag the port as easily and will yield a wider contact surface to the cylinder wall to help dissipate the extra heat from the piston crown in a high performance application.
If your building a stock 61X/62T/64X big bore re-sleeved cylinder, you don't have a choice for a flat top piston unless you use the 760 Wiseco piston and re-machine the piston top.
Chuck
 
masterblaster

masterblaster

X-H2
SUPERTUNE said:
We can use the Kawasaki Wiseco pistons with 81-85.5mm bores in our 7 port cylinder (8mm stroker with the long 133mm rods) with no problems with the ring pin positions. The Wiseco 813 series pistons also use the KD rings instead of the TD rings on the Riva pistons. The KD rings are a better ring for longevity as they're a thicker ring, won't wear as much, and will not snag the port as easily and will yield a wider contact surface to the cylinder wall to help dissipate the extra heat from the piston crown in a high performance application.
If your building a stock 61X/62T/64X big bore re-sleeved cylinder, you don't have a choice for a flat top piston unless you use the 760 Wiseco piston and re-machine the piston top.
Chuck
Click to expand...

Arent there some kinds of big bore sleeves out there that allow the use of kawi pistons? I have mine runnin with kawi flat tops,the cylinder was a pita to get the rings to seat and the cylinder to drop.how much faster will it wear out the ring over the aux boost port?
 
masterblaster

masterblaster

X-H2
took it back apart and checked for wear,I have a older stock 61x cylinder lamey did with some kind of big bore sleeve in it.We marked the piston where the ring pins were and they looked like they fell just to the inside edge of the aux transfers,but not enough to fall into them.where do the rings pins fall on the riva pistons?
 
SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
masterblaster said:
took it back apart and checked for wear,I have a older stock 61x cylinder lamey did with some kind of big bore sleeve in it.We marked the piston where the ring pins were and they looked like they fell just to the inside edge of the aux transfers,but not enough to fall into them.where do the rings pins fall on the riva pistons?
Click to expand...

Between the center boost port and the primary port on a 5 port stock cylinder.
Northwest BB sleeve have the primary ports moved to use the Kawasaki pistons.
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
That ring pin gap rides right on the edge of the auxiliary transfer ports with the Kawi pistons and the NW big bore sleeves too.

Here's a picture of the ring pin locations with the oem piston on the left, Kawi piston in the center and the Riva piston on the right.
 

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masterblaster

masterblaster

X-H2
these must be northwest sleeves then that lamey used back in the day. cause they are right at the edge,it looks like with the rivas it will be right in the middle between the ports.

Chuck..why would riva and r&d request a ring that isnt as good as the kawi type? are they suppose to be less resistance,with a lighter piston? faster reving? how much less time will they go than a kawi piston? with the diff in heat transfer what should they be clearanced at on the safe side ? .0050 or .0055
 
#ZERO

#ZERO

Beach Bum
Location
Florida - U.S.A.
The Kawi pistons have a two degree dome which spreads the compression forces more towards the ring lands. The Riva pistons are completely flat which keeps the piston crown under load and gives a faster heat transfer to the cylinder wall. The Riva pistons also have a special coating on the top and underside to keep the piston from overheating. The reduced piston weight and the thinner rings help to keep the reciprocating mass lighter and the internal engine friction to a minimum.
 
masterblaster

masterblaster

X-H2
sorry chuck,could you resend it to me,I cleared it out,I thought you would respond here in the thread for a future reference for everyone.

#0 thanks I just got them in a weighed them,they were a few grams lighter than the kawi pistons,they look far nicer overall with the coating and the cnc look even inside the piston,I guess with the flater dome the squish should still be the same at the outer band edge.With the pin in both pistons the riva looks maybe just a tiny bit lower on the crown but very close to the same
 
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SUPERTUNE

SUPERTUNE

Race Gas Rules
Location
Clearwater Fl.
My reply was I said that on a 85mm bore your going to lose 2.7 cc of compression between the Kaw/R&D *2 degree piston and the *0 degree piston. Almost the difference between pump gas and *108 oct. race gas. (about 3.5cc)
 
masterblaster

masterblaster

X-H2
I figured Id lose a little comp,but thats a bonus in this case,not needing as much octane with the timing im running.how many psi is 2.7 cc worth?
 
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