1975 Yamaha RD350 Pistons size

[4schizzle]

Thanks

[4schizzle]

Does anyone know the piston ring end gap for a 75 rd350?

Thanks again!

[SoCal250]

Does anyone know the piston ring end gap for a 75 rd350?

RD350B Ring End Gap
Top:  0.2-0.4 mm    (0.008-0.016")
2nd: 0.15-0.35 mm (0.006-0.014")

[4schizzle]

Does anyone know the piston ring end gap for a 75 rd350?

RD350B Ring End Gap
Top:  0.2-0.4 mm    (0.008-0.016")
2nd: 0.15-0.35 mm (0.006-0.014")

Thanks SoCal250!

[4schizzle]

Pistons are all the same. Banshee motor did not change from 86 to 2008 or so.
The piece circled in red should be cut off  to the same level as the pieces beside it and filed with a bit of a champfer or it may catch the intake port

Why does this the center tab on the new pistons need to be cut off?  Just wondering as they are the same length.  Getting ready to reassemble the cylinders. 

[Vintagetz]

Both the RZ and the Banshee have a bridged intake that covers that little tang, without it that tang will hang on the center section of the port floor given the rod is pushing the piston against the back of the bore.  This causes a little shock wave on the lower section of the skirt and with the reed holes the skirt will fail, it will not tolerate the flexing caused.

I do not want to contradict M in SC, but that seizure can be caused when you have excessive piston clearance and rings get worn out.  It causes the flame front to travel past the rings, this can burn the lubrication oil off the piston and cylinder walls and will cause a seizure. 

[4schizzle]

Both the RZ and the Banshee have a bridged intake that covers that little tang, without it that tang will hang on the center section of the port floor given the rod is pushing the piston against the back of the bore.  This causes a little shock wave on the lower section of the skirt and with the reed holes the skirt will fail, it will not tolerate the flexing caused.

I do not want to contradict M in SC, but that seizure can be caused when you have excessive piston clearance and rings get worn out.  It causes the flame front to travel past the rings, this can burn the lubrication oil off the piston and cylinder walls and will cause a seizure.

Thanks for the response was just wondering why. Getting ready to cut them off now!

[Vintagetz]

Wrap the piston in a rag, and hold it firmly and carefully.  I have used a relatively fine saber/jig saw blade in a pair of vice grips and sawed it off by hand, then I dress it flat with a file and put a gentle chamfer along the edge.

[4schizzle]

Wrap the piston in a rag, and hold it firmly and carefully.  I have used a relatively fine saber/jig saw blade in a pair of vice grips and sawed it off by hand, then I dress it flat with a file and put a gentle chamfer along the edge.

Done! How's it look?

[4schizzle]

Where does this ring go?

[rodneya]

Where does this ring go?

In the trash can

[Vintagetz]

Wrap the piston in a rag, and hold it firmly and carefully.  I have used a relatively fine saber/jig saw blade in a pair of vice grips and sawed it off by hand, then I dress it flat with a file and put a gentle chamfer along the edge.

Done! How's it look?

Looks perfect!!!! 

On the "Where does this go" for the most part 4schizzle is correct, it is a "ring expander"  I believe it normally goes in first on the lower ring (if you check the rings one is a bit narrower to allow for the expander, we do not run them in race motor, does not hurt to leave it out.

[4schizzle]

I've rebuild a couple of two strokes and never seen one! Got yay! Thanks!

[4schizzle]

I've rebuild a couple of two strokes and never seen one! Got yay! Thanks!

That's exactly what it is a ring expander. It goes on the lower ring. Never seen one before. Was going to throw it away but put it in.

[4schizzle]

Pro X Instruction sheet per a message request.