Good Afternoon,
Thanks for all help, this forum is a great resource.
I wanted to see if anyone could identify if this is a stock bore piston out of a 1975 Yamaha RD350. On top of the piston has a 6 with a forward pointing arrow then 14. And just below the highest part of the dome of the piston it is stamped with 979. I added a pic in the attachments. Thanks for the help.
4schizzle
yup. stock bore.
should be a 64mm bore piston.
The 979 is the piston measurement. 63.979mm. They matched it up with an appropriate sized cylinder at the factory to get clearances in spec.
Mine was stamped 974
Quote from: m in sc on April 26, 2022, 02:09:01 PM
yup. stock bore.
should be a 64mm bore piston.
Thanks
Quote from: rodneya on April 26, 2022, 02:22:24 PM
The 979 is the piston measurement. 63.979mm. They matched it up with an appropriate sized cylinder at the factory to get clearances in spec.
Mine was stamped 974
Thanks
Quote from: m in sc on April 26, 2022, 02:09:01 PM
yup. stock bore.
should be a 64mm bore piston.
Any recommendations on what type of piston's to buy? Stock or what aftermarket brands?
Thanks,
Brian
my preference is pro-x
Por X banshee pistons. Just cut the little tang off the skirt.
OEMCycle usually has great prices on ebay or their site.
Quote from: rodneya on April 27, 2022, 11:36:08 AM
Por X banshee pistons. Just cut the little tang off the skirt.
OEMCycle usually has great prices on ebay or their site.
Does it matter what year banshee? I am guessing it doesn't matter the year. What tang do you need to cut off. I am new to the RD's.
Thanks for all the info.
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
https://www.economycycle.com/shop/yamaha-rz-350/engine-related-yamaha-rz-350/pistons/prox-piston-kits-sold-each-yamaha-rd350400rz350rd350lcrd350ypvs-all-years/
Quote from: rodneya on April 27, 2022, 01:33:31 PM
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
Got it thanks.
Hello all,
I am still waiting to get my cylinders/heads back from powder coater. I split the cases and replaced all the seals. I checked the crank and bearings and they feel/sound good and no play. I was just looking at the pistons and wondering why the right side cylinder piston skirt has so much wear/slap/scratches. There was some scratches in the cylinder but i am not sure if the cylinder was scratched or it was aluminum from the pistons. I am getting the cylinders bored so i am guessing it does not matter. I never heard the bike run but it turned over when i got it.
Thanks again for all the help.
Front side of piston.
it got hot and expanded too much.
Thanks
Does anyone know the piston ring end gap for a 75 rd350?
Thanks again!
Quote from: 4schizzle on November 04, 2022, 01:24:32 PM
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")
Quote from: SoCal250 on November 04, 2022, 02:29:27 PM
Quote from: 4schizzle on November 04, 2022, 01:24:32 PM
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!
Quote from: rodneya on April 27, 2022, 01:33:31 PM
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.
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.
Quote from: Vintagetz on November 04, 2022, 04:59:22 PM
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!
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.
Quote from: Vintagetz on November 04, 2022, 05:36:13 PM
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?
Where does this ring go?
Quote from: 4schizzle on November 04, 2022, 07:33:00 PM
Quote from: Vintagetz on November 04, 2022, 05:36:13 PM
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.
I've rebuild a couple of two strokes and never seen one! Got yay! Thanks!
Quote from: 4schizzle on November 05, 2022, 06:59:07 PM
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.
Pro X Instruction sheet per a message request.