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I made a mistake above. The MX 360 has a single ring and the R-1 two stroke has the ring pins too close together! Jeff

O.K. Here it is: DT-1,MX 360 and R1 And R2( all are old Yamaha two strokes) pistons are 80mm as is the TY 350 which has a chrome bore lining. Boring to a bigger size would require re-sleeving and plating(big cost).The DT-1 has a single thick ring which is fine for higher RPM, not the low RPM torque of the TY and the "piston rock"associated with single ring pistons.The MX 360 has a longer skirt(might need shortening) and no rear "port windows"( would need to be cut into the piston).This piston has two thin rings like the TY 350 but the ring locating pins are too close together and would locate the ring ends right over the rear intake port(NOT GOOD).R-1 pistons have the single thick ring. The R-2 piston has the right windows and two rings, the lower is a thin MX 360 ring and the top is a Dykes ring which is "ramped " to the outside and is exposed to the top of the piston/combustion chamber and the compression pressure pushes the ring outward for better sealing.This is the "holy grail" piston/ring replacment for the TY 350. MX 360 stock bore or "one over" rings are a good replacement for the TY 350. Any bigger would dig grooves in the cylinder even when properly gapped. All of the above are discontinued! Maybe someone knows of a source... Jeff

I just pulled my top end off and I will be taking it to my local guru for his findings as to what pistons or rings might work. His company does all of the local motorcycle shops machining and top-end/crank work. He is a wonderful 73 year old machinist who has decades of motorcycle knowledge upstairs. He is a Wiseco "dealer" and told me that lots of old Wiseco inventory got sold in bulk lots and they don't run those old parts anymore. Yamaha MX 360 parts might be close but not availible either. DT-1 maybe but needing windows cut in the piston? 8o mm Jet-ski??? I'll post my findings...

Wow! Nice explanation! Good job on the motor work. I'm looking for piston and rings for a top end job and my favorite online source doesn't show any availiblility. Are parts availible? Maybe another bikes rings? Also I got some modification info from 1996-1997 about things guys were doing to their TY's to make them "Super TY's". This includes carb mods,swingarm extensions,fork mods,linkage mods and frame mods(!) to reduce rake. I could post some if anyone is interested. Quite a bit of stuff! Are those Talon brakes pretty rare? They look tempting...

Jon, It looks like you machined the "lip" all the way off of the head. Do you run the thinner head gasket with that? Your head does have much more volume in the bowl than mine. Could I run both mods(lip removal & thin gasket) with my stock head? Could you explain your porting and pipe mods also? And why do you like some flywheel left on as compared to complete weight band removal? I'm not wanting to go too crazy but my old "73 Bultaco Alpina 350 was a torque monster compared to this TY in it's current state. This bike sat probably a decade before I got it. How would I know if my crank seals are leaking? Jeff

Great info! Are the pegs about 1 inch down and 1/2" back? Also a gent pm'ed me saying he had a lightened 250 flywheel for sale. Are AC/mono TY 250/350 flywheels interchangable? The bike I bought has some mods, but does anyone have before/after photo's of modded heads or flywheels( mine may already have been done...)

Hello to all! Can you tell me about lightening the flywheel on a 1985 TY 350? Just picked one up that has some mods( reed cage mod with two stage boyesons,Works Performance shock,PVC fork spring spacers,clutch arm extension,etc) It doesn't seem to peppy though. Also, what's the preferred peg relocation technique? Thanks in advance