New member with a new/old 73' RD350

[RDFL]

http://www.oilypipes.com/yamaha-products.html

[teazer]

Be a little careful here. IIRC stock iron calipers have 48.00 pistons and the bores in the caliper are slightly larger and that's what those alloy pistons are designed to fit.

The alloy calipers have 48.00mm bores and slightly smaller diameter pistons.  Both types are notionally 48mm but one has smaller pistons and one has larger bores to get the required clearance.

If/when you order the alloy pistons be sure to measure the pistons and bores and let the seller know. I had that issue and he sent me a set of replacement pistons ASAP - excellent service and value. 

[Dvsrd]

Rear brake is a stock early 400 that should have that flat torque arm below the swingarm.
It's possible that the swingarm is a later model that had a top mounted torque arm. 

Front appears to be a later single piston sliding caliper on stock RD forks.

Bit of a mix and match.

If I wanted a rear disc brake on s RD350, I would definitely look for something smaller and lighter. A 220 mm disc, 4 mm thick, and a small, lightweight caliper with 25-34 mm bore, most likely Brembo. That stock RD400 setup is totally overkill in so many ways.

[73Yams]

Rear brake is a stock early 400 that should have that flat torque arm below the swingarm.
It's possible that the swingarm is a later model that had a top mounted torque arm. 

Front appears to be a later single piston sliding caliper on stock RD forks.

Bit of a mix and match.

If I wanted a rear disc brake on s RD350, I would definitely look for something smaller and lighter. A 220 mm disc, 4 mm thick, and a small, lightweight caliper with 25-34 mm bore, most likely Brembo. That stock RD400 setup is totally overkill in so many ways.

I agree. It's not going back on.

[202wagon]

Be a little careful here. IIRC stock iron calipers have 48.00 pistons and the bores in the caliper are slightly larger and that's what those alloy pistons are designed to fit.

The alloy calipers have 48.00mm bores and slightly smaller diameter pistons.  Both types are notionally 48mm but one has smaller pistons and one has larger bores to get the required clearance.

If/when you order the alloy pistons be sure to measure the pistons and bores and let the seller know. I had that issue and he sent me a set of replacement pistons ASAP - excellent service and value.

Teazer is 100% correct on this...I have found the repro calipers bore and piston sizes are not consistent like the original 48mm pistons in the oem Yamaha calipers (probably when they do a certain number of production runs? I don't know how or why, but i'm done with it lol.) I took 2 different repro calipers apart and found 2 different bore and piston sizes...ever so slight, but enough to bind the alu pistons in repro caliper, but measure and work perfectly in the original Yamaha calipers as lightweight replacements. So to summarize... the Taiwan/China? aluminum reproduction calipers DO work great AS IS, and are a great value...they even come loaded with brake pads! They're much lighter than original calipers being aluminum bodies even with the steel pistons ( I use them frequently).
If you have original Yamaha calipers with rusty/pitted steel pistons, then our 48mm aluminum pistons are the way to go to lighten that heavy stock steel caliper. Every OEM caliper has the same size bore and piston...Yamaha consistency and quality.

[m in sc]

pretty sure its of an 80s ninja, rear caliper of all things.

[73Yams]

pretty sure its of an 80s ninja, rear caliper of all things.

Yep. That's the one. I found it this morning.

[73Yams]

Well, I stripped it down and am very surprised that the bike didn't fall into pieces while being on the road. There are rear wheel spacers missing, loose hardware on the front wheel/axle, hastily mounted shocks, etc.

I'm going to start cleaning up the poorly de-tabbed frame and thought about fabricating an upper mount for a mono/LC setup. I have heard about the swap, but I haven't found any pros-cons. Anyone have any input? It seemed like a fun project to do with the extra time I have in the workshop.