Restoration Yamaha RD125 A: November 2015

Wednesday, November 11, 2015

Yamaha RD125 - Specifications - Maintenance data - Production data

Production data Yamaha RD125 1973 - 1986

It can be very hard or sometimes even impossible to find production data for Yamaha's from the seventies. Apparently Yamaha didn't keep record of their production data back in the days... or maybe those books are laying, covered in dust, somewhere at an attic.. who knows. Thanks to Yamaha Australia I got production numbers of most of the Yamaha RD125's. I've put them together in an Excel file to give you an idea of the numbers of Yamaha RD125's ever made.

Production data Yamaha RD125

Tip: right click on the pic to open it in a new window for a better view.

My Yamaha RD125 has engine - and frame number 466 - 001172 which makes it one of the first batch Yamaha RD125A's .

Engine number Yamaha RD125A

Frame number Yamaha RD125A

Specifications Yamaha RD125 A/B

Yamaha RD125 B Specifications

Engine – air-cooled twin-cylinder two-stroke

Capacity – 124cc

Bore & stroke – 43 x 43mm

Carburetion – 2x 18mm Teikei

Max Power – 13.8 bhp @ 9500rpm

Torque – 7.6 ft-lbs @ 9500rpm

Ignition – contact breaker

Transmission – 5-speed chain final drive

Frame – steel tube engine used as a stressed member

Suspension – 28 mm telescopic forks twin rear shock pre-load adjustable

Wheels – 2.75 x 18, 3.00 x 18

Brakes – 150mm twin leading shoe drum, 130mm single leading shoe drum

Wheelbase – 1245mm

Weight – 115kgs

Fuel capacity – 11.4 litres

Top speed – 76mph

Source: www.classic-motorbikes.net

Specifications Yamaha RD125

Dimensions Yamaha RD125

Maintenance specifications Yamaha RD125

Service Data Yamaha model RD125 A (Printed December 1973)

Issued to all official Yamaha workshops in 1974.

Yamaha Service Data Motorcycle Model RD125A

Parts lists and Manuals

Basically the Yamaha RD125A is the same as the 1973 RD125. The 1973 RD125 was sold in Europe as the Yamaha AS3. If you're looking for parts for your 1974 RD125 A, you can use the 1973 RD125 parts manual (download http://www.yamaparts.com/manuals/ ) , however there are some minor differences which you can find in the RD125A supplement (4 pages, see below).

Yamaha RD125 / AS3 Parts manual 1973

Supplement Yamaha RD125A page 1 - Refer Yamaha RD125 1973 parts list

Supplement Yamaha RD125A page 2 - Refer Yamaha RD125 1973 parts list

Supplement Yamaha RD125A page 3 - Refer Yamaha RD125 1973 parts list

Supplement Yamaha RD125A page 4 - Refer Yamaha RD125 1973 parts list

Service Manual Yamaha RD125B
Service Manual Yamaha RD125B/RD200B

Cover Owners manual Yamaha RD125 January 1973

Road Test Yamaha RD125A

Article in Cycle from 1975

http://www.motorcyclespecs.co.za/model/yamaha/yamaha_rd125%2075.htm

Source Cycle 1975

Another article on www.classic-motorbikes.net

http://classic-motorbikes.net/wp/yamaha-rd125b-road-test/

Cable routing Yamaha RD125

Wiring diagram Yamaha RD125

Torque specs Yamaha RD125

Advertisement RD125 - RD125A

Advertisement Yamaha RD125

Tuesday, November 3, 2015

Fitting new Pistons and Rings

As mentioned earlier the pistons were in bad shape and needed to be replaced with new ones. The cylinder walls were also scratched and in need of some boring and honing.

Partly melted piston Yamaha RD125 A 1974

Partly melted piston Yamaha RD125

Damaged piston Yamaha RD125A

So I brought the barrels to Sam Milton, and after measuring they told me I could get away with 1st oversize (43.25) pistons. Original ones are pretty hard to find these days but luckily I found a new set on Ebay and bought the piston rings in France.

Yamaha RD125 466-11635-01 pistons

Yamaha RD125A 466-11635-01 piston inside

Yamaha RD125 466-11635-01 piston inside

Yamaha RD125 466-11635-01 piston top

Later Yamaha RD125A 307-11601-11 rings

When searching for new piston rings make sure you know what you're looking for; The earlier AS3/RD125A pistons (part number 396-11635-00 ) go with the 396-11610-00 rings (so called Dykes / "L" section rings) while the 307-11601-11 rings for the later 466-11635-01 piston are "square" section. The RD125A models did use 396- piston and rings but these were superseded to 466- pistons and 307- rings.

One of the heads had some of the piston top "glued" to it, but with a high pressure cleaner and steel wool I was able to remove it.

Piston material "welded" onto cylinder head

Yamaha RD125A cylinder head after some cleaning

Yamaha RD125A cylinder head after cleaning

Fitting the new pistons rings is always a bit of a challenge because they tend to break when you bend them to much. I used a couple of feeler gauge blades and a rubber band to slide them in the piston ring grooves.

Fitting new piston rings Yamaha RD

Fitting new piston rings Yamaha RD125

New piston rings fitted

I also used new needle bearings, clips (ALWAYS use new clips) and good second hand piston pins.

"Inside" piston clip fitted - yamaha RD125A

Small end rod needle bearings 93310-11281

Before I put back a piston I have already fitted the inside clip, it's a lot easier then doing this when the piston is already on the rod.

"Inside" piston clip fitted - yamaha RD125A

Make sure the arrow on top of the piston is pointing towards the front of the engine and the piston ring ends are at the right spot. Fitting the barrels over the pistons is a matter of compressing the rings back in their grooves and carefully lower the barrels. The bottom of the barrels is a bit wider then the actual cylinder to make live a bit easier. Grease the cylinder walls, rod bearings, pins etc with engine assembly lube so the don't wear in the initial start up.

First cylinder back in place

Cylinders back in place

New head gaskets fitted - Yamaha Rd125A

Before I fitted the cylinder head I cleaned, sanded and nickel plated the cylinder head bolts. For more info about DIY nickel plating see http://yamaha-ls3.blogspot.com.au/2015/02/diy-nickel-plating-bolts-and-nuts.html

Nickel plating cylinder head bolts Yamaha RD125

Nickel plated cylinder head bolts Yamaha RD125

First cylinder head back in place