(From the 1970 DS7/R5 to the 1990 reverse cylinder TZ250)
(Note: for ease of reference I refer to 73-80 TZ‘s as “early TZ‘s“)
-1957 the YD1 Yamahas first Two Stroke Twin
-1962 The RD56 Yamahas first World Grand Prix Champion winner (56x50
rotary valve 250) and the introduction of Yamahas first production road
racer the TD1 (56x50 Piston Port).
-1967 The YR1 Yamahas first 350 and first horizontally split parallel
twin (61x61 350 2 transfer piston port)
-1970-1972 DS7/R5 start of the 4 transfer port cyl base/case layout
that form the basis for the RD and early TZ series
-DS7 / TD3 250
-R5 / TR3 350
-TA250 early 1973 aircooled TD3/TZ hybrid
-4 Transfer cylinders (4 side transfer ports) were referred to by
Yamaha as 5 port cylinders to describe the scavenging system: 4 transfer
and 1 exhuast port.
Yamahas 4 transfer with boost port RD cylinders were referred to by
Yamaha as 7 port cylinders: 4 side transfer, 1 boost, 1 intake (now part
of the scavenging system on the reed valve “Torque Induction”
engines) and 1 Exhaust port.
-RD is short for Race Developed
-An interesting point: The some of the "works" TR3 engines
from 1972 sported 6 transfer ports, like the 79/80 TZ350
-1973-1980 TZ’s used a variant of the “RD” cases but used
Piston port monoblock watercooled cylinders
-1974 introduction of the TZ700/750
-1980 the TZ250 G in a last ditch effort to get ever last hp out of
the “RD” based case engines ran an intake so big it had a 4mm “tooth”
that hung down into the intake port for piston ring support and an ultra
short intake side piston skirt. It made more hp but quickly became know
as the piston eater..
-1981Yamaha totally redesigned the TZ250 engine. Having reached the
limit of intake port size in the G, the H models crankshaft rotation was
run backwards to put piston thrust on the cylinder wall opposite the
intake allowing further increases in intake port size. The cylinders
were now individual but still piston port. Also new was Yamaha's exhaust
power valve system which in it’s infancy had a few teething problems..
This was also the first TZ250 to use a gearbox oil pump to reduce
gearbox oil induced drag in the gearbox.
-1985 Yamaha again Redesigned the TZ250 engine. 1985-1987. Switching
for the first time to case reed induction to create much needed bottom
end and widen the powerband. BUT 1985’s reedcages were to small and
were quickly enlarged
-1988-90 in a last ditch effort to get every last hp out of the
parallel twin design Yamaha reversed the cylinders & tilted them
forward to 60deg putting the carbs in front & the pipes coming
straight out the back under the seat
-Because the R5/DS7 was the first Yamaha to use the 4 transfer port
cylinder base case layout (2 on each side with a 5th boost port added in
the RD series) RD, LC and early TZ cylinders will bolt directly onto the
R5/DS7/RD and LC cases though you do need to use the correct cylinder
BUT the R5/DS7 only had a 5 speed but it is super easy to swap out
the gears, shift forks and shift drum for an RD 6 speed setup.
TZ cases were a separate casting than RD cases, a very slight variant
but still a separate casting, but so close though that when TZ racers
broke early TZ cases it was super common to replace them with RD cases.
TZ cases differ from RD cases in that-The oil drain is in the middle of TZ cases but
offset one the RD cases. The center RD crank bearing surfaces normally
have a cast in steel insert but the TZ cases normally didn’t.
-The front engine mounts are rubber mounted,
-The grooves to locate the TZ crankshaft are cut into the crankshaft
inner bearing area instead of the primary side bearing area because the
TZ’s used a different crankshaft (that will interchange if you cut the
grooves in RD cases) that used Roller bearing outer main bearings.
-There is an oil passage below the shift drum not "drilled" on
TZ cases between the transmission and primary gear sections of the case
and the kickstarter boss has a plug in it (Yamaha part number
Early TZ’s had a different transmission, though it can drop right
in RD cases it has a VERY tall first gear and much closer gear ratios
with a longer mainshaft to allow for the TZ dry clutch.
The TZ dry clutch if combined with the TZ transmission or an RD
transmission with a special mainshaft will bolt directly into an RD.
A TZ dry clutch with a special mainshaft will bolt directly on to an LC.
A TZ dry clutch with a special mainshaft and slight modifications for
gasket sealing to the cases will also bolt onto an RZ.
Generally DS7/R5 cases had no grooves in the crankshaft seal area to
secure the seal as everything RD and later do (but I‘m told some did
DS7/R5 cases did). And they did not have the mainshaft clutch side
bearing retainer behind the clutch.
According to the aircooled RD club early RD400 Prototypes had solid
mounted engine mounts!
RD400 cases have slight differences in the castings, the earliest had
a little less material around the cylinder base gasket area at the rear
and more ribbing around the right main bearing and right transmission
mainshaft bearing in later cases.
Starting with Daytona in the US and later UK cases used a different
kickstarter mechanism. Daytona could use either kickstart mechanism, I
was told back in the day that the gear on the “Daytona style”
kickstart mechanism which on this new design was not constantly engaged
with the idler gear like the earlier mechanism, in racing had slid over
and engaged on some racers so common practice was to retrofit the old
system when using “Daytona’ cases. I did have one build that the
bikes owner would not take no for an answer (Technically you gain a
small amount of hp by not having the kickstart gear constantly engaged
“sometimes“ these small amounts are worth it.. Other times they
are..) so I used a cut down throttle slide return spring to keep the
kickstart gear positively disengaged when not in use. One drawback with
the “Daytona” style kickstart mechanism is that it does kick over
more slowly . This style also used a “single” offset idler/tach
drive gear instead of the 2 gears pressed together of the earlier style.
EarlyTZ’s used this “double gear” also but ran it with a needle
bearing. Later RZ’s used the “single” gear but added a bushing to
Since Daytona and later RD’s used the single gear kickstart idler
gear they used a longer tach drive shaft, a smaller nylon tach drive
gear and a different tach drive ratio.
TZ250 and 350 had different primary gear ratios than the RD’s so
they used 2 different nylon tach drive gears (and 2 different water pump
While the rest of the world got electronic ignition in 79/80 the US
The 79 US Daytona, got a new crankshaft without the dreaded lead
weights but improper heat treating it’s believed caused them to snap
the center section under racing conditions
Later UK RD400 and RD250 did get this style of crankshaft though with
the larger LC/RZ style ignition taper for the electronic ignition they
got and I’m told those did not have the racing center crankshaft
LC’s went a step further and went to the now well know RZ/Banshee
style crankshaft but the LC’s still had the RD 16mm wide big end
bearing (RZ widened to 17) but did use the larger big end and wrist pin
bearing outer diameters of the later RZ.
An LC crankshaft will fit in Aircooled RD cases, but you need to mod
the end of the crank, OR 'doghouse' the RH cover to take the longer
crank. (no oil pump can be used after this mod) the LC crank also allows
for a large taper cdi to be used, and yes, an RZ or LC cdi will then
bolt right on to aircooled cases. you will need to clearance the LH
cover to accommodate the cdi pickup though.
An RZ crankshaft is aprox 2 mm too wide to drop right into RD/LC
cases but have been made to fit.
The keyway on a Daytona crank is 90 degrees off the LC and RZ
RZ cylinders while will “slip in” to RD cases but have a much
different cylinder base stud pattern, the cylinder center to center
spacing and heights are the same as a RD and LC 350 they just won’t
The RZ right side cover/water pump will not work on an RD set of
cases because they are missing the rear water pipe passage and the boss
to support the pump shaft.
RZ and LC have a longer right crank snout than an RD to take the
water pump drive gear.
Some have used the wider RZ rods on RD cranks by machining .5mm off
the inside of each crankweb.
An RZ clutch cover will almost fit onto an RD set of cases but the RZ
have a little more metal in two places.
An RD clutch cover can be made to run a TZ water pump, the TZ
waterpump will be driven through the original oil pump drive shaft hole,
but it does require an adapter plate fit under the pump.
LC and RZ use the same kickstarter arrangement/mechanism. Similar to
the Daytona and later UK RD’s On the RZ/LC the inner end of the
kickstarter shaft is a smaller diameter than RD‘s, so either the cases
needs to be bushed or a sleeve pressed onto the shaft. The outer portion
of the shaft is longer than an Air cooled motor which is fine if you use
an LC or RZ clutch cover. This can only directly be done on Daytona and
later UK cases as there is a different style locator spring boss in
those cases (unless of course you weld and machine the cases).
Twice to use an LC side cover on an RD I grafted two early style RD
kickstart shafts together to extend the kickstart mechanism the needed
You can run RZ/Banshee primaries on an RD I’ve done it many times.
The Daytona and later left side covers had a provision for the
electronic ignition pickup.
The Daytona had thinner primary gears.
The Daytona 5th and 6th gears had thinner engagement dogs which made
them easier to shift into these gears but not good for racing.
The Daytona and later used a different shift mechanism ratio.
76-78 US RD400's had a small cutout at the bottom of the skirt on the
exhaust side for emissions reasons that actually let ex gasses into the
crankcase at TDC The Daytona did not have this cutout because it used
vacuum controlled external exhaust butterfly valves to accomplish the
same result so the trick was to use Daytona pistons in all the 64-65mm
bore RD's at least until RZ (and LC) pistons came out.
76-78 US Rd400's also came with an small exhaust bleed port in the
roof of the exhaust port approximately 10mm above the port, in
performance applications it's standard practice to plug and weld these
All year RD250‘s and 350's in the US had Dykes ring pistons (not
good for racing).
An RD400 left side cover will fit an LC perfectly, you just have to
make some room for the electronic ignition trigger for the LC.
The LC and RZ bottom ends are very similar.
The crank width was the same from RD to LC but they did widen the
trans gearset making the gears wider.
The RZ crank width increased slightly (approx 2mm) and with it
another increase in gearset width and shift drum. Gears differ but the
RZ uses a few of the LC‘s gears 3 I count with the LC 4L0 prefix, both
changed to the “shiftstar” type gear change mechanism. LC and RZ
crankcase mount dimensions are the same, but differ largely than the
aircooled RDs. LC/RZ engines have 2 mounting points, aircooleds have 4.
Aircooled RD’s had a first gear needle roller bearing were the LC went
to a bushing there.
LC and RZ transmissions use three shift forks and not 4 as in the RD’s
Unlike the RZ, LC’s still had the clutch pushrod that went all the
way through and out the left side of the cases to a clutch actuator in
the left side cover just like the RD’s.
LC/RZ use the same shift forks . Tach gear assemblies are the same LC
and 83-84 and US 85 RZ . Clutch basket/ primary gears are
interchangeable. Clutch hub , LC clutch cover will fit the RZ , same
gasket for both . Oil pump are interchangeable , 1979-80 RD400 2R9 , LC
and RZ . Coolant pump , LC and RZ . Reed valves , RD350 , RD400 and LC
plus RZ500 . Carburetor manifold and balance tube ,1979-80 RD400 2R9 and
LC . Motor mounts with spacers , LC and RZ and stays under the motor to
There are 2 different clutch and sprocket splines between the
RD250/350 which used 13 splines and the RD400, later RD250, LC and RZ
transmissions which used 6 splines.
Here are some engine model differences between US and UK
250/350/400's from a European viewpoint.
RD250/350. Euro 351/352 models have a blocked 6th gear (different pawl
plate in selector segment pins)
RD250/350B. Euro 521/522 models have 521 cylinder heads and gearbox. The
gearbox has all 6 speeds available and has the same ratio's of the later
250/400 with overall closer ratio's
RD250/400C/D. Euro 1A2 (250) and 1A3 (400). Similar to 1A1. Gearbox
shafts have later type splines. Cylinder heads are marked 1A0 (250) and
1A3 (400), different casting to 1A1
RD250/400E. 2R8/2R9. "TZ" style crank with no lead weights and
slotted rods. Revised cylinders, porting and CR. Revised 400 pistons
without front cut-out in skirt. CDI ignition. Revised LHS case cover
with bulge over CDI pick-up coil. Gearbox and shifter changes. Narrow
primary gears. Small “LC” X-over tube on 400.
RD250 came in models
E,F 2R8, 3M3
RD250LC 4L1, RD350LC 4L0
RD250,RD250LC,TZ250 Cyl Ht 96.5-96.6mm
RD400 Model Codes
USA Daytona Model code 2V0
Canadian Daytona model code 3J7
Oceana Daytona model code 3M4
76-78 model code 1A1 - all markets
79 European model code 2R9
The cylinders and heads from a 1A1 will fit all years, as long as they
are swapped as a complete set, along with the exhaust pipes. The
cylinders, head and head gasket for the 2V0 are unique. The cylinders
for the 3J7, 3M4 and 2R9 are the same. The 2R9 had separate cylinder
heads and the 3J7 and 3M4 had a one piece head, they should be
interchangeable. The 2R9 had separate head gaskets and the 3J7 and 3M4
had a one piece head gasket, but 2R9, 3J7 and 3M4 have the same gasket
thickness, so you could use the separate gaskets on the Canadian and
1986-88 2MA - 1KT Case reed forward facing cylinders
1989-90 3MA Reverse Cylinder
TZ250 RD400 RD250/350
RD250 68/21 3.238
RD350/400/LC/RZ 66/21 2.869
TZ250 77/23 3.35
TZ350 74/25 2.96
RD 250 90116-08065-00 90mm(72-73mm sticks out of casing)
RD350 90116-08064-00 97mm (80-81mm sticks out of casing)
RD 400 90116-08232-00 117mm (98mm sticks out of casing)
TZ250 90116-08213-00 94mm
TZ350 90116-08212-00 101mm
TZ750 90116-08212-00 101mm
RD250LC/RD350LC 90116-08219-00 106mm
Banshees had different transmission gear ratios than the RZ most
everything else interchanges between the two.
RD250/350/400 Performance Parts Upgrades
RZ350 or Banshee pistons are a far superior piston than the stock RD
Of the cast pistons OEM are arguably the best, then Vertex, then Pro-X
Of the forged pistons Wossner, then Wiseco
The center tab at the bottom of these pistons must be removed thought
And Vertex must be trimmed a bit if used in an RD400.
For Racing Bigbore Topends (66mm and up)
1980 IT/DT 175 pistons or Yamaha Blaster Pistons. Either piston is 5-6mm
shorter than stock and requires machining the top & bottom of the
cylinder to compensate for the height. The blaster pistons also have a
10deg piston dome instead of the RD/RZ/IT/DT 15deg so it does require
reccutting the cylinder heads (but if your doing a bigbore you need to
recut the cylinder heads anyway)
Sleeving these cylinders is not ideal because of the decreased heat
dissipation from the pressed in replacement sleeve and the thickness of
a replacement sleeve cuts into the already limited transfer port tunnel
There have been some Extra Big Big Bore cylinders done with H2 pistons
For High HP applications Shot Peening the connecting rods is recommended
2T2 rods are the best of the OEM rods
Need Hollow crank pins? I use Kawasaki 13035-1010-01
Big End Bearings
I use OEM RG500 Big End Bearings 09263-22060 for all out racing and
Wiseco RG500 part# B1047 for EVERYTHING else
Crankshaft Main Bearings
73-80 TZ250/350/750 outer roller bearings are part number 93310-00012
but these days hybrid ceramic bearings are the way to go
Exhaust Flange Gaskets
76-78 US spec cylinders use Suzuki 14181-01D00 They have a larger I.D.
But a newer option is to use Blaster exhaust flange gaskets.
FZR1000 friction plates 4H7-16321-02 have about 40% more surface area.
RZ350 have surface area than the RD400 because they didn't use the large
rubber "cushion rings" to reduce noise but less than the
Steel Plates Earlier RD250/350 steel clutch plate didn't have "The
balancing notches" so have more surface area or Barnett
The RD250/350 had a 6 plate clutch but that can easily be swapped out
for the later 7 plate clutch.
If you put an RD400 trans in an RD250/350 with the 400 clutch
(because the RD400 transmission has closer 4th, 5th,
and 6th gear ratios) you will have to clearance the inside of
the RD250/350 right side engine cover, or I've heard you can use a
thicker side cover gasket.
RZ350/Banshee Clutch Basket and Primary Gears fit right on to Rd’s
Dry clutch conversion
I’ve heard that Harry Barlow used YZ490 parts to do this conversion
TZ250/350.(Takes a little work) Use the clutch and primary sidecover.
This requires a longer mainshaft, but the stock TZ mainshaft has a
higher first gear than the RD’s and is part of the main shaft so you
can either run the TZ transmission with higher first gear and close
ratios or get a special mainshaft from this company: http://www.yamaha-tz-classicracing.de/uk/teile_getriebe.html
or Fondseca or Nova that allows you to use an RD transmission with the
TZ dry clutch parts. The TZ dryclutch cover didn’t come with a
provision for a kickstart mechanism but I have seen several of these
covers modified to use a kickstarter. I've used a billet LC cover by
Metemachex on RD250/350/400’s to do this with a kickstarter but you
have to extend the kickstart shaft 17mm. NOW Fondseca makes a dryclutch
cover with the kickstart provision.
For racing it is highly recommended for racing that you get your
transmission undercut by a company like R&D Motorsports. R&D
also does transmission micro polishing and anti friction coating
“According to Yamaha service bulletin 259 any spinning gear should
have between .003” to .005” side play for maximum efficiency. Too
little clearance and it will bind, too much and the gears can pop out of
engagement causing the dogs to become rounded. Select the proper size
shim and install it so the spinning gear is moved toward the sliding
gear that engages it. Sizes are 20.2x33x.5,.6,.7,.8,.9, and 1.0mm
(137-17427-00-05). And also 25x34x.3 and .5 (168-17428-01-03)”
Reeds and Reed Cages options are:-
-Use the stock reedcage with a single petal reed racing reeds or stock
(thinner) single petal 93-2012 YZ85 reeds trimmed down just slightly at
the front. Or