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History and differences between Yamaha RD250, RD350, RD400,
73-80 TZ250/350, LC, and RZ engines

(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 (61x59.6 - 2 transfer piston port 350)

-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 stud lengths

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 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 90338-17016)
-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.

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 it.

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 drive gears).

While the rest of the world got electronic ignition in 79/80 the US didn’t

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 snapping problem.

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 crankshafts.

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 bolt up.

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 17mm.

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 closed.

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 the frame.

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
A,B 352
C,D  1A2
E,F  2R8, 3M3
RD250LC  4L1,  RD350LC  4L0

TD3 (250) cases had their numbers on the left side (no number plate on the right side yet) and were DS7-99_ _ _ _
TR3 (350) cases had their numbers on the left side (no number plate on the right side yet) and were R5-99_ _ _ _
TA250 had the Numbers DS7-99_ _ _ _ on the left also
Starting in 73 when Yamaha switched from DS7/R5 to the RD series they started casting a number pad on the right and stamping the cases there.
The RD's used 352 (250) and 351 (350) prefix's but the TZ's continued to use DS7-99_ _ _ _ and R5-99_ _ _ _ and used these numbers all the way through the DS7/R5 case based engines accept for the TZ250G which had 4A1-99_ _ _ _
Replacement cases came with no prefix or numbers at all.

RD250,RD250LC,TZ250 Cyl Ht 96.5-96.6mm
RD350 102.5-102.6mm
RD400  111.7mm

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 Oceana Daytonas

TZR250's
1986-88 2MA - 1KT Case reed forward facing cylinders
1989-90 3MA Reverse Cylinder

Transmission Ratios
TZ250   RD400   RD250/350
.81        .888        .785
.87        .961        .888
.96        1.083      1.040
1.13      1.318      1.318
1.42      1.778      1.778
1.93      2.571      2.571

Primary Gears
RD250 68/21 3.238
RD350/400/LC/RZ 66/21 2.869
TZ250 77/23 3.35
TZ350 74/25 2.96

Cylinder Studs
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 pistons.
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 (very easy),
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 area.
There have been some Extra Big Big Bore cylinders done with H2 pistons and sleeves.

The Crankshaft
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.

Clutch
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 FZR1000
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.

Transmission
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
-1986 YZ125S reeds. “These are a 3-petal reed cut one petal off to fit your stock cages. Part number 55Y-13612-00-00”
-Modify your stock reedcages by removing the center divider and using single petal reeds, this works great for 80% of the RD’s out there, If your extensively modifying your stock reedcages you can get “The Harry Barlow cut” from TDR which is a tapered reed that completely covers the reedcage surface area.
-Stock YZ85 reedcages
-V-Force YZ85 reedcages. Part number V382A (Use AG472A stuffers)
-RZ350 reedcages
-RZ350/Banshee V-force reed cages
My favorite for 90 percent of RD applications is stock YZ85 reedcages with either stock reeds or TDR racing reeds part# 88-EE or V-force YZ85 reedcages.
Anything bigger than this and major surgery to your cylinders or replacing the whole intake reedbox is required.

Intake manifolds
RZ350 are a nice improvement and allows you to use an intake crossover tube or boost bottle. You can also get aftermarket RZ manifolds without the crossover.
TZ750 intake manifolds P/N 409-13565-00 are discontinued but TZ Mike does make very good quality reproduction manifolds.

Racing Ignitions
Motoplat
PVL
HPI Racing
HPI also makes a small external rotor ignition with lighting.
ProFlo (No longer available)
Stock TZ250/350
MZB
MZB also makes a CDI ignition with lighting

If you just want to eliminate your points which is ALWAYS an improvement in the past I adapted Dyna ignition units from inline 4 cylinder engines but Vintage Smoke makes a DYNA ignition kit that bolts right on now.