DT125R ARCHIVE

Bradders, are the barrells in your photos measured from the bottom of the liner to the top of the casting, or Just the height top to bottom, of the outer casting?

The latter measurement is the important one, and all the 3BN barrells I've seen have a shorter outer casting than any 3MB barrells. Trying to replace a 3MB barrell with a 3BN one without changing the crank will (in my experience) always result in the piston hitting the head and locking the engine (using extra base gaskets may prevent this happening, but I wouldn't like to risk it!).

All left side crankcases from 1988 to 2007 are marked 3BN above the flywheel cover. There were few changes to the crankcases over this period so Yamaha presumably decided it wasn't worth updating the model code on them?

More confusingly, all powervalves fitted to 3MB barrells are also stamped 3BN! There are no powervalves with 3MB markings in existance as far as I know. However, these 3BN powervalves will not fit a 3BN barrell.

2RH is stamped on most, if not all genuine Yamaha conrods used with 3MB barrells. I'm not sure if the early (1988) models with 3BN barrells used shorter conrods, or had the crankpin fitted slightly more centrally in the flywheels to reduce the stroke.

Yeah mate, I haven't worked out the differences between Y - 1, Y - 2, Y - 3 etc either.

I reckon the letter A is probably a red herring - anybody could have put that there.

The amount that the liner protrudes out the bottom of the barrell should also be irrelevant, as this won't effect the overall height of the barrell when it is fitted to the crankcases.

Might also be worth bearing in mind that the 1988 DTR's fitted with 3BN barrells had a red line on their tacho at 9,500 rpm, that's 1,000 rpm less than the 3MB model introduced the following year.

you will all drive yourselfs to an early grave trying to work this one out,

 found this as an example

 

 

 

 

 

 

 

 

 

 

 

Understanding the structure of Yamaha Part Numbers

 

 

1. How to read the Yamaha Part Number

A

 

Factory OEM parts are divided into two general categories: General Parts and Interchangeable

Parts.

B

General Parts Refers to parts manufactured for one or more specific Yamaha models (i.e.:

pistons, crankcases, fuel tanks etc.). This twelve-digit part number structure is as follows:

000-00000-00-00.

Due to the amount of new parts being added to Yamahas system, and the lack of available

numerals for the assigning of new part numbers, it has become necessary to use an alphanumerical

system in the numbering of new parts. An «X» within the part number structure of

the General Parts group indicates a position in which a letter may be used in place of a

number. For example: XX0-X000X-X0-X0.

The group breakdown of the general part number structure is:

1. Model Code Number Data: XX0-X000X-X0-X0

The first three digits within the general part number structure are model designation numbers.

Within this three-digit group, two numbers may be replaced with letters.

The major portion of letter substitution will occur with the second position of this three-digit

group (i.e.: 0X0-00000-00-00). This letter has no other significance other than model

identification. The model identification indicates the original model in which the part was

used, i.e.:

1A0-00000-00-00 Identifies RD 400 model

2A0-00000-00-00 Identifies XS 400 D model

3A0-00000-00-00 Identifies GS 340 model

2. Basic part number data: XX0-X000X-X0-X0

The second group of five digits is the actual parts group identification number (i.e. 11631 -

piston; 11311 - cylinder etc.). A «W» substituted in the first position of this five-digit group

(000-W0000-00-00) indicates a factory assembled kit which differs in content from the

original assembly used in production (i.e. 2M0-W0046-00-00 Rear Break Pad Assy). The

first three digits of this five-digit group (000-XXX00-00-00)indicates the general sections and

areas of the models. The fourth and fifth digits of this group (000-000XX-00-00) indicates

the specific part within these general sections and areas. In the case of number overflow, a

letter will be substituted in the fifth digit position of this five-digit group (i.e. 1T4-2814A-00-

00 Wire Tool).

3. Design Code Number Data: XX0-X000X-X0-X0

The ninth and tenth digits of the part number indicates differences, corrections or

modifications to the original part number. The ninth digit position (000-00000-X0-00) may

be substituted with a letter. This position indicates variations thet may exist within a specific

item, i.e.

1J7-12169-A1-00 Pad Adjust

1J7-12169-E1-00 Pad Adjust

1J7-12169-F1-00 Pad Adjust

The tenth digit of the part number (000-00000-0X-00) indicates the number of times the

design of the part has been changed.

4. Color or finish Code Data: XX0-X000X-X0-X0

The last two digits of th epart number will indicate the finish or color of the item if

applicable. In this latest group, only the eleventh digit may be replaced with a letter (i.e. 1T4-

24785-00-U8 Seat Moulding)

C. Interchangeable parts

These part numbers always begin with the number «9» and are divided into three sections.

The first two sections contain five digits each, with the remaining two digits in the last

section.

The following is a breakdown of the interchangeable part numbers:

9 00 00 00000 00

Major classification Type Material/surface finish Shape/size zeros to make 12 digits

At this time, a letter may be substituted in two positions on interchangeable part numbers:

1. Type/kind code: 9X000-00000-00

With the large amount of new types and kinds of interchangeable parts, it will be necessary to

replace this with a letter in some cases.

2. Shape/size: 90000-000X0-00

In the case of bearings, the last two digits of the second group of five digits indicates the

registration (identification) number of that bearing. Because of the large amount of new

bearings being developed, the ninth position of the part number (90000-000X0-00) may be

replaced with a letter (i.e. 93310-422E6-00 Bearing, Big End).

D. Part number sequence

[This only relates to finding parts in the price list and is of no importance today]

2. How to use this parts list

A

Except for steel balls (ball sizes are indicated in inches) all parts are indicated in millimeters

as in the following examples:

Hose (rubber or vinyl) Inside diameter - length

O-ring Section area - inside diameter

Washer, shim, collar Inside diameter - outside diameter Thickness (length)

B

Parts supplied in the form of sub-assemblies are identified by an indentation of one letter

space, and the description is preceded by a dot (.). If 2 main assemblies are listed, each

different yet having the same basic description (i.e. left and right sides of the same assembly),

one will immediately follow the other. If each of these main assemblies is made up of almost

the same components, these component parts will be listed immediately under the second

main assembly line and will be indicated as noted above.

If the component is the same for both assemblies, the quantity indicated will be the total

required. If the component is not the same for both main assemblies, the quantity for each

separate item will be listed separately.

Examples:

Description Qty

Carburetor assy, left 1

Carburetor assy, right 1

. Jet, pilot 2

. Nozzle. main 2

------

.Lever, starter, left 1

.Lever, starter right 1

C

Keys to symbols

U.R Use size (thickness) and/or number as required

U.N. Use as many as you need

T Number of teeth in a gear

V Voltage for light bulbs

S «S» type oil seal or «S» type circlip

SD, SO, SW «SD, «SO» or «SW» type oil seal

E, R «E» or « R» type circlip

F/No. Frame No. (Applicable machine no.)

D

Basis for determining Right and Left in Relation to Parts

Right or left is determinated by the rider facing toward the front of the machine.

E

Superseded part numbers

1.

If part «A» has been superseded by part «B» and bot «A» and «B» are interchangeable, the

superseding part number (part «B» will appear in the part number listing with the superseded

part number (part «A») appearing in parenthesis immediately following the description.

Example:

Ref no. Part no. Description Qty

(Part «B») (Part «A»)

8 123-45678-00-00 Cylinder (111-12345-00-00) 1

2.

If part «A» is a substitution of part «B», and parts «A» and «B» are both available in stock,

part «A» will appear first in the part number listing and part «B» will appear directly under

part «A». When the stock is depleted on part «A», the computer will automatically ship part

«B».

Example:

Ref no. Part no. Description Qty

8 123-45678-00-00 Cylinder 1

111-12345-00-00 Cylinder (111-12345-00-00) 1

3.

If a part is no longer available, the part number will appear in the part number listing in

parenthesis and N/A (no longer available) will appear in the remarks column directly to the

right of the entry.

Example:

Ref no. Part no. Description Qty

8 (111-12345-00-00) Cylinder 1 N/A

4.

A part that has been superseded to a kit may be identified by a 99999-00000 part number

appearing in the part number column. The old superseded part number will appear in

parenthesis immediately following the description. Listed directly below the 99999 part

number will be those parts making up the kit. The description of the parts making up the kit

will be preceded by a small black dot (.) and the description will be indented one letter space.

Example:

Ref no. Part no. Description Qty

8 99999-12345-00 Cylinder (111-12345-00-00) 1

234-56789-00-00 . Head, cylinder 1

345-67890-00-00 . Gasket, cylinder 1

 

 

eG x LoGiKzZ wrote:

---

dont know if its of use to anyone, but the 3mb barrel on my 04 DTRE has a 3bn powervalve

---

 Apparently they all have 3BN stamped on them lol. I've got some more info on this anyway.

 

Does anyone know what year the 3BN cylinder came from?

 

From what I can find out it came from a 1988 DTR.

 

See photos.

 

 

 

 

 

 

 

 

And then you get this sudden change in bore size...

 

 

 

 

 

So if that's correct the barrel most come off a 1988 DTR. But I thought that year was the year of the MKIII LC's?

Mine came with the 3bn head and 3mb barrel, that standard on a 2002 or not?

they wont change the rod length but the big end pin location on the crank its self. that determins stroke length, so if anything the cranks will be different, this is all bull**** tho y make it all different n complicated!??? lol

no matter how long or short the rod is it will still move the same distance, say the crank web is 5 inches in dia thats 2.5 inches from centerline of main journal and the centerline of the big end pin is 2 inches from that. the total distance traveled of the centerline of the big end pin is 4 inches from tdc to bdc.. what ever the rod length