Yamaha Fastener Sizes

The Yamaha fastener part numbers actually tell you at minimum the bolt size and most of the time the length as well. This is not new information but rather there is a lot of scattered documentation found online and collected here where it pertains to the Yamaha Bolt. If you are trying to identify a bolt or nut size you can usually find the part number on sites like Bike Bandit or Partzilla where you can see an exploded diagram of parts and their corresponding part numbers, then use the following specification to identify the size and other attributes.

Part Number Specification #

For the purposes of this explanation we will use the part number, 91317-08016-00.

Digit 1 – Type of hardware #


The first digit indicates the type of hardware where 9 indicates it is a fastener. Not sure on other types of hardware but 9 is definitely a fastener.

Digit 2 – Sub-type #


This specifies the sub-type of the hardware. Where in our example this fastener would fall into a category of a bolt since it is designated with a 1.

DigitSub-type description
0varying type (misc)
1bolt or cotter pin
2screw or nut
3oil seal, O-ring, or bearing
4spark plug
5bolt or nut
7ISO bolt
8ISO screw, nut, and etc.

Digit 3 #


Unsure of what this digit means.

Digit 4 – Material #


This signifies the type of material used for the fastener. Unsure of what the digit options are in this position but most motorcycle engine parts are made from carbon alloy and stainless steel. Most of what is seen in this position are 1’s and 2’s.

1Carbon Alloy Steel?
2Stainless Steel?

Digit 5 – Finish #


Could be chrome, unfinished, etc. Not sure one what each digit value stands for.


Digits 6-7 – Thread size #


This is the thread size. In this example it is an M8. and 10 would be an M10.

Digit 8 – Pitch? #


Unsure on this one but it may signify the pitch, maybe 0 is standard pitch for this particular fastener and a 1 might indicate non-standard pitch?

Following is a list of the usual (or in some cases standard) pitch for most nuts and bolts depending on the fastener size.

Fastener SizePitch

Digits 9-10 – Length in millimeters #


The length of the bolt, however when the sub-type specified in digit 2 is zero (0) this typically is not accurate and there is no indicator of the actual length in the part number and it is unclear what these two digit then mean. In our example we have a bolt that is 16mm long.

Digits 11-12 #


Unsure if these are ever used but they always seem to be two zeros.

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