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Chain Case Swap - 06 Attak into an 05 RX-1


Jan 6, 2018
Derry, NH
2014 Nytro XTX 1.75
2005 RX-1
Can I easily replace the chain case (has reverse) in an 05 RX-1 with one from and 06 Attak? Part numbers for the housing and cover are different. RX-1 housing is 8FA-47541-00-00 and Attak is 8FP-47541-00-00. Covers are similarly different. 06 Apex and Attak share the same housing and covers. I understand in 06 the case material changed from aluminum to magnesium. I also read that the ebrake holes may be in a different location but not sure if that affects an 05 or just an 03 RX-1 which had a larger rotor. I assume the core geometry is the same (mounting holes, bearing locations and etc.)? I also saw that the Attak has a 23T driver sprocket vs. the 24T on the RX-1, but both have the same 70 link chain. So unless I replace the 23T with a 24T I'd give up a little top end but no big deal there. Bad seal lead to loss of oil and destroyed the original chain case and most everything inside. Swapping the entire case is much cheaper than buying all the parts that would be needed. The 06 Attack seems like the best option based on what I can find right now. Thoughts?

Edit: Just found one for an 08 Apex which has the 24T sprocket so might even be a better option.
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guys used to put the rx warrior/attack/apex ltx top gear in on the 121 apex/rx 1 for better hole shot.

if memory serves, the 05 rx sleds shared the same drive shaft as the apex/attack sleds. from what i am seeing in that part # that chain case should work. this article i found explains how yamaha part # work.

Decoding Yamaha Part Numbers​

Written by Makotosun . Posted in How To Articles

About Yamaha Part Numbers​

Did you ever wonder what the different parts of a Yamaha part number stood for? There actually is a method to their madness. Here are the details - Unplugged!

Part Number in the format XXX-XXXXX-XX-XX
The first three digits are the Model Code (every model in the Yamaha Product Line has a unique model number) all parts are given a Model Code of the first model they were used on.
The middle five digits are the Basic Code number and indicates the actual part, i.e. 11631 = piston; 11311 = cylinder, etc.
"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 assembly).
The next two digits are the Design Code and Design Change digits (so 01 means the part has had one design change). This part may or may not appear different, but it will be interchangeable with the original part.
The last two digits are the Color or Finish Code.
For a Part Number in the format XXXXX-XXXXX-XX
These are Hardware (fasteners). they all start with a '9' and end in '00'. - 9XXXX-XXXXX-00
The second and third digits tells us what type of fastener:
  • 0 - 'various'
  • 1 - bolts, cotter pins
  • 2 - screws, nuts
  • 3 - oil seals, O-rings, bearings
  • 4 - spark plugs
  • 5 - bolts, nuts
  • 6 - ISO bolts
  • 7 - ISO screws and nuts
The fourth and fifth digits tell us what material/surface finish (i.e. chromed).
Digits six and seven give the diameter (inner or outer) e.g. 08 would be an M8 size.
Digits eight, nine and ten are the length (except for '901' bolts for some reason)
There are also standard fastener types...e.g.
90105-XXXXX are Washer based bolts
90116-XXXXX are Studs
90401-XXXXX are Union bolts
99999-XXXXX means that a part has been superseded by a kit.
In addition to what maim provided, your top gear from your RX-1 should work with what ever chain case you end up swapping with as they should be compatible as well.