1972 CT2 and my kickstart seal was leaking, so I ordered a "NOS" seal...now the seal that was on my bike, which I'd assume to be original, sat flush with the case cover. This allegedly "NOS" seal is about half as thick and is indented back about 4.5mm from the outside of the case when installed. It'll probably work fine, but I'd like to know what's original. Anyone tell me which is correct, flush with the case or a little inside it? Thanks!

I also don't know how most of you here keep your shop so spotless...mine isn't

A new OEM CT2 shift shaft seal is 6mm thick. Do you have the numbers from the seal you replaced? Shift shaft seals are flush with the case in my experience.

Seller claimed it's 93104-20007-00 but it's 4.5mm thick, clearly not the correct seal. Thanks for the clarification, assumed the prior 6mm thick seal in my bike was stock but wanted to be sure.

Crap, I was thinking shift shaft seal for some reason. Sorry man, I'm losing it... OEM Kick start seal is 4.5mm thick.

Edit: Here's a link to the Yamaha 93104-20007-00 seal with good pic and description showing that it indeed is 4.5mm... CT2 Kickstart Seal

Thanks for the clarification again, someone must have replaced the oem with a thicker one on mine. A bit recessed makes sense for wear and tear on the seal.

Sometimes in aftermarket seal kits the seals can differ slightly from oem. Usually they work fine.

Nice bike btw, my favorite year for Yama enduros

Now here's a curious thing, I don't think this seal should 4.5mm wide, I think it should be 7mm wide.
I'm just working on my CT1-C and I'm replacing some seals including the kickstart seal as I have the clutch cover off.
I went online to order the replacement seal and checked the part number and size on CMSNL and it gives 93104-20007 as the part and dimensions of 20x30x4.5, however the seal I removed is 20x30x7.
I checked the part number against the part listings here and the part number is correct and the "Remarks" column says S20-30-7 as does the assembly drawing.
Also, as others have explained to me the part number itself carries dimensions, the 20 representing the diameter and the 7 the length.
The recess in my clutch cover is 8.2mm deep which will allow a 7mm seal to fit below the face.
Just like RT360FAN I've seen pictures of that part clearly showing a 4.5mm wide seal, whether these really are OEM or NOS who knows, but anyway for anyone replacing seal I believe it should be 7mm wide.

The part number carrying dimensions really only applies to bolts, pins, and screws... 91 and 92 series numbers as far as I know.

Although generic bearing numbers are often embedded in the non-model specific bearing part number (93 series) so there could be some seal dimensions in the numbers. It just doesn't appear to me that you can reliably decode seal dimensions from the part numbers? At least I haven't seen a reliably decipherable pattern for seals.

As far as the 4mm vs 7mm you are correct that the original seal was thicker. The 9XXXX-XXXXX series of part numbers are for parts that are used on many models... You could often use a 4mm thick seal in place of a 7mm thick seal but not the other way around. So to minimize parts Yamaha probably decided to change the thickness dimension to 4mm.

One thing about the older parts lists is they show the dimensions of many parts like seals and industry numbers for bearings so you can get them from any good supplier, not just from Yamaha.

www.yamaha-enduros.com/index.php/worksho...and-ct-parts-listing
Hi Mark Happy Christmas, have a look at page VII, it says 930 numbers are seals etc. and 940 are tyres, rims etc. and shows the sizing format for the part number.
I think it was probably one of your posts or Gr8uncleal's that enlightened me to the sizing format typically used for bolts.
Again, I've learned from you guys about ordering some parts from other suppliers and have ordered a couple from Simply Bearings.
Thanks for all the help, will do an update when I get the cover back on in a few days.