update: meant to say DT 74-... I accidentally referenced all bikes in title. I know the 125, 250, 360 have same lock.

Note, the fuel tank lock has 1 tumbler that is activated by a base part of the key.   See photo below.  Note, I measured this with an old gauge, hopefully measurements are close. To the best of my knowledge, tumbler location is constant.   The 2 keys below are different bikes.

Pic of disassembled Lock:


lock face before recovery.


lock face after recovery.



basically, the lock inserts about 0.332" as measured from lock face and front of tumbler.  The tumbler is apparently activated the same on these series of locks, by the base area of the key.  See vertical blue line for tumbler contact location on key. 

Basically, if you have a blank key, I guess this means the fuel lock will open also.  Note, tumbler can be removed and then ANY object that fits opening will allow unlock.  

lock description related to key.


 

Thanks for posting.

Just had a play with my own DT360A, using various other Yamaha keys (RD, DT3 etc) - some operated the tank lock, some didn't.

I therefore more or less agree with you, but would observe that Yamaha used about 10 key templates at that time. Some would probably have had the same shoulder shape as each other, others wouldn't. So basically, find a key with the shoulder shape that fits the lock, and you are good to go.

Going back to Gerry's original post, which I'm assuming is what prompted this thread, I'm not sure now that the 1974 locks had numbers on them - I can't see one on mine, although it has been forced at some stage.

GERRY - if no number on yours, then you might be able to use the number on your ignition switch. Saying that, you've probably tried this key already?

The other 9 types of keys are irrelevant.  The only keys I mentioned were for the ignitions of DT 125, 250,360 w/same fuel tank locks. Based on the images I have outlined, would you agree this is the case for these keys?  Looks to me like the tumbler uses the base part of the key,  I could be wrong.    
You can also see from the post, a screwdriver might also be effective as an RD key.     

The post was intended for viewing the general setup of the lock and general discussion.

I would recommend you keep that tumbler in though. You never know who will come in the night for that liquid 2 stroke gold in a 50 year old rusted tank.

 

Nice write up!  Thank you!

Sorry pab, I didn't mean to contradict you, just fine tune things a bit - sorry for any offence caused. 

Within the same models, keys with different profiles would have been used - this gave the scope for different lock permutations. So you would have keys that go into a lock and operate it ok, keys that go into a lock part way, or all the way, and not turn it, or keys that won't even go into a lock.

A table of the Yamaha key numbers and profile number is attached.

Playing Devil's advocate a moment...

In the earlier Yamaha parts literature, the key part number actually had the bike model name in it...  and each model had a limited "range" of key numbers...  with generally no more than two (similar) blanks used over several model years.

That chart shows keys for models going back to the early 1960's

For example, the original "214" switch used the "411" or "412" key blank depending on the key number range of 2311 to 2418.  Very limited range was used, you wouldn't get a new CT1 or DT1 that might use any of the keys on that chart. 

I don't know if I have 1974 key information anywhere, but it seems very likely Yamaha may have continued the convention of using a very limited range of key numbers and key blanks for the DT models that year... 

And it also makes sense that Yamaha designed the 1974 cap to accept any 1974 "DT" key...  which aligns with my limited experience (which is less than "irrefutable proof") from back in the day that DT flip cap ignition key would open many different caps... 
(Discovered this accidentally...  when I was a kid, friends Dad and brother all had 74 DT's with the key cap...   different size bikes and different ignition keys, but any key from the three bikes would open any of the caps...  we tried it on other bikes and never found a DT flip cap with key that didn't open with a different DT flip cap key)

Thanks Mark.

That could be good news for gerryz!

Some of my Yamaha keys fitted my DT360A, some didn't. However, you guys over there are in a far better position to comment on what the situation was when the bikes were new.

Not directly related to this topic, but I note that the early locking round petrol caps, as fitted the RD125/200 etc, had a very limited number of locks (I think with three digit codes), whereas the later ones had four numbers matched to the ignition switch.

gr8uncleal, no offense taken. Thanks for posting that doc.