Gas cap spring..

[LMS]

In an attempt to rekey the tank to match the ignition, which by the way did not work. The spring that causes the lock to spring back once key is turned ended up somewhere in my garage as it flew off. Does anyone know where to get one of these without buying an entire assembly? Rd ones are expensive as heck, maybe another path?
Thx.

[LMS]

A pen spring fits almost perfectly but is too short. Found some springs on amazon that might work with some trial and error, will try that route.
In regard to rekeying, the lock/key for the tank looks original. The ignition key will not fit the tank lock as the main part of the keys, if it was blank, is cut opposite of one another. This leads me to believe that the ignition is from a different bike. Which makes sense because one gauge was a xs gauge. Oh well.

[m in sc]

take the tumblers out of the tank lock. then any key will work.

[SoCal250]

If you've got an Ace nearby their hardware/fastener section should have what you need for a spring. The one here has a huge assortment of just about any little doo-dad you could need.

[m in sc]

fyi, it has a part number. maybe speed and sport has one?  341-24637-00

[irk_miller]

I hope you guys don't mind me asking here, since it's related, but is there a source for the latch pin on the RD400 tank that the cap latch hooks around?  Right now, I'm using a cotter pin which works fine, and I can certainly find some rod of the same dimension and make one, but hoping there's a source for the real deal somewhere else.

[SoCal250]

The spring that causes the lock to spring back once key is turned ended up somewhere in my garage as it flew off. Does anyone know where to get one of these without buying an entire assembly?

fyi, it has a part number. maybe speed and sport has one?  341-24637-00

Ahh, your needing the latch return spring. I misunderstood which part you were missing. I can guarantee that as soon as you locate one and have it delivered you'll find the old one on your garage floor. (I speak from experience.)

FYI the original part # that Mark supplied above was superseded to 90508-07235-00

There are a couple VERY expensive ones on ebay right now, but CMSNL has them for a lot less: https://www.cmsnl.com/products/spring-torsion-341246370000_9050807235/?recommId=ddfc83c316029d72a58c81bcadb9ad19

[SoCal250]

I hope you guys don't mind me asking here, since it's related, but is there a source for the latch pin on the RD400 tank that the cap latch hooks around?  Right now, I'm using a cotter pin which works fine, and I can certainly find some rod of the same dimension and make one, but hoping there's a source for the real deal somewhere else.

part # 90249-03123-00  PIN, SPECL SHAPE
That part is NLA but there are a couple very expensive ones available on Ebay 
I would think it would be pretty easy to fab one up.  It's a pretty simple looking shaft with a small head flange and a C-clip groove.

[LMS]

Found it, lol. I remember where it flew off to, spent some time in that dirty part of the garage and there she blows. Here's a pix of the spring I was referring to, you can barely see it hiding.

[LMS]

take the tumblers out of the tank lock. then any key will work.

I tried that and the ignition key will not slide in at all.

[m in sc]

you need to take the tumbler springs out as well .

yeah, thats def not the spring i was thinking of.

[LMS]

you need to take the tumbler springs out as well.

yeah, thats def not the spring i was thinking of.

I did, I had the whole thing apart, cleaned it, etc. The ignition key, god knows what bike it's from, will not go into the tumbler of the gas cap. As you can see,the main groove is cut on opposite sides.

[m in sc]

ohhh. well, then the lock cyl in the ign isnt right

[automan]

Get a blank with the correct keyway.
$5 max.

[Hawaii-Mike]

I drilled out the tumblers, now any key of that size will open it.