I recently lost the oil cap for my 175, reason being it fit loose and never would tighten as it should. So I bought another from an ebay ad for a CT3 tank. When I recieved it, it too was loose. So loose it would fit into the hole and not make contact with the threads. So 2 caps that didnt fit properly. So I took the cap off of my AT3 which fits properly and tightens on the AT3 oil tank. It fits correctly on the CT3 tank.... :/ Question is were there 2 different size oil tank opening? Remember the ebay cap was advertised from a CT3. Help!

I'm guessing the ebay cap was used or old? The caps sometimes shrink with age. I have some old ones that won't thread in (too small) and some that do. I don't know why some of them shrink.

I'd buy a new cap from Yamaha.

Yeah my HT1 i just sold was like that, so i cut a bit of thin pushbike tube & stretched it over. greased it with rubber grease & worked good as a simple fix but when the guy came to collect the bike & asked about the oil, i had to undo it carefully with pliers as had grabbed quite tight. I remember 'that' happening to the fuel tank caps on out MX250's & the like. Think we got aftermarket alloy replacements.

I've seen oil caps that have shrunk on old Honda and Toyota cars.

Thanks. I'll order a new one.

Recently read your post from 2018 about your oil tank cap not fitting. Having the same problem. Have ordered cap that is advertised as OEM. Cap is WAY too small. Did you resolve the issue?
Thanks

Old caps shrink for whatever reason.. Unknown what you bought, what it's for, how old it is, or where it came from?

I've never had a problem with a new cap from Yamaha. You can get one online from many Yamaha dealers or your local dealer.

Here's the parts list for the tank... still available brand new. Buying a cap except from an authorized dealer is a gamble in my opinion.

www.partzilla.com/catalog/yamaha/motorcycle/1973/ct3/oil-tank

A slight thread hijack here (sorry!), but is anyone able to confirm which Yamaha bikes used the grey oil tank tap?

All roads for new ones lead to black, but some models did have a grey one fitted. Current favourite theory here in the UK is that the 1976 and 1977 RD250C, RD400C, RD250D and RD400D had the grey ones fitted, before later models reverted to black.

Thanks.

This is for a 1972 AT2. Ordered cap from partszilla Way too loose. Maybe I have the wrong tank on this bike? All the mounts fit right.

Hmmm... Partzilla doesn't really "advertise as OEM" like people do on ebay or someplace.... Partzilla sells OEM...


Posting pictures of the tank, cap, and parts bag and label of the cap Partzilla sent you would help.