Big O ring in oil filter kit

Windmill John

Windmill John

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Hi All,
What’s it for in case I’m missing something?
I‘m talking about the big round one. Is it for different models?
My bike is a 1981 CM400A and I have the square with curve o ring.
IMG_2026-05-27-193826.jpeg
 
It fits like the square/curve one because Honda cheaped out and stopped molding shaped ones.
Service bulletin said they seal better but I think it was just cost cutting, bit more difficult to keep in housing without contact adhesive
Probably fits dozens of different bikes.
I don't like them
 
Honda supplies both and it is clear which one is correct for the 400/450 series. You have a spare for your next Honda bike which will take the round one. It is actually the best fit being very slightly larger in the cross section than the aftermarket ones supplied with some no name filters.
 
Flyin900 said:
Honda supplies both and it is clear which one is correct for the 400/450 series. You have a spare for your next Honda bike which will take the round one. It is actually the best fit being very slightly larger in the cross section than the aftermarket ones supplied with some no name filters.
Click to expand...
Interesting. I'm going to piggyback on this thread. I was riding today and when I came out from a stop, I had a 2" diameter oil spot under my '78 CB 400A. Leaking right at this gasket. So I went to find a 'kit.' One on Amazon (Wix?) had one review saying this exact thing: the o-ring is smaller and it leaked.

When I changed my oil last fall, I believe I used a 4into1 kit. It was fine the remainder of the season and for a couple rides recently this season. But today that leak. So now I'm thinking I better at least go back to an OEM gasket.
 
I
esh21167 said:
Interesting. I'm going to piggyback on this thread. I was riding today and when I came out from a stop, I had a 2" diameter oil spot under my '78 CB 400A. Leaking right at this gasket. So I went to find a 'kit.' One on Amazon (Wix?) had one review saying this exact thing: the o-ring is smaller and it leaked.

When I changed my oil last fall, I believe I used a 4into1 kit. It was fine the remainder of the season and for a couple rides recently this season. But today that leak. So now I'm thinking I better at least go back to an OEM gasket.
Click to expand...
I have done a lot of different bikes and the early Goldwing's had issues sometimes with the aftermarket large round O rings supplied in aftermarket filter kits. Someone on the NGW site came to the conclusion that the aftermarket O rings were slightly smaller in the cross section measurement. I experienced it more than once on those early Wings with seeping at the O ring on the filter canister, so now I only use OEM Honda filters on my newer models.

The semi-rectangular seal ring used on the smaller filter of the CB/CM/CMX 400/450 were never an issue for me leaking. I used aftermarket filters WIX and HI FLO there all the time on a few different models I restored. The 1984 CB450SC has an aftermarket HI Flo filter and O ring and no leaks with over 3K on the oil change.

That said I have many old stock parts items bought years ago squirreled away. So just like shrinkflation things are getting cheeped out everywhere these days.
 
Last edited:
esh21167 said:
Interesting. I'm going to piggyback on this thread. I was riding today and when I came out from a stop, I had a 2" diameter oil spot under my '78 CB 400A. Leaking right at this gasket. So I went to find a 'kit.' One on Amazon (Wix?) had one review saying this exact thing: the o-ring is smaller and it leaked.

When I changed my oil last fall, I believe I used a 4into1 kit. It was fine the remainder of the season and for a couple rides recently this season. But today that leak. So now I'm thinking I better at least go back to an OEM gasket.
Click to expand...
I've been using the WIX filters for years now without problems but then again I don't buy from Amazon, local parts store orders them for me.
 
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