Topic: CB550 tachometer cable mount ("cap") o-ring stumper

[carnivorous chicken]

Chasing down an oil drip in the 550F, and figured since I'd replaced all the allen head bolts on the head cover with oem that might've led to a seep. And that's where it looked like the oil was coming from -- and may still be -- and I've got the o-ring and the breather o-ring and the 6 pucks but... when I pulled the tach cable out the housing (aka tachometer cap) was busted. This might be the source of my drip, and luckily I had two extras on hand that I scavenged from Bob's while they were scrapping all of the bikes in the yard (and since I knew these were rare and had seen them go for $$ on fleabay).

Off I go to check them, and on one of them the screw that holds the cable in came out easily. Someone had painted it black, so I spent time cleaning off the pain with a wire brush and got ready to mount it when I realized... something different going on. There is no groove for the o-ring! My broken one had an o-ring. And the other one does too. The screw wouldn't budge on the other one, heat didn't work, so I drilled out the mounting screw, cleaned it up, and mounted it. Gonna take it for a long test ride in the next few days to see if that stops the drip.

But now it seems like I don't still have another spare for my 550 -- see the photo below. I am 98.7% certain I pulled it from a 550 in the yard -- I know what those engines look like, and I knew what I was after. I looked at a few bikes in the year range of the 550s and even 500s -- all seem to have had the groove for the o-ring. It slipped right in to the mount in the engine and looked pretty identical minus the groove and some rougher casting. Anyone have any ideas? And how would it seal anyway without the o-ring? Small flat seal against the body? but since there is only one screw on the top side, not sure how well that would hold oil in at the bottom. Anyway, happy to hear anyone's ideas about it.

[newday777]

Well that is a good question. I looked at the parts fiches of the 500 years and all the 550 years and models, they all call out for the same part numbers for the cap, drive, seal and orings, so there should be a groove for the oring on all the 500s and 550s to 1978.
I haven't worked on the 550s other than the normal maintenance of my exes 77 550K back when it was new.
I didn't look at the 650 fiches and don't know anything about them.

Maybe a groove could be cut in with a lathe?

I take it the rusted piece was the cable end you removed from one of the Bob's caps?

[carnivorous chicken]

I take it the rusted piece was the cable end you removed from one of the Bob's caps?

Yep, that's right. I clipped the cables of both of them to get them out more quickly at the time.

It's a stumper. The top of the 650 engine is pretty different looking than the 550s, but I had a look at the fiches yesterday too just in case -- and it looks like they have grooves too. The bike looked like it had been sitting for decades so I doubt that someone had made an aftermarket part for it back then (although now would make sense, I've seen them sell for over $100).

And I thought about that too -- cut a groove into the one that doesn't have one. If they're that rare, makes sense.

[Stev-o]

Hey Chris...sounds like a shade tree mechanic fix, he just used whatever part was laying around since he didnt have the correct one.

[carnivorous chicken]

Hey Chris...sounds like a shade tree mechanic fix, he just used whatever part was laying around since he didnt have the correct one.

Could be... but what other part is the exact same (minus the groove)? And didn't it leak oil if it didn't seal?

Inquiring minds want to know, but the answers might not be found I guess. Or maybe someone knows...

[MauiK3]

Hard to understand some having an o ring groove and some not. Is there a gasket on the one without the groove? Must be something to keep it from leaking. Maybe an internal groove inside the cover?

[carnivorous chicken]

Indeed. I would have kept the gasket with it, I imagine, when I pulled it. Maybe I missed it if it was somehow stuck to the engine, but I doubt it (I can actually remember that day pretty well, walking around the third yard -- I'm gonna miss that place).

There has to be something to seal it though, as underneath there is a small hole and groove for oil to flow and lubricate where the shaft of the gear turns inside of the housing, just barely visible in the photo on the one that doesn't have a groove.

[Stev-o]

Hey Chris...sounds like a shade tree mechanic fix, he just used whatever part was laying around since he didnt have the correct one.

Could be... but what other part is the exact same (minus the groove)? And didn't it leak oil if it didn't seal?

Inquiring minds want to know, but the answers might not be found I guess. Or maybe someone knows...

Maybe from a CB450?

https://www.ebay.com/itm/192222676623?chn=ps&mkevt=1&mkcid=28&google_free_listing_action=view_item&srsltid=AfmBOoqd1QuAZiIcZn0trUYMkZksgJqKYypW7IFTaKssn3qpId9a4WarTyI

[carnivorous chicken]

I had a quick look at 500Ts and 450s -- different housing.

[newday777]

I take it the rusted piece was the cable end you removed from one of the Bob's caps?

Yep, that's right. I clipped the cables of both of them to get them out more quickly at the time.

It's a stumper. The top of the 650 engine is pretty different looking than the 550s, but I had a look at the fiches yesterday too just in case -- and it looks like they have grooves too. The bike looked like it had been sitting for decades so I doubt that someone had made an aftermarket part for it back then (although now would make sense, I've seen them sell for over $100).

And I thought about that too -- cut a groove into the one that doesn't have one. If they're that rare, makes sense.

When I looked this morning, it looked like the cap is available still from CMS and I would check with South Sound Honda too as it didn't say NLA

[carnivorous chicken]

When I looked this morning, it looked like the cap is available still from CMS and I would check with South Sound Honda too as it didn't say NLA

I had another that had the groove and so I installed that one... But good to know they're still out there. I've ordered a few things from South Sound but the last two times the site said it was in stock and then the next day the cancelled my order because they were out of stock.

[bryanj]

Cms and dss have had them made inby a manufacturing firm and are not Honda nos.
I see no problem with this as long as they dontvtry to say they are genuine

[carnivorous chicken]

Cms and dss have had them made inby a manufacturing firm and are not Honda nos.
I see no problem with this as long as they dontvtry to say they are genuine

Me neither, and as long as the seal correctly...

[newday777]

When I looked this morning, it looked like the cap is available still from CMS and I would check with South Sound Honda too as it didn't say NLA

I had another that had the groove and so I installed that one... But good to know they're still out there. I've ordered a few things from South Sound but the last two times the site said it was in stock and then the next day the cancelled my order because they were out of stock.

Best to call and ask