Topic: CB650 - Is my muffler rebuildable?

[fizzlebottom]

1982 CB650SC Nighthawk. Stock exhaust.



While reinstalling my exhaust last night I noticed a nice rattle coming from only 1 pipe. I turned it upside-down several times and got some debris out, but there is something loose inside still. It doesn't leave the muffler, so it is sitting inbetween the pipe and the outer muffler casing, where the long-gone baffling was (I'm guessing).

There are no rust holes that I can see anywhere on the exhaust, so I'm wondering if folks believe these mufflers to be rebuildable (or at least can be disassembled so I can remove the loose debris inside. The allen fasteners in the pic all move freely, but I'm not sure at all what they're attached to and don't want to undo them without knowing what to expect.

Any insight at all?

[Flyin900]

Allan bolts are not stock and possibly an attempt by the PO to silence the same rattle your hearing. They cannot be repaired and trying to take them apart will likely destroy the muffler. The four rivets are the stock original parts and if they are removed it still doesn't allow access into the can for repairs.
Even though they are not rusted outside the internals are probably falling apart and the rattle is from a disintegrated internal piece; they are 40+ years old and lots of nasty chemical stews have sat in there over time.

[Alan F.]

I'm gonna say those pop rivets don't look stock to me. Who knows what the PO did in there until you drill out the rivets and have a look.

[fizzlebottom]

Allan bolts are not stock and possibly an attempt by the PO to silence the same rattle your hearing. They cannot be repaired and trying to take them apart will likely destroy the muffler. The four rivets are the stock original parts and if they are removed it still doesn't allow access into the can for repairs.
Even though they are not rusted outside the internals are probably falling apart and the rattle is from a disintegrated internal piece; they are 40+ years old and lots of nasty chemical stews have sat in there over time.

Hey you're right about the allen bolts not being stock. I hadn't looked before, but I just noticed on several eBay postings that they're definitely not present in any of the units for sale on eBay. Really wondering what the hell one of the unknown number of POs was doing.

Well alright. I suspect this bike is starting to come to the end of its life. Aftermarket support for the CB650s (especially the 82 Nighthawk) simply doesn't exist. I had too many metal shavings in my oil this last change and even some pieces of the cam chain tensioner. It still runs great, starts up fast, shifts quickly and without issue, but I think I'm about done sitting on eBay for usable salvage parts to show up. Maybe I'll try to find one of the other SOHC4 models with way better parts inventory and aftermarket support. I'll just ride til this one grenades.

[Flyin900]

Sounds like a plan if your good with that course, as metal in the oil is never a good sign.

I have done lots of Honda’s over the past dozen plus years and have attempted to repair mufflers along the way. I have drilled out the pop rivets on that style of muffler and the rear cap still will not come off. The cap is welded to an internal baffle it seems which is still held in place once the pop rivets are gone.
You end up destroying the rear of the muffler in trying to get it apart. I have lots of spares of various items, so it is easy to experiment when it isn’t your only part that your messing with and possibly destroying. 

[calj737]

If you’re finding tensioner pieces in the oil pan, you are riding a time bomb. Pure and simple.

Sell it now for parts. Or later after the motor seizes and it’s a pile of crap.

[fizzlebottom]

If you’re finding tensioner pieces in the oil pan, you are riding a time bomb. Pure and simple.

Sell it now for parts. Or later after the motor seizes and it’s a pile of crap.

I'll sell for parts when it grenades. As long as it makes it through this summer I think I'll be happy. I've had the bike for 10 years now.

[jonda500]

keep your cam chain 100% tight gents or you risk the fairies hiding a time bomb inside your engine!
John

[fizzlebottom]

keep your cam chain 100% tight gents or you risk the fairies hiding a time bomb inside your engine!
John

I'm actually quite suspicious that this is from one of the POs. I have not had cam chain issues since ownership. I've even rebuilt the top end a few years ago and had the tensioner out, but honestly did not look at its condition before reinstalling.

The huge part that is definitely my fault is that in 11 years, this was the first time I removed the oil pan, and really only did it to replace the gasket due to a slight oil leak. Go me! Maybe if its had some bits of tensioner slipper in there for this long it isn't going anywhere soon? Who knows.

[jonda500]

I found so much cam shaft sprocket dampening material in my sump that it had all but completely blocked the oil pickup screen - you can see how much it caved the screen in! Yet those pics are from nearly five years ago and my engine still hasn't exploded.
I cleaned out all the debris, scraped off all the rest of the dampening material from the camshaft sprocket and changed the oil pickup to a nice spare one I had. Then after running it for a few weeks took the sump off and found quite a lot of debris to clean up again! I did check it a third time at some point and was happy to find it clean.
John