What rattled out of my exhaust?? also running super lean

[Guest]

1982 GS450L

Bike has been running VERY lean through the entire rev range, popping / backfiring on decel. Can't find any intake leaks after months of searching (new boots / o-rings / dipped carbs / vacuum synced carbs / valves adjusted / new exhaust gaskets...).

Found exhaust leak at crossover pipe (where pipes join). Removed pipes to inspect and this little thing was rattling around in the right exhaust pipe (pencil tip for scale). Any ideas of what it is? 20200621_125938.jpg


Took a bit of shaking to get it out of there.

The right side is running leaner than the left. Nothing else sounds loose in the exhaust. Re-installed exhaust pipes and still have a small exhaust leak at the crossover pipe (I can't seem to clamp it down to get it sealed completely). Slight improvement after re-seating & clamping exhaust, but bike still super lean.

Is it possible a small exhaust leak could lean it out that much (spark plugs are white to shiny)? It idles well (no hanging or creeping idle), revs up well.

Previous thread about this unending problem: https://www.thegsresources.com/_foru...t=#post2567840

What else can I do / check?

[Steve]

That part looks like a broken-off top of a brake bleeder.

If you found that in your exhaust, you likely have something more serious going on.

.

[Grimly]

Looks like a pop rivet that's had a very hard time.

[Gorminrider]

Don't know what that is, but a leaky crossover pipe shouldn't have such a large effect...mine ,I replaced the pipe across and it's a decent fit but not perfect- it makes little difference to running, having a little leak except I can hear it.

Get a piece of tin can (the ridged part of the can)- and shim the space that won't clamp but I doubt that's your core problem....

[rphillips]

Possibly a press-in alemite? I think someone dropped it in from the rear. Nothing that large could come thru a valve & there are no parts downstream of the ex. valve. I'd think there should be a round flat fiber gasket at the crossover connection & clamp.

[mrules]

I don't think it could have come through the engine either, because the engine has not kerploded. Possibly dropped in from the rear, but that seems unlikely because it would have had to be so carefully pushed into one of the holes. Will have to remain a mystery I guess and I can't imagine that it is related to my bigger problem, which is the running super lean. Thanks for the responses!

[Rob S.]

Maybe not totally relevant, decades ago I was redlining my Kaw 900 on the "boulevard" (females in front of bar) and the baffle shot out the 4-into-1 like a canon. I asked the bartender to hold onto this filthy hunk of metal, but never reinstalled it. (Pushed her down the block before starting, coasted home each night. Even a dog knows not to shyte where he eats.)

Blessed thing about that Z1, it needed no rejetting, not when I went to pods, not when I went open exhaust.

I'm sure you'll figure out where that thing came from.

[Buffalo Bill]

Looks like a pop rivet that's had a very hard time.

Have to agree, must have come from the muffler, or some kid back in history, dropped it in there while playing in the garage.

[mrules]

This thing looks like it might have come from one of these holes in the back of the exhaust: 20200706_171023-resized.jpg

Not sure how these little rivets got loose (this pic is from the left side exhaust for comparison, but the part rattled out of the right side). All three of the holes on the right side are open. I looked on ebay and I didn't see any exhausts from any 450 that had open holes in the back like this (but I couldn't find one that was an exact fit for a 1982 gs450L with a good picture).

Could this be contributing to the lean-running? I plan to block these holes and see what changes, but I wonder if these rivets popping out could have changed something else inside the mufflers.

[rphillips]

I've never seen the back side of one of those rivets, very possible that is what you found. NO those little holes will never effect jetting enough anyone could tell, I don't think, even with an exhaust analyzer. As always, Just my opinion.

[mrules]

Update: seem to have solved the running lean issue. This part (enrichener plunger?) was loose (super loose, not even finger tight): 20200716_171154.- resized.jpg

Tightened it and no more intake leak symptoms. Still have some slight popping on decel. I was able to tune that out a bit by backing out the pilot mixture screws; but I'm not sure why that should be making a difference. Going to vacuum sync the carbs again as I've had them apart (a bunch of times) since I last did that and see if it helps.

[mrules]

More update: After vacuum syncing carbs and then tuning the mixture screws, bike is running great! No popping from exhaust! I tried plugging the holes on the back of the mufflers with some exhaust putty (I let it cure fully) but it was gone after a 20 mile ride. As rphillips suspected, it did not seem to affect running / jetting.

The mixture screws are 3.5 turns out each. Prior to the exhaust popping on decel (that started oh-so-long-ago), they were at 1.25 and 1.5 turns out. Since then I have adjusted the valves, cleaned the carbs (& new o-rings), adjusted the floats, put on new intake boot O-rings, new airbox boots, new exhaust gaskets, synced the carbs....

Does it make sense that the pilot mixture screws would change that drastically to get it tuned???

[dorkburger]

I think it makes sense. If all the rubber is new and the air is going exactly where it needs to go, and not where it shouldn't, things will definitely change.

[mrules]

great! then I'm not going to worry about the mixture screws being a bit outside of what seems to be the normal range for most. I rode again today and it's running as good as (if not better than) ever

[rphillips]

Your great results make me feel good, can only imagine how you feel. Congrats