Strange engine braking noise

[DukeRed]

When I get up to a high rev and let off the engine breaking is not a pleasant sound. It kind of rattles and chokes like loads of tiny backfires.

Its there at every point in the range but it can be heard better higher up.
It's not doing any noticeable damage but it just doesn't feel right.
I was thinking maybe it would need dynoing?
____________________
Enjoy Life There's Plenty of Time to be Dead
https://www.janoner.com

[stinkwheel]

Have a good check for any leaks in the exhaust system, especially around the headers and splitter box. Small exhaust air leaks are a common cause of popping and banging on the overrun.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[DukeRed]

Whats a splitter and the header box?
____________________
Enjoy Life There's Plenty of Time to be Dead
https://www.janoner.com

[mchaggis]

The headers are the pipes which directly leave the engine block. They are normally clamped into place with with vaguely circular collars with a pair of bolts on. It's not unknown for these bolts to go bye bye. Tighten them all up, and check to make sure the semi-circular inserts aren't bent as a result of past over- tightening or otherwise misplaced.

The headers are also known as downpipes as that is normally what they do.

The splitter box (I presume) is the section of the exhaust where all the header pipes join together to come into one single pipe. If it's a multiple piece system (endcan, headers and connecting pipes all distinct from each other), then they are normally held together with springs, and possibly some kind of gasket/ collar/ wadding/ something to keep them gastight. (I've not actually seen inside one, just taking a best guess).

If any of those joints between pipes or between the engine and downpipes get loose and lose their 'gastightness' then you get the symptoms you described, as the unburnt hydrocarbons get the additional oxygen they need to burn and so burn away in the exhaust, making that popping sound. (Petrol engines almost always run slightly richer the stoichiometric ratio.)
____________________
I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.

[stinkwheel]

[mchaggis]

[Redd]

Amazing, I was just about to ask the same question. Reading my workshop manual troubleshooting section (all of about a page and a half of it), it suggested it might be a lean mixture in the slow circuit.

That didn't mean a whole lot to me. I know what a lean mixture is, and I'm guessing the slow circuit is something to do with the way the carb acts at low speeds but the solution to this problem...no idea. Your explanation seems to make more sense.

Will be checking out my exhaust asap. Thanks mchaggis
____________________
Professional Uberslacker
2006 Kawasaki Z1000 - Black at the front, airbrushed fade to red at the back.
1998 Kawasaki KDX 200 Enduro project bike

[DukeRed]

Yup, a nice rusty crack undeneath my exhaust. Will bandage sort it? Spot welding?

Was thinking that since I don't have baffles does that make a difference as well?
____________________
Enjoy Life There's Plenty of Time to be Dead
https://www.janoner.com

[stinkwheel]

Welding depends on a few factors including:

What the exhaust is made of, steel would be a good answer.

How much solid metal is left either side of the crack.

If it has gone at a seam or just generally rotted away.

Ideally if it has just split along a seam on mild steel and there is minimal rust then welding or brazing after cleaning away the rust would be a good solid fix.

If it has just generally mouldered and rotted away, you might need to use bandage. The bandage either works well or fails within the first fifty miles.

My top-tip is to find an agricultural engineer to weld it for you, it will probably cost you six cans of premium lager and they are experts at welding rusty metal. If they say it can't be welded then go for bandage. If the bandage fails, you need a new pipe.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[DukeRed]

Cheers .
____________________
Enjoy Life There's Plenty of Time to be Dead
https://www.janoner.com