Engine breaking noise. popping?

[wipeass]

hey, i was just braking in my new engine today and i noticed when i let off the accelerator and started engine breaking my bike kept popping.
my mate i was with recons it was the jets and that i needed different ones for australias climate.
is it that the issue or could it be something else?
and is it bad to ride it whilst its making that noise?
thanks in advance

 

[krazed0451]

hey, i was just breaking in my new engine today and i noticed when i let off the accelerator and started engine breaking my bike kept popping.
my mate i was with recons it was the jets and that i needed different ones for australias climate.
is it that the issue or could it be something else?
and is it bad to ride it whilst its making that noise?
thanks in advance

Not bad at all; what you're hearing is called "over run". Basically this is fuel flowing into the cylinder/exhaust and detonating during engine breaking. It's probably a good thing during breaking in as it usually indicates a slightly rich mixture

If you are worried about it, pull the plug and see what colour it is; adjust the needle clip as necessary (or if the bike is running well and the plug is a nice 'coffee brown', just leave it).

Have fun!

PS, breaking = bad... Braking = slowing down

 

[MuckUte]

Backfiring on deceleration can be a sign of running lean, this isn't good because it can cause overheating. Lean running can be caused by jetting or an air leak in the intake somwhere. An easy way to check for air leaks is to spray aerostart, carb cleaner or crc type products around both ends of the intake manifold and listen for a change in revs. Just be real careful as these products are flammable so try to keep them away from the exhaust.

Another cause of backfiring is a leak between the exhaust and the head, are you sure the gasket you chose is sealed up, maybe try the other one?

 

[Cactus Jack]

Bad exhaust valve seal can cause it too ... To tell you the truth I've never had an engine that did it regardless of how good or bad the carb was tuned ... my valves were always properly seated and my exhaust pipe was always properly sealed ...

 

[sean01]

my wr450 does it.(not tuned by me but richer than factory) and really bad.. actually i lie... o-ring mod done by me to reduce off idle flat spot..

my yx engine does it... not too bad but noticeable..

ill put money on it being the exhaust... where the header pipe slides into the muffler it will leak cold air causing it to pop.. (more to it than this but basic understanding)

no biggie.... but like said above check your plug colour at different throttle positions to check the carb tune...

 

[wipeass]

ill give the plug colour a shot first, and if thats not the issue ill change the exhaust gasket. i noticed where the exhaust pipe slides on to the muffler its just metal on metal? there may be some room there for some air to get out.
thanks for all the help,
i will post back when i know more.

 

[wipeass]

ill give the plug colour a shot first, and if thats not the issue ill change the exhaust gasket. i noticed where the exhaust pipe slides on to the muffler its just metal on metal? there may be some room there for some air to get out.
thanks for all the help,
i will post back when i know more.

 

[hman]

keep posting man. i get a good laugh every time i see your user name. i hope you just miss spelled it. is the whole bike new or just the engine? sounds like an air leak to me. check the carb manifold as well.

 

[wipeass]

haha, no i didnt miss spell my username, its the same as my psn name. but its a brand new bike. and i was just working on it then and the exhaust bolts were slightly loose. im gonna go ride it up and down the street and see if the noise is still there.