derbi senda unusual noise

[charrington96]

I have a derbi senda 50cc 2 stroke engine, I realised that there was a noise coming from near the front (engine/exhaust area), it was a deep popping sound, its been derestricted,
I have done a compression test and its good results
Its only when I slow down (engine braking), with no throttle, breaking or pulling in the clutch, it doesn't make the noise at standstill or accelerating
Any ideas?

[mentalboy]

Yo blud, ur bike is pwoper twicked up like
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Make mine a Corona.

[charrington96]

What do you mean?

[SQL]

Popping on decel may indicate its running lean, do a plug chop and check what color the plug is at WOT

[charrington96]

Thanks what if it is running too lean?

[mentalboy]

Sigh.

Running slightly lean, usually found on highly tuned engines, not ordinarily a problem. Has this just developed or have you derestricted/purchased this recently? (ie have you been tinkering?)
____________________
Make mine a Corona.

[SQL]

If it is running too lean then it could melt the piston.

[charrington96]

The bike is stock... Tops of 55mph even though Ive never tried
I need have a lost circlip to the jet needle once and replaced it.

[charrington96]

I have had *

[mentalboy]

Nice clean air filter or is it missing? As SQL said if you are running very lean then you can expect problems sooner rather than later. Not sure if the needle has multiple positions for circlip, if so did it go back as before? Has the mixture screw been tweaked recently?
____________________
Make mine a Corona.

[charrington96]

Just replaced air filter, well I never used to have one as it wasn't connected... I know it can do serious damage and the bike shop had adjusted all the mixture screw after I replaced the air filter... I only heard it today, and I know the cold affects 2 strokes

[bikersupermot...]

[charrington96]

It could be maybe my ears are popping

[Rogerborg]

Is your piston or exhaust perchance fouled with carbon build-up?
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[Hugh Farking Cant]

Nobody else think this could be a header pipe gasket issue ?

[Rogerborg]

[charrington96]

The spark plug is fine, chocolate tan colour... I have a problem with checking for carbon build up, my exhaust is rotten, been putting WD on the bolts for a few days... Its due an MOT in 2 weeks, bike shop know me well so I'll ask them about it

[Robby]

On a bike in standard tune, popping and banging on the overrun is usually caused by a leak in the air inlet or exhaust - so a holed exhaust or a split inlet rubber.

If the exhaust is not holed and the inlet rubber not split, and you have been cocking around with it, sort the bits that you have cocked around with first.

[charrington96]

Ive looked at the manual, gonna put carb to its original setting and see how it runs

[mentalboy]

[charrington96]

Yep, I adjusted the mixture screw and now no loud noises, thanks