Anyone know what happened....

[ListerTheStupid]

I want to know mechanically what happened to me motor... was it a miss fire?

not it popped and when off, or do I need a new flux capacitor?

https://youtu.be/k9ixP7DZ_oM" onclick="window.open(this.href);return false;

[rumpoldstilskin]

Sounds like the valve clearance is off leaving unburnt fuel around which can back fire into the intake (not to be confused with an after fire/exhaust pop) my 175 sounded the same until i got it sorted.

Take it back if it does it agin and get it re-shimmed

[Cabernet]

Guessing your engine was cold.
ECU will have had a rich mixture, bit will have been trying to lean it back.
Confused by throttle blipping, it leaned it off too far.
On the stroke it stalls on, the ECU tries to recover and dumps a heap of fuel.
The wasted spark fires burning off unburnt fuel as the engine final stops against the inlet valve spring loads up.
The flame front then runs back up the inlet track to the air box and exhausting in a pop.
That's my theory. Sure Doofers will be along shortly.

[ListerTheStupid]

Guessing your engine was cold.
ECU will have had a rich mixture, bit will have been trying to lean it back.
Confused by throttle blipping, it leaned it off too far.
On the stroke it stalls on, the ECU tries to recover and dumps a heap of fuel.
The wasted spark fires burning off unburnt fuel as the engine final stops against the inlet valve spring loads up.
The flame front then runs back up the inlet track to the air box and exhausting in a pop.
That's my theory. Sure Doofers will be along shortly.

I like it, I'll go with this.


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[ListerTheStupid]

Sounds like the valve clearance is off leaving unburnt fuel around which can back fire into the intake (not to be confused with an after fire/exhaust pop) my 175 sounded the same until i got it sorted.

Take it back if it does it agin and get it re-shimmed

Valves won't be off after 300miles???


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[rumpoldstilskin]

I did 200 miles on my Nelli last year, the reason she wouldn't run....... No valve clearances.

Sometimes the shims just aren't hard enough and get hammered thin.

That'd be my first guess anyway, sounded just like both my bikes that turned out to be valve clearances.

[ListerTheStupid]

I did 200 miles on my Nelli last year, the reason she wouldn't run....... No valve clearances.

Sometimes the shims just aren't hard enough and get hammered thin.

That'd be my first guess anyway, sounded just like both my bikes that turned out to be valve clearances.

its common on the grom apparently the fuel injection gets confused and gives up..

[rumpoldstilskin]

I wonder if your timing is set and controlled by a phonic wheel sensor, ie non-adjustable timming, that would explain it.

[ListerTheStupid]

I wonder if your timing is set and controlled by a phonic wheel sensor, ie non-adjustable timming, that would explain it.

yer..... English please..

[rumpoldstilskin]

I wonder if your timing is set and controlled by a phonic wheel sensor, ie non-adjustable timming, that would explain it.

yer..... English please..

For injection bikes that do not have adjustable timing, at the bottom end of the engine connected to the crankshaft at one side, usually opposite to drive side may be an internal slotted wheel which turns respectively with the engine.
A sensor bolted through the engine casing reads the peaks and spaces, this inturn tells the ecu when to fire and for how long. Its a rough way of doing things but it also means maintenance free timing as it is pre-set.

If you know how a CD is read digitally, then imagine that transferred onto an actual metal disc for instance.
Usually an engine will run a bit rough at idle with this set up bit has a very smooth torque & power curve as who needs a bike to be sweet at 1k rpm?

See photo for better understanding