Loss of power for some reason, engine tone changed

[simon1221]

The engine sound is different (smoother, with a less harsh fire to it), but less powerful.

It sounds like fuel starvation, but:

Fuel level is correct in carb as that is what i have just checked this afternoon.

I have an inline fuel filter , but that has an arrow on it that is currently pointing in the direction of the carb, so I think that is the right direction.

Breather pipes in carb are clear as petrol spurted out of them when i turned the carburettor upside down (oops!). Not sure about the one on the tank.

Anything else it could be?
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[nick.h]

While applying the throttle you get no response for a few seconds from the engine at high revs? Thats what my bikes been doing, but I just put it down to the cold weather.
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[palmer]

have you tried thrashing it? usually fixes my 2t problems

[simon1221]

Dont know, never tried.

But its the time after that is annoying.

I am not going to rag it as if it is fuel starvation then the higher revs you go, the less fuel you will have, making the mixture leaner as the revs increase, so by the time i would have got to the redline it would have blown up!
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[ZRX61]

The engine looses power when ya close the throttle after revving the nads off it? who'da thunk it?

[mchaggis]

Sticky throttle cable taking its time to return?
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[simon1221]

1) It isnt the throttle itself, it just doesnt fire correctly.

It does it all the time now, not only in high revs.

Instead of a roar (sort of), its more like a pffff sound.

Maybe the oil pump is set to high?

2) And it has also started to (almost) stall when going through junctions, at say 2000rpm, the bike 'runs out of fuel, misfires, then carries on.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[mchaggis]

Dodgy spark plug/ HT lead? Clarted up carburettor? Coked up exhaust? Leaky carb rubber?
____________________
I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.

[simon1221]

Pretty new spark plug, iridium one.

Last thing really, piston rings?
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[cagiva gezzer]

If its sounding soft its a lack of compression. Crank seals, reed valves, rings, head gasket.
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"because one stroke isnt enough and four strokes waste two"

[simon1221]

There the most difficult to check.

Not head gasket, otherwise there would be water everywhere.

Havent touched the reed valves.

Either rings or crank seals.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[simon1221]

How do i check compression?
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[Hex]

[mchaggis]

You need a compression test to screw into the sparkplug hole to test for certain, but a general guide is whether you can hold your thumb over the hole. If your thumb is forced off with the pressure, then it (the compression) stands a chance of being okay.

It's entirely possible that you've got dodgy piston rings - the sign of an imminent rebuild?
____________________
I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.

[simon1221]

I will try and be as useful as possible:

Only starts on about 4th or 5th kick

May sometimes stop while warming up (starts 1st kick afterwards though)

Tends to be unresponsive when doing junctions (in any gear) after decelerating from national speed limit

Tends to have a flat spot between 4 - 5000 revs, which only usually happens if the engine is flooded, but it isnt

Doesnt fire well and is pretty spluttery at low speeds, but the mixture is correct (or as much as it can be)

I will get a new plug tomorrow, I think.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[Hex]

Try a different temperature plug? Maybe the recent cold weather aint helping matters.

Flat spot around about there is normal.
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[Tarmacsurfer]

What sort of mileage is the bike, and has it been rebuilt since new? I'm inclined to agree with the piston ring theory going on current info
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[simon1221]

Its on 15000 miles.

I dont know if it has been rebuilt since new, i have only had a few months and the last guy was useless.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

[simon1221]

It was alright today, I was fed up of feeling it was going to die so just ran up to the nearest town and back at 8-9000 revs.

Oh yes i also put redex in (havent had any for a while due to me being lazy) so im thinking its just another godamn fuel blockage.
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DNA50 (sorry) ->> TZR125l >> GPZ500S

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