Two stroke won’t rev out???

[Farmingstock]

I own a Honda NSR125 that has a 36mm carb, carbon reeds, tyga exhaust and potted barrel.

The bike starts and runs at low revs fine, however high up in the revs it limits and won’t rev out.

So 8,500 upwards sometime later it sounds like it’s got a rev limiter and just won’t rev out.

The power valve is working and I have tried upjetting from a 160-170 but absolutely no change.

I have ordered a new plug, but am waiting for it to come. The current one is dry and brown/burnt.

Any ideas??

[Nobby the Bastard]

Was it revving out before? What have you altered between it working and it not working?
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

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36mm carb on a 125?! Standard is 28mm isn't it?
Did it ever run correctly with this carb on it?
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Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[Farmingstock]

I had it rolling roaded and it was fine, but I’ve put carbon reeds in and a different exhaust. It’s been stood all winter, cleaned the carb and changed the jets but no difference at all!!

[bacon]

Can you swap out the reeds and exhaust back to what you had before?

Changing something that affects the fueling then wondering why it doesn't run properly is obviously one of your issues.

Get it back on the rolling road to be setup properly if you are dead set on using your new parts

[Farmingstock]

This is full throttle but when riding it’s doing this at 8/9000 rpm or anything from 3/4 throttle basically

[Nobby the Bastard]

[Fin]

This is posted in the wrong section.

But as stated above 36mm is a bit big.

Have you done the basics and cleaned the jets? you sure the power valve is opening fully?

Spark plug being dark would indicate running rich, putting in a larger jet will make it worse. Try moving the choke and seeing how it runs with it on or off.

[MarJay]

Engine tuning is not as simple as just fitting bigger parts. If it were that easy we'd all be riding 200mph monsters.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Farmingstock]

Changed the main jet to a 145 instead of the 170 and it’s had an instant improvement, maybe a little too small now but looking like the main jet was far to big for this set up!!

[Nobby the Bastard]

[P.addy]

Put it exactly to how it was when it ran fine on a rolling road.

Ditch the carbon reeds.

[Farmingstock]

It’s much better now with the smaller main jet, i no longer have the other exhaust or reeds and the carbon ones are duel stage boyson ones.

I may take it back to the dyno when the weather is better as it’s a fair trek!!

[P.addy]

The make of the reeds matters not.

Smashing a smaller jet in there isn't a magic fix, at least I'd expect a plug chop but ideally having it properly set up..

Also, that carb is far too large.

[Evil Hans]

We ought to have a Workshop section for questions like this
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Triumph Sprint ST 1050. And it's Red.

[Farmingstock]

please feel free to move to the workshop section, on my phone and I could have sworn it was in the right section when I posted!!

Got a new plug today so will be doing a plug chop although now the radiator has sprung a leak!