Rieju RS2 50 Jet Size

[Lightyear2000]

I know this has been discussed on here before, but I've finally finished building my Son an RS2 50cc (which has a Yasuni exhaust and K&N filter) - but I cannot get it to Redline. I've changed the Jets and fitted (and tested) every size from the standard 88 that was in there, all the way up to 120, but it refuses to Rev past 5K?
It seems the general consensus is that with this setup it should need around a 116-120 main jet, but do I keep going up to 130 and beyond?
Or am I missing something else?

Thanks in advance.

[Lightyear2000]

Ok so I've just bought more main jets (120 - 148) and fitted them all and it hasn't made any difference!? It still won't rev past 5k? I've tried adjusting the needle height, but anything either side of centre just makes it worse, leading me to the conclusion that it's not a jet problem. Anyone got any ideas?
Thanks

[Pol Anorl]

If hes 16 then don't bother its illegal..

if not then..

https://www.ebay.co.uk/itm/New-de-restricted-CDI-Unit-Fits-Rieju-RS2-Matrix-50cc-/190993867949
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[_Iain_]

RS-50's with the AM6 motor have run well over 120 mains on a pod filter - a twist & go Zip 50 with a pipe runs a 100 main to run a pod filter

Is the Yasuni pipe brand new? If so have a good look at the inlet to it as they come with a restrictor washer fitted as standard. This combined with an upjet can make the bike run poorly. I've seen this happen with an SR50 with suspected jetting issues.

The K&N will also make it run very very poorly & is proven to cost power as advised by Adrenalin Pedstop. I'd ditch that if you do have an original airbox availible to you.

Side note - they'll rev past 5k even restricted, so chucking a magic CDI on it in the hope it'll remove a rev limiter isn't wise. It will however probbably remove the rev limiter completely, so when you do fix the issue it'll have a knackered motor within a week as he repeatedly spins the rev counter off the clock
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