rs140 jets premix

[Tegerra]

So i have recently changed to italkit 140, and am planning on switching to premix. Im running a vhsb 34 racing carburetor and of course de-restricted. What jet sizes should i change to?

[MarJay]

Hmm... I feel like you might want to have done a bit of research on this before commencing... Premix is not necessarily better. You'll need a BIG jet upgrade because premix effectively makes the bike run lean as you're getting oil and fuel instead of just fuel. I can't tell you what jet to use. I'd take the bike to a decent dyno operator who knows what they are doing... Where abouts in the country are you based?
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[MarJay]

(also I assume you're talking about an Aprillia RS125 but you haven't really said so directly.)
____________________
British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Tegerra]

oops. yes, aprilia rs125. I know that it will become leaner with oil flowing, but also that way if my pump ever fails (which i haven't read happening though), i wouldnt have a problem. I live in Finland, but didnt find an area i live in from the list. We don't have many dynos near. Dynos are a bit further away. I was hoping someone running a similar setup would share their premix ratio. I haven't even driven it in yet, so i don't want to start guessing.

[MarJay]

[redeem ouzzer]

I’m quite the fan of premix, saves weight, less drag so engine spins up faster and you know the oil is getting in even at max RPM. I would run any seriously modified 2t on premix. You’ll need to get it on the dyno though to get the jetting right, anything else is guess work.
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Be a REAL MAN!

[Tegerra]

The engine gets lubricated the same way with oil pump and premix. Its not broken, which is why i was always skeptical about switching, but as Forced said, it gets faster lubrication. But i will see if i can get my hands on a dyno, but first i would have to run it in, which is why i would have to figure the right jet sizes.

[stevo as b4]

What is it with you guys over there?

You quite often buy or mess with tuned 125's, and you're spending money on fancy big carbs and expensive big bore engine conversions, yet you won't pay for or travel to a dyno centre. That's just total bonkers!

Does every one over live in the same place, and that the one and only dyno is right at the other side of the country or in an inhospitable impossible to reach area?
Or is everyone just a tight bastard maybe?

[MarJay]

[Tegerra]

well said MarJay. But we'd rather tune and test them ourselves than take to a dyno, one reason probably being that they're relatively far away and we could basically just put the bike on a paddock stand and we have a free dyno already. and its quite easy to tune them once we're led to the right direction.

[stevo as b4]

Interesting points and fairly enlightening.
But I don't tune my own two strokes, I pay a man with alot of kit, skill and a bloody expensive dyno to do it for me. In the same way as I don't build my own brick walls.

Maybe it's a cultural difference thing, but apart from a few stubborn awkward bastards, the British in general tend to believe in using a professional service or company for doing technical/critical/difficult things for them. We in general have less spare time than we'd like, and paying for a specialist service is generally seen as money well spent, and helps with our work/life balance.

I've ruined enough two stroke engines to know that I'm no dyno tuner, and unlike many adamant folk I also believe that it's impossible to read spark plugs accurately with unleaded fuel.

I do know of the odd person or so who say wanted a sports car, do they decided to build their own from scratch. It's not generally the British way we do things though.

[MarJay]

[Tegerra]

Im being trained to become a mechanic, so that's likely a reason to why i'd rather do it myself too. Of course to save time and frustration, it is good to send it to a dyno.

[MarJay]

[1198]

Were you not from Finland, you’d now be 17 chapters into a ‘brief’ about the UK licence laws, power to weight ratios of cat A1 bikes and lord knows what else....

[Tegerra]

I also switched from 125cc to 140cc, so if i knew what jets to use in 140, i'd try that but maybe a bit bigger. I was using a 140 or 145 main jet on the 125cc, and i was suggested to use 180 main jet on the 140cc, which to be honest seems a bit too much even with premix. So i would need guidance to even that.

And 1198, what do you mean?

[Easy-X]

Don't people get jet kits any more? Go out, have a tear up, see how it is and then whack in a larger or smaller jet... rinse, repeat!
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[Tegerra]

when driving it in, i don't want to start guessing or revving it to death. Otherwise i would get a jet kit.

[stevo as b4]

Just fucking lol!

OP is a bike mechanic, asks impossible to answer questions, and probably even expects suggested UK climate and pressure carb settings to translate to those in his climate and temperature?

How do these garage dyno's using a paddock stand work exactly then? And what do you use for a steady state load cell?

[Tegerra]

its not like we have a 40 degree temperature and 500m height difference during the summer, do we? ALL i need is the right direction, its not rocket science, or maybe it is for you Stevo? XD And im sure other than UK people wander here too, because i did, this is the only one that doesn't need an invitation and its not like these groups are separated to each country lol.
The questions are as easy as typing a few numbers for those who are running premix and a 140 kit like me. Maybe impossible for you if you don't even have a 140cc premix XD
I'm asking of things i don't know of, not things i know of lol
I've been talking of jetting so the engine wont blow up, not of power, so with a bit of situational awareness you could be able to realize that im not looking for power numbers. If i would want to do that, i could buy a motorcycle dyno for myself along with the steady state load cell... XD

[Nobby the Bastard]

[stevo as b4]

You should take it to that crazy but knowledgeable two stroke stuffing guy to dyno for you. Your closer to him than I am.

You don't fit a big carb and 140cc race kit if your not looking for maximum bhp do you? If you've spent I dunno 1000euro on it, then don't you want the most performance possible safely that you can get?

I've got a 140cc myself, but it's a different bike, different carb and even if it was an Aprilia RS of the same year as yours, my settings would be useless to you in a totally different climate and with a different set up.

Saying you're not looking for performance from a tuned two stroke that you've spent a fortune on is like saying you're going to buy a Fireblade SP and put a dirty blocked air filter in it and tape over the air box entry.

[Tegerra]

As of now, im not looking for bhp. Im looking for safe break-in... When that is done, i can easily adjust the jets and see what is rich and what is good. The only way to get the right jets is to rev the bike up to full rpm, i did that last year and it worked out great, but im not going to do it while breaking the bike in...

[stevo as b4]

Look its as easy as finding the factory Aprilia jetting specs for the 34mm carb models, and as Marjay said, fit a two sizes bigger pilot jet, main jet and raise the needle to the top position. If its not running an air box then try 4-5 sizes bigger on the main jet. It'll probably run like crap, but it will run.

Why not ask or search over on the 125cc sports bike forum for a better answer, as I bet there's someone one there who has long ago done the exact same modifications as you to the same version of RS and with the same engine. There's also several Aprilia RS Facebook groups you could join instead of asking a group of strangers with no direct experience on a generic motorbike forum.

I'd love to know how you can accurately determine the perfect jetting by revving your bike to maximum rpm too. Do tell us how that works?

[Tegerra]

ok thanks, but you just put your hand on the throttle, slowly apply it and listen if it sounds rich or lean, or hesitates to rev or splutters. Go down or up in jet sizes until it goes up and comes down fast and steady without spluttering and sounds clean af. When it sounds perfect, you could try to go a bit leaner for a bit of extra power at the cost of reliability. And if you want to experiment, keep going leaner until symptoms show up, and you know the border, and should go a few of jets higher for reliability. As easy as that. You just need to know the symptoms of rich and lean very well visually, theoretically and aurally. And i did make it do 0-100 in 6 seconds. Dyno saves time, but this saves money.