2013 Aprilia SR 50 R, Carb, no power after install of Yasuni R (derestricted)

[WOTsUP?]

Hey All,

Posted on the forum for some guidance in tuning my SR50 carb a few month ago, was hoping this post would be to report my success but unfortunately I have hit a bit of a problem.

So I purchased:-

1. Yasuni R
2. Main Jet kit 60-78
3. Roller sets 5-6.5g
4. Malossi "Sports" Air filter
5. Malossi "Sports" clutch spring for original varo (yet to be installed)
6. Malossi White Contra spring (+30%) (yet to be installed)

Last weekend I got out the dremel, removed the restrictions from the exhaust intake and silencer as per guides on the web.

Prepped and painted the Exhaust in VHT high temp, white undercoat then matte black, looks awesome.

Installed the Exhaust
Blocked off the SAS
Installed the Malossi filter
Removed the rubber bung from the air inlet but kept the snorkel
Cleaned the carb
Removed the 53 stock main jet and upjetted to 60 to test
Checked the varo
Replaced the stock piaggio belt with a new one, same part #
Replaced the rollers from the stock 6.5g to 6.1g to test
Raining hard so left testing until later, also didn't have a stocket big enough to take off the large clutch bolt so just left the springs and contra stock for now.

A day or two later the rain cleared, awesome, time to test.

Fired up and sounded good
Jumped on it and had slow initial take off, then just no power at all, it would not take me past 30m/50km it just had nothing, a small hill and I needed to push it.

To back to the garage,

Trained the fuel and topped it up with fresh
Checked the spark plug, all good but replaced it anyways
Popped the stock air filter back on
Tested again, same result, no power

Then checked for air leaks, was suspect on the intake manifold as it had cracks on the outside, pulled that off, checked it.

Outside was cracked but inside was still fine, replaced that with a new one anyways.

Tested again, no change.

Returned the carb to stock, including the re-install of the 53 main jet, quick test, nothing.

Retuned the carb again with the 60 main jet, checked the spark

It's still running worst than stock and I am starting to think I may need to reinstall the stock pipe just to get it back to what it was.

As always, any input it welcome, thanks.

[sublunacy]

the whole setup is screwy.


the problem is your doing it ass backwards. to much reading at other sites concerning slow yamahas and not enough attention to your own. your piaggio variator and cvt is huge and it steps the rpm down 500rpm twice for the best accel and top speed. ~ simply you cannot go lighter than 7-7.5 gram rollers.

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-clutch springs will overheat the clutch because you made it it overheat.

-the soft contra spring is not at all made for your bike the way it sits now. put the stock contra back on before you destroy the belt from the aggressive piaggio vario and cvt. same for the clutch springs. and the horrible tune you just gave it....

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put the stock complete airbox on or spend 200 dollars on a malossi phbg 17-19mm and filter/ or it will just be slow and untunable untill you do.

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the pipe is not much better than stock till you get a 70cc cylinder.

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your reeds will leak...
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i think that covers it. do you have a rpm gauge or not?

[WOTsUP?]

Hi,

Stock rollers were 6.5, have tried them, no change.

Have not touched the clutch or contra springs as explained, didn't have the socket to fit so there stock.

Have tried with the stock air box and filter, no change

Waiting for an RPM gauge to arrive, none build into the display.

Thanks for the reply.

[sublunacy]

a correct setup for peak performance

yasuni r
malossi 70cc
stock vario/cvt/rollers and carb/airbox/snorkel/slide/needle
malossi fly clutch- its the only 5000rpm clutch.
reed petals


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i think your rollers might have been drilled out because the stock ones are 7.5 grams and the bike did 75up hills and 90 down hills.

[2Strokesforlife]

Agreed. The "R" is a great pipe, but not on the stock cylinder. You'll know when the cracks on the manifold go all the way through when the idle goes sky high. I'd replace it before that happens.

[sublunacy]

thats correct. im sorry i cant picture it being as good as stock untill the 70cc cylinder is installed. you might get the carb happy but the cvt will not allow it to pass 75km/h with the light rollers the pipe will need without the 70cc bbk.

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when it is a 70cc and setup like i explain the whole bike will work very well and wont be beat by malossi cvt on any 50cc-70cc anywhere without having a full race engine and pipe. im sure that will mystify novice and amateur tuners the world over.... but thats why your here and not at the chinese/japanese scoote forums.

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let me know if i can help.

[WOTsUP?]

As always, thanks very much for your advice.

Heaps of online retailers I checked out suggested it would work with a 50 which is why I went with it, The Yasuni site says "It works very well with 50 or 70 cc cylinders, but its true efficiency becomes apparent with 70 cc Sports cylinders. For superb performance, we recommend modifying the variator application." So I guess that's high rev 50 heads.

I could get another exhaust until the 50cc is ready to be swapped but I am going to end up with a BBK at some point so it may as well be now.

Thanks again guys, will start a new post with further progress as soon as I can get the time to work on it.

[sublunacy]

your a very nice person to talk with/ you deserve some credit and you will get it.
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to start this off a 70cc is what is holding you back. the airsal sport 70cc is half the price of a malossi 70cc. the airsal is just as good but it uses the stock dome head. it runs smooth and powerfull...



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i think for now perhaps the stock pipe will be better performance if you need to drive it...

but if you want to try a 68-66-64-62 main jet on the yasuni it might work nice with the lighter rollers. your origanol post was excellent by the way.... i just see a bright light at the end or the tunnel and im forced to recommend the 70cc.


holler at us if there is anything else on your mind.