Aprilia sr50 "slipping" feeling when cold starting

Hello fellows,

I have a small issue again with my 2016 Sr50 Carb version. After fully derestricting it and fitting a new pipe and tunning the carb, i have this small issue when the scooter is cold. The motor works fine, everything is good , but when i leave for a ride, FIRST time when the scooter is cold, it sounds like something is slipping and i max at 20km/h. Progresively, in 5-6 seconds, everything seems to come to normal if i keep the throtle open, and scooter works fine again. I have to mention that after i run 1km, everything works flowless and the "slip" feeling does not come again. It only comes back every time the scooter is cold, and i leave for the first time in that day.

Please help me with some opinion how to fix this. I have to mention the scooter is new, it has 600 km done.

Cheers,

 

First off, you shot the warranty with the de-restriction and new pipe and carb jetting.
I would check your jetting again, it sounds like it is either getting too much air and not enough fuel, or vice versa, or it could be the choke (already), plus check the position of the mixture screw.
Check the colour of the spark plug, should be a nice dark gingerish colour. Too light and you are running lean, too dark and it's too rich.

 

thank you for the response..i currently run a 68 main jet..spark plug is the right color as you described..but indeed i guess i messed up the idle and mixture screws. Scooter runs 1700 rpm idle now...but i think the original setting was better. I messed with them because i had a hard time to keep the scooter ON, at idle. I will try to rejet again without screwing this.

Do you have any advice which is the order that i should apply? the main jet is fine..maybe i go back to 66. But whats the order of idle/ mixture tuning? i know i should get as much idle rpm as i can from the mixture..and avoid making it to lean. But i had a hard time keeping the scooter at 1700 rpm idle and i think my idle screw is almost all the way in.

Thank you for your answer

 

Move the clip on the carb slide needle to the bottom slot, that will raise the needle to it's highest position, allowing more fuel in on idle.
Set the fuel/air mix screw to 2 turns out.
See how that works.
It should idle about 1200rpm normally.

 

Hello Steve, thanks again for the response. So i opened the carb again..i figured out the stock needle had the clip on the leanest position (stock position). I now use 66 main jet, and needle moved to middle position (my needle has 5 positions). The scooters runs fine...but i still encounter the problem when i first start it.. and i want to leave..it wont accelerate..feels like something is slipping, after that, all day everything runs fine. I will try to move the needle like you said on the lowest position.

My idle rpm from the book says 1800. The idle is fine atm, the only issue i have is the rough start that i have every time the engine is cold. And i also encountered another small issue, this is when i run 70km/h lets say, i close the throttle, then i open wide again, i have 2 sec lag..when nothing happens..and i feel like a small bump from the motor. I think this is also from some lack of fuel during hard acceleration?

Thank you in advance