hello everybody,

I've got a little Scorpa 125 4T.

Nice little bike but I have a problem:

when I rapidly open the throttle the engine tends to stop...

I got all the revs only if I open the throttle in more than 300/400 ms.

I've done the rejetting (as described in this forum) bit without any

effects, apparently. Any suggestions?

Do I have, for example, to play with the air/fuel mix screw?

Please, is there a 125 ownner that can test this:

just open the throttle VERY rapidly, as you can do without problems on a 2T,

what's happen?

Thanks

Mario

I had the same problem, I installed a larger pilot jet (18 or 17.5 in the place of 15). Now when i open the throttle, the increase rev is correct without needing to leave the choke.

I had the same problem, I installed a larger pilot jet (18 or 17.5 in the place of 15).  Now when i open the throttle, the increase rev is correct without needing to leave the choke.

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I've fitted the 102.5 mainjet and the 17.5 pilot jet,

without any results (it only starts from cold a bit easier).

Maybe there's something else wrong in the carb...

mario

Yes, you will need to adjust the air screw. As a starting place, screw it in all the way, and back it off 2.5 turns. Make sure your engine is nice and warm, and then set your idle up higher than normal. Now, you have to use your hearing, and slowly adjust your air screw. You should find a sweet spot, where you hear the idle increase. Turning the screw in, and out, you should find a place (on both sides of the sweet spot) where the idle speed starts falling off again. Once you find this high, and low spot, set the screw at the mid-point between them.

Provided your jetting is correct, and needle position is correct, this setting should allow you to snap open the throttle with a fairly clean response. Don't expect a 4-stroke to act exactly like a 2-stroke when doing this. You have a lot more rotating mass there to accelerate, and half as many firing strokes to accelerate it.

My Tys 125 f does exactly the same Dont realy see it as a problem! but hey!

I've run honda 4 strokes for a couple of years, seems to be a characteristic of 4 stroke motors from other people i've spoke to. Check the accelerator pump in the carb is working ok - it gives a small squirt of fuel from tickover to help this problem. It's quite a fine jet and i've had mine get blocked before now.