Px bogging when I shut the throttle at speed

[trojanpx]

Hi I wonder if anyone can help me iv got a px125 with a dr180 kit a gasflow crank and a sito plus exhaust it had a 24/24 carb with a 55-160 be3 160 and a 125 main jet . The scooter runs and starts brilliant my problem is tht wen I'm riding at high speeds and let of the throttle it's like the engine looses all power and I have to sort of pump the throttle to get it back but it happend every time . At low speeds it runs like a dream and very quick . I no the a 125 main is to high but iv got a 107 110 114 118 and 125 . After tryin all of thm it definety runs better with the big 1 in it . It runs like a dog with all the others. Wen a brought this scooter it already had the. 125 main init and all the other stuff. Iv completely rebiult the scooter but not the engine and I also put in a new crewsiform and shift rod . I just need this problem sorted for the long ride outs .

[henri]

i think i'd try a new float n needle valve first ,an if ya can find 1 a cosa200 float bowl top , (german e bay,hint-hint), as it sounds like float n valve aint shuttin of the petrol flow quick/cleanly enuff,an temporarily flooding ,
could be other stuff , is it hard to start if left with fuel tap on , start with a needle valve an check the float ,an then a plug chop from half/2/3rds throttle , this will tell you if atomisers right , or try a be5 , carefully as ya dont want to lean the mid-range out too much , an see what diff that makes , H

[pxguru]

While you are doing some shopping; the Pilot jet is too big. Should be a 50/120 at most.

[trojanpx]

It starts first kick every time I normaly leave the tap open but at the min as I'm not using it because it's to cold it's off

[trojanpx]

Plus it's also pre mix oil tank is no more

[shaunbond]

I've read recently that this is a symptom if not fitting the plastic drip tray in the frame. I have the same issue on my PX200 but haven't got round to trying the solution but you said you've rebuilt the scooter so did you also not fit the drip tray?

[pxguru]

Could also be a slight crankcase airleak

[trojanpx]

Thanks for all the inputs. I have read about tht on another forum . I never had a drip tray to begging with since iv had it . I was speeding to a friend who is also a vespa macanic he seems to think tht that is silly his never Hurd of sumthink like tht . I hope it's not a crack in my crank case I don't think it is tht thow :/ I hope . I'm gunna look at it tomorrow with macanic and go throw sum stuff . It a shame because it runs so nice other thn tht

[henri]

ive never had this myself but do remember now a guy who writes for scootering mag reporting the lack of plastic frame tray gave him some funny carb effects similar to yours , a few months back,if i can find issue will have another read , myself i didnt believe the reasoning behind it that it changes the dynamics of the frame as a airbox , its more likely to my mind that pullin the tank n fitting it an re-tuning the carb cured the actual fault an made it look like the tray was the problem, H

[shaunpx]

I was chatting with a guy recently who'd had running problems with his p2 which was due to the drip tray being left out and the symptoms exhibited felt more like fuel starvation ie motor kept holding back as if its about to nip at wot rather than bogging which suggests to me that its running rich on top end so personally id look at the jetting first as I only use a 125 main on my p2 when I'm using a drilled air filter

[trojanpx]

I do have a drilled air filter aswell but it doesn't actuly bog until I let go of the throttle and try throttling again

[trojanpx]

Ok guys thanks for all the idears but I think it's sorted now I wanted to test the drip plate theory so I took the tank off and blocked any air comin thru the frame wiv sum sponge stuf from work and it seems to have done the trick so I'll go get me self a drip tray now

[sbwnik]

I bet it's a Spaco carb, not a genuine Del'lorto. If it is, then I bet I know what the problem is

Just confirm it first...

[trojanpx]

Yes mate it's a spaco?

[trojanpx]

Actuly it says both it's got spaco on the front nere the throttle pin and both on the side