Hard starting when warm

[jellerby]

Hi everyone, 

I have just taken a friends Vespa P200 in for an engine rebuild last week, after rebuilding my Smallframe engine a few times I have abit of confidence in rebuilding the 200. The scooter was in my possession last year and had the same problem.

The scooter won't start when it's warmed up.. Riding for half an hour or so, everything fine. Take a break from riding and come back to it and it won't start again after however many kicks but, will bump start easily. My thinking is the CDI unit is breaking down? 

[jellerby]

Also, he has said he's only been able to get 55mph out of it tops, I had put a SIP Road II exhaust back when I had it and got up to 70. He's put new clutch plates in, what would be the cause of decrease in speed? I'll know more on the condition of parts when I get round to splitting it.

[me]

I'd be looking at worn piston rings and a badly adjusted-set up carb, or air leak of some sort.

[mijapxman]

A quick check with a compression tester should let you know how worn the barrel or rings are ( if you have or can borrow one). Rough guide, the more over 100psi, the better.😉

Good luck.
Mij☺

[bryno]

Jul 16, 2017 20:53:44 GMT jellerby said:

Also, he has said he's only been able to get 55mph out of it tops, I had put a SIP Road II exhaust back when I had it and got up to 70. He's put new clutch plates in, what would be the cause of decrease in speed? I'll know more on the condition of parts when I get round to splitting it.

Is the clutch slipping badly?

Can't think of any other reason clutch change can effect performance unless he took other things apart at same time

[bbuchan]

hi I have px200 with the pinasco 225 kit in it been going great for 2 years now but had to get a new exhaust due to the old one bursting so put on the exact same one a sterling r/h but since then scooter going great but if i stop have to wait about 1/2 an hour till it will start again ant idea what causing this .cheers

[bryno]

Issue won't be related to exhaust. Is it 'chokey' when it does start? If so, leaking float needle and/or fuel tap.

Or does compression feel low when it's hard to start?

[ianmartin40]

My polini kitted px 125 motor is not great at starting when warm and always starts after a bump start but it is because it is set a bit too rich

[ironsloth]

Mines an absolute pig to start... I get to the 5-6th kick, to realise, 'turn the dam key you t**t....' After that, 2nd kick every time.

[bbuchan]

compression feels ok starts 1st kick every time when cold just will not restart when warm the side panel is very hot as well tried a new CDi but that was the same.

[ianmartin40]

It has got to be worth starting with a carb srtip and clean and check the float needle closes off and the jets are all the correct size and clean, clean air filter etc and go from there as it is not a big job and will only cost time.
Ian
ironsloth did make me laugh though, I mean who hasn`t done that at some point!

[bryno]

^ agreed, if it feels a bit chokey when it does go, it's fuel leaking into the barrel when at rest, though tbh it would do this all the time so cold start challenging. I would do all the carb stuff first, and check the choke is releasing ok.

it could be an electrical issue related to heat, the stator pick up, an iffy joint expanding, but you would tend to get a misfire when hot then, not just poor starting.

If carb all ok, I'd then do HT lead, plug, cap and go on from there.,

[bbuchan]

ok thanks for that will give the carb a good clean and see what happens

[bbuchan]

clean out the carb and checked the float needle tried a long run today everything going great started no bother .
cheers for the advice