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Re: wont start when hot ?
Posted: Sat Feb 15, 2014 4:08 pm
by mick1
Had something similar with my PHBH. Turned out the choke "valve" wasn't seating correctly and the choke (although off) was partially on. Replaced choke valve/slide and now starts fine.......... So, check if choke is sticking...
Re: wont start when hot ?
Posted: Sat Feb 15, 2014 5:06 pm
by coaster
Good advice above re not screwing the throttle when starting and also the choke not seating. Also, next time it happens, pull the filter elbow off the carb and see if it starts then. Sometimes fuel is spat back out of the carb and collects in the elbow causing a rich mixture when you re-start when it's warm. I had a Mugello that was like that despite everything I tried. In the end I tried turning the fuel off 100 yards or so before I wanted to stop and left it off until after I restated it, Still a nuisance though especially when you stall in traffic
Re: wont start when hot ?
Posted: Sat Feb 15, 2014 5:47 pm
by sean brady scooters
a little drain hole through the bottom of the hose often cures this
Re: wont start when hot ?
Posted: Sat Feb 15, 2014 10:48 pm
by brianc
ah,think I might be getting somewhere now,ive not got a centre stand but a side stand,could it be fuel throw back from the carb sitting in the elbow causing rich mixture ?
brian.
Re: wont start when hot ?
Posted: Sat Feb 15, 2014 11:57 pm
by coaster
brianc wrote:ah,think I might be getting somewhere now,ive not got a centre stand but a side stand,could it be fuel throw back from the carb sitting in the elbow causing rich mixture ?
brian.
Yes it's a possibility but the stand will have nothing to do with it.
Re: wont start when hot ?
Posted: Sun Feb 16, 2014 11:46 am
by brianc
just had another look at it,took the elbow off and its got a puddle of fuel in it from carb blow back,whats the cure ?
brian.
Re: wont start when hot ?
Posted: Sun Feb 16, 2014 12:00 pm
by bristolmod
1) make sure the float is free to move up and down
2) check the starter jet- go down a couple of sizes (and use genuine Dellorto ones!)
3) as stated above- a small drain hole in the bottom of the carb bellows ( Innocenti scrapped the drain system c1969 to save money!!)
4) don't wind the throttle open as you kick it over
Chris
Re: wont start when hot ?
Posted: Sun Feb 16, 2014 12:15 pm
by brianc
thanks for all the advice,will a small hole in the elbow not draw in more air ?
brian.
Re: wont start when hot ?
Posted: Sun Feb 16, 2014 12:45 pm
by bristolmod
a tad more although it shouldn't affect it too much.
Innocentis original system was a one way valve which let fuel out but shut on the intake stroke stopping air in- quite a complex little set up and not cheap in the grand scale of things. However, penny (or lira) pinching caused it to be phased out during GP 's build run- some very early GP's did have this valve system in place..
Worth a try to see if it improves it.
Chris