cutting out problem 1964 Vespa 150

[arniej]

Help

Purchased a Vespa 150 Last year and seem to be having a problem with cutting out. The Scooter starts first kick every time but dies after riding for a few mins.
I have shortened the fuel hose and cleaned out all the filters (carb and Fuel tap). Cleaned out the carb and put in a new spark plug but the problem still persists.
I thought it might be fuel starvation as once it cuts out it starts up after about 30 seconds but runs bad. I have tried to adjust the mixture screw but to be honest it
does not seem to make much difference. Any idea's

[henri]

1st idea a stuck on choke , drowning it . after that i'd start looking at electrics , a failing condenser or ht coil would be my main suspects . H

[arniej]

I'll check the choke, never thought of that. The Scooter has electronic ignition fitted, all the connections checked out ok.

Thanks for your help.

I thought I had it fixed earlier today then it cut out after riding for about 10 mins ?

[henri]

with air filter off theres a drilling on top near were choke cable/connecter is, if ya look down this you can see the brass choke plunger moving as chokes operated .when off it needs to cover/fill the bottom of the hole to prevent air getting thru to choke jet .
if choke checks out , i'd nxt check the cdi , tho a failing cdi or pick up normaly need 10-20 mins to cool down before scoot will re-start . vespasmallframeforum.proboards.com/thread/9612/torque-figures-ignition-measuring-values . heres a set of values for metering a cdi an stator/pick up ,its pk but there identical to px in all regards .
if all this checks out i'd start suspecting a air-leak developing on a warmed engine , carb an carb tray an head/barrel joint would be my 1st checks . H

[arniej]

Back again.

Checked out the choke, all ok. Adjusted the plug gap and air screw and road tested. The scooter went ok but still has a misfire low to mid range revs.
When screwing the air screw all the way in the scooters revs rise at tick over but missfires even worse. I have the air screw 3/4 of a turn out at the moment
And it runs about 85% perfect. I'm thinking of refitting the carb with a new gasket in case there is a leak. Any ideas ??

[henri]

3/4 turns out , should be more 1 1/2 to 2 1/2 . might be a over large pilot jet , but start with a carb an carb box gasket renewal ,rule out a leak there . an then i'd check the timing with a strobe ,on points there set to fire at 21 btdc ,electronics on px's 18-19 btdc .with modern fuel i'd set to 19 , once ya sure its not leaking an is timed we can look at the jetting to get it right . H

[arniej]

Re sealed carb and air box, thought it was ok. Revs now dropping when screwing in mixture screw. I left to ticking over for five mins and tried to to take it out.
As soon as I opened the throttle it bogged down and cut out, it started up ok and ticked over but died when opening the throttle. It will only rev up if I hold
the choke on.. I can't even ride it now as it won't even pull away.

Help

[scooterist]

has your scoot got an immobiliser fitted,

[arniej]

No.

[djloone]

Im no mech wizard but 1 of the other threads on herewith the same sorta symptons was a blown oil seal..tbh i know little about the 150 (p range engine layout?)H/Sime Guru and many others im sure will have the answers

LOON-E

[arniej]

I now have the scooter running too rich, on plug check the plug is wet and oily. Adjusting the mixture has little or no effect.
The scooter ticks over and starts fine then after a few mins when opening the throttle it just bogs down and eventually dies.

[bryno]

The mixture screw has very little effect once you are off light throttle, only really makes a difference to tickover and that first 1/4 turn of the grip

How was the engine running before? Have you recently done work on it? may narrow it down a bit with a bit of background

Wet and oily plug sounds like seal gone to me or it is way over jetted, is it smokey?

is it a PX 125 engine, rather than a classic 150?

[henri]

wet n oily , which plugs in it , if a older 2 port motor should be a ngk b6 , a b7 or 8 might foul up like that as not getting up to temp. or as bryno says the oily ness might be a clutch seal on its way out . H

[henri]

idle thought , have you tried running it with tank cap open , blocked or partially blocked breathers can give odd results . an a once over of ht cap n lead an cdi connections never hurts .H

[arniej]

Going by the engine number it looks like the original unit. I have never had it running as it should since buying it. It's been totally restored by the previous owner so I'm not sure what has been done to it. It was running about 85% good until I resealled the carb and air box. When I say 85% I mean that it was rideable now it will not go over 100 yards without bogging down. I'm going to have another go tomorrow weather permitting.

[pxguru]

Even if the carb has a small air leak it will still ride with the throttle wide open. Sounds like it might not be a carb problem at all.

As pointed out already, when it all goes weird its usually the main oil seal. Check the gear box oil level and see if there is any left in there.

[arniej]

Removed the carb again a renewed the base gasket. Checked the oil, all ok, checked the plug, wet but not that oily. Scooter produces a good spark, not really sure about the timing as I don't have the tools or even sure what ignition system it has. I think the carb is knackered. I've tried adjusting the mixture screw for hour and it seems to work at first then soon returns to bogging down when you open the throttle. I can't ride it so I'm not sure about top end running. It's really frustrating as it was almost running ok three days ago.

[henri]

freashly rebuilt an never run right ,ok . 1st one ,is piston on right way round ,arrow pointing to exhaust . an who built it ,as its very easy to get a clutch seal wrong ,even when ya know what your doing . make a note of jet sizes an report back , also size of carb . H

[bryno]

Ok, so its the original 2 port 150 with an Electronic Ignition conversion fitted and never really run right.

I think you need to check the ignition timing, followed by a check that the carb is jetted correctly as Henri suggests.

Still maybe a problem with the clutch side oil seal, did you check if there is fuel in the gearoil? you'll smell it if the seal has gone, that said, there may not be much yet given you've not been able to give it a good run yet.

Damaged rotary sealing pad may also be the issue but I'd look at that as a last resort.

[arniej]

Tonight I fitted a new plug, scooter started first time, revved up good and ticked over fine. I left it ticking over for about ten mins and occasionally revved it up. All was good.
Switched it off and re started it and instantly turned to sh*t. As soon as I touched the throttle it bogged down and died then started ok but would not rev up. I removed the spark plug and found a slight stickyish oil on it. Not thick oil. I was thinking of getting a new spaco 20/17 carb and starting again. I don't have much time to spend on it during the week so I can't check the oil for fuel smell but will do on Saturday. I'm assuming it has electronic ignition because I cannot see a hole in the flywheel which looks pretty new. I'm pretty new to two stroke Vespa's so I'm sorry if I'm asking stupid questions. As for checking the timing I'm guessing that would involve removing the flywheel and special tools etc.

[henri]

the only stupid questions is the one you should of asked but didnt ,in case ya looked stupid . some may say i was born with a spanner in my hand ,i wasnt i just asked a lot of questions from guys who knew .no hole in fly makes it lectronic , setting timing ya need a timing light , an flywheel holder an puller if it needs moving . H

[arniej]

What's your views on a new carb. The one on it could be make up from a box of old bits ?

[henri]

worth a try , but still wondering on timing an clutch seal . H

[bryno]

Honestly I would get the timing checked first for peace of mind, if that has never been set up properly, its just not going to run right.

Try a carb swap if you have one, though I'd suggest check what carb and jets you have fitted now, again, may just not be set up.

TBH, I never got my VBB to run on anything bigger than the 17mm original carb (I lost patience in setting it up) so if you have say a 20/20 carb on the original 2 port engine, it will take some messing around with jets to get it to run OK (Henri will prob know the set up for a VBB)

[arniej]

Potential success, fitted a new spaco 20/17 carb this evening and bingo. Scooter runs perfect, rode it around the block and it never missed a beat. I did notice that the carb fitted to the scooter was a 20/20 D Dellorto so hopefully that was the problem. I'll keep you posted after a longer run and maybe an mot. Thanks to everyone for their input. 

[bryno]

ah that's good news mate, as i said, I never got a 20/20 working smoothly on my VBB 2 port, it can be done but lots of trial and error involved!

[pxguru]

Thats great news that its running fine now was all sounding a bit weird before.

Just out of interest, can you list all the jet numbers (pilot, main jet, atomiser, air corrector)that were in the 20/20D?

[henri]

as pxguru says , i'm wondering if its 20/17 vbb type none air corrector jets in a later air correcter type carb .or vise versa . didnt think of that possibility earlier . H

[arniej]

More good news. Scooter passed its MOT this morning and been riding about most of the day without any problems. Thinking of chancing a run out to Oddballs Rally in Oxfordshire tomorrow. I tried to read the numbers off the old jets from the 20/20 carb but the old eyes ain't what they used to be.only slight issue is a very intermittent jerk from what seems to be the clutch when riding at the top end, only lasts a second so I'll keep plugging on. ?

[henri]

good news , keep on just keeping on , an pack a AA card in ya pocket an ya off to oddballs . stuck scootless away from home so jealous but happy for ya . H