Vespa VBB 150 fuelling issue?
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Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 1:16 pm quote
Hey - hoping to tap into the collective hive mind.

Need some help with a stock 150cc 1965 original engine. Issue is as follows:

This Morning
Engine hard to kick start. Taking 4-5 kicks and a few 'false starts' before the kick that gets it to turn over but never quite catches. I pull the plug assuming flooding but it looks suspiciously dry. I check for spark on the fins - all good. Pour in a bit more petrol and move the tap off the reserve and voila - success in 5 kicks. Idles fine once running. Did a little carb tweaking (mix screw set at 1 turn, idle 2 1/4 turn) and got a clean rev and stable idle. Left to warm for 10 mins and then went for a spin around the block to check all good. Went well - bogged and almost stalled on an uphill section but caught it. Stalled on a flat section where I came off the throttle. FYI Went about 3 miles. Worth mentioning that once warmed, the engine was kicking first time so I assumed all good.

Pulled the plug and looked decent - a little black, not choc yet but was idling for ages and only a short 5 min blast at best, most a 1/2-3/4 throttle. Running a 2% mix. I assumed it needed some fine tuning, went and did some other things and came back later in the afternoon.

The Afternoon
Bloody hard work to get it to start again. 6-7 kicks and the it would begin to grumble and then fired away. Gave throttle a blip to check things, bogged, stalled and could I get it started again? Nope. Strange, nothing changed. Checked for spark again - all good.

Reset carb back to 2 1/2 and 1 1/2 turns (http://www.vespamaintenance.com/fuel/carbtune/). Kick, kick, kick. Nothing. I pull spark plug and its black and sooty from a rich condition.

Eventually get it running with the choke after a lot of kicks. Notice here the absence of any flooding? Im regularly pulling the plug, kicking over with it out and putting it back in as I assumed it would be... Leave it to idle and warm up, tweak carb a little again but leave it at 1 1/4 turn air mix, 2 1/4 turn idle to allow for a little extra air. Again, stable idle and revving cleanly.

Drive through the gears for about 1 mile and as I go down a hill the engine bogs and stalls. Won't restart. Im at the side of the road for the next hour trying to get it to go.

Here's the weird bit - Im kicking it enough times that I'm thinking this is going to be flooded. So I kick no more than 10 times at a go, then pull the plug. It's dry... hmm... I slacken off the fuel line from the carb and no residual fuel comes out. I reattach the fuel line and give it a squeeze down the length of it and wiggle it a little. Kick a few more times, get a grumble, manage to catch it with choke (I've reset the carb to 2 1/2 and 1 1/2 turns again by this point I've been here this long - also tried the fully wound idle and 1 3/4 air mix to no avail). However it idles lazily and unreliably then stalls. I pull the plug and its now wet and oily. I give it a good clean down and stick it back in (didn't have a spare on me frustratingly). I pull the fuel line again at the carb and this time I get some residual fuel spillage. Hmm.

I decide to kick the machine with the air filter off and look for spray. Can't see anything - should I be able to see spray onto the slide when I kick it? I also have never seen any spray out the spark plug hole when Im kicking without the plug in - should I?

I'm thinking this is a fuelling issue...

Some history
Been sat in a garage for last 10 years by previous owner, adding only 20 mile onto the clock since then. He has regularly dropped fluids and turned over the engine. Thats what I'm working with.

Current setup
Taken the original SI 20/17 C carb off and realised I couldn't get the correct size jetting anymore. So I have purchased a new SPACO 20/17 D and switched jets to match the stock 150 VBB settings as per scooterlounge.

http://scooterlounge.com/vespa/reference-library/vespa-stock-jetting-reference-guide.shtml

Setup is this:
    SI 20/17 D
    100
    42
    140
    E1
    60


Prior to this mornings events, I had done the following:

Compression 120psi, kicked it a few times and got a consistent number.

Dropped the gear oil, looks fine and no smell of oil.

Im reasonably content the spark is present and in attendance.

Pulled the fuel tank, fiddled and cleaned out the petcock. Interestingly it was full of rubbish and grey gunk and previous owner had over-tightened it causing the tap to be stiff to turn and tearing the rubber. The fuel filter on the petcock looks in shoddy shape as well tbh but couldn't get a hold of a new one today so popped it all back in on a hope and prayer given the tank internally is in good nick, fresh fuel and the carb was brand new with a view to doing it later this week.

Before connecting fuel hose to carb, checked petcock works in all three positions - no fuel at off, dribble at on, slightly less dribble on reserve. New gasket on airbox, new carb gasket (and carb) and everything torqued correctly to 15nm.

Fuel hose is reasonably new by previous owner, 600mm end to end.

Petrol is fresh, 2% mix of putoline classic.

*****

My legs knackered from all the kicking today - really hoping one of you lovely folk give me some pointers where you think it might be going wrong for me/something obvious I've missed.

My thoughts at this stage are that it is an intermittent fuel starvation issue. Im suspecting that petcock - I stupidly forgot to blast the breather hose and dismantle the actual filter itself. If there is debris in either, that guess that may cause the fuel starvation issue. Hoping therefore that a new petcock will resolve it.

If its not that - any insights from anyone?!
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2249

Wed Sep 09, 2020 2:23 pm quote
Something easy to try is loosen off your gas cap.
Hooked
1977 Super 150 (PT Danmotor), '64 VBB, a few old motorcycle projects
Joined: 01 Apr 2017
Posts: 182
Location: Western Mass., USA
Wed Sep 09, 2020 2:34 pm quote
I was having a similar problem on a VBB2 project of mine -- been sitting for donkeys years too -- with a (freshly rebuilt) 20/17 c dell'orto as well. I dropped the gear oil and found a strong smell of gas, so I suspect a seal has blown up and the motor could use a rebuild, given the non-use. Never a bad idea if it's been years.

Of course, in your case from what you described your fuel tap seems due for a replacement. You weren't getting proper flow into the carb, it sounded like. Or a possible air leak that was overlooked? Also, is your carb's starter jet screwed in all the way?
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 2:40 pm quote
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 2:50 pm quote
zachyzach wrote:
I was having a similar problem on a VBB2 project of mine -- been sitting for donkeys years too -- with a (freshly rebuilt) 20/17 c dell'orto as well. I dropped the gear oil and found a strong smell of gas, so I suspect a seal has blown up and the motor could use a rebuild, given the non-use. Never a bad idea if it's been years.

Of course, in your case from what you described your fuel tap seems due for a replacement. You weren't getting proper flow into the carb, it sounded like. Or a possible air leak that was overlooked? Also, is your carb's starter jet screwed in all the way?
Thanks for your input

My thoughts did include an air leak and that canít yet be ruled out - the engine is to have an overhaul at some point soon. But Iím hoping to make that a winter project so I can have some short nip about before I pull the cases provided they are air tight.

Will double check the starter jet, that is a good idea.

Iím really hoping itís this petcock. Sick and tired of kicking without hope.
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2249

Wed Sep 09, 2020 3:51 pm quote
Xeres wrote:
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
My first runs on my new motor it shut down on me , revved up just before it died, first time I was on normal gas position and switched to reserve and it wouldnít start, I had just painted the bike this past winter and had a thought maybe paint blockage on the tank vent so I unscrewed the cap and it started right up. Did this a couple times afterwards with the cap screwed down but not tight . Maybe youíre cap isnít venting.
Hooked
1977 Super 150 (PT Danmotor), '64 VBB, a few old motorcycle projects
Joined: 01 Apr 2017
Posts: 182
Location: Western Mass., USA
Wed Sep 09, 2020 5:12 pm quote
Lynn's point about the cap venting being key is a good one. There's a small hole in the hollow center of the cap that has to be clear also.

This whole thing with the poor running, dying out and then stubborn restarting reminds me of what eventually turned out to be a dirty carb jets issue on my Super a few years back. In that case, I was a mile from home when it died. I barely got it running and limped home. After I took the 20/20 carb back off and recleaned it, the problem never repeated itself.
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 11:30 pm quote
Lynnb wrote:
Xeres wrote:
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
My first runs on my new motor it shut down on me , revved up just before it died, first time I was on normal gas position and switched to reserve and it wouldnít start, I had just painted the bike this past winter and had a thought maybe paint blockage on the tank vent so I unscrewed the cap and it started right up. Did this a couple times afterwards with the cap screwed down but not tight . Maybe youíre cap isnít venting.
Ah I see - I never knew there was a ent on it. I canít see one...

Thank you Iíll try that and feedback
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 11:32 pm quote
zachyzach wrote:
Lynn's point about the cap venting being key is a good one. There's a small hole in the hollow center of the cap that has to be clear also.

This whole thing with the poor running, dying out and then stubborn restarting reminds me of what eventually turned out to be a dirty carb jets issue on my Super a few years back. In that case, I was a mile from home when it died. I barely got it running and limped home. After I took the 20/20 carb back off and recleaned it, the problem never repeated itself.
Thanks. Definitely not a dirty carb. Itís brand new. Iíve taken it apart multiple times to double check and blow out the jets when all this was happening - theyíve always been fine.

RE vent hole - is almost certain this is blocked. Will look for it.
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 11:41 pm quote
Lynnb wrote:
Xeres wrote:
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
My first runs on my new motor it shut down on me , revved up just before it died, first time I was on normal gas position and switched to reserve and it wouldnít start, I had just painted the bike this past winter and had a thought maybe paint blockage on the tank vent so I unscrewed the cap and it started right up. Did this a couple times afterwards with the cap screwed down but not tight . Maybe youíre cap isnít venting.
This hole? Where for it exit at the top?[/img]

70B1AB9C-8109-470B-B934-4F75C84D3739.jpeg

Jet Eye Master
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 2376
Location: London UK
Wed Sep 09, 2020 11:52 pm quote
Have you checked the gear oil? If the seal is gone the gear oil will be lower or full of petrol.
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 09, 2020 11:53 pm quote
Jack221 wrote:
Have you checked the gear oil? If the seal is gone the gear oil will be lower or full of petrol.
Dropped it and all looked good. No smell of gas.
Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 2793
Location: Chicago. Well, Evanston, but that's almost Chicago
Fri Sep 11, 2020 3:08 am quote
A couple things come to mind from my VBB project, neither of them VBB-specific.

First off, have you pulled the fuel line off the carb and ensured that it has decent flow, period?

If it's flowing well, given how long it's been sitting, you probably have a bunch of rust and other garbage in the tank.

Take a look at the fuel from your flow test and see if there's any debris in there.
If so, you'll want to install a fuel filter. On my 1962 VBB, it still had the original glass sump fuel tap when I first got it and it was full of crap.

I had almost constant blocked carb jets until I properly cleaned the tank and eventually installed the fuel filter. Now, I run one on all my bikes and haven't had a clogged jet in a good five years or so.

Good luck!
Ossessionato
1963 VBB2T
Joined: 07 Nov 2012
Posts: 2249

Fri Sep 11, 2020 5:10 pm quote
Xeres wrote:
Lynnb wrote:
Xeres wrote:
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
My first runs on my new motor it shut down on me , revved up just before it died, first time I was on normal gas position and switched to reserve and it wouldnít start, I had just painted the bike this past winter and had a thought maybe paint blockage on the tank vent so I unscrewed the cap and it started right up. Did this a couple times afterwards with the cap screwed down but not tight . Maybe youíre cap isnít venting.
This hole? Where for it exit at the top?[/img]
C/P from my project topic ...After having the bike on the road for a bit I was finding it was shutting down every once in a while and had a look at the gas cap, I could see the vent hole on the tank side but not the top . I took it off the bracket and sure enough there was no top exit hole. I got my dremel with a small bit and drilled on an angle through with the inside hole, reassembled and did a few miles, I think that fixed it.
I will be ordering a new cap and bracket.

Hope this helps

sept 11 gas cap.jpg
vent hole

sept 11 gas cap 2.jpg
top of gas cap, no exit vent , painted over

sept 11 gas cap 3 drilled.jpg
drilled from inside vent hole outward on an angle

sept 11 gas cap 3 drilled 2.jpg

sept 11 gas cap bracket.jpg
pulled the pin from bracket

Molto Verboso
Vespas 1964 GS160, 1965 SS180, 1977 V9A1T, 1983 PX150E
Joined: 16 Apr 2011
Posts: 1504
Location: Siam
Fri Sep 11, 2020 6:43 pm quote
Xeres wrote:
Hey - hoping to tap into the collective hive mind.

Need some help with a stock 150cc 1965 original engine. Issue is as follows:

This Morning
Engine hard to kick start. Taking 4-5 kicks and a few 'false starts' before the kick that gets it to turn over but never quite catches. I pull the plug assuming flooding but it looks suspiciously dry. I check for spark on the fins - all good. Pour in a bit more petrol and move the tap off the reserve and voila - success in 5 kicks. Idles fine once running. Did a little carb tweaking (mix screw set at 1 turn, idle 2 1/4 turn) and got a clean rev and stable idle. Left to warm for 10 mins and then went for a spin around the block to check all good. Went well - bogged and almost stalled on an uphill section but caught it. Stalled on a flat section where I came off the throttle. FYI Went about 3 miles. Worth mentioning that once warmed, the engine was kicking first time so I assumed all good.

Pulled the plug and looked decent - a little black, not choc yet but was idling for ages and only a short 5 min blast at best, most a 1/2-3/4 throttle. Running a 2% mix. I assumed it needed some fine tuning, went and did some other things and came back later in the afternoon.

The Afternoon
Bloody hard work to get it to start again. 6-7 kicks and the it would begin to grumble and then fired away. Gave throttle a blip to check things, bogged, stalled and could I get it started again? Nope. Strange, nothing changed. Checked for spark again - all good.

Reset carb back to 2 1/2 and 1 1/2 turns (http://www.vespamaintenance.com/fuel/carbtune/). Kick, kick, kick. Nothing. I pull spark plug and its black and sooty from a rich condition.

Eventually get it running with the choke after a lot of kicks. Notice here the absence of any flooding? Im regularly pulling the plug, kicking over with it out and putting it back in as I assumed it would be... Leave it to idle and warm up, tweak carb a little again but leave it at 1 1/4 turn air mix, 2 1/4 turn idle to allow for a little extra air. Again, stable idle and revving cleanly.

Drive through the gears for about 1 mile and as I go down a hill the engine bogs and stalls. Won't restart. Im at the side of the road for the next hour trying to get it to go.

Here's the weird bit - Im kicking it enough times that I'm thinking this is going to be flooded. So I kick no more than 10 times at a go, then pull the plug. It's dry... hmm... I slacken off the fuel line from the carb and no residual fuel comes out. I reattach the fuel line and give it a squeeze down the length of it and wiggle it a little. Kick a few more times, get a grumble, manage to catch it with choke (I've reset the carb to 2 1/2 and 1 1/2 turns again by this point I've been here this long - also tried the fully wound idle and 1 3/4 air mix to no avail). However it idles lazily and unreliably then stalls. I pull the plug and its now wet and oily. I give it a good clean down and stick it back in (didn't have a spare on me frustratingly). I pull the fuel line again at the carb and this time I get some residual fuel spillage. Hmm.

I decide to kick the machine with the air filter off and look for spray. Can't see anything - should I be able to see spray onto the slide when I kick it? I also have never seen any spray out the spark plug hole when Im kicking without the plug in - should I?

I'm thinking this is a fuelling issue...

Some history
Been sat in a garage for last 10 years by previous owner, adding only 20 mile onto the clock since then. He has regularly dropped fluids and turned over the engine. Thats what I'm working with.

Current setup
Taken the original SI 20/17 C carb off and realised I couldn't get the correct size jetting anymore. So I have purchased a new SPACO 20/17 D and switched jets to match the stock 150 VBB settings as per scooterlounge.

http://scooterlounge.com/vespa/reference-library/vespa-stock-jetting-reference-guide.shtml

Setup is this:
    SI 20/17 D
    100
    42
    140
    E1
    60


Prior to this mornings events, I had done the following:

Compression 120psi, kicked it a few times and got a consistent number.

Dropped the gear oil, looks fine and no smell of oil.

Im reasonably content the spark is present and in attendance.

Pulled the fuel tank, fiddled and cleaned out the petcock. Interestingly it was full of rubbish and grey gunk and previous owner had over-tightened it causing the tap to be stiff to turn and tearing the rubber. The fuel filter on the petcock looks in shoddy shape as well tbh but couldn't get a hold of a new one today so popped it all back in on a hope and prayer given the tank internally is in good nick, fresh fuel and the carb was brand new with a view to doing it later this week.

Before connecting fuel hose to carb, checked petcock works in all three positions - no fuel at off, dribble at on, slightly less dribble on reserve. New gasket on airbox, new carb gasket (and carb) and everything torqued correctly to 15nm.

Fuel hose is reasonably new by previous owner, 600mm end to end.

Petrol is fresh, 2% mix of putoline classic.

*****

My legs knackered from all the kicking today - really hoping one of you lovely folk give me some pointers where you think it might be going wrong for me/something obvious I've missed.

My thoughts at this stage are that it is an intermittent fuel starvation issue. Im suspecting that petcock - I stupidly forgot to blast the breather hose and dismantle the actual filter itself. If there is debris in either, that guess that may cause the fuel starvation issue. Hoping therefore that a new petcock will resolve it.

If its not that - any insights from anyone?!
How long did it take you to type that?😊
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Fri Sep 11, 2020 11:49 pm quote
nomadinsiam wrote:
Xeres wrote:
Hey - hoping to tap into the collective hive mind.

Need some help with a stock 150cc 1965 original engine. Issue is as follows:

This Morning
Engine hard to kick start. Taking 4-5 kicks and a few 'false starts' before the kick that gets it to turn over but never quite catches. I pull the plug assuming flooding but it looks suspiciously dry. I check for spark on the fins - all good. Pour in a bit more petrol and move the tap off the reserve and voila - success in 5 kicks. Idles fine once running. Did a little carb tweaking (mix screw set at 1 turn, idle 2 1/4 turn) and got a clean rev and stable idle. Left to warm for 10 mins and then went for a spin around the block to check all good. Went well - bogged and almost stalled on an uphill section but caught it. Stalled on a flat section where I came off the throttle. FYI Went about 3 miles. Worth mentioning that once warmed, the engine was kicking first time so I assumed all good.

Pulled the plug and looked decent - a little black, not choc yet but was idling for ages and only a short 5 min blast at best, most a 1/2-3/4 throttle. Running a 2% mix. I assumed it needed some fine tuning, went and did some other things and came back later in the afternoon.

The Afternoon
Bloody hard work to get it to start again. 6-7 kicks and the it would begin to grumble and then fired away. Gave throttle a blip to check things, bogged, stalled and could I get it started again? Nope. Strange, nothing changed. Checked for spark again - all good.

Reset carb back to 2 1/2 and 1 1/2 turns (http://www.vespamaintenance.com/fuel/carbtune/). Kick, kick, kick. Nothing. I pull spark plug and its black and sooty from a rich condition.

Eventually get it running with the choke after a lot of kicks. Notice here the absence of any flooding? Im regularly pulling the plug, kicking over with it out and putting it back in as I assumed it would be... Leave it to idle and warm up, tweak carb a little again but leave it at 1 1/4 turn air mix, 2 1/4 turn idle to allow for a little extra air. Again, stable idle and revving cleanly.

Drive through the gears for about 1 mile and as I go down a hill the engine bogs and stalls. Won't restart. Im at the side of the road for the next hour trying to get it to go.

Here's the weird bit - Im kicking it enough times that I'm thinking this is going to be flooded. So I kick no more than 10 times at a go, then pull the plug. It's dry... hmm... I slacken off the fuel line from the carb and no residual fuel comes out. I reattach the fuel line and give it a squeeze down the length of it and wiggle it a little. Kick a few more times, get a grumble, manage to catch it with choke (I've reset the carb to 2 1/2 and 1 1/2 turns again by this point I've been here this long - also tried the fully wound idle and 1 3/4 air mix to no avail). However it idles lazily and unreliably then stalls. I pull the plug and its now wet and oily. I give it a good clean down and stick it back in (didn't have a spare on me frustratingly). I pull the fuel line again at the carb and this time I get some residual fuel spillage. Hmm.

I decide to kick the machine with the air filter off and look for spray. Can't see anything - should I be able to see spray onto the slide when I kick it? I also have never seen any spray out the spark plug hole when Im kicking without the plug in - should I?

I'm thinking this is a fuelling issue...

Some history
Been sat in a garage for last 10 years by previous owner, adding only 20 mile onto the clock since then. He has regularly dropped fluids and turned over the engine. Thats what I'm working with.

Current setup
Taken the original SI 20/17 C carb off and realised I couldn't get the correct size jetting anymore. So I have purchased a new SPACO 20/17 D and switched jets to match the stock 150 VBB settings as per scooterlounge.

http://scooterlounge.com/vespa/reference-library/vespa-stock-jetting-reference-guide.shtml

Setup is this:
    SI 20/17 D
    100
    42
    140
    E1
    60


Prior to this mornings events, I had done the following:

Compression 120psi, kicked it a few times and got a consistent number.

Dropped the gear oil, looks fine and no smell of oil.

Im reasonably content the spark is present and in attendance.

Pulled the fuel tank, fiddled and cleaned out the petcock. Interestingly it was full of rubbish and grey gunk and previous owner had over-tightened it causing the tap to be stiff to turn and tearing the rubber. The fuel filter on the petcock looks in shoddy shape as well tbh but couldn't get a hold of a new one today so popped it all back in on a hope and prayer given the tank internally is in good nick, fresh fuel and the carb was brand new with a view to doing it later this week.

Before connecting fuel hose to carb, checked petcock works in all three positions - no fuel at off, dribble at on, slightly less dribble on reserve. New gasket on airbox, new carb gasket (and carb) and everything torqued correctly to 15nm.

Fuel hose is reasonably new by previous owner, 600mm end to end.

Petrol is fresh, 2% mix of putoline classic.

*****

My legs knackered from all the kicking today - really hoping one of you lovely folk give me some pointers where you think it might be going wrong for me/something obvious I've missed.

My thoughts at this stage are that it is an intermittent fuel starvation issue. Im suspecting that petcock - I stupidly forgot to blast the breather hose and dismantle the actual filter itself. If there is debris in either, that guess that may cause the fuel starvation issue. Hoping therefore that a new petcock will resolve it.

If its not that - any insights from anyone?!
How long did it take you to type that?😊
Not as long as itís taken me to trouble shoot this fa thankfully!
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Fri Sep 11, 2020 11:52 pm quote
Lynnb wrote:
Xeres wrote:
Lynnb wrote:
Xeres wrote:
Lynnb wrote:
Something easy to try is loosen off your gas cap.
Not quite sure what that achieves? Can you please explain?
My first runs on my new motor it shut down on me , revved up just before it died, first time I was on normal gas position and switched to reserve and it wouldnít start, I had just painted the bike this past winter and had a thought maybe paint blockage on the tank vent so I unscrewed the cap and it started right up. Did this a couple times afterwards with the cap screwed down but not tight . Maybe youíre cap isnít venting.
This hole? Where for it exit at the top?[/img]
C/P from my project topic ...After having the bike on the road for a bit I was finding it was shutting down every once in a while and had a look at the gas cap, I could see the vent hole on the tank side but not the top . I took it off the bracket and sure enough there was no top exit hole. I got my dremel with a small bit and drilled on an angle through with the inside hole, reassembled and did a few miles, I think that fixed it.
I will be ordering a new cap and bracket.

Hope this helps
Thatís really helpful thank you.

I couldnít see a corresponding hole on my fuel cap but I can see the inside hole. My rubber bung might also be fouling that breather hole location.

Going to kick it with the tank open once the petcock has been switched so I know I can hopefully isolate one thing at a time. Wonít get back to it for a week as on holiday now (frustratingly lol)
Member
VBB 1965
Joined: 02 Sep 2020
Posts: 17
Location: Lancaster
Wed Sep 23, 2020 12:02 am quote
Re: Vespa VBB 150 fuelling issue?
A little update - resolved! (Been on holiday so taken me a while to get back to it.)

Replaced the fuel tap and also switched out the 'miscellaneous' fuel hose for a clear tube. Double checked tank before refitting was clean, pulled and stripped carb just to be doubly sure and torqued everything back down - kicked her after 5 kicks and now starts consistently.

I couldn't see a breather hole in the fuel cap either so I ran a 1.5mm drill bit through the hole to create a new one. Great tip that.

Now new problem which I have a plan for - struggling to get a well maintained idle and running lean after 1/4 throttle but too rich at idle. Been doing some reading that the SPACO 20/17D carbs mix screw is a finer thread an needs 2-2 1/2 turns to meet the original dellorto 1 1/2 turns out when tuning.

Also have an obvious ai leak at the head now that I've taken her for a spin so going to strip, clean and build the top end, drop leak test everything and hopefully off we go....

Thanks for your input all.
Xeres wrote:
Hey - hoping to tap into the collective hive mind.

Need some help with a stock 150cc 1965 original engine. Issue is as follows:

This Morning
Engine hard to kick start. Taking 4-5 kicks and a few 'false starts' before the kick that gets it to turn over but never quite catches. I pull the plug assuming flooding but it looks suspiciously dry. I check for spark on the fins - all good. Pour in a bit more petrol and move the tap off the reserve and voila - success in 5 kicks. Idles fine once running. Did a little carb tweaking (mix screw set at 1 turn, idle 2 1/4 turn) and got a clean rev and stable idle. Left to warm for 10 mins and then went for a spin around the block to check all good. Went well - bogged and almost stalled on an uphill section but caught it. Stalled on a flat section where I came off the throttle. FYI Went about 3 miles. Worth mentioning that once warmed, the engine was kicking first time so I assumed all good.

Pulled the plug and looked decent - a little black, not choc yet but was idling for ages and only a short 5 min blast at best, most a 1/2-3/4 throttle. Running a 2% mix. I assumed it needed some fine tuning, went and did some other things and came back later in the afternoon.

The Afternoon
Bloody hard work to get it to start again. 6-7 kicks and the it would begin to grumble and then fired away. Gave throttle a blip to check things, bogged, stalled and could I get it started again? Nope. Strange, nothing changed. Checked for spark again - all good.

Reset carb back to 2 1/2 and 1 1/2 turns (http://www.vespamaintenance.com/fuel/carbtune/). Kick, kick, kick. Nothing. I pull spark plug and its black and sooty from a rich condition.

Eventually get it running with the choke after a lot of kicks. Notice here the absence of any flooding? Im regularly pulling the plug, kicking over with it out and putting it back in as I assumed it would be... Leave it to idle and warm up, tweak carb a little again but leave it at 1 1/4 turn air mix, 2 1/4 turn idle to allow for a little extra air. Again, stable idle and revving cleanly.

Drive through the gears for about 1 mile and as I go down a hill the engine bogs and stalls. Won't restart. Im at the side of the road for the next hour trying to get it to go.

Here's the weird bit - Im kicking it enough times that I'm thinking this is going to be flooded. So I kick no more than 10 times at a go, then pull the plug. It's dry... hmm... I slacken off the fuel line from the carb and no residual fuel comes out. I reattach the fuel line and give it a squeeze down the length of it and wiggle it a little. Kick a few more times, get a grumble, manage to catch it with choke (I've reset the carb to 2 1/2 and 1 1/2 turns again by this point I've been here this long - also tried the fully wound idle and 1 3/4 air mix to no avail). However it idles lazily and unreliably then stalls. I pull the plug and its now wet and oily. I give it a good clean down and stick it back in (didn't have a spare on me frustratingly). I pull the fuel line again at the carb and this time I get some residual fuel spillage. Hmm.

I decide to kick the machine with the air filter off and look for spray. Can't see anything - should I be able to see spray onto the slide when I kick it? I also have never seen any spray out the spark plug hole when Im kicking without the plug in - should I?

I'm thinking this is a fuelling issue...

Some history
Been sat in a garage for last 10 years by previous owner, adding only 20 mile onto the clock since then. He has regularly dropped fluids and turned over the engine. Thats what I'm working with.

Current setup
Taken the original SI 20/17 C carb off and realised I couldn't get the correct size jetting anymore. So I have purchased a new SPACO 20/17 D and switched jets to match the stock 150 VBB settings as per scooterlounge.

http://scooterlounge.com/vespa/reference-library/vespa-stock-jetting-reference-guide.shtml

Setup is this:
    SI 20/17 D
    100
    42
    140
    E1
    60


Prior to this mornings events, I had done the following:

Compression 120psi, kicked it a few times and got a consistent number.

Dropped the gear oil, looks fine and no smell of oil.

Im reasonably content the spark is present and in attendance.

Pulled the fuel tank, fiddled and cleaned out the petcock. Interestingly it was full of rubbish and grey gunk and previous owner had over-tightened it causing the tap to be stiff to turn and tearing the rubber. The fuel filter on the petcock looks in shoddy shape as well tbh but couldn't get a hold of a new one today so popped it all back in on a hope and prayer given the tank internally is in good nick, fresh fuel and the carb was brand new with a view to doing it later this week.

Before connecting fuel hose to carb, checked petcock works in all three positions - no fuel at off, dribble at on, slightly less dribble on reserve. New gasket on airbox, new carb gasket (and carb) and everything torqued correctly to 15nm.

Fuel hose is reasonably new by previous owner, 600mm end to end.

Petrol is fresh, 2% mix of putoline classic.

*****

My legs knackered from all the kicking today - really hoping one of you lovely folk give me some pointers where you think it might be going wrong for me/something obvious I've missed.

My thoughts at this stage are that it is an intermittent fuel starvation issue. Im suspecting that petcock - I stupidly forgot to blast the breather hose and dismantle the actual filter itself. If there is debris in either, that guess that may cause the fuel starvation issue. Hoping therefore that a new petcock will resolve it.

If its not that - any insights from anyone?!
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