Modern Vespa

Hi Everyone,

First let me say thanks to all those with knowledge who share it here. Second let me say I've looked at a lot of posts about ET4's that won't start but none are quite like my situation. (I have no experience with scooters but work on all my cars myself) The post is long because I wanted to get as much detail in as I could. Here goes:

2002 ET4 150 Leader engine, Walbro carb. 1400 miles. Bought recently from a friend. Had been stored for approx 2 years. Like new condition. See picture.
Gas drained before storing so no bad gas issues.

I took it to a shop & they wanted $1100 to do all kinds of stuff to it. ($70 just to look at it. $95/hr shop rate seemed like a lot to me). That's more than I paid for it and from everything I'd seen online that made no sense to me.

Took it home (last week). Put a new battery in it. Put 87 octane gas in it but added a bottle of octane boost when I realized it's supposed to get 91 octane. Only filled to about 1/2 tank so I don't think I flooded the evap canister. It started & idled but would die when I tried to throttle it up.

Removed & cleaned the carb after watching you tube video. The last person to disassemble the carb had used blue gasket seal in addition to the factory gasket on the float bowl. I had to use air pressure to "blow" the float bowl off. Some of the blue stuff had gotten inside the bowl. I cleaned all of it I saw. Idle jet was blocked. Got it opened. No tears in diaphragm. It started & I rode it several miles.

Noticed it hesitated a lot on acceleration and when coming to a stop. Ran GREAT when on main circuit.

Cleaned the carb again & sure enough the idle jet was clogged again. Cleaned more blue stuff out of the bowl. Put a new spark plug in. Turned the idle screw to raise the idle a bit. Started & idled fine. Rode several miles but still hesitating (maybe a little better than before).

Cleaned the carb again. Idle jet clogged again. More blue stuff. Was extra careful to get all of the blue stuff I saw this time. Tried to get the floats out so I could get under them to make sure there was no more blue stuff but the pin wouldn't come all the way out so I tapped it back into place. Floats still move freely. Diaphragm still good. No changes to air/fuel or idle speed settings this time.

Put the carb back on. Started fine. Rode about 100 yards & died. Haven't been able to get it started since.

Turns & turns but won't turn over. When it does seem like it's about to turn over, it seems to backfire & then goes back to just turning. Makes me think the carb is rich. Have checked the jets & diaphragm again. They're good. Battery is on tender. Turned the air/fuel mix to 1.5 turns from seated which I think is just a little on the lean side. Set the idle speed to as low as it will go. Still won't start. Plenty of fuel coming out of the fuel line when disconnected, so don't think it's the fuel line. When I take the carb off, lots of gas comes out.
Checked the air filter & it literally disintegrated in my hand. Will replace it but have been trying to start it with no air filter in place - still no luck.

Did notice that fuel flows freely from the fuel line when it's disconnected from the carb. I think I saw that it's not supposed to do that (fuel only supposed to flow freely when vaccum is applied to the petcock, opening the valve?). Put my hand over the intake side of the carb when trying to start it & my hand was very wet with gas. Again, think that makes it look like the carb is rich(?)

I'm at my wits end! Really disheartened. Thinking of taking it to the shop & hoping they don't screw me too badly but thought I'd try here first. Sorry for the long post but thought all the detail would be helpful.

Thanks for any help/thoughts.

Well...it sounds like you definitely need a new vacuum petcock, and I would suggest replacing all the vacuum and fuel hoses.

You might want to install a new carb, which will probably be cheaper and faster than paying a shop to fiddle with the old one. I would guess based on your description that the float height has gotten out of whack after so many carb disassemblies. It is also possible that some additional carb passages are clogged. You can look into this stuff yourself and hope for the best...or just put on a new carb and at worst rule out carb issues.

Thanks for your reply. Can you recommend a good source for a carb? The only ones I’ve seen online have either been $300-$400 or I haven’t been sure they would work.

$400? That's crazy. I'll sell you this one for $350.

https://scooterpartsco.com/vespa/et4/et4-air-and-fuel/piaggio-carburetor-for-vespa-et4

Thanks. So the Keihin is a direct replacement for the Walbro? Is any modification required to make it fit? Are re-build kits available for the Keihin if needed? Haven’t been able to find one for the Walbro? Also... based on the symptoms, do you think it’s the carb?

Before you spend the money on a new carb, sorry Motovista, pull the carb and take the diaphragm and jets out. Also pull what you can of the accelerator pump. Take the enricher off as well. Then give it a good long bath in an ultrasonic cleaner, Harbor Freight has them cheap and they do a good job. This will hopefully open all of the holes. It can take a few times to get it clean. I have only had one carb not come back and it had sat for 20 years with fuel in it.

It sounds as though he’s cleaned the carb several times and things started getting worse. Maybe adding ultrasonic cleaning to the process will be the solution, maybe not. If that sounds appealing, by all means then press on, actually the Harbor Freight cleaner is kinda nice. But the continuing presence of the unnecessary blue gunk sealant is troubling to me. Maybe the bowl got bent somehow, etc. requiring extra measures to seal. I still think the most recent issue lies with the recently disassembled float level.

But there comes a point at which biting the bullet on the new part offsets the frustration of the time spent unsuccessfully and uncertainty of success with the old part. My point at this stage last year with a Buddy carb I just could not get into shape was after ultrasonic cleaning. Following about 7 hours of futzing and $75 in parts including the cleaner, dropping $175 on a new carb and zooming off two minutes after installation felt pretty good even though it was a technical defeat.

But whatever you decide, do make sure the hoses are clear and in good shape. Do not pump fresh gunk into your cleaning work or new part.

PS: Motovista is being funny as usual. Note that his price for the replacement carb is only $229. My sense is that the newer Keihin is easier to support than your original Walbro. It at least brings the system in line with the configuration of the popular LX/S models, which also have the Leader engine.

The Keihin is what Piaggio went to when they stopped getting Walbro carbs. I'm not sure about the service manual for the ET4, but in the one for the GT200, they mention both carbs. It is a direct replacement.
AFAIK, there are no rebuild kits available from Piaggio. You can get generic rebuild kits for the Keihin carbs, and about 80% of the parts are similar.
If there was a cheap fix out there, it would be easy to find on MV.
One thing many people who remember the "good old days," when you didn't have to deal with all this electronic stuff nobody can work on forgets is how much more often everything had to be fixed. Carburetors wear out, parts idisintegrate, and most old motorcycle shops had a pile of used carburetors somewhere in the back, because they replaced a lot of them. And a lot of people have no real experience with carburetors. There are technicians out there who really can't adjust them properly. By the same token, there are a lot of technicians who can't true spoked rims. Because they don't see enough of them that it's a skill worth having anymore.

Scads of small engines continue to be made with carburetors so there will be somebody around somewhere to fiddle with them, even if motorcycle/scooter shops sub that work out as they often do now with alternators. My math is not so much about the dwindling availability of shop expertise, which I don’t doubt, but the fact that pro labor costs have gone up much faster than the cost of a new carb.

The question is, how economical is it to pay somebody $95 an hour hoping they can eventually find parts and fix the current issue with an 18-year-old carb, when the curious and careful DIY person can probably do 70% of what an experienced carb pro can do - just not quickly? That was a no-brainer, as the OP mentioned. Paying for all of the labor to solve that last 30% of situations, versus trying to climb up the more advanced part of the DIY learning curve, versus dropping $230 and getting a new carb almost right away...is where the OP finds himself right now.

You can hear the approaching heavy steps of the new part....

Last edited by Juan_ORhea on Sun Apr 26, 2020 12:47 pm; edited 1 time in total

Thanks guys. Sincerely appreciate the knowledge you're sharing.

Took the carb all the way down to the throttle body today. Choke off, heater off, fuel screw out, jets out, diaphragm/needle valve out, throttle pump out, floats out. Don't have an ultrasonic cleaner, so did not do that... but blasted it with carb cleaner air pressure. I am very confident that all ports are open. Did get a bit more blue stuff out but very little this time. Also found some caked on white stuff. Got it out. The "c-retainer" on the needle valve is at the lowest of the three slots. Backed the fuel screw out 2.5 turns. Idle jet is open. The bowl does not appear to be bent. It appears to seal properly using just the original gasket. Everything appeared to work properly. Another person from the forum PM'd me - suggested that I disconnect & clean the ignition coil. Did that with no luck.

One thing I forgot to tell you... when I disassembled the carb the first time, I found that the same knucklehead that used the blue stuff also had put the diapgragm in with the spring in the wrong place. The spring is supposed to go on the top side of the diaphragm; down into the slide so it pushes the diaphragm/needle valve down into the main jet when there's no pressure on it. This person had put the spring on the bottom side of the diaphragm, inside the throttle body, pushing the diaphragm/needle valve "up". It was literally inside the throttle body. The only thing holding the spring in place was the needle.

When I took the needle out today, I noticed that there were wear marks on the sides of it that I'm assuming came from the spring rubbing against it. Honestly, I'm shocked that it ran that way, but it did start and idle that way. Just wouldn't rev up.

Would appreciate any other thoughts you may have before I start buying the parts I need (definitely a petcock and air filter. Maybe a carb)

Cleaned carb in ultrasonic cleaner today. Looks brand new. All blue stuff gone.

Ordered fuel tap, air filter, oil filter and allen head float bowl screws from Motovista.

Will put new fuel and vacuum hoses on when I replace the fuel tap.

Will update after everything is in place.

If all this doesn't get it running again, I will order the new carb.

Thanks all!

Update:

Installed new fuel tap (added an in-line fuel filter) and air filter. Would not start. Checked the spark again. It's good.

Ordered new carb from Motovista. Took a while for it to start with the new carb. It idled OK. I went to ride it & it wouldn't accelerate. It just kind of bogged down when I twisted the throttle. Then it died. Now it won't start again.

I'm hesitant to put a lot more money in it. Feel like I may be throwing good money after bad at this point.

User jamesguernsey has been extremely helpful but we still haven't figured it out.

Would appreciate any ideas. Sucks that I don't have a local shop I feel like I can trust.

Have you unplugged the emissions line to the carb inlet/manifold?? Sounds like that is the problem.

Thanks for the reply.

Yeah... unplugged it when trying to get the old carb to work & just left it off when I installed the new carb. Thought about taking the entire evap system off but don't want to create any additional variables to the puzzle right now.

You’ve pretty much ruled out fuel, the most common problem. Are the fuel lines all good?

If it ran for a while, that seems like a very good sign that you’re getting somewhere...how is spark and compression?

Thanks Juan.

Fuel lines are good as far as I can tell. I installed the in-line fuel filter to try to ensure no junk gets in the new carb. There shouldn't be any junk because the tank was drained before it was stored but after cleaning the old carb so many times I wanted to be sure.

Spark appears to be good. Blue spark that pulses just a little. Spark plug is new. I took it out again & re-checked it after it died yesterday. Cleaned the connectors on the ignition coils yesterday too, so I could rule out a bad connection there.

Compression feels good. I put my finger over the spark plug hole & cranked it. I could feel suction on my finger. Aosl, before I ordered the new carb, I put my hand over the air filter side of the carb & felt good suction there.

Motovista suggested it could be vapor-locked because of the evap system. That might explain it running for a little while, then dying. There may have been enough air in the gas tank to keep it running until the air was all sucked out, creating a vacuum. I tried to start it yesterday with the gas cap off to test this theory but it still would not start. I started to wonder if vapor-locking it would ruin the valves in the (brand new) fuel tap? I haven't tested that idea since today is Mother's Day & I didn't think spending all day in the garage would go over well . I'm assuming I could just take the fuel line off the carb & see if fuel is now running freely through it - or watch the (clear) fuel filter when trying to start it to see if fuel is being pumped into it. Does any of that make any sense?

Removed the evap system today.

Replaced the fuel and vacuum lines with clear lines so I can see that they're working.

Drained the gas tank & carb bowl. Re-fueled with non ethanon 90 octane.

It's like it's dying to start but just can't get there. It starts & stumbles for a few seconds, then cuts out again.

Would appreciate any thoughts.

I'd confirm compression - you mentioned you could feel suction when you put your thumb over the spark plug hole, but what you should be feeling is pressure. Your thumb will get blown off the hole at about 100psi which is close to the minimum required for ignition to work.

Also, is there an original CDI module in there or did somebody swap in a cheap substitute? Those are not as swappable as the eBay listings suggest.

Could bad valve clearances cause poor compression?

I'm planning on checking / adjusting valve clearance tonight. I watched a video from scooter 911 last night that makes me think that may be it.

Valves being off could be your problem. Get a compression tester to confirm what your compression is.

Thakns Pinkscooter. Exhaust valve was off by about .002. Intake may have been off .001 but no more. Adjusted. I've never done that before but it was pretty straight forward so I'm pretty sure I got it right. Still won't start.

No matter what you do, the first time you try it, it really seems like it's going to start. It catches & stumbles for a few seconds, then it catches & barely stumbles for a second, it does this several times, then it stops catching & just spins.

It has beautiful blue spark so I don't think it's the stator.

I see you're in Winston-Salem. I'm in Greensboro. There's a shop in Graham called Scooter Garage. I'm thinking about taking it there tomorrow. They have good reviews online. I don't have a compression tester & feel like I'm about at the end of my rope...

If you know anybody local that you trust to work on one, I'd love to hear. I'd drive it to Winston if you know someone there.

Thank you.

If it’s the guy in Mebane named Josh he is great. He was a Vespa mechanic at the Vespa dealer in Greensboro. Very knowledgeable. There is no one in Winston that I would go to. It’s why I work on my own scooters. If you want to bring it here I’d be more than happy to look at it. I have a running ET4 so parts swapping will be easy. It sounds like something easy.

It is Josh. Great reviews online.

I'd be happy to bring it to you any time that's convenient for you. My work schedule is pretty flexible most of the time.

I'm trying to learn as I go, so the opportunity to do that would be greatly appreciated.

Agree it seems like it should be something easy. I paid attention to the immobilizer light last time I turned the key to the "on" position. It flashed for about 2 sec & went out. I just read that might mean your CDI isn't programmed? Does that make sense?

FFS.

What bloody units? Furlongs?

What is an '.002' when it's at home?

Please use metric, as everything, everything else on an ET4 is metric!

Grr...

.002 would be two thousandths of an inch.

According to what I read tonight, when the piston is at top dead center, the intake valve clearance should be .004 or four thousandths of an inch. The exhaust valve clearance should be .006 or six thousandths of an inch. I bought a set of feeler gauges that have these & used them to measure the gap between the top of the valve stem and the rocker arm.

.004 inches = .102mm

.006 inches = .152mm

Thank you.

Next time, perhaps you'd be polite enough to say so straight off.

Use UNITS (or miss Mars...)

When I run into this situation I turn to the old standby....starting fluid. When it just won’t run pull the air cleaner and spray a shot of starting fluid into the carb. If it starts then you probably do not have an ignition problem. Because you must have spark. If it starts and then immediately dies do it again but this time be ready to spray another shot of fluid into the carb before it dies. If you can keep it running with shots of fluid for a short period of time you may have a gas delivery problem. I believe there is a good chance that a vacuum line is leaking air and not opening the valve. Then again, I may very well be wrong about that.

You need to be careful when doing anything like this. I suggest you do this outdoors and not in a building. You probably don’t want to set anything on fire!

Do not try to run the engine for long on starting fluid.

Do not use starting fluid on a diesel engine!

And a handy fire extinguisher is a great idea. I’ve never set anything on fire doing this. And I’ve used this on big expensive gas powered boats for years.

YMMV

Bill

Pinkscooter,

Please note that I have tried to respond to your PM last night. For some reason, my reply sat in the outbox all night & did not send. I just deleted it & typed another response (which appears to be stuck in the outbox as well). Sorry about that. No idea what's going on.

I'd love to accept your offer to help. I can drive to Winston this afternoon or tomorrow afternoon this week.

My cell is 909-992-9806 if you'd like to call since it appears I can't reply to PM's.

Thanks again.

jimc,

Thanks for pointing that out. I assumed since the subject was valve clearances that thousandths of an inch would be understood. Poor assumtion. I will try to remember to include the units moving forward. Thanks again.

I still haven't fathomed social distancing.

I dont think there was anything wrong with your PM, it's just the behavior can be confusing. When you send a message, it stays in the Outbox until it is actually read by the recipient. Only then is it moved into the Sent folder.

I just saw your message and replied by text. Hope you can make it.

Thanks berto. I'm really glad to understand that. I thought I had a problem.

Have you checked the rubber manifold for cracks?? They tend to crack underneath so it’s not visible most of the time...

Thanks SaFiS. Manifolds are in good shape.

Worked on this for about 3 hours with Pinkscooter last night at his home. (What an incredibly cool guy pinkscooter is to spend so much time & effort trying to help me with this). Update is below. Would appreciate any thoughts. To me, this is getting more & more difficult to understand. Hopefully someone out there has direct experience or insight....


So after a couple of weeks chasing his tail he has a new air filter, and Keihin carb. Because I live one city over he reached out to se if I would look at it. Having a running ET4 sitting here I thought I could swap parts. So I tried starter fluid and nothing. He pulled the plug and it was dark but not real wet. He had strong spark. We pulled the engine to check compression and 150psi. I decided to check the oil just because and a geyser of oil and gas shot out. I asked if he had changed the oil and he said no. He checked it when he first got the scooter & the oil level was good. So we did an oil change. We pulled the engine to check compression and 150psi. I pulled my CDI and put it in, mine doesn't have the immobilizer so we could solve any of that problem. He had adjusted the valves so I checked them and they were spot on.

It was getting late so he left it for me to keep playing. So here is a run down of what I tried:
Compression 150psi
Spark strong and blue
Keyway and woodruff key in perfect alignment
Not feeling real positive its getting fuel


The scooter had run when he got it but was losing power. Bad petcock and a carb full of blue stuff. With the new carb it idled for a bit but died when he gave it throttle and never started again. I sprayed starter fluid in the spark plug hole, nothing. Sprayed it in the airbag without the filter, nothing. Pulled the intake to see if that was clogged by part of the old air filter and it was clear and no signs of it by the intake valve. If it started with fluid I could say it was the carb but it didn't. my next step is to pull the new carb off and put mine on to see of that does it.

Edit: I keep thinking the timing is off and I did ask how he git the cylinder to top dead center and he said he turned the timing chain sprocket. Not sure how that would do it but when we pulled the fan to check the woodruff key the timing mark didn't seem aligned to anything so I just checked the manual and it shows what it aligns to and it was no where near that point. Ahaa, I think I found the problem. Time to further investigate, of course with a 4t engine you don't just pull the plug and see where the piston is put I thing I can still see if it's close to right. Thank you for your time reading this and I will report back when I have checked that.

Timing is spot on. The air filter was soaked in oil though. Time to put it back together and try and get it to start.

But still no kick or cough with starting fluid sprayed into the spark plug hole?

If not...there is no or inadequate spark.

Greetings:

It's the carb. Sometimes after 3 (or was it 4?) dismounts + disassembly +reassembly one can grow complacent. Symptoms (Fuel flowing without vacuum, Hand very wet holding the bellmouth, oil filter soaked, etc...) lead me to believe the petcock (with years of varnish inside) got startled after its long sleep, got stuck open and/or your float valve still has some spooge or perhaps wasn't hooked back on correctly. From a second thread scan, it appears it ran fairly well twice, but stalled out shortly after the 3rd startup and stayed dead.

Sure, electronics can suddenly fail, and timing goes out IF you disassemble the flywheel, but I believe the only thing you've touched was the fuel system. Look there, again.