Modern Vespa

Hello
I have a 2001 ET4 150 that I bought christmas 2015. It had 600 miles on it at that time. Bike had been sitting for 14 years but would still crank and idle.
At that time I Installed a new battery, new iridium plug, a new (chinese made) petcock, new fuel line, new rear tire (nearly bald after only 600 miles?) cleaned the carb as best I could, a float needle from a 50cc chinese scooter carb rebuild kit that looked identical to the original and the bike has served me well over the past 6 years and 12k miles.

Now a strange thing is happening. When the gas light starts to flicker the engine will start to hesitate like its running out of gas, and sometimes will let out a backfire. It actually cut off on me twice last summer and I had to be rescued. I tried ANOTHER ebay chinese made petcock with same result. I just installed an OEM petcock and same result but not as bad. If I keep on the gas it soon clears up and I can carry on as normal. I'm stumped. Bike still has the original Walbro carb. I have another float needed OTW.

Has anyone seen anything like this on an ET4?

in the last 12K have you done any other maintenance?

Yes
Tires
oil changes
belt once
rollers
I should have said before that I ditched the oem air filter for a washable one that I have cleaned several times. I usually do this when I change the oil and filter every spring. I guess its time for that too.
It's yet to have a valve adjustment

I'd say your china petcock has met its life expectancy.

but, on a 20 yr old bike I'd be looking at fuel and vacuum lines. check the intake and air box.

your problem is unlikely due to low fuel-- fuel light coming on.

more than likely, you just need to service the vehicle and/or replace parts that have met their service limit.

I'm thinking when I open the airbox i'm going to find a gas soaked air filter. We'll see.

mea culpa, I didn't see that you'd replaced the petcock with an OEM

but fuel line 7 years ago? probably due for a new one and vacuum line. if your intake is OG I can nearly guarantee it needs a new one. if you haven't touched that carb in that long it's due for a look see as well.

ET/LX tank floats are known for being nonsense, so figure that into your equation.

ETA: I own two ET4's and have worked on a few of them

I replaced the fuel line last week when I installed the new oem petcock. I feel like I am not being clear enough. My apologies.
The Vac. line is still the 20 year old original but I snipped the hard ends back to the pliable rubber so they make a better seal on the intake nipple and the petcock nipple.

if your intake is OG I can nearly guarantee it needs a new one.

The intake manifold? its OEM. What happens to them? I thought they were like ....metal coated with rubber on the outside.


if you haven't touched that carb in that long it's due for a look see as well.

When it left me stranded last summer I walked home to get tools (1 mile) then rode my classic back to it and took the carb off and took the bowl off. Due to the fact that I run non ethanol religiously it was super clean on the inside. I was expecting to see a little dirt in the jets but...nothing. The diaphragm looked ok too no rips. It finally started back up and hesitated back home about a mile.

They are solid rubber and tend to crack eventually.

ooo i bet thats it! i'm going to look right now!

A GY6 50/150 is a metal piece covered with rubber, I had assumed these were too. I saw this crack last summer but I thought it was like the REDACTED bikes i've seen where its metal on the inside. This must be it.

ETA from G125: that type of language is not accepted or allowed here. please to do better in the future.

Is this the intake that requires the paper gasket or does it have a groove where an included o-ring goes?

Seems I recall sticking my finger in there while I had the carb off and could not feel the crack. Silly me. I'm 51 now and i'm losing some of my mechanical edge.

you keep circling back and editing your posts with additional information.

I'll wait until you've consolidated all the facts before offering up any advice on a repair.

sorry. I think you and znomit both figured it out already.

your intake is wasted. get a new one and a gasket and you'll be fine.

I started the bike up and sprayed some ether on the crack and the rpms picked up so definitely sucking air there. I smeared a liberal amount of automotive adhesive across the crack, some stuff called GOOP that works really well for lots of things. The petcock should be getting plenty of vac. now! thanks guys!

Thanks for your help Sir!

ETA from G125: that type of language is not accepted or allowed here. please to do better in the future.
[/quote]

So what do I say regarding those? SOB's? I don't even remember what I said.

Okay so this is the intake that takes a paper gasket? I saw Robot say ...some years....have a groove where an o-ring goes.....i guess those are lx and newer?

This post was not quite
What we were hoping to see
Try again, perhaps?

Greetings:

For whatever it's worth, I replaced the Walbro carb on my '03 ET with a Keihin from the later LX models. When I installed the 187cc cylinder I was unable to find jets for the Walbro and despite considerable experience working with carbs in general I was unable to get the Walbro to work well. The Keihin worked perfectly, and even better when I deleted the recirculating system that had some dodgy hoses and probably was creating a bit of a vacuum leak. The Keihin was around $200 at Scooter West, if I recall correctly.

Thanks Wheelman, very interesting!

Bike seems to be "fixed". The gas light was close to coming on so I rode until it did and intentionally hit as many bumps as I could to try and get that crack to open but it ran fine. The GOOP shown above seems to have plugged the crack up. I love that GOOP stuff, so useful!
All is well for now! thanks greasy125 and znomit who helped! I feel stupid for not investigating that crack a bit more, I knew it was there! I guess it was lowering vacuum to the petcock just enough to let the petcock close which created a fuel starvation issue.
Going to leave it like this awhile and will get a new intake when I do my 187cc kit later this season....and a LX carb as Wheelman suggested.
Thanks again guys you rock!

Addendum: a tube of GOOP should, in my opinion, be in everyone's road kit!

I spoke too soon, the problem persists.

Was this on fire?

no

judging by the fact there's two different bolts holding down the intake, I'd suggest that you've got a deeper problem.

gooping up the intake was just a band-aid.

Greetings:

Tha intake bolt discrepancy is actually Factory. One of them is a "breakaway" head mandatrd by some party-pooping environmental bureaucracies to prevent would-be modders from tinkering and ensure nobody has any fun.

Yes, just to get me by awhile, but I guess I didnt let it dry long enough.

I've worked on a whole bunch of these and have never seen that. other bikes, sure. but not a vespa.

I've seen people use shrink tube as well.

but really, the best repair is to replace it. and do the gasket at the same time.

'Rescue Tape' aka self-amalgamating tape works brilliantly on occasions like this. Even for holes in coolant hoses - but a few zip-ties are needed then to help contain the pressure.

But it's not that expensive to replace.

I'm done jacking around with it, i'm getting too old to be able to find stuff that I used to be able to find pretty quickly. I can HEAR the leak but I can't find it. New intake and gasket are on order from Scooterwest.

Found the crack, it was UNDER the clamp. I didnt find it until I took the clamp off to put it on the new manifold.

New manifold got here from San Diego to RDU in 3 days flat including sunday. She's back to running great now! Big thanks to greasy125 and Znomit for knowing exactly what the issue was. On the road again!

We called that 'Aqua-seal' in the electrical business. I used to have a bunch of it.

Back to square one. The gas light started flickering on me on the way to autozone to get a spark plug for a 2003 Vino i'm working on and the ET lost power, hesitated, backfired and stalled just as before not 10 hour ago. I let it sit for about 10 mins and it fired up. lucky for me I was less than a mile from home. When I got home I sprayed around the carb and intake with carb cleaner just as I did before to see if I could find a vacuum leak....RPM's held steady.

The new intake made it run like new again for one day. I am seriously bummed out.

Going to try this next. Seen plenty of these go bad over the years. This one is for a chinese scooter so I don't think it's going to fit.

It flooded out on me today, apparently the float has been sticking in both the open and closed positions somehow. When I take the carb off, take the bowl off and move the float with my fingers it's nice and smooth, no sticking.
Sick of messing with this carb, bought a new one from scooterwest today.