piaggio and hobbit

problem,,

the bikes run but won't keep running,

the piaggio bravo, runs, but only for awhile and sometimes when you turn the throttle it stops it. Also it goes faster whenyou push that little airbox cover switch down(I am not sure what you call it).

Do you really have to drop the engine on a Hobbit to clean the carb,, seems ridiculous.

Our Hobbit also runs but only with a little magic spray of the starting fluid, then it stops, where do we start,..

please help, thanks

Re: piaggio and hobbit

Sounds like both bikes have carburetor-fuel delivery troubles.. fuel is already restricted... By also restricting air, you get a better air:fuel ratio and the bike sorta runs better . (its called a "choke")

If the Hobbit runs with Starter fluid it tells you the carb is clogged up but ignition is OK. And yeah, the Hobbit carb cannot be removed unless the engine/swingarm unit is allowed to drop away from the frame.

So, a thorough carb cleaning, examination and adjustment on the PA50 is not to be taken lightly.. do it right or do it over.

........

dropping engine:

Disconnect the decompression valve cable at the engine. Disconnect the fuel line to the carb. Disconnect the throttle cable at the carb. (The rear brake cable may need disconnection at the rear wheel) Disconnect the condenser wire at the wire harness bundle near the petcock. The tail light/brake wire bundle is secured to the swingarm with clips so unclip that. Some of the other stuff is clipped onto the swing arm so unclip that stuff too.

Have someone hold the bike steady. Put blocks of wood under the muffler so the engine can only drop an inch or two. Remove the long engine pivot bolt/nut.

Pull the engine slightly forward as you lower the engine an inch or two to rest on the wood block.

Now check for and disconnect anything else that may get stretched or broken when the engine drops all the way to the floor. My memory of my first time is faded.. just take a good look with a flashlight.

Once the engine is resting on the muffler on the ground, remove the 4 reed-block / intake manifold screws and remove the manifold/carburetor as a unit. These screws can be tight and you might want to use a hand impact "wrench" and a sharp tap with a hammer to get them started. A long fat phillips screwdriver may be enough but try not to strip the heads.

........

On reassembly, use some Permatex 2 non-hardening gasket sealant on the intake manifold mating surfaces to prevent vacuum leaks.

......

Reassembly:

First lift the engine and reinsert the pivot bolt. Now re-route as many cables and wires as possible in such a way as to not interfere with dropping the engine the next time. Or route them as original.. it's up to you.

It is possible to reroute almost everything so that nothing but the throttle cable, decompression cable and fuel line need be disconnected next time around. Clips that hold wires /cables neatly in place are no big deal to attend to.

Re: piaggio and hobbit

Before dropping the engine, check and see if the fuel flow problem is upstream from the carb. Remove the fuel line and drain some fuel into a jar. Fuel should flow in a steady thick stream in both Main and Reserve petcock positions.

If not, the petcock screen inside the tank or the petcock filter (on the petcock body) could be clogged.. the fuel line itself could be clogged.

In any case you might get lucky and the bike will run after fixing that.. But the carb could still be dirty. If the bike doesn't get up to 30 MPH in a hurry on flat ground something needs work.

Check for a clogged exhaust port. Also remove the bolt on the muffler and stick something in there to clear the little baffle tube right inside that bolt hole..

Last resort is to drop the engine and clean the carb.

Re: piaggio and hobbit

thanks for the tips, they're much appreciated. what is occuring when the fuel rushes out when the carb is not attatched, but as soon as you attatch the carb it ceases to flow? some sort of pressure incident...but I am too rookie to understand it.

I can't believe honda would design something like this...it makes me appreciate my magnum so much more. I think we're going to hold off as long as possible on dropping the engine on this thing.

Is there anything else you can think of we should check with the piaggio? We've cleaned out the carb twice, checked the exhaust...but still no go. It fires up easily now, instantly, but only with choking does it stay running. I did a few laps around the block, but I had to sit for a second (choking) then give it some throttle and I would speed away...for about 50 yards, then it would just lose all its power and I would choke it again....and then we'd make it another 50 yards before... is there anyway electrical systems can get involved in something like this? I'm a little mystified, happily so (at least for now), but still mystified. the piaggio's fuel delivery seems to be fine, till the carb. Now that I think about it I am going to check the gas caps air hole tomorrow.

Re: piaggio and hobbit

the ignition is ok.. you are running out of fuel for some reason.. tank vacuum, maybe ... but doubtful..

I think the carb bowl is not refilling fast enough or some tiny sliver of crap is floating around in the main jet passage..

Using the choke restricts air to match the restricted fuel intake, so the engine doesn't die. But i think the sitting and idling for a while gives the bowl time to refill .. and then you can take off again.

.......

As far as the Hobbit, if fuel flows from the fuel line, reattach it to the carb, loosen the drain screw on the float bowl with a flat screwdriver about 5 turns. (Access is through the pedal sprocket and through a special little hole in the right-side swingarm.)

The drain hose should be near the center stand spring (or hanging under there someplace). Drain some fuel into a jar.. it should pour out in a steady stream unless the float or needle is messed up.

If fuel flow from the drain is good, you gotta get into tthe carb..

The hobbit can't be appreciated until it's running right. It's got reed valve induction, boost transfer port.. variator .. other stuff.. nice solid quiet 30mph bike that runs forever with no problems..

Variator keeps RPM high when hill climbing so 20MPH @ 5,000 RPM up a hill is normal. Bolt an expansion chamber on and it will fly along at 38+ mph with no other changes..

Re: piaggio and hobbit

Two things:

1. there is a float bowl drain screw that can be removed by removing the right side chain cover, then you go thru the hole that can be seen by looking through the chain sprocket.

Take the screw out then open the fuel shut off valve. If the carb float valve is working the fuel should run out of the hole.

2. Try running it with the fuel cap just loosely installed. This will tell you if the problem is with the gas cap vent hole.

Also, try running it with the fuel tap in the reserve position.

It is possible that the fuel screen inside the fuel tank is plugged. It will let a little fuel thru at a time but not enough to keep it running.

The problem is fuel, not electrical.

Good luck

Re: piaggio and hobbit

thanks again joe. It's becoming much more enticing to get the hobbit running now. I'm sure it is a charger, it's just a pain to have to take so much apart just to get to the carb. we'll probably take it apart in the coming day or two. As far as the piaggio goes we'll have to dig around some more I guess...we've cleaned the jet twice now. I have a few ideas...

Re: piaggio and hobbit

Regarding the Vespa Bravo, you need to remove the carb one more time and clean the Idle jet.

There is a plastic shim you have to remove from the carb in order to see and access the Idle jet. Use a needle, pin or single strand of a control cable to probe and clean out the hole. Carb cleaner alone won't do it.

After you use the wire or pin, squirt some wd40 in there and then blow it out with compressed air.

https://www.mopedarmy.com/forums/discuss/download.php?f=6&file=1096431071_idle_jet.jpg

Re: piaggio and hobbit

There are two ways to access the carb on a PA 50. The first as JoeW described is to drop the engine.

The second method is to leave the engine in where it is, have the bike on the center stand and remove the two rear bottom shock bolts and one front main frame bolt and use ropes or tie down straps over a garage cross member, to lift the frame away from the subframe leaving the subframe as a nice little engine stand.

Before separating the frame and subframe it is best to remove rear brake cable at the rear wheel. remove the throttle cable from the carb and the black and white coil white and be sure to note where it plugs in before you disconnect it.

You'll probably need an impact hammer to loosen the four phillips head screws that secure the carb. I usually replace them with hex head bolts or Allen head bolts.

While you have the carb off , remove and inspect the reed valve that is directly under the carb.

Make sure you don't put the float bowl on backwards, easy to do and a common error when working on PA50 carbs.

Re: piaggio and hobbit

Thanks everyone for all of the excellent input. WE really appreciate it, we must get the ball rolling and a sweet chapter continueing. we'll let you know the outcome,, thanks -g

Re: piaggio and hobbit

hey

about the vespa.....i have found that when it runs better when you push the choke on that its usually the crank seals

are leaking. sorry, big job replacing those seals...may as well replace the main bearings too.

if it runs for awhile and then its hard to start. i had this problem and always thought it was a bad coil. but likely as not it was bad crank seals

Re: piaggio and hobbit

Hey- But there's only a flywheel side seal on the vespa engine. You don't even have to seperate the cases to replace that seal. Take off the flywheel, and seal is behind the timing cam.

Re: piaggio and hobbit

Kyle Guerrette /

how does the flywheel come off? I dare not go at it with a puller on the edges and where can i find seals and bearings? Doed anyone have a site? Google has shot blanks for me.

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