more vespa problems :-(

miguel /
Nov 05, 2001 03:22PM

ok ... so my vespa's not running again. i rigged up the decompression cable and that worked ... briefly. now i'm back to manually holding it down w/ my hand while i try to start. that used to work ... until ....

i got an airbox today, so i put that on. while i was at it i cleaned the carb. it was rather dirty w/ rusty fluid. so i got that all out. cleaned it really nice. then i put in a 51 jet (replacing the 49) to see if i'd get a bit more power. the bike ran nice for about two blocks ... then just died on me.

i haven't yet got back to it ... so i'll have to work on it some more (but no time now). anything i should look for? or is it just the jet? the sparkplug is only two weeks old ... and the bike ran fin before. the only thing different now is that it has an airbox (none before) and a 51 jet (instead of 49).

i'll try the smaller jet again first chance i get. i hope that's all it is. i'm used to larger dellorto carbs that take larger jets ... so i'm not sure what jet size i need for a dellorto 12.12

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Re: more vespa problems :-(

XBrandon EdgeX /
Nov 05, 2001 03:28PM

When I first got my Grande, I rode it about a mile and it suddenly died. It was a clogged jet. It seem like the vespas use way smaller jets than most other peds, so they seem to clog easier and quicker. If you were just doing some work to the carb, you probably knocked some crud loose in the fuel line or something. But go throught the usual (spark, compression, carb)

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Re: more vespa problems :-(

Ron Brown /
Nov 05, 2001 04:07PM

Miguel,

Installing an air box and increaseing the jet size both make the mixture richer.

Look for a fouled spark plug first.

Ron

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Re: more vespa problems :-(

miguel /
Nov 05, 2001 05:30PM

ok .. i put in a brand new clean plug and replaced the jet. still not starting. could it be that this vespa needs no airbox? i just can't believe that. something must be wrong here.

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Re: more vespa problems :-(

Mike (MA) /
Nov 05, 2001 05:35PM

Miguel,

I had similar symptoms on my Puch recently. Turns out I had cleaned the carb and put it back together wrong such that the choke was always staying on (i.e. the carb piston wasn't pulling it back up (Bing carb)). Just a thought... GOod luck, mike.

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Re: more vespa problems :-(

Chris S /
Nov 05, 2001 06:02PM

Miguel,

The Grande definitely needs the airbox w/filter screen. Before I read your second post, I assumed that the mixture was too rich. Remember, the other vespa mopeds use essentially the same engine but with a slightly smaller carb and jet (12.10 with a 43). The Grande should have a 49 in it. Over time, I've experienced the exact symptoms (sometimes to greater degrees than other) with Vespas I've worked on as well as my 2 Grandes, two Ciaos and a Bravo...

It was caused by different things at different times. Here is what I have found to be the culprit (in no particular order):

1. clogged main jet

2. bad carb float

3. bad needle valve seal (caused once by a bad needle, once by a needle valve seat that had been widened by the previous owner)

4. bad HT coil

5. demagnetized flywheel

6. clogged idle jet (hard to find in a 12.12--it is a little hole in front of the brass tube in the venturi)

7. fouled/worn out spark plug

8. clogged fuel valve (petcock)

9. empty gas tank

10. air leak in carb (not installed fully)

11. ??? (I am working on a Grande for someone else right now and I can't seem to find the problem yet).

I think that covers it.

Good luck.

Chris

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Re: more vespa problems :-(

miguel /
Nov 05, 2001 06:19PM

i've considered most of those. but the grande ran strong until i messed w/ it ... so i'm guessing that i can narrow it down. i'm familiar w/ the dellorto (and other than the size, it was essentially the same as a 14.12 or similar model) and so i'm pretty sure i put it all back together properly.

i'm thinking it might be that the carb is not on tight enough, so that it has air leaking. i'll take it all out (again!) and fiddle w/ it some more next time i have time and it's a nicer day out.

i'm thinking that maybe i'll need to figure out a way to make sure the carb is tight on the manifold ... that might be the culprit.

oy! ... but i'll keep working ...

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Re: more vespa problems :-(

Chris S /
Nov 05, 2001 07:17PM

When I've had air leaks, it has been one of two places: the carb wasn't fully on the manifold and tight, or the top (the throttle slide cover) wasn't tightened down. You can tell if you can get it started, then spray carb cleaner or WD40 on the carb while it is running. If the engine idle changes, then there is a leak. It sucks the liquid in through the leak and then burns it, changing the fuel/air mix.

Good luck.

Chris

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Re: more vespa problems :-(

miguel /
Nov 05, 2001 07:37PM

right now it won't start. so i can't use that method to test. but i'll take out the carb again and clean it and reassemble it ... very very carefully ... and then tighten evenhthing down as hard as i can.

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Re: I did once..

Jim C. /
Nov 05, 2001 10:23PM

I accidently hit the kill switch on the right handlebar once and didn't notice. My switch is very easy to flip.

Took several minutes to figure it out the first time.

Jim

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Re: I did once..

Chris S /
Nov 05, 2001 11:38PM

And I'm embarassed to say how many times mine have quit and I did a bunch of troubleshooting before I realized I had an empty gas tank. The most recent time was today...

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Re: At the beginning..

Jim C. /
Nov 06, 2001 11:02AM

miguel:

You mention the decompressor cable worked for a while. If the replacement cable end came off, you need to solder the end of the cable so the strands hold together.

This will prevent the cable from fraying later also.

Jim

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Re: At the beginning..

miguel /
Nov 06, 2001 12:18PM

nope, the end is still working (though it took it off). i tightened the cable, and everything worked fine. i squeezed the lever and the cable engaged. i was looking at it. but then after i took the carb apart ... that's when my bike stopped working.

i'll play w/ it again. i think the air leak is the right idea. it has to be that, since nothing else changed on the bike, eh?

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Re: At the beginning..

Ron Brown /
Nov 06, 2001 02:58PM

Miguel,

Never overlook the possibility of a totally un-related failure. Do the usual and check for good spark, fuel etc.

Ron

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You could also check..

Jim C. /
Nov 06, 2001 10:24PM

miguel:

Be sure the six or so wires in that junction block there on the right side didn't get jostled. The violet one is the one that comes off the points to the kill switch, and the blue one at the coil is another one to check.

This of course, is if you find you have no spark.

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