Vespa, No Comps? No Gas?

So I have a Vespa Bravo. Tonight I got it all together. I have the 64cc Malossi kit with the 13.13 carb. I tore the engine all the way down and bored the intake (like it says in the instructions 18mm down, the rest with a file).

I have spark, I have gas in the float bowl. But no matter how much I pedal gas never gets to the spark plug. I double checked the carb and there doesn't seem to be any problem there.

I tried to use a compression tester, but I could only get 60 psi out of it. The only thing is I don't think that is a good reading because I can't turn over the engine without pulling the decomp. So I would like get the motor spinning like crazy then drop the decomp and the motor would stop spinning immediately. The psi reading would only go up by like a few psi at a time.

The thing is I'm like 99.9% sure it isn't losing compression in the top end. Its all brand new gaskets, cylinder, and head. So that pretty much leaves a bad carb or bad secondary compression. I don't think I messed up the rotary valve when I bored out the intake. When I first put it together I could blow into the intake and spin the crank, when the rotary valve would close I couldn't blow into it at all. So that leaves the flywheel side seal. Or maybe the crank case seal, though I Honda bonded the shit out of it.

I am going to drop the engine tomorrow, is there any thing else I should be looking for. Any ideas would be awesome.

Re: Vespa, No Comps? No Gas?

Case seal is pretty much foolproof, I'd not worry about that. Have you tried putting a little premix or some carb cleaner directly in the cylinder and starting? Thatll tell you whether it's fuel.

What size jet? I run a 78 on my 64 Malossi with a Leo Vince and a 13.13.

Also when you tear the engine down, cut the crank if you havent already. You want it to open 10mm sooner and close 5mm later than stock, measured around the outside of the crank webbing.

Re: Vespa, No Comps? No Gas?

I cut the crank when I was in there. I did use a torch to split the cases, I could have damaged the seal while splitting the cases.

Re: Vespa, No Comps? No Gas?

Quite possible. I always just do mine on the like a charm, and I've never damaged a seal, even when I havent cared about them cause I had a new one or whatever.

Again, tried some combustible directly in the cylinder?

Re: Vespa, No Comps? No Gas?

hey nick i had the same problem but sold my ped. My hunch is that the crank mayhave been cut to much allowing gas to blow by at the wrong time.

Re: Vespa, No Comps? No Gas?

Try some starter fluid, no joke.

Re: Vespa, No Comps? No Gas?

also, a failed seal because of the torch would require obvious, physical and visual malformation in order for it to leak like mad around the crank itself, it could be out of alignment on the outer diameter of the seal against the cases themself. not likely.

are you sure the jetting isnt just too far off so that it wont even run? timing? wet plug?

Re: Vespa, No Comps? No Gas?

Nick, we cleaned the jet, but we didn't run a wire up/or clean out the venturi tube. You should probably try that before dropping the motor. I thought about that after I got home.

Re: Vespa, No Comps? No Gas?

Mike, I cut the crank exactly to the spec provided by malossi for the kit.

Peter, the timing is fixed, and I set the point gap to the high end of the range in the manual so that I advanced the timing a little bit. The plug has been bone dry every time I checked it.

Jon, I cleaned out the emulsion tube with carb cleaner before I put the jet it, I could see fluid blasting out of the emulsion tube when I shot carb cleaner up through the jet hole.

We tried to use starter fluid, but the only bottle we had was one with a broken nozzel, that you had to push down with a screw driver. It never fired but I think that might be because we never got enough starter fluid in there. I'm gona buy a bottle and try that today

Re: Vespa, No Comps? No Gas?

hey nick you have the same problem i did. me and you did something wrong. Maybe the crank seal? I set my timing about 20 times and re sealed the jugs just as much i could only get it to run at WOT.

Also take your flywheel off if oyu have a top crank your prob sheering the key i had that happen a few times till i filled down the fly wheel and key to fit exactly. I hope you get it running i gave up and sold it.

If you figure out what it is let me know becuase its prob the same with my old bike.

Re: Vespa, No Comps? No Gas?

So I got it running today. First thing I bought a 24mm socket so that I could use a electric drill to turn the engine over. Once I did this I noticed that the spark was kind irregular. Like it would go in and out but once it got passed a certain RPM the spark would steady out.

I check the comp with the drill and I am getting 120, better than what I could get pedaling before. Still probably less that what it actually runs when it is going.

I upped my jet size to 68 and then used the drill to really get the RPM up. Then I dropped the decomp and it started right up. I messed with the electrical a bunch. Ends up the I can't read the resistance of the spark plug boot, its supposed to be 5k ohms, but it only reads open, so I swap out the boot with a different one and it evens out the spark a lot.

I still have two problems. I can't start the bike by pedaling or pushing because the belt slips and can't turn the engine enough to get it started. And once I get it started with the drill, it doesn't make enough wamps to variate. It just hangs out in the bottom gear. So I rip up to like 15 and then just hit a wall.

I stole some heaver weights out of my buddies Pollini variator and they helped a little.

So I ordered heavier weights and a new toothed belt from treats. Hope that is the end of it. Thanks for the help.

Re: Vespa, No Comps? No Gas?

even using the decomp to start?


Re: Vespa, No Comps? No Gas?

I've been considering the BOD, Next time i'm down there I might try it out to see how well it works.

Re: Vespa, No Comps? No Gas?

dude do you have a performance varriator on it if so u need to put the rear spring in they give you and it will grab that belt like nobodys business and clean out your clutch with alcohol and aluminum oxide sand paper. Mine did the same thing before i had that spring in there and heavier weights im at 10g weights now to get it to open all the way. good luck cant wait to check it out at ghostride

Re: Vespa, No Comps? No Gas?

Yeah, I put in the rear spring. With the weights that came with the malossi variator. I should be getting the 10g weights later this week.

Re: Vespa, No Comps? No Gas?

yeah my ten gram ones are on the way if i get my bike back together we can compare vespas at ghostride

Re: Vespa, No Comps? No Gas?

You got the right belt dude? Shouldn't slip, but it's it's loose, it's not going to variate...

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