Vespa bravo refuses to idle

Andrew Snowberger /

Sorry everyone, I did read a lot of posts about vespas with id

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le issues, but I might have a unique situation. I have a 78 variated bravo, and I had a rattle coming from what I thought was crankshaft bearings. This bravo sat for years, stored the wrong way, so I thought, hey, rebuild the motor. I bought a budget crankshaft and stock size cylinder kit, installed it with new bearings seal and gaskets, all from Denny cycles, and thought hey while I'm at it what could opening up the intake hurt? So I also drilled the intake to 13mm and used a rat tail file to open the intake patch only a few mm up and down. I got a carb rebuild kit and Tecno exhaust from treat's, rebuilt the 12.10 (45 jet) carb (now with 50 jet from treat) and gave it a shot. It refuses to idle, but runs great at part to full throttle. I know I cleaned the carb all the way, not my first carb. So I figured, let's throw $18 more at it and got a clone 12.12 carb (48 jet), stripped that rotten monkey to bare bones, even had the emulsion tube out, used a dremel to clean up it's nasty cheapness and tossed it on the bike. Same result, no idling, but way more power when revving, it maxxed the poor little stock variator in about two seconds. What have I done to make it not idle? All comedians and mechanics welcome to reply thanks guys the pic is the clone carb after I horsed around with the emulsion tube

Re: Vespa bravo refuses to idle

Why are you using a 12.10? That's your problem. Drilling the intake out to 13mm just to restrict the carb heavily is like adding a spoiler that weighs 800 pounds to a car.

Re: Vespa bravo refuses to idle

The idle circuit could be clogged. It’s a tiny hole under the slide if you look in through the clampy bit.

Re: Vespa bravo refuses to idle

Are you using that aluminum base gasket? If so try swapping to a paper gasket.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Well, I tried the stock 12.10 and then tried a 12.12, got same results. It's worth trying to clear out both carbs idle passages one more time. Do you mean I need to drill a carb to 13 or quit drilling and just get a 13.13? As far as the gasket, I bought several head and base gaskets and used the best fitting paper gasket for the base, aluminum gasket for the head. (edited)

Re: Vespa bravo refuses to idle

You don't need to use a 13 carb, but if you don't you're not getting any of the gains from drilling out the intake. What's your jetting? I was just battling this tomos that wouldn't idle and I had to upjet despite it running alright otherwise

Re: Vespa bravo refuses to idle

Matt Grantonic /

Try chocking the engine at idle, see if that helps, this could help point you toward carb issues or something else. The fact that both carbs are acting the same sorta says its somewhere else. If you do strip down the carbs again, use a single strand of copper wire to clean passages....assume nothing.

Compression issue? This will rear its head mostly at low revs.

You can even put some gas in a spray bottle and see if you can keep in running with a short shot of fuel. If you can keep it going with this DIY carb, tear into that carb again.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

The 12.10 has a 50 in it, and the 12.12 has a 48 knock off jet. By that I mean, I've tried putting the 48 jet from the clone carb into the dellorto and the threads were close but not enough to put dellorto jets into the clone, and the dellorto 45 and 50 jets won't go into the clone. I'll clean the idle passages tomorrow morning. I did notice that this Tecno exhaust has a poor fit to the exhaust outlet. The exhaust clamp area has two bent sections. I'll post a pic tomorrow of that. The leaks are causing a decent amount of partly burned fuel to get on the engine.

Re: Vespa bravo refuses to idle

the exhaust leak shouldnt keep it from idling but bot running the stock airbox and filters will, especially if your using a stock size jet, 48-52.

It has been well documented that the idle jet/passage sits below the throttle slide and for some reason your cheepo clone carb it is not there? Take a look at some more posts for images of its location or just use your stock carb. Also, did you service and set your points? Are they good condition original or are they cheepos as well? Is compression good? get a few new non resistor spark plugs too.

Re: Vespa bravo refuses to idle

also i've never seen a sha original or clone wherevthe atomizer does not fit itself into the casting of the body on top. The one pictured is wide open.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Darn I need a batter pic of the clone carb. I had the emulsion tube out, the monkey's that made it literally hammered the tube into the carb, upon disassembly I found the emulsion tube had been crushed in there to the point the four holes at its base were compromised and the tube was bent. Got out small tools and Improved it's condition, and shortened the other end of tube, so it doesn't touch the top of the venturi. I put the tube back in the carb by using a short stiff wire placed inside the tube and then gently tapping on the exposed end of the wire, driving the tube in place, being careful to align the dinky holes. This pic is of the emulsion tube when I first got it out of the carb, you might be able to see the bend near the bottom. I know you can see the badly drilled holes ha ha

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Re: Vespa bravo refuses to idle

Andrew Snowberger /

Dookie still no luck. So the clone carb now has a more clear path for the idle passage, but seems to be having float or needle issues, fuel stops flowing until I tap on the carb with a wrench. I tried with no airbox and with both clone and stock carbs. The stock 12.10 flows fuel beautifully, and idles for a minute then dies, performs so so when I run no choke but dies eventually. I noticed the carb seems to be leaking fuel from the venturi... Here's another picture of the clone, doubt you can see the idle hole but it's there. The exhaust clamp with it's spit holes. And how did I miss this? The moped fired up so I didn't suspect the coil, and it's been like this all along, but I think the coil I ordered from treat can't get here soon enough.

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Re: Vespa bravo refuses to idle

Andrew Snowberger /

Oh sorry pat splat, I ordered a couple ngk plugs, and the points are effe points and they're in good condition, I set the gap with a metal blade type gauge. Haven't done a compression check. What numbers am I looking for with that, are there hot and cold values available?

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Ok used a car compression gauge and the engine wasnt stone cold and I got 121 max psi from pedal cranking. Hey! I noticed I said I used a paper base gasket and I was wrong, there's a metal gasket for base and head. When cranking the engine, I did notice that the engine would hit some spots where it was impossible to crank, I'd have to grab the variator and turn the engine by hand to continue pedal cranking. I'm afraid of what I'm gonna find when I pull it off to check the rings

Re: Vespa bravo refuses to idle

hopefully its something under your flywheel causing your resistance. dont try to run it till you figure out where its coming from.

coil needs replace, always upjet if you are not going to run the stock airbox and stock screens. The motor will not idle properly without. that clone is pretty much done, stick with the og dellorto. On a vespa the ignition is externally grounded thru your brake circuit. what happens on a bravo is the rear wiring is ofthe compromised especially the fenderbead area o the rear fender.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

The brake light wiring was the first thing I took care of besides replacing the condenser when I got this bravo... The wires were touching metal from broken insulation but all good now. I really hope the issue is under the flywheel. I'll pull it apart when the new parts arrive. Someone asked if I am using a metal or paper cylinder base gasket. Would this make a difference?

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Re: Vespa bravo refuses to idle

What is the last picture ??

Re: Vespa bravo refuses to idle

Looks like the inside of a fender?

Re: Vespa bravo refuses to idle

> Marc Friedman Wrote:

> -------------------------------------------------------

> What is the last picture ??

"brake light wiring" ... Inside the rear fender .

Re: Vespa bravo refuses to idle

Andrew Snowberger /

That pic is indeed the inside of the rear fender. I used a very large nail to pry open the rolled edge that contained the wire and padded pliers to crimp it back down when done. You can't tell I even did it from looking. Aaahhh, so... Replaced the coil with an Olympia #2 external coil THANK YOU TREATLAND and a new B5HS plug and now it will idle and has a little more low end torque. Still stalls out with the choke off though. Noticed the fuel line barely has a trickle running thru it, probably from me screwing up and leaving the petcock on for a couple days. One more carb cleaning coming up.

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Re: Vespa bravo refuses to idle

you wrote: "used a rat tail file to open the intake patch only a few mm up and down"

that is a vital sealing surface, more to be gained using / cutting the crank anticipato.

if you know, and understood the consequences of messing with that, you're fine.

only use the correct puller on the flywheel, it's a bitch if it's never been off.

make sure there's a solid ground path between the motor, coil, and brake light, as it's part of the ignition circuit.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

I didn't know crank cutting was required if I filed the patch more open. I knew to not file left and right. I was just hoping to get more free power out of the motor. If this is what the issue is, I have to get a new case don't I?

Re: Vespa bravo refuses to idle

Dude, if all you did was take a file to the inside of the intake and it's not perfect and you didn't really enlarge the actual final opening into the rotary valve, so what !!!!!! Mike, who had all the usa vespa stock that subsequently he sold to treats used to get pretty adequate speed with only two mods

1. New dr kit

2. 13.13 carb.

And why the 13:13 carb when the intake was at most 12 mm and maybe even less ?? Answer: it was a new dellorto carb not some skanky chinese copy. He didn't even bother with an air filter. All this yanking out bent and deformed emulsion tubes etc etc and figuring out what's wrong can eventually succeed, maybe. There are numerous posts in previous years on idling/starting issues using modifications of the slide to get the right mix for successful 0-1/4 /wot slide positions. Treats stocks over 6 different slide variations. Screwing with the emulsion tube for better mid slide performance is detailed in grahams old blog on how to pull and mod the emulsion tube. First thing is to make sure the case is tight and doesn't have an air leak. If it passes and the carb is working , all the above should not be happening. If the insides of the grande is all rusty and your gas is partially particulates...you are screwed....doesn't that suggest that one good pothole will be your doom?? I've never read a post on really bad tank rust on a grande.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Oh no, the only grande I've owned was neglected bad, to the point the petcock area broke off due to the worse case of tank rust I've ever seen. The one I'm working on now is a bravo. Ok... Freaking out here: I used my flywheel puller, took some effort to thread it's bolt in and the flywheel popped off with that oh man I'm glad I had the right tool kind of fit, and now on reassembly, the flywheel won't sit properly on the crankshaft, the flywheel wobbles! I can torque down the variator and nothing wobbles then, but remove the variator and the flywheel goes back to wobbly, pretty much held in place by the magnets. Is this ok?! The woodruff key isn't the problem, I pulled the key and it slides in and out of the groove in the flywheel, and I can see it engaging in the groove when put in place.

Re: Vespa bravo refuses to idle

Oh sorry if I was thinking it was a grande it's a problem okay I got a problem don't worry about it I completely restored one so so you're saying currently your flywheel( spins around the coils) and your crankshaft are not necessarily at right angles to each other? So when you spin the crankshaft with a drill ( put but on end of crankshaft also need a piston stop u can buy a plastic one at any lawn mower small engine shop in town , to remove. Watch the crank as it spins and demonstrate it's perfection or not. If looks good then examine the inner bronze bushing of the piaggo flywheel. Chances are the bushing is possibly partially unpressed. Post pictures and possibly get an other flywheel.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Here the flywheel. It looks good. I think I'm running into the aftermarket crankshaft issue that happens when you buy a crankshaft from DennyCycles.com. I had to shave half a mm from the inside diameter of the ignition cam to get it to slip down on the crankshaft. I am not shaving the flywheel. Damn this is crazy, bordering on depressing!

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Re: Vespa bravo refuses to idle

Andrew Snowberger /

Looks like I'll be ordering another case gasket and switching back to the stock crankshaft, just to make everything fit like it used to. If nothing else it will give me a chance to post a pic of what I've done to the intake. So I don't go finding stuff like this as I search for the right pic

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Re: Vespa bravo refuses to idle

the flywheel sits on the taper, that taper is a snug fit, hence no wobble. If you take off the woodruff and that spacer below then you could lap your taper with some lapping compound. Sometimes the woodruff doesn't sit down causing the fluwheel to sit cockeyed creating a wobble.bit basically if you torque it down it should be pretty straight.

Re: Vespa bravo refuses to idle

Andrew Snowberger /

Just now resorted to a gear puller to get the cam collar off. So, while I thought I had done a good job taking off just enough material from the inside of the cam collar, it wasn't enough. It wasn't sitting fully on the shoulder that's on the crankshaft, and it got stuck bad when I torqued down the variator. So a little more off the cam collar and it should work. I switched to a paper base gasket and went with no head gasket, hopefully this gives a compression bump. And tomorrow I'll switch to ethanol free gas and stop using regular gas.

Re: Vespa bravo refuses to idle

Vespa wiki on enlarging intake

Polini instructions on crank / case modification.

but you have plenty else to straighten out first, points cam, carb.

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