bravo

John Wangkangbangnang /

so my bravo has really bad low end torque, its fine as soon as i pick up a little speed, its the non variated one but its still really bad, at first i thought i was because of the air filter(https://www.jmpbparts.com/vespa-ciao-si/engine-parts/carburettors/luchtfilter-std-citta.html) thats the one i have and i find it weird with that metal plate(and at first i thought it was that), anyway got it jetted 99% right but it still has shit torque, what could it be?

thanks in advance

Re: bravo

Dirty30 Dillon /

It's the fact that it's single speed, with a stock clutch and stock topend.

Vespa mopeds came slow and deliberate from the factory.

Re: bravo

John Wangkangbangnang /

well its just really slow, like tried a friends ciao that has much better acceleration, it goes 25mph(same speed as mine) we don't know if it has been modified but that things wheelies easily and has much better accel which i find very weird

Re: bravo

are your carbs identical? (both 12.10? both are 12.12? both are 12.7?)

are your gearboxes identical ratios? (eg are both 11:1? 8.5:1? other?)

are your rear pulleys identical? (eg are the both 80mm? 90mm?)

are your front pulleys identical (you will prob have to pull the belts and measure the inner "race" belt pulley surface diameter to tell because not all front clutch bells have the pulley diameter cast into the surface)

identical stock pipes? (all stock vespa pipes btw are "buzz" killers ...pun intended... but some are really small headers or short chambers compare to others)

it is very possible for two different single speed vespas to get the same top speed but have noticeably more or less torque than the other.

For example, if the ciao is on a 12.12 carb with hiflow airbox and a tall rear pulley 90mm or 100mm and it has pretty high transmission ratio like 14:1 or some such, it will certainly pull very hard off the line but ultimately max out its top speed at around 25ish because the gearing is so high

On the other hand your bravo has 16" rims which is technically a speed limiter and though it could be on nice fast transmission ratio like 8.5:1 or even 7:1 but because its got a small 12.7 or 12.10 carb and small stock pipe, it ends up being a dog off the line and eventually revs out enough on the small carb to get that rear end spinning finally at 25mph-ish before its just cant breath any deeper

All that said, lets pretend you are literally identical setups with the exact same carb and airbox and jetting and exact same pipe capacities and exact same front and rear pulleys races mm and exact same transmission ratios.... the issue can still be typical stuff like worn rings, leaky decomps or nasty head or base gaskets, carbon filled exhaust manifolds or pipes or very very often, different intake spigot "intake patch" boring inside the cases rotary valve surface (the factory shipped some really tiny ones as well as healthy sized ones but then slapped on everything else the same so you dont know it until you get a look inside the spigot at the rectangular valve port outline, or when you split the case and look at the patch from the inside.

Re: bravo

John Wangkangbangnang /

mine 12.10(45 jet 6 hole air filter, actually more than 6 holes) his 12.7(3 hole airfilter with 47 jet)

as for the gearing i cant check it right now but when i can i will, however i found out that but we should have the same rear pulley but my(the thing pulley belt is a little longer like 1060 instead of 960 or something like that, i believe he has a stock pipe(says some number on the muffler) and i have a citypower thats quite tourqy except for the acceleration

pardon errors written from phone

Re: bravo

i would tap/plug decompression hole and get rid of that 2mm thick head gasket, am i thinking of the right head, i forget, anyways take a look while yr in there.

Re: bravo

John Wangkangbangnang /

not sure what you mean by tap/plugging it? btw doesnt most vespas come without a head gasket

Re: bravo

The decomp valve in the head can build up with carbon and tend to leak. Tapping it and plugging it with a set screw and jb weld can remove any possibility of a leak. Not like you need it for a stock motor unless your 85 years old. Every Vespa I’ve owned has had a head gasket. Replace the base gasket with a good quality gasket (make your own to be safe with gasket material from an auto parts store) and also check the ring gap while the top ends off. It’s in the wiki if you need help.

Re: bravo

John Wangkangbangnang /

wait so plugging will make the decomp not able to turn off the bike?

Re: bravo

John Wangkangbangnang /

actually rembering i dont have a head gasket right now but i have a spare one just laying around

Re: bravo

Turn it off with the switch.

Re: bravo

John Wangkangbangnang /

fuel switch? because like the decomp is the Thing i use to switch it off

Re: bravo

"most" bravo's have a (run/stop) kill switch on the right hand side of the bars by the throttle

Re: bravo

John Wangkangbangnang /

mine doesn't :((

also using the decompression doesn't really help starting from what i remember but thats no biggie

also i've read the wiki on how to calcute gearbox ratio but how do it do it on a non variated one? also i've found this on a site: De mest almindelige er 8,5:1 og 12,5:1 translated it means the most common are either 8,5:1 12,5:1 im really bad at the gearing stuff but could this be possible,

Re: bravo

just put a chalk mark on the tire and a chalk mark on the lip of the pulley..... hand spin the pulley slowly and count how many full rotations equal one exact full rotation of the back wheel.

Re: bravo

John Wangkangbangnang /

i just checked and i've got the 8,5:1 gearing thingy not sure if thats good or bad, also when its just started(this time it sat for 2 hours with fuel turned off and when i start it it won't really pick up any speed and i have to give throttle to keep it alive thing

however it doesn't happen if i put it in "neutral" which just means putting in into bike mode while it runs, the things stops after like 20 secs of driving though

Re: bravo

John Wangkangbangnang /

the acceleration thing stopped by just giving some choke yaay

Re: bravo

not Yaay, you have air / fuel issues.

but yay for doing basic diagnostics to get to the root issue, airleak.

8.5:1 i think is preferred for top speed

listen to Uncle Monty

"nice fast transmission ratio like 8.5:1"

Re: bravo

John Wangkangbangnang /

soo 8.5.1 is the "slow acceleration high speed?

the thing fuel thing,i think this could be due to my fuel needs to fill up its kinda hard to explain but the is installed sideways instead so it has to like fill up the bottom before it can run further

also is it ok to check for air leaks with wd40, i actually triede checking between the carb and the intake and cylinder to cylinder head and no Change in rpm

Re: bravo

John Wangkangbangnang /

forgot to write fuel filter instead of just fuel ^^

Re: bravo

1. A decent decomp probably isn't your problem of poor power.

2. If you know how to use and have a compression tester use it

3 if you understand how to really perform a leak down test on a two stroke do it. If u don't read a bunch of posts on how it's done. If u have no idea what im talking about then u need to do some reading.

4. If compression and leak down are good then it's either your pipe is clogged, the fuel delivery sucks or something is up with ur ignition system.

If u are mechanically inclined then consider pulling the engine out leak test correctly if fails figure out where the leak is and fix appropriately.

The trouble is that when new not all vespas we're intended to go 30 mph. A whole group of them were made to go 20 mph and now 40 years later with various deteriorations that speed drops to 10 mph. The differences are suble and involve the way they ported the cylinders.

So the easiest way if you are sure on the basis of a correctly applied leak down is to buy a Dr kit with a new head and learn how to transfer your decomp valve after cleaning and a bit of valve coumpound grind to rebuild engine and while u r at it get a new 12:12 carb or even a 13:13 carb that of course is Overkill but in the future if u mod the intake it will be appropriate.

Re: bravo

John Wangkangbangnang /

yes a cylinder kit would be nice but, it won't be legal anymore, and if need a bigger carb i will have to bore out a restriction in the engine which im kinda scared to do because i could ruin the engine doing that and it won't be able to reverse if it has to be legal again. Also i have already read the wiki on how to check for airleaks and watched the video by some travis guy i just wondered if i could use wd40 but seems like a better idea to try with carb cleaner, exhaust is not clogged and brand new and i don't know how good the quality is but it should be ok and not cause that issue. Also i will probably be selling the bike and getting a ciao instead(various reasons not just this) so a complete rebuild probably won't be worth it, and i'd rather do a rebuild on the new one instead

Re: bravo

Dirty30 Dillon /

Your decomp is doubtfully the source of your problem. And I highly disagree with tapping and plugging it, because it literally takes 30 mins to pull, lap and reinstall a decomp. If you can't figure that out and make it seal, you should just buy a tomos.

Having the aftermarket exhaust on your bike (in your city) is probably illegal anyways, so why not get some extra power from a larger displacement.

You an't effectively check for airleaks with WD40, because of it's viscosity and low combustability. Carb/brake clean or bust.

Seems like you abandoned this project for another vespa which will ultimately provide you with the same heartache as the Bravo. Good luck.

Re: bravo

John Wangkangbangnang /

well no tomos for me just yet, exhaust is fine its mostly speed cops and insurance cares about, doubtfully decomp do you mean that it might be that or it probably isn't, english(sry) isn't my first language and i don't really get what you mean since a guy lower down disagrees that it's that

also i prefer working on a bike that itsn't as ugly as this one but thx!

Re: bravo

Dirty30 Dillon /

The Vespa decomps have (in my experience) been rather reliable, with small leakage and oil normally coming from using it as a kill switch.

Re: bravo

How would anyone even know you've changed the displacement?

Re: bravo

John Wangkangbangnang /

just realised there is a 50cc DR kit thought there only was a 65cc, so the 50cc isn't illegal, and if you mean the 65cc one, police here litterally has "dynos" where they test the exact speed it runs

Re: bravo

John Wangkangbangnang /

ok so looking again trying to figure out the decomp off switch thingy, the cable i use to switch it off goes between cylinder and head and out to the decompression spring(which is all greasy and black) outside on the head, this seems weird to me since but looking at my spare headgasket there is 3 bigger holes and 1 smaller so is this normal or no

Re: bravo

everybody says dont do it, just do it tapp plug. i forget cylinder or head.

Re: bravo

John Wangkangbangnang /

Ok so i don't know if it has anything to do with this but someone said my timing could be off, when it idles it kinda stalls like its like someone punches it. This almost stopped after i cleaned the points. However just today i noticed that it has begund again. (edited)

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