Vespa 43mm Olympia kit jetting

This is my first time building a Vespa. What size jet should I start with?

Vespa 43mm Olympia kit

Stock grande head

Stock 12:12 SHA

Malossi red air filter

Giannelli stocking pipe

Polini variatior

Malossi belt

I’m considering starting with size 60

Thank you!(edited)

Re: Vespa 43mm Olympia kit jetting

im thinking high 60's

Re: Vespa 43mm Olympia kit jetting

I’d say low 60s high 50s on that pipe without a expansion chamber.

Re: Vespa 43mm Olympia kit jetting

With that setup, somewhere between 62-66.

Start with 66 and step down if it's too rich. But I bet 66 would be best. Try and then let us know :-)

Re: Vespa 43mm Olympia kit jetting

Richard Eberline /

Try a 13/13 carb and a 66 main jet. b5hs plug .019. Will go mid forties with points.

ARROW towards intake on the piston.

Re: Vespa 43mm Olympia kit jetting

> Richard Eberline Wrote:

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

> Try a 13/13 carb and a 66 main jet. b5hs plug .019. Will go mid forties

> with points.

>

> ARROW towards intake on the piston.

Arrow on the piston should be pointing towards the exhaust, not the intake.

And the carb size is relative to the intake size. If you have a 13 mm intake = go for the 13 mm carb. If your intake is 12 mm = stay with the 12 mm carb.

Re: Vespa 43mm Olympia kit jetting

some of the vespa heads leak at the decomp when you put them on a 43mm cylinder. Not a risk that i would take, I always use an aftermarket head on them, vespas are hard enough to keep from leaking as it is.

with a proma and 13 carb, mine is running a 68 jet, gets moving pretty good too. definitely not the fastest vespa kit out there but its a nice boost over stock. I'm at about 45 but thats 13 carb, drilled intake, cut crank, proma pipe and mopedfactory variator

Re: Vespa 43mm Olympia kit jetting

with a 12/12 sha and a proma im at 72 no filter, it gets a bit warm, mid 350's but it always runs strong

Re: Vespa 43mm Olympia kit jetting

> Toledo Riot Wrote:

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

> im at 72 no filter

hmm i never went above a 68, maybe i should see what it does with 70. it runs good but not a ton of top end power, figured it was just the kit but it might be a lil' lean at WOT

Re: Vespa 43mm Olympia kit jetting

> Graham Motzing Wrote:

> hmm i never went above a 68, maybe i should see what it does with 70. it

> runs good but not a ton of top end power, figured it was just the kit

> but it might be a lil' lean at WOT

Sounds to me like you're already at peak performance with your current setup and that cylinder kit. I doubt you will get it any better than it already is but let us know what happens :-)(edited)

Re: Vespa 43mm Olympia kit jetting

> Gle Cas Wrote:

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

> > Richard Eberline Wrote:

> > ARROW towards intake on the piston.

>

> Arrow on the piston should be pointing towards the exhaust, not the

> intake.

>

> And the carb size is relative to the intake size. If you have a 13 mm

> intake = go for the 13 mm carb. If your intake is 12 mm = stay with the

> 12 mm carb.

I previously wrote: "Arrow on the piston should be pointing towards the exhaust, not the intake."

This is the most common on Vespas to my knowledge, but I guess Olympia is different. Thank you Richard Eberline for the info.

Re: Vespa 43mm Olympia kit jetting

> Graham Motzing Wrote:

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

> > Toledo Riot Wrote:

>

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

>

> > im at 72 no filter

>

> hmm i never went above a 68, maybe i should see what it does with 70. it

> runs good but not a ton of top end power, figured it was just the kit

> but it might be a lil' lean at WOT

you know its funny, with the same set up on another Zeros bike, he has a lower jet on his 13/13, I think it has something to do with the smaller carb and velocity blhablhablha

Re: Vespa 43mm Olympia kit jetting

> Gle Cas Wrote:

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

> Thank you Richard Eberline for the info.

What info would that be ?

Maybe we went through this once before .

In all my years , I have never seen a piston arrow point to the intake .(edited)

Re: Vespa 43mm Olympia kit jetting

> P D Wrote:

> What info would that be ?

>

> Maybe we went through this once before .

>

> In all my years , I have never seen a piston arrow point to the intake .

I agree - I have never seen this either. I got a PM from Richard Eberline that according to the instructions the arrow should point towards the intake.

Since I've never seen an olympia cylinder kit, or the manual for it, in real life - I just assumed that Richard had his facts straight.

Maybe someone can show us the manual or the piston so we can make sure?

Re: Vespa 43mm Olympia kit jetting

Being as this such an odd thing , maybe Richard Eberline could post a copy of those instructions .

Re: Vespa 43mm Olympia kit jetting

Dirty30 Dillon /

Arrow never points towards "intake", as you don't have an "intake port" per se on a 3-stud vespa cylinder.

Re: Vespa 43mm Olympia kit jetting

> P D Wrote:

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

> Being as this such an odd thing , maybe Richard Eberline could post a

> copy of those instructions .

> Dirty30 Dillon Wrote:

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

> Arrow never points towards "intake", as you don't have an "intake port"

> per se on a 3-stud vespa cylinder.

Yeah I already replied to his PM asking for the same. I'd love to see it since I've never came across a piston like that myself.

I've always seen pistons where the arrow points towards the exhaust. But I guess if the OP should buy an Olympia kit, I would advise to double-check both the manual and the piston itself.

It's not unusual for manuals to have print errors or more likely; translation errors.

I look forward to the truth about the Olympia piston :-)

Re: Vespa 43mm Olympia kit jetting

The largest jet I currently have is a 59. Plug looked slightly rich but I haven't really opened it up enough to tell if I'm lean. Ill put a temperature gauge on and check again when the weather warms up.

I used a head gasket. I haven't checked for air leaks but it seems to idle nicely even with the stock grande head (offset plug)

In regards to the piston i believe the 'arrow' did point towards the exhaust. I ordered mine from Treats and it did not include an instruction manual. I just matched the piston window up with the boost ports. Seems to run great!

Thank you everyone for your input. I will provide an update when I get a chance to tinker further.(edited)

Re: Vespa 43mm Olympia kit jetting

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992DB1FF-8424-4B93-A6D8-37502F9EF5F5.jpeg

Ok, I’m sending a pic, Im completely lost here.You tube , Vespa shop manual, MA, arrow points down. So this one points down at 5oclock in the box. Looking at the backside shows perfect alignment for connecting rod. No instructions in box. (Must think I know what I’m doing) Thoughts?

2518D7F0-B64E-4196-9287-11E71893C51C.jpeg

Re: Vespa 43mm Olympia kit jetting

Dirty30 Dillon /

That's correct Les, the arrow points at the exhaust.

Re: Vespa 43mm Olympia kit jetting

667B679A-FD19-4C78-9765-E485F801F685.jpeg

Thanks again Dirty! I’m in no hurray to mess up! It seems every time I start a new project, I’ve learned more than previous builds. Then I start thinking too much! Got the tank soaking, found some bell wire repairs that need attention, hopefully I’ll be ready to break this in slowly!

Re: Vespa 43mm Olympia kit jetting

Along side the bearing lining up , note the cutouts in the piston skirt line up with the cutouts in the cylinder skirt .

If you had it opposite , those would not line up . ;)

Re: Vespa 43mm Olympia kit jetting

cut your own base gasket.

Re: Vespa 43mm Olympia kit jetting

Richard Eberline /

where is the ring gap at? hopefully not in the middle of a port. If you install both ways noting the ring gap. Let us know.

Re: Vespa 43mm Olympia kit jetting

Dirty30 Dillon /

The gaps are, of course not in any port.

Re: Vespa 43mm Olympia kit jetting

I saw that on YouTube about the pins getting snagged at the ports. Will triple check tomorrow. 8) .

Re: Vespa 43mm Olympia kit jetting

Richard Eberline /

Its a shame that the instructions are missing. The most important part, the manufacturer of the kit sets the bar. I worked on a lot of equipment, where the installed parts were backward to USA Standards. Of coarse no instructions to go by. We had a piece of equipment fail to early in its time cycle. I changed the bearing alignment, fixed and expansion, got a normal time cycle. Got a attaboy, big deal!

The piston arrow is for end gap alignment to the port openings. I have seen pistons with no arrows. Just my luck! No Arrows, what do you do?

Re: Vespa 43mm Olympia kit jetting

Dirty30 Dillon /

Vespa moped pistons are asymmetrical, so you don't actually need the arrow. As stated, the skirt cutouts will always match the transfers.

If there is no arrow, and no boost/intake window, and completely symmetrical skirt cutouts, then you have to look at the ring gaps

Re: Vespa 43mm Olympia kit jetting

> Dirty30 Dillon Wrote:

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

> you have to look at the ring gaps

Ring end gap placement should be one of the first things considered .

My Simplex replacement piston came with no ring locating pins .

I ran it that way for a short while . Every time I took the top end off , I found the ring ends traversing intake ports , even though I had them set at 120° ( straddling ports ) when previously installed . I installed roll pins and reshaped the ring ends to eliminate the problem .

Re: Vespa 43mm Olympia kit jetting

Dirty30 Dillon /

> P D Wrote:

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

> > Dirty30 Dillon Wrote:

>

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

>

> > you have to look at the ring gaps

>

> Ring end gap placement should be one of the first things considered .

>

> My Simplex replacement piston came with no ring locating pins .

>

> I ran it that way for a short while . Every time I took the top end off

> , I found the ring ends traversing intake ports , even though I had them

> set at 120° ( straddling ports ) when previously installed . I installed

> roll pins and reshaped the ring ends to eliminate the problem .

>

> https://i.postimg.cc/FFqrk09M/HPIM1987_zpsrisotftu.jpg

To be fair, the Simplex is the exception rather than the rule. I have pulled/changed probably 60 moped top ends and cylinders and never seen one that didn't have ring locating pins. And I can also say that off those, 0% had a gap that terminated in a port both stock and otherwise. Were they all optimally located? No, but they were not incorrectly placed for failure.

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