Modern Vespa

Hi all,

This might be a simple question, but as I was about to take apart my latest malossi 210 engine, I was relooking at advance curves of variable ignition timings and was wondering what RPM is everyone running their malossi 210 setup at?

I was around 1000rpm... but seems a little low when thinking about it...

1500 seem better?

I set mine to 800rpm. Slow tickover confirms the engine is in good condition.

I was hoping for a higher number... lol

Will try to aim for 800RPM... not sure how to re-jet though now... especially the pilot jet... :/

Currently I'm using a 42pilot, 3 turns out... screwing it in stalls the engine

I set mine to ~1,000rpm's.

Lot of turns out for an airscrew. Got a picture of your carb?

If you can get an 800rpm tickover and pull the clutch in without stalling it, then its all set up great. If you can't, it's telling you somethings wrong. Can set it to 1000 rpm after if you prefer but this is a valid test.

The next test is while ticking over at 800rpm for a while, open the throttle full WOT and close quick. Engine should rev up to like 6000rpm immediately, then swiftly return to tickover without cutting out.

These two tests are the same for either a factory stock engine or a race bike. No difference.

Another nugget.

PWKs are considered easy to set up and give great performance but if it is not genuine Keihin you will need to "blueprint" the carb.

Google PWK blueprint and OKO USA setting up procedure. Set up right you will have better performance and economy than the more usually used carbs.

Carb has a power jet and is for an autolube bike. Power jets are harder to set up and not so much needed sub 10,000rpm. Although 28mm is a bit small.

Onto the issues from the old photo. Fuel pump fitted under the tank is a lot tidier. On a rotary, the pump vacuum line has to come directly from the crankcase or it doesn't work properly. Can't see the airscrew but I'm sure it is one. Need to see into the front of the carb to be sure it's suitable (PWK make a lot of carbs and not all are set to work on our scooters).

Yeah I can see the power jet not being needed... honestly, I don't think it's ever been "activated" but full throttle isn't an issue at the moment.... dialing in idle, 1/8, 1/4-1/2 has been a bit of a challenge

Agree with the spaghetti of hoses it's not ideal. But being the first time I've installed it, thought best to be able to access all the hoses... took some inspiration from the savage scooter guys in Germany

Sharing a video of the fuel pump in action... seems to work ok... granted vacuum from the crankcase would be best, I didn't want to drill into the cases and I couldn't find any threaded outlets that were long enough to pass all the way through the cases...

Let me get a better photo of the carb

Sharing a picture of the front of the carb...

I've managed to get a stable idle between 900-1000RPM... anywhere near 800 ran like a bag of spanner's... had to go down to a 38 pilot too, but managed to arrive at 1.5 turns out... still feels a little rich

I definitely don't think it's possible with my current setup...

Just FYI, variable malossi ignition set at 21Deg @1000rpm
Low compression s&s head squish is around 1.1mm
Intake timing extended earlier 20deg via the rotary pad
138deg mazzu crank


Surely 800RPM is only achievable with setup with low intake timing or something near a stock setup..? Expansion pipes must need higher RPM to sustain? Just throwing this out there...

Picture of the carb with the slide open directly from the front would be better. Looks ok so far but can't be too careful.

Your pump connected at the carb will just not work properly. It will work maybe 50%. Maybe less. Not a small deal. Almost any small spigot will go in the casing.

The 1/8 1/4 1/2 set up is not easy. Doing it in the right order shortens the process by many months. Significant problems with the pilot jet are usually needle diameter related.

Was working on mine and made a video of what it should rev like from tickover. Engine was stone cold but you'll get the idea.

Thanks for the video Jack...

So good to get reference of the engine sound....

Let me get another photo with the slide open...

I'm using a jjk needle at the moment... I think it might be too thick at the top, hence problems dialing in the pilot and tick over...

With the new engine cases, I'll try installing an opening in the case to draw vacuum...

Back to your original question, is that a lightweight flywheel I see, if so you gonna need higher tickover than 800rpm. I use 1200.

Lightened malossi 1.2kg + 400g weight

Comparing to you video jack, I'm at pilot 38, 1.5 turns out, jjk needle, turning the throttle, I'm getting back to 1000rpm quite quickly, but from there it takes about 10seconds to drop to 900rpm... if I idle for about 2-3mins it stalls... but before then, pulling the clutch in doesn't stall the engine

I'm wondering which direction I should be testing in? Leaner pilot? Or richer needle to balance the whole 1/8-1/2?

That hanging return means too weak. The issue is often the needle diameter. The slide cutout, diameter, pilot and airscrew all work the same area. The skill is on separating them for adjusting. This might help.

Temporarily put in a pilot jet so small that it will only take one turn out. Any more air and it lean bogs off tickover.

Then with your throttle grip marked, carefully ride at no more than 1/8 throttle and decide if it is rich or lean. Accelerate to 1/8 and decelerate to it. This test isolates the K part on your needle. Use other needles with different diameters to decide.

So this can pinpoint the needle diameter... this test makes sense...

Is the next step from there, is to choose a pilot which can keep idle at 800rpm with 1.5turns out? How much of the slide factors into achieving 800rpm?

None. Slide is adjusted for other issues. Much later in the set up. If a 40 - 60 slide is fitted it is fine for now.

Get the diameter set first. Use whatever PWK needles you have to decide on the diameter. Once you know what letter this is, it can be kept the same for buying more needles. Because you are going to buy a few and have many duds by the end.

Got you... trust me after my adventures with the PHBH 30 and TMX combined... I have jets coming out of my ears... and it's been such a long journey of guesses..

I already have the BGM pwk jet set... and I have a feeling it's not the right set as 60% of the needles seem too lean...

I'll be test riding later today, trying the 2 needles I think would work... if not it'll be another order online

I've managed to go to reeds and have a hose coming out of the crankcase for the fuel pump (instead of the intake side of the carb)

And you're right... 800rpm is achievable at idle with the right jetting...! Thanks for the inspiration... now I'm having trouble the the midrange... I've swapped to an airstriker and the right needle seems to be difficult to pin point at the moment...

i dont measure my tickover per se

i set it at a value that is low enough to sound right and not too low as to send vibration through the frame.

Thats actually a good reminder of how to look at it...

The ideal situation to have... low enough revs, sounds smooth and no vibrations...

Similar to setting old vintage motorcycles... but even then I use a vacuum gauge as a benchmark.

Would just be good to have a number to aim for with the idle, but it might not actually matter...

1,000 rpm, plus or minus,

but that depends on a lot of factors... state of tune, condition of engine.. you know the score

i.e - my malossi needs a higher tickover to be smooth as opposed to my stock 200 lump, which is different again from my T5 screamer

The more I think about it and seeing Jack's video and what you're saying too... (I'm also looking at rejetting my carb right now), it's not about the rpms per Se but achieving what the engine needs in terms fuel and rotational balance... to have a good idle...

I was trying to find the right pilot for the pwk build and I achieved 2 "types" 1000rpm idles

1 lumpy but constant idle (a leaner pilot)... 1 very smooth idle but ultimately felt rich (the bigger pilot)

It's taking a while to jet as I see I siphoning effect that the main jet seems to be having... it's a 150, but there's fuel and oil spurting out of the exhaust manifold... it's like the needle and main have created a pressure to pour fuel in, when I close the throttle...

I've up to a 160 and it seems to have gone away and 3/4 throttle seems to be a lot smoother