Vintage vespa with sidecar
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Addicted
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Sat May 04, 2019 10:12 am quote
Awesome.
Had not registered that scooter speed was in our hood - if you consider Azusa our hood. Haha. But within reach! Thanks!

Looks like they have stuff I could use.

:-)
Addicted
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Location: california
Sun May 05, 2019 9:43 pm quote
Spent day finding twisty turny roads to ride - such a good day.
I thought driving a side car was going to be some kind of compromise.
Just the opposite.

Turns out you "drive" more than ride.
And it's not a spectator sport - you have to be on your feet working the bike all the time through the corners - first to set up - then to power through.
If feels more like a dirt bike to me than a scooter. Lots of leg and hip (thanks Ebeth!)

But dayum - the experience when you get a chicane right is pure heroin.

Which brings me back to this pic posted by Aerochip.
When he first fired it up here - I didn't fully appreciate the moment captured.
(editor's note: I turn all the corners with my wheels on the ground still unless I made an error).

But it is worth appreciating - this is like leaning your chair back on its legs - in class - while acing a test - and laughing at the teacher who thought you weren't paying attention ( I probably wasn't) ... at 30MPH... with no hands.

Take a look at the grip he has on the throttle. That is not for twisting. He is counter steering to hold up 250Lbs on a knife edge of balance (Aerochip - full respect to your lovely wife/companion - I am strictly measuring the side car)

Decided what I'm gonna do with tuning after running out the bike for a day.
My next move is to optimize the current motor - it's not far off. 5% would be great while I work on my new side car frame and elec. motor scheme.

When this motor comes out - I will put it on the bench and tackle a full high torque performance tune with Cosa clutch.

In the mean time - jet kit arrives Tuesday.

:-)

Screen Shot 2019-05-05 at 9.54.23 PM.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Sun May 05, 2019 11:53 pm quote
Sounds like a lot of fun. With the engine improved a little it can only turn dangerous into lethal.... go for it.

What jets did you buy? As it is now you're going to need an AC160 and a BE3. Main jet somewhere between 96 and 110. And pilot jet 48/something or 45/something.
These carbs are not like jetting in anything else you've ever done before. Theres so much overlap its like doing it all at once.
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Mon May 06, 2019 9:37 am quote
Jack - awesome. Thanks.
Noted on wholesale exchange and cross over.
Gonna be interesting...
Collecting bits and bobs to match your shopping list.
Had some of that on the way based on Ginch's comments.
Have some pesky work travel for a couple days - puts me back mid week.
Looking forward to playing to see what we learn.
Hooked
P125x (P200 Motor)
Joined: 06 May 2019
Posts: 159
Location: Alexandria, VA
Mon May 06, 2019 1:09 pm quote
Fun thread! I always wanted a sidecar, though I think more modern for practicality and safety. Still, interesting to see your progress.

Thanks for sharing.
Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and new to 2018, '66 Blue Badge Smallframe
Joined: 30 Nov 2011
Posts: 6950
Location: Victoria, Australia
Mon May 06, 2019 7:10 pm quote
SoCalGuy wrote:
I seem to recall another member looking to eke out a little more power via some O tuning. Worth a read... #slipperyslope

Malossi 210 build thread - PWK30 tuning / perpetual torture
You're really trying to put him off, aren't you?

charlieman22 wrote:
Have done some internet searching.
FMP has a few of his semi-intelligible videos on it. Making me semi-intelligent.
German PDF that looks like the bible - is unfortunately... in German...

But haven't found an O tune bible.
The German pdf is actually written by FMP. I had a go at translating it some time ago and gave up... asked him for help which he was willing to do but it was just too hard.
Anyway I'm still in regular contact with him... send me a pm with some constructive comments and I'll pass them on. He does take constructive criticism eventually. Not well, but eventually.
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Mon May 06, 2019 7:12 pm quote
Jim - thanks - glad the joy translated to a good read.

Practicality?

See below: Gratuitous exposure of wine texted to my wife announcing my triumphant return with family's dinner - on way in from an afternoon of riding yesterday.
Don't be selfish - think of your family.
Everyone needs a sidecar...

:-)

FullSizeRender.jpg
Reason #11 everyone needs a sidecar

Molto Verboso
08 GTS 250, 79 P200E, 62 Allstate
Joined: 11 Jan 2006
Posts: 1178
Location: Florence, OR
Mon May 06, 2019 7:58 pm quote
I love it! I picked up a pizza from Papa Murphys the other day and put it in the crate. Gotta love the practical side!
Member
Stella 2t / '05 PX 150 / Honda Trail 110
Joined: 20 Jul 2016
Posts: 42
Location: Park City
Mon May 06, 2019 9:49 pm quote
Thanks for the kind words. Flying the sidecar should be practiced so you know what to do when it accidentally happens. Go practice with an empty sidecar in an open parking lot and progressively add weight until you can confidently handle different situations. I like to give passengers or bystanders the occasional fly-by, but typically keep the wheels on the ground as flights definitely stress the frame and connecting hardware. However, #SidecarAbby, our 70 pound dog is just about the perfect amount of ballast to keep the wheels on the ground or go for an easy flight without feeling too much stress on things. And a flying sidecar with a dog passenger...that gets people pretty excited!
Hooked
P125x (P200 Motor)
Joined: 06 May 2019
Posts: 159
Location: Alexandria, VA
Tue May 07, 2019 6:54 am quote
charlieman22 wrote:
Jim - thanks - glad the joy translated to a good read.

Practicality?

See below: Gratuitous exposure of wine texted to my wife announcing my triumphant return with family's dinner - on way in from an afternoon of riding yesterday.
Don't be selfish - think of your family.
Everyone needs a sidecar...

LOL You should see what I can carry on this:


Or this:


What I meant by practical is modern brakes and power to do all legal freeway speeds. But no way it would be as cool as yours!
Addicted
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Tue May 07, 2019 4:59 pm quote
Quote:
LOL You should see what I can carry on this:
Indeed. Nice machinery.
Quote:
Flying the sidecar should be practiced so you know what to do when it accidentally happens.
Indeed. Solid advice!
Addicted
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Tue May 07, 2019 4:59 pm quote
Lemme know if this sounds familiar
Scoot not running correctly.
Presents symptoms - missing, bogging, what ever.
Certain conditions appear to cause or exacerbate.
Cold out. Hot out. Night. Day. Venus rising over a full moon (editors note: Solid porn name).

Is it ignition?
Is it fuel supply?
You have a hunch.
But sometimes…
Doesn’t fix.

Go to the forum - search for like conditions for the dead spot.
And your symptom has some variant, some weirdness, that just doesn’t quite align.
Ahh - its just like Chandlerman’s coil. It must be the coil!
Wait - its just like SoCalGuy’s dead at top - must be a resistor plug. Wait - no! - its the HT coil - of course!
But attempts you make don't solve the issue.

So you throw a post up in search of insights.
Responses vary.
Other people’s hunches confirm or conflict with yours.
And you try some of the items - and you think maybe its better - but then it happens again.

But at some point - through some confluence of persistence or luck or insight - you find the true problem.
And you KNOW it when you find it - even before you restart the bike.
You SEE the frayed wire on the back of your condenser.
You FIND the wire that is grounding out your CDI.
Or… what ever.

Which brings us to…
My post about the carb box top being off & the bike running better.
It pained me to write it the first time - I was like - how can that be?
I braced for the collective eye roll.
Hey - didn’t this guy think he had a 250 main jet…?
(yes, yes, I did).

So I put the carb box top back on.
And I told myself - maybe it’s just the sound of the air that makes it SEEM like its got more power.
But the bike just didn’t perform the same - I could feel it.
So off the cover would come again - and the bike just seemed to run better

But I kinda wondered - was there some condition that the improvement was measurably there?
And there was…

When I go into a tight right turn entering my hood, and get on the gas at apex, it just wants to hesitate and bog. Same corner - every time.
Unless I remove the cover - in which case - it doesn’t.
So I thought about that right turn.
And how it is different then similar left’s - ‘cause I have a side car.
I slow down more headed in to really tight rights - and my revs at apex are usually lower.
And I am putting the bike under load - at low revs - rolling on the throttle.

The wierd thing was - I had the fix - but couldn’t understand why it was the fix.
And then I came across this… (I know, I know - that was a really long walk…)

What do you guys think - is it possible that with box top on - the bike runs a hair richer as it tries to suck air through the straw of the bellows?
And my set up - at least at that critical rev/throttle - is already a little too rich?
Look at the fuel air mixture graphed on this thing!
Maybe with top off - it is a touch leaner at that lower rev area - making it more peppy.

By the way - this should all come out in the wash when I re-jet.
Just wanted to share the experience should you want some other possibility rumbling around in your head at the job - while your supposed to be working - but you are instead pondering WHY your scoot isn’t running right.

:-)

-CM

site I got it from - http://www.vespalabs.org/labs/lab-research/dyno-results/airbox-and-filter-removal-test

Screen Shot 2019-05-07 at 5.39.58 PM.jpg

Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Tue May 07, 2019 11:33 pm quote
Blowback (ewww, not a good porn name at all)

Here is possibly the main reason, so you can get on with your work.
With the box lid on the blowback is processed twice (or more like three times). With the box lid off it just sprays all over the scooter. If the rotary timing isn't balanced to the cylinder port timing, or the rotary pad is not sealing at it's best, there will be a lot of blowback. Blowback goes forward through the carb twice and back once, so is therefore extra rich, as the rpm picks up this happens less. After a good O tuning this is minimised.
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Thu May 09, 2019 11:33 pm quote
Quote:
Here is possibly the main reason, so you can get on with your work
Jack - if you manage to get me to stop thinking through stuff while working - then you truly are a magician.

:-)
Quote:
With the box lid on the blowback is processed twice
That would make it run richer down low as you note.
That's definitely how it feels - "bog corner" entering my street - low RPM, high load, rolling on throttle, bog - though just to be clear - I am running it with the air filter still on - just not the box cover.
What ever is causing - I have a strong hunch it's rich down low.

Also - based on your prior comments on internal signs of overheat - light brown color of plug - honking big air corrector (250) installed - gutless top end, and random backfire when I run WOT in top 1/3 rev range - I am guessing I am lean up top. All those align.

So before I sack you with another full time request for re-jet project - I am going to take a quick swing at upsizing my main jet and lean out the primary ever so slightly - with the carb box cover back on...

I get that it may unravel and not work linearly due to overlap of jets.

Will give it a go in the morning and see if I can quantify. At minimum - maybe we learn something about this motor that's useful down the road.

Tks!

Oh - and Qascoot. Missed the pizza post. Hahahahah. Awesome!
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Fri May 10, 2019 7:35 am quote
Air filter or not, once the box cover is off much of the blowback escapes and weakening it down.

Interesting for the science but upping the main jet will make the low rpm rich bog worse. Try it and see for yourself.

Needs a whole modern rejet in one go (approx Jet sizes given earlier).
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Fri May 10, 2019 8:51 am quote
Quote:
Interesting for the science but upping the main jet will make the low rpm rich bog worse. Try it and see for yourself.

Needs a whole modern re-jet in one go (approx Jet sizes given earlier).
Tks Jack - your a good man for helping out.
Won't be surprised to find that's the case - i.e. richer main gives me better top end but new issues arise lower side - but since I have a month or riding on current set up - and swap out so quick - want to experience results.

Can then move to full rejet.
Ordered the jet ranges you and Ginch threw out.

Current idle: 40/130= 3.25
Current Main: 100
Atomizer: E4 (old school)
Air: 250

In stock ready to play:
45/160 = 3.5
48/160 = 3.3
45/140 = 3.1
55/160 = 2.9
52/140 = 2.88
50/120 = 2.4
52/120 = 2.3
Mains: 90-110 in increments.
Air corrector: 160 and 185.
Atomizer: BE3

So after my first play with existing - can move to the suggested starting point in the "45 & 48 somethings" range with BE3 and 160AC.

Question going in:
- Best way to protect against putting too lean an idle jet in/ know if you have gone too lean for safety?
- Does one clean the color off a spark plug between jet adjustments to help with read?

Gonna use long run top speed on flat/slight uphill long run/ & bog corner as my performance measures.

Let's see how we go!
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4761
Location: So Cal
Fri May 10, 2019 9:30 am quote
Ginch wrote:
SoCalGuy wrote:
I seem to recall another member looking to eke out a little more power via some O tuning. Worth a read... #slipperyslope

Malossi 210 build thread - PWK30 tuning / perpetual torture
You're really trying to put him off, aren't you?



Pffft, nah... hey I’m a big o-tune fan, done plenty of grinding and dremeling to my own engines. Just sayin since it’s a sidecar rig he needs to keep in mind the job he wants it to do.
Addicted
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Fri May 10, 2019 10:03 am quote
Multiple POV's is awesome.
Gives you a chance to consider other peoples opinion before ignoring it and going in the direction you planned anyway.

:-)

When O tune was pitched - we didn't know I had a three port w/modified inlet.
It was that discussion tho that sent me (a few glasses deep) into the garage with my endoscope camera to shove down the cylinder.

Much appreciate the crowd weighing in strong - on all sides of an issue.
Sometimes provides new direction - sometimes multiplies navigation of existing exponentially.
Priceless!

Tks!!
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Fri May 10, 2019 10:41 am quote
I’m still a fan of a NO-tune stock P200 with a Sito+ (well, except for lining up the ports and carb intake). But then again I’m not a tuner like a lot of others are here. I have always just popped in a 128 main jet in the 24/24 carb after installing a Sito+ and a T5 short fourth gear. That’s my super secret setup for long stretches of reliable highway cruising.

On my way out to the “big” city yesterday, I was fighting headwinds the whole way, cruising at 55-60mph. On the way back home I had a little bit of a tail wind...


I suppose I should have taken the picture while I was riding so that it would be better documentation, but my hands were busy holding onto the grips.

C5C27444-47FB-4977-B047-995092B607AB.jpeg

Molto Verboso
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Posts: 1570

Fri May 10, 2019 10:45 am quote
A closer up view...

F816AA7E-4D82-4F6C-B94B-A7B21DEEE1F0.jpeg

Addicted
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Fri May 10, 2019 11:36 am quote
Dude:

Screen Shot 2019-05-10 at 12.35.37 PM.jpg

Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4761
Location: So Cal
Fri May 10, 2019 12:51 pm quote
Impressive whodats.

sdjohn said to me years ago “It’s all about gearing.” He was right.

My Soops’ll do 60 without much too effort and they gobble up hills. The yellow one tops out around 65. Neither is heavily modded. The close ratios & dinky wheels keep the power where it can be used.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Sat May 11, 2019 2:40 am quote
charlieman22 wrote:
Dude:
Impressive for a stock 200. guys struggle to get that from a 210
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Sat May 11, 2019 2:54 am quote
charlieman22 wrote:
Question going in:
- Best way to protect against putting too lean an idle jet in/ know if you have gone too lean for safety?
- Does one clean the color off a spark plug between jet adjustments to help with read?

Gonna use long run top speed on flat/slight uphill long run/ & bog corner as my performance measures.

Let's see how we go!
Too lean an idle jet runs rough, scratchy, cuts out on pick up, takes too long to return to idle speed (and the biggy), re pick up after coming down from high rpm feels crap.
Some of this can be the same if the mix screw is too far in, so be sure not to confuse yourself.

Anything that happens under 1/4 throttle is associated with the pilot jet.

Anything at WOT is the main jet. Two or three whole jets down from full on machine gun splutter on WOT is usually near correct.

An AC160 and a BE3 are correct for a near stock 3 port 150. Thats two variables out the way. All you need to do is set the main and pilot. Easier said than done but thats it.

Spark plugs will eventually change colour to show the jetting. This is the only way to do the final WOT size.
Hooked
Honda elite
Joined: 19 Jun 2007
Posts: 497
Location: California
Sat May 11, 2019 7:45 am quote
whodatschrome wrote:
A closer up view...
wow
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Sat May 11, 2019 8:16 am quote
Jack221 wrote:
charlieman22 wrote:
Dude:
Impressive for a stock 200. guys struggle to get that from a 210
I'm just as skeptical as the rest you all. I run a flyscreen, had a tailwind, and a very very slight downhill. I just kept it pinned for a few miles at around 72mph. I didn't even bother getting into a speed tuck. Maybe it started to run lean, and that's why the extra few miles an hour?...I dunno (I guess weather, temperature, and elevation play a roll as well). Anyhow, whatever the reason, that's why I try to keep my junk stock. It seems like any time I try to tune something, I'm having to buy a new piston come Monday morning (well, except for my tuned T5, for some reason I've had zero issues with that scooter). I guess that's why I preach keeping a 200 stock...though I am open minded enough to listen to others beliefs on tuning.
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Sat May 11, 2019 4:54 pm quote
Quote:
I'm just as skeptical as the rest you all
Misread the tone of my "Dude" - it was amazement.

Jack - Teach a man to fish...
Good stuff. Thanks!

Ran some tests on existing set up.
Applied basic reasoning and rode for the day once optimized.

Suspected rich primary, lean main.
Downsized primary ever so slightly - from 40/130=3.25 to 48/160 = 3.3
Upsized main in increments to 108 - from orig 100 - then back down to 105 - as recommended.
(Kept existing big-ass air corrector and weird-ass "E4" atomizer for this round.)
Bike was night and day better - wow - especially pulling up hills.

Used road near home for test.
Looks like abandon hwy from 70's CHiPs episode (probably is).
Long straight then U turn and return back.
Run is aprox 1 min - WOT.
Slightly downhill "out" uphill "in"
Top 10 seconds of speed avg shown below:

Main jet 108 = 42.41MPH out, 41.33MPH in
Main jet 105 = 44.22MPH out, 42.63MPH in

Massive improvement.

Then, of course, I pulled the carb box cover off... cause u knew I would.
See below.
Next move is to re-jet with modern set up (BE3 & 160 AC) and run again (box cover on to start with of course).

IMG_9952.PNG
She likes it with the cover(s) off.
What's a guy to do?

Hooked
bare metal cafe racer
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Sat May 11, 2019 10:32 pm quote
I don't know squat about this stuff... but would one of these help?

Bell-mouth intake
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Sat May 11, 2019 11:20 pm quote
charlieman22 wrote:
Quote:
I'm just as skeptical as the rest you all
Misread the tone of my "Dude" - it was amazement.
...and you misread the tone of my misreading skepticism- I was amazed myself!
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Sat May 11, 2019 11:27 pm quote
About your scoot running better with no carb top, is there adequate air flow starting from the frame, bellows, and carb box intake? Maybe try another run with the air box on, and bellows removed? Maybe remove the cowl as well?
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Sun May 12, 2019 6:44 am quote
Some solid results. Will be different again after the BE3 goes in. Then would expect another 10mph on each of the same 'in' and 'out' runs after an O tune.
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Sun May 12, 2019 11:28 am quote
Quote:
Some solid results. Will be different again after the BE3 goes in. Then would expect another 10mph on each of the same 'in' and 'out' runs after an O tune.
Agreed on results - such an improvement to drivability. Does seem to blow through gas faster (don't ask me how I found out...) Now I have a solid baseline. Will be fun to see if I can improve either top or through range with BE3 set. Stay tuned.
Quote:
I don't know squat about this stuff... but would one of these help?

Bell-mouth intake
Pheas - your quality research as usual. Interesting. Ginch - looks like one of your buddies is already on the "less restrictive" air flow inlet path?!
Quote:
About your scoot running better with no carb top, is there adequate air flow starting from the frame, bellows, and carb box intake? Maybe try another run with the air box on, and bellows removed? Maybe remove the cowl as well?
The scoot does run better without the carb box top.
It could be more air flow.
It could be richer.

The science of it kinda makes sense.
Air flow is dictated by fluid dynamics.
Very similar situation in HVAC ducting.
Corrugated - or bellowed - duct creates significant flow restriction through friction - sorta surprising just how much.
This effect is magnified with smaller diameter duct - as you get higher velocity.
In our case - we are pretty small diameter compared to HVAC ducting - so would not expect it to be less of an effect.
This also suggests higher revs would likely feel it more than idle.
See chart below: Multiple studies show same.
15% corrugation = 2x friction vs ~none. 4x at 30%.
Vespa bellows are minimum 30% = >4x restriction through bellows vs smooth bore duct - and probably even more vs no duct at all (like in my case).
That's probably meaningful.

The guys that ran the dyno testing with filter and air box off showed exactly that.
Data from removal of both bellows and filter had about a 4% peak HP increase. There was an increase through full rev range.
Fuel/air ratio also tested leaner through full range.
That correlates to less restricted inlet.
Might explain their HP jump if they were running unoptimized/too rich prior.
But in my case - I was running too lean - bigger main was jumping my power.
So leaning more should have created more starvation, not more HP.

I see all the performance tuning kits come with a high flow air filter to replace the bellows.
Those guys must be doing that for a reason.

Seems like all these things align to me.
Have any of you who are running traditional aspiration with carb box and bellows run your bike without carb box top for a day, or with tuning kit air filter kit - just to see if you get a little more oomph?

Would be curious to know!

air-diffusion-council-flex-duct-installation-standards-2-friction-rate-compression.png

Screen Shot 2019-05-12 at 8.55.30 AM.jpg

Screen Shot 2019-05-07 at 5.39.58 PM.jpg

Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4761
Location: So Cal
Sun May 12, 2019 12:12 pm quote
Without both the filter and the lid, yes, the carb will suck more air and run leaner. But without just lid? Sorry, not buying it.

Try a run with the filter off and only the lid on.
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Sun May 12, 2019 12:42 pm quote
I watched the SIP install video that covered the Polini air filter kit just a few days ago on youtube. My problem with the kit is that the aluminum ring adapter made the carb box inlet even smaller. A quick seat of the pants math makes it look like you loose about 50% of the intake area where the bellows would be. I never got past math 111 in school, so i can't talk HVAC fluid dynamics with authority though.

said SIP Polini video- www.youtube.com/watch?v=9EobKczfVaQ
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Location: california
Sun May 12, 2019 1:39 pm quote
Quote:
Without both the filter and the lid, yes, the carb will suck more air and run leaner. But without just lid? Sorry, not buying it.

Try a run with the filter off and only the lid on.
Gauntlet down - let's find out!
But I challenge you back.
Pull your carb box top off and run for a day. Lil more power?
Say for a cold beverage at next swap meet/whatever in our homeland?
There is a reason they removed both for that test - but obviously I don't wanna drive around long without a filter on - so I chose carb box. Repeatedly surprised by results with my set up. See if same for yours - but give it more than just a run up and down the street.

BTW - try breathing through a straw. Your lungs taking in fraction of air that motor does - and of course straw is fraction of the size of bellows... The friction effect is evident tho.
Quote:
My problem with the kit is that the aluminum ring adapter made the carb box inlet even smaller
WDC - good eye. Not sure why they would choose to do that. Also - funny how one of these conversations often leads to new discovery/insight of a product I need. :-)

Keep in mind - the known effect in HVAC is due to repeated opening and closing of the accordion rings - causing significant loss - rather than single restricted opening as per SIP's case.

I need to find a dyno near me!
Molto Verboso
Joined: 26 Oct 2015
Posts: 1570

Sun May 12, 2019 2:28 pm quote
For years the "butt dyno" has been highly regarded by many a tuner to be the most authoritative and accurate way for reaching those higher horsepower numbers. It's also more affordable in the short term as well. Sometimes I have to stand back when I'm looking at the mirror at myself, and decide if I want to invest my money into one.
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Sun May 12, 2019 3:08 pm quote
Quote:
For years the "butt dyno" has been highly regarded by many a tuner to be the most authoritative and accurate way for reaching those higher horsepower numbers. It's also more affordable in the short term as well. Sometimes I have to stand back when I'm looking at the mirror at myself, and decide if I want to invest my money into one.
Well - I'd be glad to hear the test results of y'all's butt dynos to compare to mine on your own bikes with carb box removed.

Take the carb box top off butt dyno challenge!
Hooked
bare metal cafe racer
Joined: 01 Sep 2017
Posts: 424
Location: Aotearoa (New Zealand)
Sun May 12, 2019 4:17 pm quote
I've heard the bigger they are the more accurate...

Should not be used in conjunction with the straw test tho.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1363
Location: London UK
Tue May 14, 2019 12:28 am quote
For a scooter jetted in and running fine, removing the air filter or carb box top will make it run weak. And we all know what weak running does to shiny pistons.

I doubt removing the bellows will do anything. The diameter is way bigger than the carb bore and friction losses, although there, would not matter.
The only Vespa air filter that works is the T5 one, as it is bigger better and has a vortex built in.

Got the parts to jet properly yet?
Addicted
Joined: 26 Jan 2019
Posts: 530
Location: california
Tue May 14, 2019 3:49 am quote
Quote:
I've heard the bigger they are the more accurate...
Quote:
Sometimes I have to stand back when I'm looking at the mirror at myself, and decide if I want to invest my money into one.
Oh - you guys are funny.
Quote:
For a scooter jetted in and running fine, removing the air filter or carb box top will make it run weak. And we all know what weak running does to shiny pistons.
It's possible I am feeling some leaning effect. Agreed.
Quote:
I doubt removing the bellows will do anything. The diameter is way bigger than the carb bore and friction losses, although there, would not matter.
Clearly I am not going to win any converts - and you guys hold the experience.
I am going off a "butt dyno" - that as you note - could be related to leaner conditions.
Carb has to be jetted in correctly - mine is likely not there yet.

With that said - There are strong hints that tuning engineers think friction could be a factor.
Saw a post yesterday with the GS carb box.
First time I had seen this.
Noted they upsized the bellows.
Matched that to a relatively small hard metal tube into the frame.
That suggests to me that at minimum - they felt there was a significant friction differential between the two.
Maybe this was just gimmick - but assume they were trying to optimize flow/limit friction loss, with this oversized bellow?
Quote:
The only Vespa air filter that works is the T5 one, as it is bigger better and has a vortex built in.
Conversation has educated me on some Venturi options I didn't know existed. Insightful/helpful for me.
Quote:
Got the parts to jet properly yet?
Right. Traveling this week so have to wait for my return. Whack of recommended jets waiting for me back in my garage. Looking forward to getting carb properly jetted in. Committed to optimizing with modern jetting - and suspect I will get a better overall performance/drivability outcome from current.

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2019 Fall Gathering - September 12 - 15, Hungry Mother State Park, Marion, VA   vespa scooterwest scooter west Motorsport Scooters   AF1 Racing Vespa Austin
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