Modern Vespa

Float bowl just touch the cylinder cowl? If so you don't need one. Vader ran without and his MHR could do 93mph (said it used more fuel than his truck). I ran without for some time, when I needed to weld up a tank I decided to add a tab on the bottom to hold a pump. It's a just in case thing... pressure will obviously drop as it nears the bottom. But if you are keeping it topped up for these runs you can probably forget about it causing an issue.

Thanks gents.
Problem solved! Caused a chuckle.

Float does in fact just sit above cowl.
So pump is not an issue - thanks - makes sense.

Speaking with smart carb guy today - I asked about float level.
It just felt like it was running out of gas.
The giveaway - it would climb up - then start to feel like I needed to flip the reserve on (if I had a reserve...)
And once it did - even at lower revs - it kept doing it until I let it settle for a moment.

Smart Carb guy noted that cavitation was possible - and that their normal installation on a dirt bike has the carb slanted down hill.
Mine is slanted up hill - cause its shoe horned in there.

Ran a quick test - see below - and then opened up and adjusted float level.
All that practice with the SI paying off.
Solved issue immediately.

Bike runs extremely smoothly.
There are no "pip pip pips" as I come off the throttle hard - just clean wind down.
With that said - GSF Dyno says its at least 1+HP less.
But GPS says I am hitting 59MPH in 3rd - same as best runs with SI.
Not sure quite what to make of that.
Wonder if the difference in tone has an effect.
Will speak with Smart Carb tomorrow and see what they have to say.
May see how it performs on hwy at the right moment as well.
Top speed seems pretty good test of peak HP also.

Sensation is - its working great - but GSF data suggests its lost a step.
Will go back at it tomorrow and see.

Oops - the speed run I took:
Note the downshifts as I come to the first turn at the end of the run.
Sounds like Im coasting - Im not! The motor is under load and I am coming off the throttle hard - but there is no "pip pip pip". Super smooth.

https://youtu.be/D3lUvFZTZpc

sounds awesome! so jealous! Looks like you might not be going back to SI. Would love to hear what your fuel economy differences are between SI and SC. Probably hard to judge given you are doing test runs and not a normal drive for full tank on either lately.

SC has significant gains in fuel economy.
I will figure a way to show - not sure yet.
Speed runs with SI drank fuel.
It was throaty, and strong, but thirsty.
Keep in mind - I had a bell mouth on the SI.

After about 8 runs today just hammering it - I flipped open the fuel to refill - and was shocked that I hadn't used that much.
For all their marketing - I will say this for the Smart Carb: there is something to their "fine atomization" claim.
You can feel it in the smoothness and the fuel economy.

It's got a nice sound to it

The SI might have been a shade quicker. Think the SI got to 59 and held it a while for the same run. 1hp would probably be about it. SC was quick to adjust. Keeping it?

SoCal - I like it as well.
It's more formula 1 than Nascar now.
One ponders a 3D printed bell mouth...

Jack - good memory. Yes.
And here is the Smart from today doing same.
https://youtu.be/oqCFoD7EJUc
Posted other as it had the downshifts that showed off the silkiness.

I will post a full run down on the carb and its metering rods.
Here is a primer.
I think I get the best performance on 1/4 throttle and under on one metering rod, and best top end performance on another. TBC.
Its close - and I can adjust either in to the other's range - but one is slightly better for one thing and the other for the other.
Wonder if there is a "custom" taper to be had...

My intake manifold is also a hot mess cobbled together to see if I could just get the damn thing working.
Not sure if shape and path make that much of a difference.
3 home made spacers stacked on ea. other with enough Honda Bond to float a boat - combined with a piece of radiator hose with a slight bend in it...

Picked up some thick aluminum rounds today - and intend to make a nice custom spacer like Whodat posted somewhere recently. Should allow a straight section of rad hose to connect the carb and clean up the pathway a touch. Addicted.
This one is actually a loaner - I had planned to go up to the 28MM when available. Good learning with this one. Not sure what to expect from larger - will eventually find out![/url]

Which method are you using again for measurement? Just audio, no electronics?

Perhaps you could make a comparison by timing the videos - how long does it take it to get to a certain speed compared to before?

Really think for all the money and the effort, although the SC is very interesting, its not making a great deal of difference. A little more work on set up of the SI and it would be just as good.
Biggest carb for your old style inlet is 26 or 28 at a push but probably not quicker than a 26.
If you ever go reed put a 35mm on it. Now that will make a difference.

A mic in the sidecar. Welcome some info on the direct electric connection - but it may just be that the SI was able to produce an extra HP? Doesn't feel like it but its been weeks so hard to really compare. Might be. From a peek power standpoint - I agree - but I dont want to take it off.
There is something to this thing. It is whisper smooth - uses less fuel - and responsive.

I had intended to upsize the carb - but couldn't as they didn't have in stock - so this is 25mm.
I think its just the way the bike runs that is so damn fabulous - that has me hooked.
More power is always nice...
28mm will be the upgrade when they are in stock. Did this t'day. Numbers are within .09 seconds on best runs for both SI and SC. Dyno repeatedly shows SI with 1 more HP tho. Hard to say.
Interested to put a bell mouth on this and see if that changes.

All things being equal - I would put the largest SC on I could. I suspect that would give me a touch more power - while maintaining all the good of this thing. Someone else is gonna have to give it a go and comment on what they think. I think the smoothness is plain terrific.

Sounds really nice! Glad you got the issue worked out and it was simple with just a float level fix. You wouldn't happen to have temperature differences (if there were any) between SI and SC? Just curious.

Wow sounds great, nice accomplishment.

Update: Worked my way to the leanest metering rod at end of the day today.
Gracious.
Has this sort of this ripping sound and feels just-plain-fast.

This may be my favorite investment so far.
I spent about $1000 making my old VBB stop on a dime with a hydro disc fitting nicely under the mudguard (Whodat - look back at how I kept it from binding on page 5! 🙂 )
I dropped $300 on sticky rubber tubeless tires and rims that make me feel safer.
I bought a Polini cylinder and a shinny 60mm crank to make it more powerful (leaving half what I spent in shards and chunks on the garage floor).
But this thing might be the best upgrade of all - or maybe it just squeezes the value out of all those other things.
I'm a fan.

Lynn - thanks - but frankly - I have done less work on this one than any of my other upgrades. Sure does make them come to life tho.

Poidog - after coming off about a mile of Hwy - running WOT - it was at 243 degrees. I have seen higher - when I lug it which is extra easy to do because it just doesn't feel like you have to rev up to get in to the power. That's as good or better than where I was with the SI. I won't claim viceroy yet - but the fat lady is warming up.

Sound is getting better by the day - and I have a "horn" in design that I am going to try (aka bell mouth).
Its got an almost ripping sound to it now when throttle is pinned.
I just want to keep going out to the garage and running it again.

I'll be interested to take some more GSF runs to see if it captures what I am now feeling.
I suspect I am getting a broader band of power at the top - I can feel power in reserve at 8/10ths of throttle in 4th at 60MPH - which is about 7K RPM.

Next step is to solidify the install and minimize some of the bodgery I did. It's not pretty. Then need to think about getting the body work in shape...

#1, i'm impressed that you could find just which page the front mounting of the shock was on! There are LOTS of pages to go through to find that.

So at the top of page 5 you had the top of the shock tilted in far enough (6 degrees?) that it would make Pythagoras and all of his followers cringe...but further down the page it looks like maybe you modified the caliper carrier so that the bottom of the shock could be pushed towards the wheel...therefore making the shock traveling parallel with the fork? And i reading that correctly?

If you can find any power gain, then it might be justified but if you are weak anywhere on the curve it will will feel great but wear too quickly. Although there are still two cylinders in reserve, so not so important.

If you do settle on the SC get a 35 and reed block. You'll need a new manifold anyway. This will be money well spent.

. Was it really on page 5? 🙂

Short version: shock mounts at top with flexible (rubber) - at bottom with upper and lower bolts. If you lean it in - when it compresses - it fulcrums on hub behind the top bolt. Talk about side load!
To avoid this - I ground the hub back at that point - and cut out the shock so that it had clearance - even when completely compressed by the trailing arm being as high up as it could go.
There is still a bit of side load - true - but it is fairly minor & not being bent around a point - has worked great since install. ¯\_(ツ)_/¯ Caused a chuckle.

35 and reed block?! HA!. I just got it running!

Tho now that you mention... kinda growing on me. Been offered a set of cases on the house - that were opened up for a reed. They are old LMLs. Perhaps one of these cylinders belongs to that project. Lemme ponder - we will have to talk timings...

Smart Carb update. This thing just puts a smile on my face. Kinda the ultimate touring solution I think.
I should post a 1/3 throttle cruise - it just goes and goes with so little gas.
However - instead I am posting this...
Welcome to the Ventura Highway.
https://youtu.be/rkSFypuvu3Y

Oh - and Jack - ran it WOT on used plug - then cut motor and coasted. Below a few shots. Am I still a little rich? See anything else that comes to mind?

*Edit - am also seeing a good bit of blow back. Might that be related to my snaking intake manifold? Other? What causes?

Holy F. 70mph with a sidecar. You just made me so jealous of a leaner sidecar!

Swiss - u r the one that flagged the SC. Much appreciated. Great find!

If they will just deliver ur parts - U'll be back on the road!

I called USPS customer service today to find out if it went lost or something cause its been 5-6 days stuck in transit to my local PO. They said it is at my local PO but they are severely understaffed due to COVID so it may be another week or two before I get it. Surprisingly we made it 2 months into this shutdown before it started affecting mail delivery. Hopefully everyone at my PO gets through it and eventually my small box of parts gets here. Hard to complain when your parts mean nothing in the grand scheme compared to the issue.

Glad you are enjoying the SC. It looks fun to play with and maybe some day long in the future I will take a chance. But for now, enjoying vicariously through you!

That plug looks like it might be really lean. When it goes grey from a WOT run it is melting the piston.
Put a camera down the plug hole and have a look, just to be sure.

Can't stop the blow back. Put the bellows on and it will suck it back in and not spray it all over the place.

Melting piston?!
That would not be... well... Smart...
That said - I did move to the leanest metering rod I have.
Then ran it pinned (pinned pinned) a certain number of times.
Repeatedly.
That plug pic came after a 5-10 second true WOT max RPM run in second (good 5-10 seconds of surely this thing is going to blow up).
It didn't - but I was kinda miffed by the color.
It didn't look wet.
It wasn't chocolate milk either.
Is that rich?
Is that lean?
Thus the post for help...
I'll run a camera down it in the morning and see what I see.
Many tks. ahh. Well - If they make an S shaped bellows - no problem. Otherwise - I will have to get a bit creative with a solution - but good insight on options. Tks. Had taken that as a sign I might be running rich. Perhaps not...

It does sound like slightly rich at the bottom and weak at WOT. Obviously not so weak but if you held that 70 for 10 miles it wouldn't end well.
On a normal carb you would need a needle with a smaller tip or bigger angle

Jack - you have a damn good ear.

The bottom end is controlled by lifting or lowering the metering rod - with a turn of a nob on top of the carb. I've kept it turned to be a little rich - even on the leanest rod - as I was thrashing it this week and wanted some cushion when I came off the WOT runs hard. So the bottom is a little rich.

But I have also gone leaner and leaner on the rod through the week (affects mid and top) as I have tried to squeeze the power out of it. So the WOT runs that produced that plug pic/ and that hwy run - were in fact done on a relatively lean rod. I absolutely blasted it before the plug pic (twice if honest)...

Virgin territory.
🙂

Ok - who am I kidding?
Can't just climb in to bed wondering if I have a moon crater carved in the top of my piston.
On Covid time anyway - so...

Really keen. Midnight in the garage. Looks like you got away with it. At the edge of the piston there are detonation marks. There would have been a pinking sound when at WOT, didn't hear it on the video but it would have been there.

Probably need to go a few metering rods richer and check again.

Late night garage time - cool concrete floor - little music - sip of something brown - one of my favorite times to tinker. Certainly wasn't going to sleep well wondering if I had dremeled a new hole...

Edges of the piston look kinda fine to me. Hard to see much - but perhaps it's there. With helmet on - and on recordings - cant pick up the pinking - but don't doubt it.

Evidence of some soft seize on the cylinder walls.
best guess - that might have come from my testing with large air leak - but no way to know.

Question - if the issue is detonation - and temps are reasonable (Hwy run was 248), would another approach be to introduce some octain boost? Best our pumps offer is 91 here.

Edit: approach will be to go back at least a step on metering rod and look at the plug again after WOT thrash.

I would imagine running that weak is more than one metering rod.

Still think the SI ran better. The speed you were getting from that would run WOT all day. Think this SC is going to ruin your motor. I know you really want to run the malossi.

CHT is not a lot of help when running that weak. The EGT would have been quite high though.

There are tradeoffs.
The SI may be more powerful at the top. Smart can match or better, but may have to run to lean to do so.

The Smart is crazy responsive and silky smooth - that is like crack. However - when I drop down 1 or 2 metering rods, I lose about 2MPH off the top on the HWY run - and the top feels a bit dulled.

I'm after best of both worlds.
Hooked on the way the Smart runs.
Want that snap at the top tho.

Do you think we can squeeze a bit more out of it?
If pinking is the issue - what about retarding the timing a hair.
Or upping the quality of gas to a higher octane?

What effect on heat would these have?
Wonder how a bell mouth would help the top.
Welcome some ideas on what tools in the chest we might have to optimize.
Too good to put down - but hate to give up that snap.

And the Hwy run - with the riches of the three rods - EQ28.
https://youtu.be/KNffPI-xjM8
Yes - That is me passing someone on the hwy...

¯\_(ツ)_/¯

On a 4 stroke that would be a bit rich, you'd be looking for a cigarette ash color . On these 2 strokes I couldn't telling you, I'm only hear to cheer you on and learn.

Perfect.
Me too.

While pondering and trying to convince Jack to dig in and help this through how to optimize (timing/octane/IDKWTF) tuning on this thing - I did a little clean up work.

Carb was pointed at frame - spewing blow back on my leg - and I have designs on a bell mouth and Jack's bellows solution. To do so - needed to replace my bodge space with something a bit taller and less prone to leak.

Had some fun with this:

Nice work on the block!

How is the piston top looking now? Sounding really rich at the low end making the plug look confusing. Weak jetting does feel good and go faster but does blow up after a while. Need to be careful your not just running in the blow up zone and liking it.

91 MON US fuel is the same as euro 95 RON, so nothing to do there. Why do they do that, so similar but different .

If you retard the timing it will go slower, really need to be advancing it.

Without running bellows or filter on the SC, the blow back will be lost. Really need to be have one or the other or it will be difficult to set up. This is why the SI is in a box.

Set the clicks to run weak at the bottom and there will be less confusion.

Thanks - Inspired from some pic you posted! Stopped in to the metal shop up the road and found those rounds for less than a tenner. Cheepo drill press and bandsaw are slow but pretty damn reliable with decent bits and belts.
Maybe you posted that pic on this thread?
Pages are like days right now - they all feel the same... Clear. Side project today was to get it pointed in a reasonable direction where I might tackle. Pointless when it was pointed at the frame. Like. Agreed. Was well rich on that run at the bottom. See what a handful of clicks at the bottom brings us. Good thought. Local station sells 100 octane racing fuel. No idea why. This is California - its just how we roll. . Funny you should ask...

Lots of the OHV guys like the 100 proof gas for their 2T dirtbikes.
So how much a gallon is it down there?

Thanks.
Only way to find out is to buy some I guess. Will let you know... 🙂
I use premix - so its not like I just pull in to any station and fill up now anyway.
Willing to give this a look if it buys me some Saftey net on pinking damage.
That station is about 10 min. away - plus they have cold beer.

Gonna take first steps first tho.
Spin the dial and lean out the bottom end on one of the richer metering rods - combined with some form of air filter or bellows to help capture the blow back. Not sure if this is normal for all side drafts - but have to say - if I had to identify a downside - this would be it.

Ask and ye shall receive.

https://www.sip-scootershop.com/en/products/air+bellow+sip+air+filter+_25739200

Thanks!.
But wait!
Its pointed the wrong way?!

I cant even figure out from that picture how the exit side of the carb gets down to the inlet on the cases.
No matter - it gave me the idea once I saw it.
Grabbed a radiator hose that had the right ID/OD and cut a little section out of it that had a curve in it.
Used that as an adapter.
So nice not to have my leg being sprayed with fuel.
My wife and family thank you.