PX200 Tourer

[sime66]

Wow, that is a lot more; and a lot of tweaking by the sounds of it.
It brings to mind what jimscoot was saying on my build thread this time last year with his AC190.
Was your current set up reached before or since the change to very cold weather?
I was going to have a session this morning, but got bogged down with numbers on E#3; it might not get another tweak this year now, I might just keep it OK to ride till New Year; only a few weekends, and it isn’t fiddling weather. It went from very wet and windy to freezing, with little opportunity for progress. Maybe some of the difficulty I was having, and putting down to my inexperience, was actually this sucking on the MJ at tickover due to the drilling issue.
Maybe you would squeeze a bit more out of Si26 with the vortex; what else would you do differently from scratch though? A PHBH 26/28?

[pxguru]

Done in cold weather. Getting it right now means it will be great for long runs in the Summer. I think yours won't be quite as bad as mine but the same issue. With your vortex it will help with the extra air and yours being a 177 won't have as much suck (mine started as a standard PX200 barrel but over bored to 68mm, 210cc).
The AC is like the needle in a big carb. I would say yours might be ok with the AC185. Certainly not a standard carb set up at all but after you have done this one you will be able to set up any.
After putting the AC185 in up your MJ until it just splutters at 1/4 throttle, then do a WOT plug chop. this will determine if the AC185 is enough or if you need an AC190.

[pecker]

Alright boys,
I'm thinking I should be looking towards using a high numbered air corrector on my set up,
Could you lads please give your thoughts ,ideas logics,reasoning for using the high numbered AC,s

I've managed to get my mj down to mid late 120s with that nice colour plug we long for.( But I'm not all the way there yet.)
I will update my thread when I can remember everything and get a few more results ( it's been a long road).
Keep up all the good work
Cheers
Pek

[vespasco]

Wow. Thats a lot of air in there.
So you are working on the principle that the AC acts as brake for the MJ.
Thats something I've been led to believe.
Will be interesting to see if that plug is a good colour at WOT.
Did you try the large AC first, with a stock BE2 or BE3?

[pxguru]

The way I see it is the high numbered AC changes the fuel delivery curve. With a 185AC my scooter is still too rich at 1/4 throttle and too lean at WOT.

With the AC190 it was better. If I up the main jet to run ok at WOT, the scooter is then un-ridable, as it just floods out totally, like double choke on, at 1/4 throttle. If I dont upjet MJ and just put a jack up kit on the floatbowl. WOT is fine but mid is no good and low is choked.
With the AC190 and BE2 it was running lean but ridable at WOT was bearable but no good and was still struggling through the 1/4 throttle richness.

The AC mostly affects low to mid throttle but does affect WOT slightly. So bigger AC weakens the bottom more than the top. Changing the curve. I am feeling at the moment that BE2+2 and AC205 is about the correct curve for mine.

Next step is the main jet needs to be finally set. After the pilot jet. Then check round all jets again to fine tune. Will be on it again later tomorrow

[pxguru]

I have been riding it but still not done a plug chop. Running great but still needs a little more, something. I'll get back onto it after lunch.

[vespasco]

Thats a big lunch you're having there guruji.
You must be having an unlimited Gujarati thali.
Hahaha

[pxguru]

Takes a lot longer eating with one hand behind your back

Did a WOT chop and was too rich. Downjetted to 128MJ and it seems even better at low/mid. Still a slight richness as the MJ takes over. I don't want to downjet any more and I think it is already too low. Putting in a bigger pilot will just make this transition richer. Next thing to do is an even bigger AC. I will drill this one out a little bigger (will aim for 220) and see if that is enough to get in the 55 pilot.

Will be back onto it again today, after lunch.

Edit: OK, drilled out the AC some more. Guessing it is now something like 220. Way better once it was fully hot. It is going great, really pulling well and no feel of being too rich anywhere at all. Behaves in low throttle traffic like a standard engine.
I would still like the bigger pilot but seems thats slightly out of reach, although it would appear that 50/160 maybe enough. Too small pilot jet (small number of jet, big number doesn't matter for this)is most noticed when returning to tickover after a WOT session, this is ok so far. No signs of any issue.
Going to leave it alone for a while now and just do three crusing plug chops (quarter, half and WOT) and trim as necessary.

So the story so far, for my benefit as much as anyone else;
SI26/26E carb. 2.0mm drilled MJ hole, Drilled air filter, 50/160 pilot, 220 Air Corrector, BE2+2 (1.5) Atomiser, 128MJ, 04 slide, working Autolube, SIP Road II

[sime66]

Pxguru; I’ll leave the explanation in until you reply, then simplify this post to just the important data, so bear with me.

Your wav should start at low revs in 3rd, and I think this was a quick acceleration through the gears, so your 3rd gear curve doesn’t start until 7,000ish, and is only 5 seconds long, so might not be particularly accurate. I’ve highlighted the bit of the Wav I’ve used:



I’ve taken the parameters (weight, gears etc.) for the dyno front screen to be the same as you used in the microdyno thread; most aren’t critical, and you can change any you don’t like and I’ll tweak it (maybe if/when you do a better Wav). I’ve used temp and pressure for midday Portsmouth today (again you can change it):



This is your result; it isn’t a full curve - I’d be happier if we had a wav that went from nearer 3,000 to 9,000rpm and the front sheet checked and agreed as well, but it’s something. You should also say whether jetting was as your last post, or tweaked.

In any case, somewhere over 20PS seems feasible and pretty impressive; was your hoped 15PS a bit modest?



22.1PS @ 8625rpm
18.9NM @ 7994rpm

Wav:

[pxguru]

Thanks for doing that. Well that is a lot more BHP than expected With a full 3rd gear curve that might come down a little. It does go well though but after the polossi it is going to feel a little slow.

The 1/4 throttle plug chop is still a little rich. Feels and rides ok but will be wasting fuel. I have reduced to 48/160 already and I don't want to drop the pilot jet any more, so I'll open up the atomiser a little and see how that goes.

Edit; Still impressed. This is an original 200 iron barrel btw. No kit here

[pxguru]

Had a last fiddle with the atomiser and it is now really nice all round. Literally goes like a train on the dual carridgeway. Cruises at 60mph on about 1/4 throttle. Was really windy yesterday and it really pulls hard into it.

Jetting now (and this is it until the Summer);
SI26/26E carb. 2.0mm drilled MJ hole, Drilled air filter, 48/160 pilot, 225 Air Corrector, BE2+4 (1.5) Atomiser, 128MJ, 04 slide, working Autolube, SIP Road II

[sime66]

The answer really does seem to be with the big AC then (and atomiser to handle it). It makes sense really, but wish we'd thought of it in the Spring.......
I'm especially noting the point you make about this being a standard 200 barrel; the porting skill really does release the power if you know what you're doing.

[pxguru]

When we stop learning we stop everything

At least the 22 BHP explains why I was having so much trouble. There was me thinking it was 15+ BHP and trying to jet it for that. This is certainly the most power I have seen from an SI carb (would usually be PHBH by now). And this is the weirdest jetting too but at least there is now a model online for anyone else struggling with the same.

I put a lot of work into that standard 200 barrel, not the kind of thing that the usual tuner would even consider.

That being the case, have you changed your AC yet? I am guessing the AC185 could be enough for yours as you have a Vortex on it.

[sime66]

I'm trying to avoid talking about mine on your thread.
I have previously made a note that my solution won't be so drastic, and have the jets already organised to swap over.
The Beast is currently unwell though, and I am currently disinclined to faff about with it. It does not start well, it does not idle, it wants to cut out if I don't keep the revs up, it sometimes stutters at low revs when cold, I'm unsure what that's about because it doesn't always do it, it stinks of petrol, and there is a leak down the back that I haven't yet sourced. Before the jetting I need to do a pressure test and general inspection. If there is much needing doing to it, then I will the engine indoors to sort; it only takes an hour to get the engine upstairs. - I can do some work on the frame while it's out and I can do the engine mounts at the same time. BUT it isn't coming in here over Christmas, so it is currently in the naughty corner of the garden where it will stay for a couple more weekends at least. I'll update my thread when I get back to it, and keep this thread tidy for your progress, which is very interesting and best left uncluttered.
I suspect with your barrel we're getting close to the dark arts of it that you want to keep some detail to yourself, but the performance you can squeeze out is an inspiration in itself.

[mijapxman]

☺

[vespasco]

That all sounds very impressive
And it makes me want to buy a dremel for one of the few remaining 150 scooters out here

Nice to here its running nice

[pxguru]

Really pleased with progress. Will be back onto this next month to do the final jetting tests. Then that's it until I break it

You coming back to get your Rally out for the Summer?

[vespasco]

Well, I'm itching to get back on the rally.
I've got some catching up to do....but I'm not actually sure I'll be able to keep up with you tuning folks.

[pxguru]

Was still not quite right as the revs picked up at 1/4 throttle and felt a little rich. Opening the throttle a bit more cleared it. The run down from high rpm felt a bit fluffy and the mixture screw was at 1.5 turns out.
Reduced the pilot jet from 48/160 to 45/160. Re-adjusted the mixture screw, which ended up at 2 turns out.
Running really well now need to do some more motorway testing to finalise the MJ but that can wait until its warmer.

My new phone takes c**p close ups. Must be a setting for it somewhere

[sime66]

It's perfectly in focus (for the seat though).
It has gone very cold again; forecast next weekend looks more sensible for Spring-jetting.
Still watching your thread with great interest.....

[pxguru]

The 45/160 pilot just wasn't big enough. Was fine for throttling up but no good on the run down and way too lean on cruise. Going to put it all back as it was pre air filter. It is just drawing too much air for a standard air filter.

I have ordered a 26/26 Vortex.

I really liked the idea of it all being standard looking (SI carb and filter, SIP road, Iron 200 barrel) but with something like 22bhp. Just a minor change taking off the air filter and no one will know anyway.

Running it for now with an open carb "80's style". Jetting AC190, BE2, 50/160, MJ135, slide 04, 2.0mm drilled. Once I took that air filter off the whole re jet took one hour of riding and tweeking up and down the bypass. Going great now, just slightly over at mid, ready for the Vortex.

[sime66]

Always interested to see your jetting progress.

There’s a thread on (not so) Modern vespa if you (or others) fancy a look.
It’s our chum Oopsclunkthud again, designing and 3D printing bellmouths and investigating best geometry, airflow, effect of obstructions and also filter and lid options.
You might think most of it is OTT or not relevant, but it’s interesting to get other people’s ideas anyway – made me think again about how well the Polini vortexes would actually work under a low carb box lid, with the Idle screw right through it, and with the jet-access cut out - all interfering with intended bellmouth airflow. Here it is anyway (later pages get closer to his final model for Si20):

modernvespa.com/forum/topic57998

Notice what he’s done for a filter (so keeping bellows to frame):


3D printed item here (just for interest, not for 24/26):
www.shapeways.com/product/ZFBJ7HCAE/20mm-largeframe-vespa?optionId=451888

When you’re done, you’ll have to do a decent full rev-range dyno recording, so we can confirm the 22Ps.

[pxguru]

On mine I have the autolube box lid, so slightly more volume.

I feel the main advantage of a vortex is that the air enters in a more organised fashion. Similar but not like a ram air system where its funnelled in. Without the vortex the carb inlet becomes effectively smaller with all the turbulence surrounding the rim. What i have learnt so far, no standard fliter is running way better than with standard filter (135 MJ instead of 128)

As the vortex makes the venturi longer there will be more vacuum on the main jet pulling more fuel but as the jet sizes need to be bigger with the vortex it confirms that even more air is getting in than the increase in vacuum can supply.

Ingenious idea for a filter, wonder if it's ok?

Will do a recording once I have the new cylinder head on. I have decided that the compression is too low. I like to be able to cruise around town from low 20's in 4th gear and it can't quite manage like the Polossi does.

[pxguru]

Just back from a 2 hour ride about. The slight richness as rolling the throttle back on after run down was getting on my nerves. Got it off the end of the speedo while sitting up at one point. Going really great

Jetting now AC190, BE2, 48/160, MJ135, slide 04, 2.0mm drilled

[sime66]

That looks very similar to what was suggested for mine (I'll read back later, but AC185, BE2.....)
I'll go back to trying bigger AC once I've got back to where I was last year.
Anyway, I don't want to clog your thread up, sounds like you've had a productive weekend.

[pxguru]

Back with my other girl now and buying her presents. This time it is a Pinasco 26 vortex

Upjetted to 138 and could possibly go more. Seems to be running much better overall. Scooter is a tourer and really well behaved but can rev out when required.
I might go down to a 45/160 pilot next time out. Has a faint splutter as the revs build up and the main stack takes over. It is either the pilot or needs an even bigger AC. I know if it was a needle carb I would put in a smaller diameter main atomiser and that would sort it but in the SI carb it could be either. Whichever I choose first it will be the other

Jetting now AC190, BE2, 48/160, MJ138, slide 04, 2.0mm drilled

[pxguru]

Ran out of time working on it but we might just be down to the final tweek now. Has a wet cough at 3000rpm so will need more air and is still slightly weak at WOT and once the BE2 goes the bigger 142MJ (maybe 145MJ)in will help the lower revs not be too weak with extra air of the BE2.
Overall really impressed with this vortex, really does flow more air. Like having a bigger carb on. Has richened it up right accross the range.

For the record when I get back to it. Jetting is now;
AC185, BE3+2, 48/160, MJ140, slide 04, 2.0mm drilled

Next time out will be;
AC185, BE2, 48/160, MJ142, slide 04, 2.0mm drilled

[sime66]

Sorry if you’ve already said; I’m preoccupied with other stuff lately – is this with bellows to frame and no filter now?
Your jetting is similar, and looks close to final tweak; are temps on this one behaving?

[pxguru]

No filter at the moment just bellows. I have a spare ram air that I will fit under the tank when I get round to it but no great concern for now.
No temp gauge on this one. Doing it the old fashioned way by feel and plug colour.