Modern Vespa

All good! I definitely welcome more input into the discussion...! Getting to this setup, (on a personal level) has been a long road...

Super glad to get inputs from everyone.

Yeah I'm using the stock 4.5 slide... I was seeing folks on the GSF site using a 6 slide... and I've seen a lot of people end up with the 4.5... so I was wondering if it's worth getting one as they're not cheap... so wanted to jet it first so it runs and tweak after (if needed...)

Just put the fuel pump back on and took the head gasket off, will do the runs I had before and see how it goes...!

With the squish at 1mm, the torque is much better... should've started with that...

But seems like it prefers to run lean... I thought I was suppose to go richer with the jetting...

Retested the previous needle work... all seems to be the same, just now, it's even more revver and more responsive... got to 9200rpm at 3/4 throttle

(But the spooge is back after installing back the fuel pump... I'm going to add a longer vacuum hose and see if it solves the problem)

For this 1/8-1/4 step, ended up with the smallest pilot possible, 30... 1 turn out, revs out (1.5 turns would bog and hesitate before return to idle) and put in a BGP, BGN, BGM needle and at 1/8 the BGP and BGN felt pretty similar... (BGM was way too spluttery...) BGN might have been smoother at 1/8, but at 1/4 it was spluttering... the BGP seemed best from 3/16 to 1/2...

But the pilots couldn't hold idle that well... stalled after about 20secs of stopping after riding... blipping the throttle at standstill would be fine though

Feels nice doesn't it? This is as expected. next time you take the cylinger off, slip on another stock Malossi gasket. This will make the squish 0.8mm. Once the jetting is finished, so will the spooge. You make me think P isn't weak enough. Try a BJP needle. This is the best compromise that is a legal combination. Shorter taper will make the diameter feel bigger. Nothing so good in A taper. If this works you'll dodge changing the slide. The weak pilot is just for set up. Keep doing what your doing and no high speed runs. Note for the other 3 readers, lean pilot doesn't hold idle.

Head and piston are looking great. Nice an black keeps it free from detonation and holes. So they stay put, I stick alignment sleeves in with Loctite on one side, usually the head.

Wishing I used the stock gasket now on the bottom to get the squish tighter... getting good returns now

Yeah I think the BGP isn't weak enough either... there's the BGQ, but something tells me it might be too weak near 1/2 throttle... will have to make a needle order then... but can't seem to find a BJP... might have to be the slide then... but that's like 60quid

I used hylomar for the cylinder head... hence the blue stuff. Just a extra layer between the o-ring. The alignment sleeves are a must... my first build, when I had to pass it to a mechanic, he forgot to use the sleeves and the piston chipped away the head and left a hole straight to the o-ring... that's never gonna happen again

Found an AJP in the US. This would be better.
https://www.jetsrus.com/individual_parts/017_415_su.html

Ordered the slide (might as well, knee deep in it now) and the needles now...

Whilst waiting for the carb parts, I went and added a longer vacuum hose and fuel line from the pump to the carb to mimic under the tank to see if it helped with controlling vacuum and pressure.

(But hose setups on other bikes would be shorter I'm imagining?? Anyways...)

Making a mess of the hosing because I didn't want to cut it yet... and the spooge seems to have gone... because it's collected in the vacuum hose!!

Seems like the spooge is collecting in the crankcase, probably because of the jetting at the bottom end...

About to give up on this and stick the PHBH back on and call it a day...!!

The ID on that hose is too big for a vacuum line. Looks like an 8mm. The volume of the pipe adds to the crankcase volume. I use 3mm ID line and it seems to work fine. Better to put the pump under the tank, then you can really forget about it.

Which needles you buy? If you have the 6mm slide coming the diameter is less important now. We could have avoided that but it would have taken more than £60 of time. The BGP might work but the AJP could be better. Always end up with a pile of needles. Once you can set up a large flat slide carb properly, you'll use one on all your projects.

The spooge will go away when jetted better.

Might be the angle of the photo and no reference to anything else, but the ID on the hose is 6mm, the Mikuni pump is a 6mm so just stuck with that... I have a 8mm from the tank to a 6mm barb going to the pump (not that it makes any difference at the bottom of the tank...)

Ordered the BGQ and AJP, literally covering all bases...

Here's a video of the hose spooge moving around... especially obvious at the end... around 11secs

https://youtube.com/shorts/OL_tjs8Ka_c

Allens Performance in the UK has the AJP N427-48 in stock, and maybe quicker delivery and less on postage. I tend to get most of my Keihin bits from Allens (slide, needles), and main and pilot jets from KMT

When mine emerges from winter hibernation, it's getting a Meggele v2 head (waiting for delivery), an extra 0.5mm cylinder lift (129 TD), and a Vape variable. Will follow your thread and Jack's wisdom for some carb fine tuning

That Meggele v2 head looks great with the extra fins...

Interested in the vape too, but most likely be going with a road version... keep it simple...

Good to know another channel to get needles and jets

6mm hose is less bad. Leave it until the end but will need revisiting.

While waiting for needles (and if you brought internationally, that might take some time at the moment), you could set the float height.
Just out of interest try to read the number off the float needle seat. Something bigger than 250 is good but not bigger than 300 is better for this set up.

Float height. This is 16mm on your carb. From gasket face to float arm, when float is closed under its own weight, is traditional. For yours with the needle diameter spooge thing you could reduce this a little maybe 18mm (more is less).

After that, for a Sunday ride get some numbers for your main jet. Fit your BGP needle clip 3. Start with the biggest main jet in your box (hopefully 190) and do WOT runs in 2nd or 3rd gear reducing jet one at a time until the splutter at max rpm has just about gone and stop there. check clip 4 is still worse than clip 3. Write down the main jet number. leave it fitted.

Got it for the main jet... will give it a go later. Looks like I need a long long road to go at again...

For the float seat, it's the one that came with the carb (brought from scooter center) it says 38 on it... I'm presuming it's 3.8... which looks huge... something I should be changing? (There doesn't seem to be other sizes)

The float needle is barely big enough... I can see the ring it's seated on... it's really low down on the rubber pyramid...

I set the float height at 16mm when I first installed it and I've had to go higher I think it's around 18-20mm now) because of the angle of the carb and fuel was coming out of the overflow tube... I'm wondering if it's worth going even higher on the float height but I don't want to have fuel starvation and with the pilot at the back, I'm thinking it might not be getting the right level of fuel...

Would seem you have an issue. Carbs are designed to work at angles. More than you might think. If you are leaking from the breathers there is an issue. In this case it's a 3.8mm seat and a pump.
Here's one I found. Same as kehin. This is 2.0mm, so a bit small. 2.5 is available somewhere.
https://www.ebay.co.uk/itm/2-0-Float-Needle-Valve-Seat-kit-KEIHIN-FCR-35-37-39-41-FCR35-FCR37-FCR39-FCR41/273618262584?hash=item3fb4eb5a38:g:JoQAAOSwfwpcGqSu

They lever out with a small screwdriver at the indent in the gap.

If the float height isn't right the fine tuning will be difficult.

Ah, its from the float bowl overflow tube not the other breather tubes...

The 2.0 and 2.5 seem to be for the FCR carb... i found those too, not sure if it fits... the PWK AS35 seems to only have the replacement 3.8 and no other sizes...

I had a search. Smaller than 3.8 will be not PWK but seems like an FCR one will fit. Need to pop yours out and compare it to all the many types to find the kehin one. 3.8 is never going to hold back a pump.

That doesn't sound too optimistic...

Surely someone's managed to tame the PWK airstriker...

Waiting to go for a few runs to figure out the main

Double checked the float height, bang on 18mm...

Leaving the float height at 18mm, I would run the pump with an open bypass line until the jetting is roughed out.
How you get on with the main?

Open bypass line without restrictor? Will give it a try

Went for a few short runs... but need a longer road...!

Tried 185, 180 main, spluttery past 3/4 couldnt get to WOT properly and ran out of road and had to give up and refuel...

Will be trying it again tomorrow...

To get near the correct jet, the runs can be done in 2nd gear. Only when getting closer to correct are the longer runs needed.

Keep looking for a 250 float needle. There will be one somewhere. Everyone must have similar issues. 3.8 is great for gravity fed but not ideal with a pump.

Small hiccup... seems like my tacho has failed... went for a run and at 55mph (gps speed...) it was reading 4000rpm... looks like it's earthing somewhere along the frame... must have snagged on something...

Ordered a new one from Amazon with CHT...

What's the best way people are routing the wires for CHT? I know some are using the tacho via the ignition, which is probably a lot more accurate than an inductive Rev meter...

Don't need a rev counter to adjust the main jet. Reduce the main jet carefully until the wot spluttering barely stops. This is all you want for this stage.

Get what needs to be done with main jet, just need to allocate some decent time in between work to go for enough runs...

Would be nice to know what revs I'm hitting to keep an eye that things are able to rev out or not...

Back after taking a break from the PX (work commitments...)

Received the 6slide, and stuck a 45 pilot just to do a quick ride around and it goes like the clappers...! front wheel comes up in 2nd gear...

Anyways, back to testing for the main jet stuck a 35 pilot back in went through 175,170,165,160 main... gonna try a 155 but will test the 160 a bit more as its scarily fast in 2nd because it's clearing up... can't tell if it's still spluttering properly...

Try a plug chop at 160 and see how it's doing. The damage happens quickly. 160 is getting quite small.
Keep the 6 slide out until the end. Run on the 4.5 until you know you need weaker.

Will try a chop, luckily I brought a bunch of new plugs last week passing some garages... see if I can manage it tonight!

Looks like this is on hold till I sort out the gearbox/clutch issue