Modern Vespa

I retarded the timing a bit, retorqued the head and went for the usual ride. Temps briefly hit 345. They seemed to recover more quickly when I slowed down. Change in timing didn't seem to affect how the scooter ran. I don't see any evidence of hot running in my piston photos. Not sure if there is something else I should look for or if I should just ride in and see what happens.

Sorry, I missed your message. I will stay under 300. My jetting is currently 50-100, 110/BE3/135. What should I try next?

Thanks!

Everything confirms the same thing. Might be spluttering low down but it's not rich enough higher up.
When rich enough the piston crown is black in the centre, with gold areas around the edge. Simply put, it's so rich/cool at the edge, the carbon doesn't stick.

Change the AC.
Check the fuel flow at carb height. Even if good flow when held at floor runner height it might be poor where the carb is. 0.5l/minute minimum.

Ok. I will redo my 110 to a 100 and check fuel flow.

I'm guessing the idea is to richen up the mid range by richening up everything, then reducing the main and pilot. I'm sure both will get smaller.

100 air corrector ready to go. Maybe ever so slightly smaller. After soldering up the air corrector, I make a pilot hole with a micro drill bit. Then I sneak up on the measurement with welding torch reamers. I check them with a micrometer. Digital calipers aren't accurate enough. Nice to be able to make almost any size jet or air corrector.

Fuel flow test is next, though I haven't had any issues with flooding, cutting out or hard starting since changing the fuel line and float needle.

Went for the usual test ride with jetting at 110/BE3/135 50-100.

CHT's hit 325 on the way out and quickly came back down when I turned around. On the way back, they briefly hit 340, but my carb box had come loose. It was idling strangely, it's hard to describe…like it was idling faster than indicated without really hearing distinctive firing of the plug. Wondering if I retarded the timing too much. I adjusted the idle and mixture screws and it was normal after that.

It feels boggy through half throttle, then clears as revs pick up. If I nail the throttle in forth, it slows, more like not getting fuel or missing than bogging. There was quite a bit of fuel on the back of the engine, probably from the carb box almost coming off.

ah man you gotta go longer, we all want to know how it does at 350

Probably nothing. According to the Scooter Lab site 320-380F is what scooters run at. But I'm still not really going all that fast. Max speed was GPS was 53.4, which is 60 indicated.

I did the fuel flow test: 1 minute with hose held at carb height which gave me 650 ml.

i just wondered if it was accurate there, not if you should run there (probably not)

Lol, next time I will strap my cast iron skillet to the cylinder head.

I put the 24/24 carb from my 200 on just to give it a try and as a point of comparison. I tried it before but the slide would hang up. I cleaned up the slideway and put in a newer flat slide. All smooth now and carb base measured flat.

Got the new bearings in the 200 engine and the clutch side seal. I ended up using a blue Corteco seal with some Loctite 603. Cush drive is rebuilt. New race on the crank. Just gotta button it up now. It went easier than the last build.

Finishing up the final sanding on the 200 and will bring it back to my garage at the old place and paint it myself. Worst that can happen is that I end up doing a lot of color sanding or shooting it again.

VW bus brakes are all finished. Steering box is now smooth and lubed. The boys and I are headed out for a 10 road trip to Quebec, New Brunswick and Nova Scotia in mid August.

Back to the 26/26 carb…mostly because that's the one Jack has been helping me with. The 24/24 ran great, but CHT's went right up. I realized after riding with it that I wasn't sure if I had drilled the float bowl passage. But it ran beautifully, as lean does.

My 2nd Runleader CHT sender died. I had to pull the spark plug to shut off the motor as the throttle had hung and it was revving it's nuts off. The other sender died when the plug wire came off while riding. Nothing on the senders was physically damaged. I don't get it.

I pulled the head last night to tap a hole for a screw-in type CHT sender. Found a small spooge leak between the cylinder and head. The aftermarket o ring I used wasn't in great shape. The top of the piston and barrel looked fine. Stupid question, but which way is up on the VMC center mount cylinder head? I have seen it mounted both ways. Not sure whether to install the sender above the plug or below…or if it matters.

Just about to close the cases on the 200. Nice to have a spare.

I think I found the shirt that is draining my battery. Dimmer switch wire running to the headlight.

First pic is the correct alignment for the head. If you watch that FMP video he switches the head around later saying he messed up and it goes the first pic way. I had that same question when I drilled for the CHT gauge as well.

Thank you! I guess that means the sensor goes above the plug.

Ok, found the info I needed in various threads:

Sensor should go in the lower space.

man oh man.

I had built a bike with a completely new engine and ended up selling it to a club mate in town.

VMC Stelvio 177, BGM 57mm crank, Polini Box Exhaust, Pinasco 24.24 ER carb, malossi cases, stock ignition, 23/65 EFL gear set. Case transfers match to the cylinder. The main jet stack is 160/be3/128. i cannot remember the idle jet, but not stock.

This guy has put 10,000 miles on the engine and has never torn it down. He did switch out the Pinasco 7 spring clutch to the VMC Molle. The engine is consistently being ran 60-65 mph outside the City. Initial CHT readings are 300-325 at 65 mph.

Not saying anyone is wrong, just my experience.

Head is hotter nearer to the exhaust port. On air cooled bikes it's usually the front, small frames the back but large frames the bottom.

I believe you. I haven't been trying to make it complicated on purpose. There have been a number of jetting combinations that have made it run quite nicely, including a combo similar to what you mentioned. I have been trying to figure out solutions for the high CHT's. I haven't found the ceiling yet. Highest has been 350F.

Timings are:

Transfer: 121.6
Exhaust: 177.8
BD: 28.1
Squish 1.2mm

Passed the pressure test.

Timing was set T 18* but retarded to 16-17.

Case ports aren't matched.

If something jumps out at you, give a yell.

I don't understand why your timing is so retarded.

Someone suggested it to help lower CHT's.

But temps didn't come down so timing isn't the issue. IMO 16-17° is too retarded timing for the relatively moderate level of tune you have. You're putting heat down in the barrel instead of up in the head where it better cools and dissipates.

I will set the timing back where it was at 18*. It didn't do anything for CHT's. Worth a try.

He's riding with a 60mm crank, 26/26 un-reworked Spaco carb ( ), reed intake. Different animal.
And a cylinder head leak.

The leak…Didn't look big. But still a leak. I mentioned the aftermarket o-ring I took out. It was wet with fuel and crumbling. I think this was due to the cylinder head loosening and combustion gasses burning the ring. I now have the correct o rings from VMC.

I am going to pull the studs, check/cleanup the threads and set them in the case with loctite.

I also muffed tapping the hole for the temp sensor by drilling it free hand. Hoping I can set the sensor in with JB weld. If not, I will have to tap a larger hole and screw in a copper sleeve I made.

Ray8: You mentioned going with a reworked 26 carb. Do you have a link?

Thank you.

Leak of no immediate concern. Just make sure its tight.

Whats the jetting progress?

Raining all day here today, so hoping to continue jetting tomorrow.

Ordering this temp gauge from Koso North America. Unfortunately the sensor that comes with it is for UK pipe thread, but you can buy sensors in any size.

https://kosonorthamerica.com/product/dl-01t-temperature-meter-2/

I had the same oil dribble on the VMC. CHT shot to 377 and soft seized.
"False torque" using those optical tuning nuts.

If you still want to ride with a 26 (25?) carb and can't get that Spaco to work, both the BGM faster-flow and Pinasco ER are popular. The older BGM's had a 1.8mm bore to the mj. They may have changed, but check with a drill bit.

I'm not saying you can't jet a Spaco out of the box, but I have three collecting dust.
Could not get them to work. I've also seen the amount of aluminum bits that come out of the channels of an un-reworked one. It's wild.
Of course, they do more than clean them. Read their descriptions.

Sorry, I know nothing about reed intakes.
You're shifting torque to the left with a larger bore, though. I'm riding with a 22mm sleeve on my BGM 177 and it's as stock smooth as a kitted bike can get.

If that air leak isn't the cause of your higher-than-fun CHT's, try a larger fuel # on the pilot jet. 50/XXX seems too small. It can be rich in the equation/color the plug, but not able to deliver enough fuel to support the main stack with fuel in the mid rev range. A simple way to see this is imagine there were a 10/25 jet.

Alternative to finding the mysterious splutter while screaming:
Take it (with a 140 ac ) to your dedicated (the one you can go back to and compare things later) hill with your set of mj's. Whichever pulls smooth (from short shifting on up) WOT with the most power is your rich jet. You can leave the airbox cover off while playing here.
I've seen more than a few with your setup in the 140-145 range, FWIW.

Have you tried putting the drilled filter back on?

Spec squish is 1.4.

https://www.scooter-center.com/en/carburettor-bgm-pro-faster-flow-dellorto/spaco-si26/26e-oe-25mm-vespa-px200-type-with-autolube-bgm8572?number=BGM8572

https://www.scooter-center.com/en/idle-jet-set-bgm-pro-dellorto-type-9892-si-58-60-62-65-68/160-bgm857kt?number=BGM857KT

https://www.scooter-center.com/en/fuel/air-mixture-screw-bgm-pro-conversion-short-si20/20d-si24/24e-si24/24h-thread-m5-x-0.50mm-thin-pin-oe-0.65mm-type-vespa-px-with-slotted-screw-used-as-conversion-fine-thread-long/hexagon-to-fine-thread-short-slotted-screw-bgm7305?number=BGM7305

Thank you, Ray8,

I will keep the carb suggestions in mind, if I can't get this one to run.

The pilot jet: Wish I had put a couple more of them in my order from KMT. I could always make my own in the meantime. I think you are saying that the 55/xxx may provide a rich enough mixture, just not flow enough of it.

Shifting torque to the left? You mean lower down? Could you explain this more? At one point I had a combination of jets that moved the throttle range up, so that cruising would be closer to half throttle, rather than 1/4 throttle. This seemed to help CHT's.

I like the hill suggestion for finding main jet. I hate screaming down the road in 2nd gear.

The leak…The torque definitely loosened at some point. I'm using regular nuts now. Currently waiting for temp sensor stuff before I put the head back on.

While waiting, I got the 200 cases back together. The crank wouldn't turn freely and I suspected the clutch side bearing wasn't aligned. There is no place for it to bottom out like on LML
cases. Turned out to be the crank cheek bonking against a high spot of JB on the edge of the rotary pad. Shaved it down with a razor blade, but had to split the cases. Nice and smooth now.

Couple observations.
Though it's been a process - suspect this will all pay off on many levels.

Sifting through the noise - what stands out to me:
- hard to make this thing splutter - suggests flow restrictions were encountered in main circuit
- Rays experience with manufacturing swarf on other Spaco's: perhaps related to prior point.
- Head leak: if fluid can exit, air can enter…

I don't think you're that far off.
There is a barn burning, 285 degree, 1/3 throttle, 55mph, set up, in your future - provided you eradicate all leaks, and manage to get good flow.
¯\_(ツ)_/¯

Oh- and interference with pad.
- why I always recommend using release paper as gap control for epoxy.
- why having cases closed and torqued during cure - can be helpful

The bgm set I linked to is common. Many find themselves happiest between 55-60/160 on a rotary 187. On a 26 carb with reeds I don't know.

And sorry, I meant to the right with a 26
Larger bore = less air velocity = less negative pressure to draw fuel.

Once you've found your rich/safe mj, start with a higher numerator (fuel) pilot jet and work your way down with a given denominator (air corrector).
Similar to the main circuit.

You can try different air correctors later. Smaller number, richer emulsion, more overlap/influence over the throttle range and vice versa.

Not easy. Took me six weeks to sort out jetting using the Lemarxon parts (22mm sleeve, slides, atomizers).
Three weeks measuring, drilling, reaming, and re-labeling the jets I had.
Three weeks to find best jetting.

Funny story:
When I thought I was going to only have one vintage bike a few years ago I asked the group, "what am I going to do with these useless-to-me brass bits (thought I was done )."
C'man22 replied, "keep those, they're gems."
I've since used every one, save for the 190 ac.

Thank you,

Finally got some decent threads tapped for a M12x1.5 CHT sensor. Hopefully it will arrive soon. It's been one of those side jobs that eats a lot of time and has held me up.

Old parts and new parts always get the scalding hot water and Dawn treatment followed by compressed air…especially carbs. Lots of metal debris gets left in new parts.

Live and learn with the rotary pad. At least it worked out.

Hopefully back at it this week.

Nothing new to report as parts don't arrive until tomorrow; jets, CHT gauge that will fit the threads I tapped in the head. A new cover for the Stella seat! Foam is in great shape.

I will wire the new CHT gauge for realz through the tunnel to avoid breaking sensors. That hasn't helped things.

Just to recap:

Fuel flow: I did get it to splutter doing the second gear test with a 110, be3, 138. 50/100 way back, so I think that fuel flow is probably ok. Will redo as it will be different with a 100AC and 55/100 ij.

Other things to try: drilled air filter (currently no filter).
Flat slide.

Venturi?

I don't think a venturi is offered for the 26/26. When I mention going to a bigger carb, my bus guru friend asked if it was possible to change venturi size.

Air leak: studs held in the case without turning the last time I took off the head, so I think they are good. I found hex head bolts to replace the Allen heads so I will be able to torque them properly. I also have new VMC head gaskets.

Sorry to rattle on. Part of the waiting for parts blues.

It's like watching paint dry. I know, but I'm getting there.

Got the Koso sender in the head. The M12 version needed some filing to fit. The 1/8 BPT version will fit a 1/8 NPT thread or M10x1.0 thread. Going to mount the gauge temporarily near the handle bar and later on the glove box when I (hopefully) don't have to look at it as much. I like the big bright digital numbers.

Whilst snaking the sensor wire, I checked out some other wiring issues on my list. My battery won't charge and goes dead without putting it on a charger every so often. Stator/regulator output is great until the headlight circuit is hooked up.

Chandlerman suggested that a short in the headlight circuit might be sucking up the voltage, with ensuing wire crispy-ness likely. See below. All crimped, soldered and connected now. Fingers crossed. Another detour, but worth it to solve such a nagging problem.

Even if that wasn't *THE* electrical problem, it was definitely *A* electrical problem. I'm surprised you weren't blowing a fuse (probably the one under the horncast, super-conveniently located) every time you went over a bump.

Lol, I think that fuse was removed. There is one near the battery. Couple other things to chase down, but I feel like I got it surrounded. And I've reached the point of having a lot of the wiring memorized. The horncast has no junction box like every P series ever. They are all stuffed into the head set.

Finally got everything back together. Hoping the rain will stop long enough for a decent ride. I had to use a little JB weld to secure the sensor to the head, just on the top threads. Gauge seems to work. Not sure if I fixed my charging issues. The Stella wiring is so pointlessly complicated. The headlight and gas gauge are on their own circuit…a grey wire that makes many stops powering powering assorted bullshit before it reaches the headlight…one of those somewhere…

When you get your test run in - you are going to see much higher temps from the in head gauge.
For your piece of mind - consider running the old CHT under the plug simultaneously.
You can unplug the new - and plug in the old - to the same lead - while the motor is running.

JB weld on insert should be fine.
It gets its temp from the tip.

Thanks. Will do. I figured it might show higher temps.

I still don't know what the max temp should be for the inset sensor on an aluminum jug.

I was up around 360 for a while over the weekend with the smallie on the highway. Now, I'm thinking I need to richen up my half throttle. Once you go down the path, the tuning never ends.