Modern Vespa

That's what I always use. New o-rings arrive today. Some new hardware and a bit more finesse. A little anti-sieze on the allen bolts as Mr Gick suggested.

With hard to seal things I get more anal about torquing and sneak up on it with lower torque values. I leave it overnight and check it again. Then a couple times in the first 100 miles or so.

It works for the VW engine. Exhaust headers are especially hard to seal and wreak havoc on the valves if not right.

I also noticed when sealing the reed block for pressure testing how easy it is to get it wrong. It's not how tight the carb nuts are, but how evenly they are tightened. This is especially true on the Stella which doesn't have the screw to hold the carb box down.

O-rings came in and it looks like I measured incorrectly for the exhaust flange. Snipped the o-ring, super glued the ends together and let it set up overnight with kopper kote. I can always replace it later if needed. If it passes the pressure test, I'm just gonna run it.

Really hoping it goes better this time.

Frustrating.
McMaster Carr, of course, sells them 20 at a time, and every time I miss order, I get another bag of high temperature, O-rings.
And I think, the description should have read:
" one size fits nothing"

I think I either measured wrong or mistyped the measurement. Was multi-tasking.

Case sealed up and was still holding pressure 3 hours later, even with the reed block installed. Gonna call that good and get it back in the Stella.

fingers crossed emoji
heart emoji
keep us posted emoji (use your imagination)

Thank you for cheerleading. I will definitely keep you posted. I spend more time posting than wrenching or riding anyway.

Just to recap:

Lowered timings slightly
Increased squish from 1.2 to 1.5mm

Replaced the cheap clutch side seal with Cortico blue+loctite 603.

Used every leaky VW sealing trick and my personal stash of designer loctite to seal up some nasty oil sucking.

Replaced the Allen bolts with better quality + antiseize. Fabbed a socket to accurately torque them.

Removed reed block center bar, reed stop and matched opening to carb box
Rebuilt autolube (which I will test)
Switched to 24/24 carb

Will recheck TDC and timing.

Re the leaky exhaust stub: It looks symmetrical, but matched up better with the cylinder exhaust port when I turned it 180*. It also stopped leaking.

Fingers crossed.

All buttoned up now and rechecked timing marks. This is how I set it up last time. Marked TDC on the flywheel cover and measured 18* BTDC with a degree wheel. It lines up pretty closely with the the factory marks in the cover and flywheel. So when I am checking with a light (at about 3000 rpm) the flywheel mark should light up when the marks align at 18* BTDC. Just checking I am doing this right.

Looking forward to having this engine back in the Stella. Apart from the high CHT's it ran well with nice power. I'm hoping to be able to ride it to work which is 15 miles of 55-60mph cruising.

Looks about right.
I'd keep the following in mind: there are easily 1-2 degrees of slop in the measuring.
1. The parallax effect
2. Any timing movement your electronics may have.

Is this stock points and condenser?
Or something else - I've forgotten.

Bottom line, u can make adjustments to increase or decrease ignition timing by carefully scribing the stator position before loosening and rotating.
1mm = about 1 degree.

Take a really good picture of your spark plug that you can zoom in on - before u start.

Check again as you tune in- looking for any evidence of very small aluminum balls from pinging.
Back off timing a hair of u see that ur getting build up.

I'm running a stock PX stator that I bought new last year and the standard Ducati ignition coil. Stator works well, keeps the battery well charged and all the electrics work…on a Stella!

Using a timing light on anything is kind of sloppy. The Parallax Paradox!

10-4 on getting it in the ballpark and paying attention to feedback from the engine to dial it in.

Chuckled

I have been riding around with this engine in the Stella and things are looking more promising.

I went out for a ride yesterday just to do some jetting and ended up riding 25 miles to visit a friend out in the boondocks. He made me call him when I got back home again and offered his truck for rescue if needed.

Engine was in and out of spluttery rich, but highest temp was briefly 320F and mostly around 280 or lower. I tested out a couple main jet changes, but mostly I just enjoyed the ride as I wasn't as worried about overheating. Beautiful day on twisty roads over rolling hills and through mountain hollows…exactly what I've always wanted from these machines, so I could live with it not running its best.

Jack has been talking me through jetting. It's making a lot more sense now and I feel like I am better understanding the feedback the engine is giving me. Still waiting for parts for the VR-1 build, but I'm looking for a win with this one first, so there's no hurry. Makes sense to see one tuning project through before taking on another.

Thanks for reading along.

I have been riding with this and it seems to go better and better. Highest temps I'm seeing are 315F, but mostly lower even as I have worked down toward leaner jetting. Still dialing it in with Jack's help. CHT's rise and fall rather than just running away and may even be going down with sustained higher revs and this is with a sensor screwed into the head.

The real test will be riding it to work…the ride I had to abandon last year because of overheating and hanging high idle. I was going to do a test run first but maybe I'll just go for it.

The issues with this engine had me thinking more about air leaks. Some random thoughts:

A successful pressure test is a good start but not a guarantee. Things may change when the engine is warmed up or after a number of heat cycles.

The signs of an air leak seem more pronounced when the engine is really warmed up and heat soaked. An air leak might not be obvious just cruising around town.

Tuned engines seem a lot more sensitive to the effects of minor air leaks compared to stock engines and more prone to developing them.

I did 3 pressure tests on my blue Allstate so far after putting the Pinasco 177 on it. Twice before start up and once after 3 heat cycles. Will do another when I change the gear oil after break in. Like you said, they do pop up.

Orwell- it looks like you've solved the mystery leak - and are finally working the motor to the desired tune. Awesome.

Hope u get a chance to ride it to work before the season is over.
Should be a joy - and confidence will build as you get used to it being far more stable.

FM-Yes, they do pop up, but it's often not the case seals, so hopefully an easy fix.

CM22: Yes, it's running in a much safer heat range now. Jack would like to see it closer to 280 when the jetting is closer. I'm pretty sure the leaks, both air and oil were the biggest contributor to the problem. Matching the intake and a little detuning may have helped a little too.

I've really gone around in circles with both bikes, but I don't consider it time wasted. More of an investment in the skill set required to ride one long distances into the boondocks without fear.

Still riding the Stella with this engine. It's been a long time that it's been fun and reliable. Jetting changes have been sort of slow motion refinement among a lot of good rides. The trend has been toward going faster and running cooler. It's surprising how far it's come along compared to what it was last season.

So far we are at: 55/100, 100/be4/130. CHT's now top out at 303F with the Koso sensor screwed into the head.

Glad I decided to see this through. Jetting and setting up an engine is baffling if you've never done it before on a go-cart, dirtbike, etc. Takes a lot of practice to develop that tuning ear. It's definitely worth taking the time to do it.