Modern Vespa

He also has to tear down (and later rebuild) a rebuild with 1k miles on it, before finding someone to weld it up in $witzerland.

you showed a video where the engine appears to be torn down.

regardless, why half ass the job?

yeah, there is something to that. . . California pricing. i hear ya. Come to the midwest and specifically Indiana, we will treat you right & fair.

Shipping is pretty cheap in the US, no reason not to, especially something as small and sturdy as a Vespa engine. I live in northern New York and shipped all my bus stuff to DPR machine in southern California. Perfectly machined crank, balanced and matched everything, balance of rotating mass. It was worth it, everything was dead nuts right on. What is my time and aggravation worth trying to have it done locally by people who can't or don't really want to.

Like Mr Gick, Jose at DPR knows what he is doing, knows how to pack stuff so it doesn't break, takes pride in his work and answers his phone old school style.

What more could you ask for?

I'm at 48/140idle, 128/BE4/140ac with drilled filter. Smooth transition from idle jet to main stack with the BE4 now (had a slight bog with the BE3). Plug and temps look good.

Great….Have you run it in yet or still getting there?
What sort of temps?

Recommended run-in is one hour

Sorry, I don't have my temp #'s remembered well. Dropped around 10-15 degrees with the current setup, though, on my known 1k ft climb. Downhill gear-breaking temperatures are dropping.

I'll take it back up this week and give you some numbers.

So I finally got my engine back from a professional Welder that welded the hole in the inlet casing.
Beautiful work and only cost 80Euros and didnt even need to split the cases.
he made a special protective metal sheild to ptotect the inlet and crankshaft before welding.
Swiss Engineering 👍.
Fit the Bgm cylinder and head today…,
I checked the gap between piston and cylinder head and have 1.1mm.
I used the 0.4 mm base gasket and supplied head gasket. I would of expected 0.9mm?
Should I leave it at 1.1mm or use the 0.2mm base gasket?
Recomended gap is 1.0mm will 0.1mm make much of a real-world difference?

Cheers
Robbie

Yes….Cylinder Head off and a 1.5mm length of solder taped across the top of the piston. Head bolted down to 16nm and a press on the kick-starter for a full circle of the crank.
Cylinder-Head off and measure the compressed edges…..

Robbie - it will certainly run with 1.1 squish.
Couple questions and a comment.
1. I recall BGM recommending .8 squish?
2. One trick I use to improve my measuring
A) Use a razor blade to cut the solder. this will give you a very flat square edge.
B) Use a longer piece of solder. shape it with a U in the center and let that U portion come up into the head.
C) Now you don't have to remove the head to pull the solder out and look at it. The square razor blade cut edges will allow it to sit right up against the cylinder wall. NOTE - if you look carefully, the solder will have bulbs on the end where it gets squished between piston and cylinder wall. DONT measure this pregnant bulb - but as close to it a you can. This is your squish.

BGM is excellent for torque.
At some point - if you lift it too high - you will lose both torque and HP at lower revs.
Where are you in Switzerland? Do you have hills to contend with? Careful about lifting the cylinder too much - it will push the power band too high and make you have to shift down a lot.

Thanks Charlieman

I maybe made a mistake measuring as I measured the solder taped across the top of the piston, and I remember not cutting the solder to the very edge of the sides of the cylinder wall, maybe a mm or two gap left of each side…

I measured the squish with both the 0.4 base gasket, head gasket and head torqued down. But Ive seen others online measure the squish with no gaskets and just the solder.
But I guess both ways are fine…
I used the 0.4 base gasket as it normally is the most used and should give a squish of 0.9, but I have 1.1

Scooter Center say on there website:
"Empfohlene Quetschkante: 0,8-1,2mm"
So I should be in the ballpark….

I live in Solothurn which is flat, but maybe will take on a few Swiss mountain passes after its run in?
I also have this temp gauge ordered to keep an eye on the temps..

https://www.sip-scootershop.com/en/product/rev-counter-polini_P1711001

Thanks Again

Great!
I like 1.1mm with the same setup as yours. It's safe(r), and still pulls like crazy.

Thanks Ray…..
Will leave it at 1.1 and see howvit runs…
Really excited to get this motor running again 👍

Motor in today….
Just a few little bolt ons and should be running next weekend….
Looking forward to getting this engine running.

As others have noted, 0.8-1.2mm is the recommended squish. I use a similar approach to CM2 for measuring.

One additional thing for max accuracy is to put the solder on opposite sides of the piston from each other so the piston stays square in the barrel.

As to port timings, TD of 124 is what you should shoot for, I'd say. I had my BGM at about 126 TD with a 60mm crank, .9mm squish, and an old PM tuning tuned pipe and it was a beast for torque and rev's.

I added a base gasket and upped the port timings to about 128 or 129 the last time I had the cylinder off and have been regretting it--like CM2 said, you go too high and you lose low end power and torque.

I also lost peak power, so the change was a fail all around. More annoyingly, because the power band starts higher, I can't stay in 4th gear at 50-55 MPH, so I wind up downshifting a lot on the highway. I also live in a hilly part of the world, which makes the situation even worse.

You'll be rolling in no time!

One last suggestion, if the cylinder is on the bench, get some hi-temp black paint and paint the outside of the cylinder. It increases the cooling and will lower your temps by 10F or more.

Thanks Chandlerman really appreciate the advice.
I will leave the Squish at 1.1 as a start and see how it runs.
Im just looking for a tourer with good torque that can sit comfortably on 60 mph.
With the 23/68, Polini box and 24 carb I think I should be able to reach my expectations….If not I can play with the squish after its run-in…

Thanks again..

I wouldn't have guess this, I would thought the opposite was true. Is dissipation on a painted surface more efficient than raw metal? also, as paint will "smooth" surface a bit, effective area will diminish no? but learning every day, thanks for sharing this.

I agree it's counter-intuitive, but black is much more dispersive than the bare metal. I tested it a few years back when I put on a new jug a few years ago after I blew up a BGM revving it on the stand and saw an immediate drop in my temps on an otherwise unchanged motor with the new painted cylinder.

Spot on, Black body radiation:

"A perfect blackbody has an emissivity of 1. In other words, the radiation of the target is 100% emitted from the target surface ... Most polished metals have emissivity values near 0.05 to 0.1. Tarnished, oxidized or otherwise corroded metals have emissivity values ranging from 0.3 to 0.9 depending on the amount of oxidation or corrosion"

https://www.flir.com/discover/rd-science/use-low-cost-materials-to-increase-target-emissivity/

Regards

Robbie,
Your actual squish is probably in the .8-.9 range though - as you measured in a few mm from the edge.
Next time - to get a more accurate measure - you can put the solder right to the edge of the cylinder with a square cut.
The bulbs formed on the end of the solder piece from the process, let you know you are truly measuring the the squish (just inside the formed end bulb).

That said - it would be fine at 1.1 as others have noted - even if its a little smaller.
The BGM is going to be a great cylinder for you.
The CHT gauge is a good idea as well.
The BGM head has a place for a sensor to screw in.
That is the nicest way to do it - so its not in the way of your plug when you take it out.

What were you running before?
What jetting changes if any are you making for this cylinder?
You want to be careful not to run it lean...

I was running a Pinasco 177 Alu…..the first generation. It was a real dissapointment.

Jetting wise I got some good advice from Jack as a starting point…
no air filter with standard carb cover and rubber bellow connected to the frame.

AC120
BE4
130MJ
pilot 55/160

I will order a venturi and use as above once run-in.

Cheers

Well - Jack is the resident expert - so that's wise.
One question - did you drill out your carb float bowl hole already?
My experience is that above 120 MJ, the carb starts to be the choke point rather than the jet - making a 130 behave more like a 120...

Yes carb drilled out to 2.5mm 👍

Your jetting will start you out rich - just where you want to be.
Don't be disappointed - there will be plenty more in it.
If it's absolutely just spewing wet greasy stuff out the tailpipe and spluttery to run (which it might be) you can always step it down a little.

Sounds like you are on the right road.
Look forward to hearing your view after you get it running.
BTW - did a bunch of work not too far from St Gallen.
They take their speeding tickets seriously there...
🙂

Yes I can imagine it will run like an old tractor 🚜 spluttering and chugging, but as you say better to start way to rich than the other extreme…

Yes here in Switzerland the speeding tickets are expensive, but then so is everything here 😜.
The worst thing is when you start modifying any vehicle. It would be easier if we were in the EU then you can change parts pretty easily as in Germany. There, all the parts need a TUV certificate from the parts manufacturer which most parts have.
Here in Switzerland they dont accept EU certificates so its a real pain in the butt.
If your caught with anything thats non standard then you are in deep trouble 👿…
My PX originally had a Kat exhaust so I have to rent one every three years when I need to go through the regular MOT safety check.
I will need to change the cylinder also back to 125 otherwise they will have a heart-attack when they test it with the BGM 😝…

I recently changed the handlebars on my BMW F900R.
I took it for the regular safety check and showed them the new fitted handlebars. They failed the test.
I then needed to get a written letter from the shop stating that these Rizoma handlebars are suitable for this bike.
The re-testing costed another 50 Euro.
The next guy making the test said that I also needed a letter from the BMW garage that they had fitted the handlebar according to the manufacturer specifications 👹.
He nearly had a heart-attack when I said I fitted the bars myself…
I then needed to ask the BMW garage to check that I had fitted the bars correctly and to write a letter stating this. Another 50 Euros and finally accepted.
One tester can say one thing the next tester another thing.
You basically have to treat them like god and smile.
I had a JL expansion chamber pipe on my 200 a few years back but the risk was simply to high that I would have serious problems if I came in a control or worse was involved in an accident.

Now I make modifications that look original and that wont usually be noticed…
A Wolf in Sheeps clothing if you like 😜

But as they say…No Risk No Fun

Robbie, happy to follow this thread, your project almost done!
Curious to know if you ended going to the SIP speedometer? Very convenient to have all the gauges in one place.

Man, you have to move to Portugal, I have a friend that had a BMW K1300R, while riding he was ordered to stop aside by 2 police motorcycles … they wanted to look the front swing-arm closer

We don't have inspections for motorcycles, I think there's a law in approval for periodic inspection on +125 cc …
I'm safe with my 177 "125 GTR"

Hi PSMA,
Yes Portugal must be fantastic…

No I didnt go with the SIP speedo for a couple of reasons.
1) I have heard they can be problematic. Im also not impressed with the quality of some of the SIP parts Ive recieved in the past.
2) I quite like the look of the Polini temp and rev-counter guage.
Simple and easy to fit…

I have one on the way..

https://www.sip-scootershop.com/en/product/rev-counter-polini_P1711001

Cheers Robbie

Yeah, I've seen that one, looks great as the price …
Thanks! Keep us posted with progress, great work so far

That wasn't a mistake. In my experiences (of 2), the squish band measurement is consistent to maybe 4mm with that kit.

BTW the BGM SC tutorial method video (no gaskets) wasn't accurate in my anecdotal experiences. After torquing it all down, things change.

I used to use the solder through the spark plug hole method, to avoid removing the head. But there can be enough play in the small end bearing -- while pressing down on only one side of the piston -- to make measurements a bit off.

Well - I defer to Ray on the idea that the Squish is constant a few mm in on this kit. Learned something new.

As for my spark plug hole method - I still put the solder to both sides of the piston, aligned with the gudgeon pin. I make it long enough to come up in the spark plug hole at the center, far enough to grab it with needle nose pliers. I preset the piston to near TDC so there is less chance of shift - and I measure both sides of the solder to see what I get… all secrets out now.

I doubt that!

Keep in mind you'll have to re-jet if you add that venturi. I have one on the shelf, collecting dust out of fear of jinxing a solid runner.

Yes on all three of these points

Well...2.5. I've never watched the SC video, but have seen the squish vary a little if everything isn't torqued to spec before testing.

Im having a hard time getting my Polini Box exhaust fitted to the Exhaust stub of the BGM cylinder.
Too tight a fit.
Will try sanding the inside of the exhaust header pipe with a dremel sanding wheel to increase the size of the exhaust header pipe.
Any one else had similar issues fitting an exhaust pipe to the BGM cylinder?

No trouble fitting SR2 or SR3. Just posting to say you'd better start hand sanding with a thin grain sandpaper? maybe your problem is just a fraction of a mm, less is better...

My 2 cents

Don't sand it. Bump it up with the side of a small sledge hammer until you hear the tone change.

Cheers Ray
Will try that after I have cleaned up the inside of the polini header pipe.
Quite a bit of carbon in there….

So I got the engine running today and was able to take it for an easy 30km ride.
The jetting is recommended by Jack.
AC120 BE4 MJ130 pilot 55/160

It was bogging down bad in the first 1/4 throttle so I gave the mix screw about half a turn in and that helped.
But it is really rich in the mid and 3/4 gas range and I cant WOT as its spluttering like hell.
Wont go faster than 60kmh
Plug is black so will slowly start reducing the main jet.
If the fuel-bowl to main is drilled does it automatically mean reduce the main jet when compared to a non drilled bowl?

Bogging down is good. Not being able to rev out is also good. If it's too hard to ride, reduce the main jet until it still splutters but improved. You'll have to do short WOT runs in 2nd gear to test the main jet. Once run in, reduce the main jet in the same way until it revs right out clean.

Thanks A lot Jack really appreciated…..