Modern Vespa

Agreed. I use a variable timing light, but I can still appreciate the heck out of that.

It also reminds me that I want to add a marker to my cases that actually extends to the flywheel rather than sitting across a gap, meaning that timing can be off by a degree or two depending on my line of sight across the gap.

Nice one. Parallax error is a bear with these normally.

The timing indicator is marketable.

Thanks.
Craig used the proper terminology for it. I can never tell within two degrees what I am setting it at with that gap between fly and cases.
Would be easy to 3D print.
I painted, the. Sanded the high spots to get the effect. But with some clear. Bob's my uncle.

I used just over 1.25 mm spacing and it's very close to 1degree timing per line.

Perhaps I will have a chance to set it this weekend.

Bracing myself - I moved to leak testing today - in what was sure to be the snatching of defeat from the jaws of victory.
And it didn't disappoint.

Some of the usual suspects.
Got creative with some mini threaded plugs on back side of case center studs.
But the killer was the DRT seal holder.

It's pressed in - with 603 - but I suspect the seal got broken when I had to re-do the main bearing.
Which is a shame.
Cause I couldn't access the leak under the primary gear.
So - I was forced to tear down the entire motor.
Drive shaft
Xmas tree.
The whole shebang.

So having been a hair from start up - I had to go back to the start.
For my sanity - I timed myself tearing it all back to raw cases 40 min. door to door.
Weirdly made me feel better.
In the am - I'll tackle the rebuild/reseal.

And now - your moment of zen.


Just couldn't face the idea of a CHT ring under my spark plug.

No idea what these cut out areas are for - but now it's tapped

Ahh - something to build on. Please for the love of all things wholly - don't tell me I wasn't supposed to use that area for anything...

Very nice modification to the head!

I suspect that's exactly what those cutouts are for. Nice addition, too. I also much prefer the tapped in CHT sensor over the spark plug ring, when given the option (or the option to create the option).

You'll never be able to install the flux capacitor now. (Not such a big problem, you'd have to have gone reed intake if you wanted to hit 1.21 Gigawatts anyway).

How'd you tap that blind hole???

Nice work.

Mounting CHT sensors is a pain in the VW world too for the same reasons. The spark plug rings often leak and get distorted when you change plugs. Your solution looks quite elegant though.

Bottoming tap or plug tap if I were to guess.

tips-007.pdf
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who says it's a blind hole?

If I never have to pull another spark plug with the temp sense ring as its washer - that would be too soon.
Temp sense unit has a point on it - that touches bottom of hole beyond threads.
So std tap was fine.
Lots of meat on the head - so to speak - so managed to keep it blind.
There is a joke in there somewhere.

Other than maybe the connector, that looks like the same K-Type Thermocouple that the Koso CHT uses and that fits the BGM 177 (M10x1.0 thread).

And be careful when tapping your meaty head. According to Christopher's PDF, you don't want to go blind when you're doing it by hand.

That's just a wives tail.
Tho I understand your grips can get hairy.
Yup - I am using the koso temp sensor that I used with the BGM - 10mm.

If you pay attention the the wive's tail, though, you won't end up with hairy grips or a blind tap.

You can get the threads down fairly deep (depending upon the material of course) into a blind hole. My trick is to use two different taps. One tap is a normal one, and the second tap I cut the tapered portion completely off with an abrasive blade. I will tap as deep as I can with the first tap, then go back with the second tap (that I cut) to go deeper. That trick has worked pretty well for me multiple time in aluminum.

Good tip!

Like it Whodat.
I do the same.
The one I cut off is hopeless to start with - no lead in - but if I have just cut with the other - then I can carefully thread in the cut off one.

Now - about this motor.
Though I haven't bothered to post the pics - I have built it up to the point of torquing down the head - 3 times - then had to rip it down again to go after a leak.

With each failed leak test - I tore it down at days end - leaving me a clean/readied case for the next day.
Some kind of patience test.
Trust me...

The leak was a bit blind - like that hole I tapped.
Shhhh. Don't say it.
The bubbles are occurred under the primary - super hard to see.
But when it leaked again for the third time today - I figured it must be something other than any of my sealing surfaces.
Uh oh.

So I tore it down again (again!) and took a closer look at the area with nothing in the cases.
Sure enough- there is a hairline crack that aligns with the grove I cut in the cases for the P200 crank.
Hmmm. Perhaps not my best moment of machining. Must have gone too deep there.

So now what?
Will sleep on that one.
Tomorrow will likely bring a weld attempt - but it's a tough one.
Access is tough.
We will see.


Some previous - shall we say - through - efforts to make certain there was no leak coming from the seal area can be seen - circle is around crack.

Oh man, I'm sorry you're going through this and I admire your perseverance! I'd have given up long ago...

Oh, man...that sucks!

Have you built a smoke machine yet? That was the only way I found two leaks in my cases the last time I tore them down. One was pores in an epoxy fix and the other was a tiny little leak where I tapped in the pressure line for the fuel pump. They were easy to find with smoke, would have been pretty much impossible otherwise.

No smoke machine (smoke machine?)
I've used soapy water - and was able to track them down.
This one was tough though - it was hidden under the primary.
Finally got a look at it with an endoscope - but even then it was tight.
Suppose the good news is - I finally found where the leak was coming from.
Was driving me crazy.
Is it fixable? Well - everything fixable I suppose - that's the nature of this entire forum!
Which opens the door for the "yes, but should you fix it" responses.

I want to see if this L shape pad works.
I am going to try and repair it in the am.
¯\_(ツ)_/¯

https://youtu.be/TVb-Yb_NUy8

Forget it - he's rolling....

Rowdy did a thread about the smoke machine he made. I was thinking modified bong of some sort, but no. Pretty cool stuff

Germans?

I'll check out Rowdy's smoke machine.
(sounds weirder then it is).

Impressive patience. And nice find on the crack. Had to be in the hardest to find spot.
Weld and Dremel, good to go by lunch time. Careful with the heat.

I was planning on doing 2 timed leak down tests.

1. With just the crank and seals installed and the cases on the bench with all crankcase bolts… it would waste a gasket (possibly, if I use sealant with the gasket)

2. Then with the engine closed up and complete with the shafts and other seals installed.

Hopefully that will determine if there's any leaks with the welding and trouble shooting those before going too far.

I'm not super confident in the state of the cases and welding, I'm sure mine are warped, might be a good approach, if not I might be wasting good bearing and seals

Balls! I have a dear friend who is the head mechanic at Harley D here in Houston. Old punk rocker, wise beyond his years, his axiom... "If it can be broken by man, it can be fixed by man... for a price." The note due here is patience and time.

You good.

I love it.

This also reminds me of what I tell people in my day job any time they say they have some sort of "perfect" copy prevention or anti-forgery device: "If it can be made, it can be copied/forged."

The thing you have to watch out for with the welds is some kind of porosity causing air leaks.
Sometimes a good looking weld can hid them too - it only takes a little pin hole.
Leak testing - if you can come up with a way to do it - the cases only is a good idea.
If you find a leak - you can go back to your welder with it marked and let him just wash over it with the welder - so that it remelts and boils out the perosity.
If that's not an option - you can coat the outside of the welds with Threebond - which would be less pretty - but probably no less effective.

Sipping coffee now.
Off to the garage shortly to see if I can get the welding torch on that area.

You're gonna get it this time, on this fine winter solstice day!

Oh for sure on the pores!

I feel like the welding has pulled the Alu in places it shouldn't be… maybe it's a bit of paranoia, but had a tight fit with dry fitting the primary shaft (which I ended up sanding down… :/) not sure if I should've reinforced it the way I did…

Yeah, don't have any good way at the moment, it's literally doing it twice… and feels a bit counterintuitive.

at least you troubleshoot early on… and you know for sure it was leak proof at least once…

Can't wait to see yours fired up!

Reinforced it this side… didn't use the plate everyone is using

108 - counter shaft looks fine to my eyes.
If you want to avoid guessing if his welds leak - just coat them with threebond or a fairly flexible epoxy.
See below.
I can assure you I will do the same - no matter how pretty my welds are in the end.
And they may not be that pretty...
Welds are there for structure - sealing agents are there to seal.
No extra points for having to strip down cases because of a pin hole.

So...
Realized when I looked this morning, that some moron back on page 20 had ground back the area that I just machined through.
What a dunce.

Left me with a razor thin material.
Tried welding today.
Total disaster.
Moment I hit it with heat - edges just curled up.
Pretty well decided these cases are done.
At least 3 times.

This project has passed its sell by date - but I can't quite let it go.
The L shape pad has my interest peaked.
When I pulled the crank - I was kind of shocked by how big a 16mm wide inlet looked.
Just had to keep going.

So even tho I burned a finger sized hole in the cases - I kept at it.
At this point - its beyond patience and on to just plane stubbornness.
Changed tacts.
Cut a patch and tacked it in place.
Then flipped the cases and welded on to that from the other side.
Looks to be solid.
Literally.

I will have to try and machine the surfaces now - to allow the primary to fit back in.
Ironically - the epoxy for the pad didn't give at all - and this cases were crazy hot from the welding.
Impressed.


oops



welded a patch on, then machined it down.

This will have to be machined out

then sealed up the edge of the patch as well. Will coat all this in an epoxy - to ensure no pin holes. Needs to be machined back. Solid for a lifetime - if not elegant.

Heck of a save.

Shoulda just used JBWeld...

At this point, those cases are more weld material than cast aluminum, but I'm consistently impressed with how you soldier on and just keep on pushing the envelope.

Are you going to be able to have it back together by Christmas, barring future incidents?

Don't think for a moment I didn't consider some epoxy.
But that area sees a lot of stress - and it wouldn't have held up...

I'll answer that at days end t'day...

I imagine this has been you every time you thought you had it...and then didn't...

I'm with Chandler. Looks like maybe you got a little trigger-happy trying to use the welder to fix that minuscule crack. A little dab of epoxy might've done the trick. There's not that much stress in that area.

Last edited by SoCalGuy on Wed, 22 Dec 2021 16:53:57 +0000; edited 1 time

Don't listen Ned... Buncha armchair quarterbacks welders JB-welders!

epoxy would definitely have sealed it - and been quick and painless.
I gave it a long hard thought - because welding set me way back - everything had to come out and now needs to be re-bonded.

But...
That area holds the crank - and every time you are on and off the throttle must twist and bend a little.
Epoxy would have in all likelihood delam'd or cracked with use.
Some good RTV - would have given a great seal - and remained flexible - so I considered that as well.
But...
With 20HP, I think the chances that that crack would propogate longer/wider were meaningful.

So as bad as I wanted to just bond over it with one of those - I decided to bite the bullet and weld the patch in.
It will be structurally sound - and sealed - and I won't have it on my mind every time I twist the throttle...