Modern Vespa

Hey R8,
1) The bolt hole was there - factory. There are also two down lower, towards the floor boards
2) 48" extension. 24" wouldn't be long enough
3) Instructions state to take the crush washer off the plug, so that's what I did...

In general, you need the 48" extension;
he had the hole there and made it work;
and while you're supposed to remove the crush washer, I never have.

nice, I'm doing it your way next time!

I've never blown up a motor because of the crush washer that I'm aware of

...oh.

that you're aware of...

Thanks. Planning something pretty similar. I have that hole, and the other two for the spare wheel holder. Stuck a wire in each and they all seemed to bottom out. Just old crud.

Cool. The weed whacker line worked well cause it was flexible enough to make the bend. I had to use thicker stuff to do the bend from the horn inlet down to the tunnel.

But it was a bitch to do....

Good news and Bad news....

Let's discuss the good news. Y'all know I've been trying, and trying, and trying, to get rid of the 1/4~1/2 rough patch on the throttle. I've tried all kinds of jetting, talked with all kinds of people, took everyone's advice and tried it out. And all to no avail. This is with the 20/20 Spaco carb.

So finally - FINALLY - I decided to try the 24/24 Dellorto carb I have sitting on the shelf. 160/BE3/122. Holy Schnikeys - success! Let me say that again - SUCCESS!

I had a 45/140 Idle jet but it was too low so I went with a 50/120 - pretty rich, but still a slight bog at beginning throttle, so I put in a BE5 mixer tube - beautiful 2 turns out and it runs beautiful. I put in a E3 for grins and it's 1 3/4 turns out perfect.

So no more weird 1/4-1/2 throttle rough patch. Amazing. I decided to go see if the 122 MJ and take it for a WOT run. I ran it up and had to back off slightly because of traffic (68 mph) and the temp was rising. It hit 337F, which was too high for my liking.

So let me say this in it's own sentence: I could not tune in the 20/20 with my setup (Pinasco 177 2 port kit with 57mm Pinasco performance crank). The 24/24 tuned almost without effort! No more weird 1/4 to 1/2 throttle rough patch...

Now for the bad....I'm doing a speed run and....the engine dies. I've got two fingers on the clutch so I immediately pull the clutch and coast, then realize I was almost out of fuel so I flip the lever to Reserve and wait until I'm barely coasting and pop the clutch. Starts right up. I'm stoked and all is well.

So I go back to the port, put a 125MJ in and do the same run. This time it got up to 313F and was holding, but bam, it died again. Pull in the clutch and coast almost to a stop, pop the clutch and it starts up, but I hear a tinging, like piston slap, or the flywheel hitting the shroud. No-no-no-no-no....Deep breath. I'm alive and not on the ground....

So I head home and take a look in the spark plug hole. Hmm, I think I see lines, so I pull the head. Yup, score marks. AAAARRRGGGGHHHHH

I took the cylinder and piston out and, yup, seize marks. Pinging must've been piston slapping. I've analyzed how I did this, and it's lasted longer than I could've had any right to last. Running without a CHT gauge, running way too lean for over 500 miles with the brass bushing, then letting it go to reserve, like, all-the-time, which is essentially starving the piston of lubrication briefly. But do this over time? Live and learn. And 68 on 8's? Not necessary

So my next course of action: I decided instead of dicking around with just putting rings in, I ordered a new piston, rings, and I have a new wrist pin bearing. Once I get the new setup, It's heat cycle mania for a while, then ride it with a fat main jet, or drop the AC to 140.


20/20 Spaco on the left, 24/24 Dellorto on the right. Yeah, I did a bit of flowing the carb to box...

Dangit, but not too bad looking....

OK, here is the issue. Bummer....

I honed out the cylinder scratches with one of those three legged stones hooked to a drill at slow speed and WD-40 for a lubricant

The score marks are pretty much gone...Now for a new piston and rings, and wrist pin bearing.

Proof of 68mph....The 23 tooth clutch gear makes a difference...

Did you try doing any plug chops before that seize?
I was going to recommend a 24 carb. So many more setup possibilities available online.

Yes, but months ago during a different configuration.

As far as setups, do you mean cylinder/piston combos?

Not saying this was your case, but until I did some real plug chops* I was running way too lean. It just felt better.
*Actually, I got a cheap jeweler's magnifying glass with an led light. I can see enough without chopping 'em. So much to learn from a plug!

As far as setups. the chart below helped out a lot.
Notice that few guys with a Pinasco 177 are using the 20/20 in the setup chart. I take that as being for good reason, since people generally post what works for them. In my case I was able to find two or three setups like mine ( including exhaust, gearing, wheel size, etc) and restarted jetting from there. With your 24 you're much more likely to find someone's happy jetting with the rest of your setup.
http://lfs.alexander-hepp.de/

Excellent - thanks R8! I'll check it out

qas - just catching up.
Oh no!
And by that - I mean I am devastated about the elephant mug.
Tragedy.

As for the cylinder - hey - it could be worse.
Couple observations/questions
1. Normally with an iron cylinder - when you overheat - you get the 4 corners scraped where piston expands and squeezes against studs. With yours - it looks like it was more dead center on the exhaust port.
2. This piston design has some big holes there - so it probably deforms under heat worse in that area. Maybe a few extra steps of precaution could be in order.
3. Specifically - I'd look at the chamfers on your exhaust port. Pics a little tough to tell - but they look pretty bleak in photos. Might be fine - do you wanna post another shot?
4. Finally - is that carb float drilled? If no - MJ is in the danger zone of not really being effective (read - carb hole is acting as main jet).

Fire back and let us know.
Glad it was relatively minor - at least the cylinder.
-CM

I know man, I miss that mug every morning, and the replacement doesn't hold near enough coffee...sigh....

I chamfered all the ports, but may run the file on them a bit more. No rough edges or anything happening. I did file the inside of the exhaust port - it had an interesting shape to it, so I made it more rounded off.

I'll take a pic tomorrow, but Chris and I are going for a ride up to Yachats, or maybe Waldport, up some beautiful, curvy coastal highway, so I might not get to it.

And all the carbs I got have the float bowl passage drilled out to 2mm. FMP says to go to 2.5mm. What do you think?

But more importantly than any of this - what's up with the Orange Unicorn not being on the road? And why doesn't KITT have it's brain yet? And what's up poking a stick at the Aussies? - Heh heh...

1. I'm glad you noticed it was actually BOTH Aussies. Took a wild swing and one of them didn't even notice! Was just making sure they were alive and well down there. They know I love them.
2. Assumed you had done a nice chamfer - pics were tough to see tho - but it clearly wasn't ring snag in any event. Piston definitely expanded where it is weakest - around those large holes. I was just thinking about trying to hedge against the weak spot now that you know how it will want to fail. Personally - I like my chamfers a bit taller on the cylinder wall than depth into the port, and I use a Dremel drum sand wheel to achieve.
2A. Best guess would be MJ related lubrication based on how it seemed to fail.
3. I've landed at 2.3 as my standard. As long as you can make it refuse to rev out with a main jet that is too large - you know it is feeding enough. Simple test is to whack a giant jet in there and see if it just doesn't wanna go past about 5500-6000 RPM. Means your drilled hole is large enough. I struggled to tune my 2.5mm drilled hole at one point - tho Im not sure that was the reason.
4. The unicorn and Kitt. I have been on the road for 2 weeks. Just back. Practiced using the mill today on the spare cases. No idea what I am doing - but trying to figure it out before I cut my actual cases. Miss it.
5. The mug. Heart breaking. I felt it. Keep an eye out on your rides for a proper replacement. Don't be shy about buying a few that just don't stack up. Give them to charity. And should you find a crawler and a cup of coffee so fine - that you know you must have that mug - I personally give you permission to quietly slip it in your jacket pocket when empty. Just sayin'

Way too lean. They seize like that when way too lean. Run super smooth but just overheat.
Good job on the hone. Run the old piston. Nothing wrong with it. A few battle scars are expected.
The 20 will jet in as will the 24. Keep the 24 on now. AC120 should be fixed and non negotiable. BE4 is most likely the one. The rest should be easy. But if it's not running smooth try going richer first.

What Jack said. I was slow to learn this lesson, and blew myself up more than once in the process as a result.

This is also the failure mode where the CHT can let you down, too, which makes it even more frustrating. On the bright side, as Jack said, you can clean that all up, put it back together, then fix your jetting and get back on the road, no new parts required.

Thanks guys. Looks like my problem may be my inability to time the little beast properly! CM1 pointed this out on The tale of two rebuilds - VNB2 and VNB5 (Page 6)

I'll report back when I get it all back together and timed properly! Dooohhhh...

So I chose to go with a new piston and wrist pin bearing. Figured I'd start from scratch and make sure I don't seize this one

I installed the piston without a base gasket which could buy me a hair on the squish factor, pressure tested it, and reinstalled.

She's running nice! I ran it through a couple heat cycles and up to the fence and back to ensure all is well. I also put the timing light on it and I'm at 20 degrees BTDC when revved up.

I'm running a 24/24 - drilled out to 2.3mm. I'm going to start the jetting at:

120/BE4/125 with a 50/120 idle jet. It started up fine with this jetting. We'll see how she goes when I take it up the block! I'll start the tuning process from here and won't go larger than the 120AC

Thank you for everyone's input!

120 is the new 160!

That jetting sounds safe. If you keep fouling plugs then your idle is probably too rich. I couldn't get that idle to work for long on plugs.. So i had to go back closer to 55/160.

Good luck and hopefully it's the only hiccup for a long while!

Good to know on the idle jet. It worked really well when I had a BE3 in with a 160AC. So I'll keep a close look on it. And thanks! Hopefully it'll dial in easy and run smooth for a while!

fyi, I ended up on a 48/140, basically same as 55/160, idle with 177 kit.

Hey everyone,

So check this out. I put the new piston in and after about 50 miles I started to hear a tinging again, like the piston tapping, just like after the 2nd time it soft seized. This is with the new piston and new wrist pin bearing.

So I took off the cylinder to inspect. What I found was the wrist pin bearing was .20mm smaller than the original one that came with the Pinasco 177 kit. I also noticed some lateral play in the conrod that I don't remember being there when it was new. I even checked out the movement compared to the original 125cc crankshaft and there was a fair amount more movement. I didn't think much of it at the time, but it comes in to play. I'll explain shortly.

So I put the old bearing back in and reinstalled. Pressure test, etc. Put the engine back in and the ting seemed to be gone. I was all ready to celebrate but I noticed the engine getting louder and the ting came back today. Dangit!

I went back through my mental notes of what was what, and I'm beginning to think that the big bearing on the conrod was the real damage, and not the wrist pin bearing.

BUMMER!!!!

So I'm going to pull the engine and see just how much play is in that conrod at the big end. It's gotta be what's causing the piston to be slapping like it is.

I'll dig into it later this upcoming week. I want to just ignore it, but it's not going to fix itself....


The bearings, Pinasco on left and new on right

Piston wear, new on right

So Chris and I pulled the engine today and measured the lateral play of the conrod. A quarter inch. and it can twist a bit also. Something happened to the big end of that conrod.

I'll pull out the crankshaft and see if I can beat it into submission. Or probably just get a new crankshaft and not seize it up this time...

Immediate thought is there is some lubrication issue. What 2 stroke and premix? Ever think you might have forgot to put oil in one time?
Could also be a crank oil seal leaking. Any other ideas?

Weird one!

Normal for some side play to develop over time - but yours looks a lot like what happened to mine (over 4K-5K miles).
I can see the degree of tilt you are getting as well as side to side motion.
(Mine sounded like a washing machine/dryer. HATED that)

The root issue was poor alignment of the two main bearings - caused by one of the seats being canted.
This created a pressure on the crank like one of those 1970's exercise bars.
See image below of me demonstrating the force angles.
🙂

This force causes the two halves of the crank to want to separate from each other.
In addition to Jack's comment - I would look at the bearings - are they well seated in the cases?
When you built, did you find a lot of resistance to turning the crank once the cases were re-assembled?

Hey Jack - I've been running 2% Motul 710. I've got a special gallon can I premix so I know I've always run premix in it. No leaks happening

BUT, I did run it with a 160AC while riding it hard, then seized (twice) at 65mph+. After the 2nd seize, the rattle and ting could be heard.

Also, I've always let it run out of gas and flip it over to reserve when it runs out - and a couple of times it caught me off guard and I noticed the temp climb while it was trying to run on fumes, so that could've contributed maybe... Hey CM22 - I'll check out the bearings. But they seated nice and the crank was fairly smooth when first put together.

I think I just did like you were demonstrating (Ha!) Bent the crap out of it by running too hard and fast, while being too lean on the lubrication. And we all know what happens without enough lubrication......

I'm going to pull the crank today and examine. I'll also order a Mazz from The Market.

Thanks for the ideas gents!

I ordered new bearings, seals, and a Mszz crank, and split the cases. The bearings were tight and heating the cases was the ticket.

The Conrod big end is super loose. No bueno. I managed to gently persuade the bearings off the crankshaft with heat and long prybar implements.

One bearing is fine, the other a little dryed out and loose, from my "gentle persuasion"

When the parts get here, I'll put it back together and try again.


Notice the new coffee mug on the bench. A gift from my lovely wife.

Be free bearing 97804

I realize that crank is toast, but if you intended to use it again, you should have the web you're applying force to locked in the vise so you're not stressing the big end connection.

Glad to see you've at least made it to the "I know what I need to do. Now I'm just waiting on parts" phase of the project.

I actually did remove the bearings while gripping the proper sides. I was pretty bad with taking pictures (as in none) this time around so this was just a staged pictute.

I appreciate you letting me know though:

Hah!

To steal a joke from Twitter, Thanks for letting me know that was a dramatic re-enactment, True Crime Show. Until that point, I was screaming at the cameraman to quit filming and help that poor girl!

Not much to report, i'm still waiting on a new crank.

But while I was waiting I managed to get the third rim painted. I'll soon have a spare mounted on the legshield


While I had the spray gun out...

Spare is mounted. I put a piece of rubber between the mount and frame to protect the paint.

At least it's a little progress while I wait....

Sometimes these little things make all the difference, looking good.

That looks great!
Been looking at wheel covers.
Only one I like ships from India

Does having the spare there interfere with the rear brake?

Thanks R8!

I might hang a bag of some sort in the tire, or make something to fit in there.

I just want to get the engine back together, then, as I'm riding it around, somethimg will come to me.

I always wanted to put like a smallies legshield basket on the inside. Maybe a holder type thing for the tire inside, similar to one under the cowl to replace the spare tire... Hmmm...

Negative. I've still got plenty of clearance, I think...But then again, I haven't sat on it yet because the engine is still on the bench, awaiting a new crank. We shall see....

I though about that too. The wheel there is surprisingly unobtrusive.
Plenty of leg room still.
IMO kind of helps with the center of overall gravity.

Sitting on mine I had maybe an inch between my knees and the wheel, I'm a hair under 6' tall. So I bought a GS spare holder that goes off the back, which didn't work with the longtail bench seat I have. So I got another bench seat one that doesn't drop over the back edge of the frame.

Now my legs feel free to roam!
Either way the tire being there didn't bother the brake pedal at all.