Modern Vespa

and today i am so happy seeing this pic, like Brother Jim aka Bitsa often said "teach them young".. big smile for you Brother Rowdyc

WOW!!
Whats in that scooter to justify such a wiering setup? Looking at the colour it seems similar to mine!?

Managed to get hold of a cheeky little 100 Sport which is hiding out in my mate's garage in the UK until I can collect it and bring it to Germany without Mrs Herman noticing. I haven't had a smallframe since 1981 when I had a 50 Special so looking forward to starting on it. It seems to be pretty much complete other than the headset, the left hand panel and the indicators. I've got hold of a panel but does anybody have a headset and/or indicators they'd be up for selling (and posting to Europe)???

Think I may have a problem with needing to polish things.

Yesterday actually I replaced both tires on Sweet P and going tubeless for the first time at least on the rear for now. Installed an FA Italia split tubeless rim. Not exactly plug and play. Being a bit thicker, the lugs came up too short. Tried backing out the studs with a double nut and the threads weren't up to the task. So instead I spun them out with a tiny pipe wrench and drilled out one. Replaced them with button bolts just a little longer. Also bought a different valve stem, a screw on type with a nut. That conflicted a bit with the brake drum, nothing the grinder couldn't handle and at last I'm tubeless in the rear!
I'll do the front in a couple weeks. Look forward too it and dread it, but it will be done. All because of the drama free blowout I had on the Big Ruckus last month. The same on Sweet P and I would eaten the road.

This afternoon, I was coming back from mailing a package and picking up a few items at the grocery store on the Sprint. I noticed a slight rattle, like the fan cover was loose and vibrating, but when I the motor died a block from my house. I kicked it, and...no compression.

So I pushed it home and pulled the head to see what was up. The bore looked just fine, but there were some shrapnel marks on the cylinder head and piston face, so all was clearly not well. As if the loss of compression wasn't already a giveaway.

I pulled the head, going with the drop the motor to vertical by removing the rear shock bolt and pipe, having had one close call too many with cylinder studs lately. Pulled the cylinder and the gudgeon pin circlip fell out onto the garage floor.

To make matters worse, Slaughterhouse is this weekend, and while I won't be able to participate all that much, I'll still be able to join the Saturday group ride, at least. And get to work normally. I guess I shouldn't forget that.

The good news is that they cylinder looks like it's fine, so I called Mark at Scooter Speed, both because he's a go-to for BGM parts, and he didn't a piston on the shelf, or even the entire kit. So he's ordering it for me, but in the meantime, I still need a working bike.

I grabbed the OG Sprint motor's Polini top end off the workbench and threw it on to check port timings. Came in a little low on the transfer timing, but a .5mm base gasket got me up to 123 and also got my squish up to 1mm, so I slapped it all back together and took it around the block for a test ride.

I'm happy to report that even with no carb tuning beyond tweaking the idle, it still runs beautifully and will even pull a power wheelie in first gear, so I'm back in business.

Haven't had much good luck lately... I wonder how it managed to work it's way out? Perhaps another use for Loctite?

3 pistons "dead" in the last 2 weeks. Someone do an exorcism!!

Today I ran my scooter with the DR 177 fitted. ( It's a 2012 PX125E) I took lots of advice from this forum. I need to skim 1.5 mm off the top of the Barrel and fit a thick base gasket. I have to wait a Month for the Turner to face off the Barrel so what did I do?

I bolted the top end on, measured the squish with Lead Solder and skimmed the head with a Dremel. You read that correctly. I used a Burr to grind off the rim. I polished the chamber. It looked like a teenagers neck. And then flattened the rim with oiled sandpaper on a glass sheet adding pressure where it was highest.

I fitted the Barrel with two base gaskets which raised it 0.4 mm and the squish is twixt 1.19 to 1.28 mm.

I took the Advice about the Jetting with an Si 20/20D. I have a 45/140 idle
140/BE5/105 main stack.

I warmed the engine and took it for a test ride. It was like shit off a Shovel until the engine locked up. Fortunately I pulled in the clutch and cruised downhill into a Garage.

I had a cigarette and waited for my arse to let go of the seat. Started up and rode home.

I think the jetting advice should have been "Fit a 115 Main jet".

Update: Here's the pics. I have since cleaned up the Piston with 400 grit wet and dry wrapped round a strip of steel. bar. Thank you Jack221 for your advice which is scattered through many of my posts. I should have tried a 115 main jet rather than a 105. I really should have gone to spec-savers. I went to the Mersea Rally this weekend and returned with new Piston Rings, Jets ranging between 115 to 120, A 122, 125 and 130. I suspect the 120 is too rich as that's the jet I fitted after the seize. I also bought a 21 tooth clutch sprocket.

Was a great story until the bit where you tried to do the jetting in one go. With any new cylinder on a two stroke the main jet should be at least 10 points bigger than the biggest you think it needs. On a BE5 the smallest jet you should have started with is 125 and ideally a 130. Once you get the heavy splutter then work down from there.
Hopefully not much damage and you get another go at it.

Those marks on the piston crown are not from the circlip. They are detonation marks. If you look carefully the aluminium is melted and missing.
This means you are running way too lean. More than 10 points lower than what is usually lean, to get this much damage.

Today I had to drop the forks again as when i replaced the spigot pin on the front hub, i didnt push it far enough in by about 1.5mm and this has caused the caliper to rub against the hub.

I'll be a little surprised if it was too lean, especially that much too lean. Other than some testing with the air:fuel meter validating that I was at 12:1 pretty much across the rev range, I haven't had it revved out at all lately. Just commuting back and forth to the train and the grocery store, which is a mile and a half of 25mph roads.

Sadly, whatever DID blow things up seems to have struck again. I got about halfway home last night and the motor died with the Polini 177 I just put on. CHT was at 200f. Compression is gone, though.

For reference, I'm running a PWK 34 with 48 idle, 148 main, and a HLJ needle on the 4th clip. Temps have generally been under 220f with that setup. Squish is about .9, as I recall.

Something is definitely amiss, but I'm not sure what. I'll maybe be able to take tomorrow afternoon off and tear into it then, but I'm mostly just irritated with myself right now. Probably no Slaughterhouse fun for me this weekend, either.

Oh man ... first the BGM now the Polini ... Are you running autolube or premix? When's the last time you added oil?

I'm premix. And other than the detonation, the BGM cylinder looked fine, so at least I have that going for me.

I think the detonation was old, because there was pretty obvious gouging in the side of the piston between the wrist pin and crown. Plus that whole circlip falling out when I pulled the jug off thing...

Now, though, I need to get to the root cause of what's going on. I'd think it's not unreasonable to expect my builds to last longer than a mile and a half of mild riding, but apparently not...

Um yeah, two different top ends going sideways back to back is just weird. Is your timing wonky? Exhaust clogged?

When's the last time you checked for air leaks?

What are you using to install those C shaped wrist pin clips? Fat needle nose or a special tool? Might be warping them on install.

http://scooter-speed.com/universal-piston-circlip-inserting-tool-c-type-12mm-casa-pro-122-x232/

yesterday i run to a deep floods


so today i clean the bike to make Brother Vader proud

They'd been in place for over a year. I think it was just dumb luck.

Yet again Cheers Jack. I really should have gone to specsavers. I fitted a 105 jet instead of a 115. I saw a "Freakmoped" video about a trashed Polini top end. I think I will get away with dressing the piston, Honing the Barrel and new rings. I have a set of jets. 130 125 120 118 115 112. I'm going to Mersea Rally and shall purchase 117, 116 Jets. I tried the 120 and it ran like a Tank on cheap wine.

worrywort, if your cylinder and piston are salvageable, there are a few options that help with a DR177. I realise that raising it and taking the top off the cylinder is good tuning, but for most people, the stock DR is good bang for the buck with a few easy tweaks. I've never tried to machine a head with a Dremel and would have thought the chance of an air leak between the mating surfaces was very high. You can get a Polini 177 head for ~35 pounds (mine was 15 on eBay), which goes some way to reducing the big squish, and the casting quality is much better. I used GS rings on mine (~30 pounds), which are higher quality and appear to be chamfered to reduce the thickness against the bore. I thought about the complete GS piston, but with the total cost, a better alu kit was only a few quid more.

All of the above plus a SIP Road 2 and a 160/BE3/112 main stack in the 20/20 turned my 2012 PX into a lovely reliable and peppy ride, until I took it out recently to test a 221 motor.

Got new key blanks for the TV and GS

Meet Brother Mike

A piston running at 200 F Will be fully black and sooty. Yours looks like one that was running at 200 C (390F). Even riding with no main jet fitted the wrong needle or atomiser will still cause a lean seize. Could be anything but two cylinders having the same seize means something is very wrong.

not sure this is true. I ran my smallframe a target of 200C, always keeping it in the 175-250 range. steady state on that bike was 8000 rpm at 200C and would run that way on the highway for hours.

No soot on the skirt or under the crown

so the soot must need more heat or another source.

Mine will sit happily at 390F on the highway for a full tank.

I am not denying that you can't ride at 390F and get away with it but its wearing out hard at that temperature. The most important thing ever is that its not making full power. Full power is at 325F. Anything hotter is damaging the cylinder while going slower than it could be. I'm only trying to help. Its your money.

So I got into the guts of my motor and found out what was going on.

The Polini died because the piston skirt disintegrated, but I think the piston disintegrated because the crank web had separated.

The crank pin has split abut 2-3mm, introducing significant play into the connecting rod. The roller bearings had also unseated and at one of them was sitting perpendicular to the crank.

Not surprisingly, there was also scraping on the side of the crank from where it all came loose.

So as of right now, I'm waiting on new bearings, new crank, a Gran Sport piston for the Polini, and various other gaskets, seals, etc. and will just be down for the count for a couple weeks.

I also threw in new 3rd and 4th gears, because I noticed mine were pretty trashed when I shattered the axle, so things should be good-as new soon enough.

Jack, your help does not go unappreciated. Have you heard though the saying "teach a man to fish"? It would be easy to take all you say as gospel, but I want to know the why... so a simple "do this" doesn't satisfy that desire to know why.
For instance, Full power is at 325F - where does that come from? If true, why have you encouraged SDJohn to use 300F as a max temp for (not quite) 40 pages, why not 325 as a median temp that should be aimed for instead? How much harder is it wearing out over 325, and is it a linear scale? Is it true for both iron and nicasil cylinders, high and low octane fuels, heads with 0.8mm of squish and heads with 1.8mm? If for example you were to say that you are a metalurgist specialising in automotive applications, then some of this could be taken as a given... so far I only know that this is your opinion based on your experience. Other people have opinions based on their experience and they don't necessarily coincide with yours, I'd just like to know the why of your opinions.

I saw this just now and felt a little sad.

and that's on dirt, in road racing the 125s are more like 54hp

That didn't help...

Then how about this? A stupid big 500cc 2 stroke in a modern frame. My
friend copied and I helped w/ the casting needed to modify the frame.
https://www.vitalmx.com/forums/Moto-Related,20/2015-CR500Af-Build,1311982









THESE PICS ARE FROM THE ORIGINAL BUILD ARTICLE

I know we had talked about this earlier, but I didn't quite get it then. Is the original part cast as well? Or pressed and welded? I would imagine that it would be a bit more fragile than a pressed part.

The Y in the frame was too low to allow for the exhaust port so it was cut out and a new cast Y was welded in. The linked article goes into a lot of detail. Here's a better pic of ours showing the casting and the raised up exhaust location.

It's very impressive.

The CHT temperature is essentially the plug temperature. All other factors about the engine are less relevant. The same spark plug in a 4 stroke will run much hotter and that's where a lot of this how high can I go contest comes from. Hot 4 strokes go fast. Hot 2 strokes go nowhere.
To get jetting under control 300F is the starting point. Once stable at 300F WOT and 250F+ at ¼, then careful changes to needle and jets are needed to get the max WOT power. 325F is typically where it is (Sdjohn may not realise yet but 40 pages is only half way through the set up).
As shown above, running high temperatures doesn't do the bottom end any good either.

setting realistic goals can help. we don't have power valves, the studs get in the way of ideal ports, have to make due with air cooling, and we don't want to be changing out the piston after each ride, so 400hp/L is out. I bet 300 could be done with water cooling and all the tricks.

But being realistic, 100hp/L can be had with old school calculations on graph paper, and/or careful selection of components that work well together.

on my lambretta build I'm aiming for 150hp/L (~26HP from 175cc) at 8000 rpm. First time using EndMod 2T and getting all the measurements right has been a bit of a learning curve, and the simulations are up to ~25hp so far. finally feels like a science (with a bit of art).

speaking of realistic goals:
https://www.scootering.com/scootering-classics-the-hard-truth-lambretta-and-vespa-service-schedules-and-component-life-expectancy/

agree that high temps are not a thing to want, just don't think that the levels being prescribed are to be avoided at all cost.

with water cooling the lower temps do deliver more power, but with air cooling you have to run overly rich to hit those numbers. have seen several engines that were not burning up pistons with a head temp of 200-250C over long distances and they made better power at that temp than they did at a richer/cooler jetting.

So, if a temp of 200C is not on it's own the cause of shorter life the soot... then what else is contributing?

Thinking of this in terms of power density is a great approach. I'd never thought of it that way before, but it makes perfect sense. When I look at it that way, I feel a lot better. With my best builds, I'm now getting about 26-28HP from a 187cc motor, which I know is pretty much top of the heap for these motors. I forget about all the engineering and technology we don't get to take advantage of. I also realize that smallframe motors have more room for improvement, which we see with the Germans building crazy-fast smallie motors.

The reduced lifespan of a hot motor is something that I fully expect. I get about 12-18 months out of a tuned motor if I'm lucky. In this case, the failure was just a little more dramatic than I was expecting.

For modeling, do you have a link to information about Endmod? That sounds pretty interesting, but a quick google didn't point it out, only lots of other stuff that was not a motor design & simulation tool.