Modern Vespa

Hi everyone. I've been reading this forum since 2007 but this is my first post. I need help, I hope you can help me.

My 1967 Vespa SS180 (all stock) rides perfectly up to 3/4 throttle. In high revs it looses power and starts bogging. I (think I) know all possible causes and I have tried almost everything to solve this problem but I can't seem to get it right. The only thing left to try is BE2 atomizer and 190 air corrector but I am missing air here (am I?) and BE2 will just make it richer (will it?).

I've searched this forum and some other Italian and German ones and they all say that I have to use smaller main jet (running rich as you say). My current set is 160/BE3/120. I've tried 118 and 117. I also tried BE4 and BE5 mixers. I have ordered BE2 (according to some books, it should be original one) and BE1.

Stupidest thing is that when I kill the engine at high revs, the spark plug is almost perfect (B8ES), it's even a little white. So, according to spark plug, I'm running a little lean?!? OK, I've tried main jets 122 and 124. Then tried changing the fuel hose (60 cm), cleaning fuel tap, cleaning carburetor, removing carb fuel filter to get more fuel, changed the float needle.....

This is what I did so far:

Electrical:
- changed breaker points
- set it up perfectly (0,3 mm; 26°)
- tried different timing (from 32° down to 22°), different point gap (0,2 up to 0,5 mm)
- all kinds of spark plugs (Denso and NGK) - 6, 7 and 8 (coldest)

Carb:
- mixture is perfect for idle and up to 3/4 throttle
- main jet 117, 118, 120, 122, 124
- atomizer BE3, BE4, BE5 - have ordered BE2 but...
- air corrector 160, have ordered 190...
- tried to ride without air filter, without rubber air hose, without a complete air filter housing...

Exhaust:
- cleaned old one (one year old)

Any suggestions? Thanks!

i would try a new external coil.

that sounds very much like what i experienced. mine started with those symptoms and progressively got worse. is this something that only recently started?

Thanks for quick reply!

It didn't start that recent, about a year ago. I have other Vespas to ride and I did ride this one but not in full throttle. It can ride up to about 80kmh.

I had one symptom that actually disappeared (mysteriously). The engine could only work with "P" type of plug (extended) and some questionably quality - Enker Bosna Super, made in Bosnia. It only worked with this plug, FE70P. Now it works with a standard plug again

Coil? Then how does it work so perfect up to 3/4 throttle? I can try to use my friend's coil and I will.

What were other symptoms that you had and that got worse?

Hello

Partial vacuum in fuel tank check your air hole.

Grumpy

Thanks, I've checked that first. I've even tried with tank open. Same thing.

I've tried with external fuel tank (improvised). Same thing.

Edit: Are you refering to two air holes in the tank cap or the air pipe in the fuel tap?

Last edited by Kivno on Thu May 05, 2011 7:52 am; edited 1 time in total

Possibly hook up a timing light, then rev up to high rpm and hold it steady. Aimed at the flywheel, everything (cooling fins) should freeze and remain fairly steady without jumping around. If it jumps back and forth a LOT, timing is inconsistent and is most noticeable at high rpms when riding. Usually caused by crank wobble, rough points cam, weak points spring, or a less than perfect electrical connection in the ignition system.

Maybe disconnect the kill wire to make sure it has no leakage to ground, or check the condition of wires from the stator. Good luck.

Thanks, it's far from steady but to tell you the truth I've never seen a Vespa flywheel strobo-steady on high revs.

I have tried disconnecting the red kill wire. Crankshaft is new. Cam is new and oiled, points are new and double spring.

I will try with Sprint external coil. I will also try double-spring points (it's ordered).

How could it ride so damn perfect up to 3/4 OT? I mean really really perfect.

i just thought of my system and remembered one item in question

did you replace the felt pad when you did your points?

if the pad is new it may be just fat enough where at speed it's causing point float....i know you said it is double sprung but the pad just needs to skim the 'cam' not bearing down to hard

weird though for sure, you obviously know what your doing and have thrown everthing at the wall..........something will stick, you'll figure it out

No I didn't replace it. It was OK, I just oiled it (two, three drops).

I do know what I'm doing but that might also be the problem. Sometimes the solution is to simple to notice if you are thinking too deep. So please do not hesitate to suggest whatever.

There's no "stupid" suggestion for these mysterious problems.

Besides, I'm motivated enough to try whatever because I just love SS180 and I really want to make it work perfect but with original parts. Actually, "convert to 12V" would be the stupid suggestion or even worse - "put a PX engine in it".

i agree any mods to the bike would be wrong.....no conversions please

that bike was fine when it left the factory and is fine today

i am all about keeping it stock and simple.....my bike is finally, as time consuming as it was, runs as good as it did in 65'

it just requires hours of personal attention and not listening to others throwing 'modern' fixes in the 'mix'

old school always works in the end

yes on the felt, just a couple drops of 3 and one is what i used

good luck

Thanks.

My next tasks:

- Playing with mixers BE2 and BE1, main jets 115-138, air corrector 190
- Trying Sprint ext. HT coil (it should work :?

i am running a ducati sprint type ext coil until my bosch replacement arrives....it solved a spark issue....the new ext coil is a great place to start as the older the coil the more suspect of heat damage

heat is the main culprit for those suckers

What type of fuel line are you using? Some types, the internal diameter is too small, and other types are prone to kinking.

STOP what you are doing !
DROP the motor and disassemble inspect every part for wear
replace all worn parts and reassemble engine.

Put motor back in scooter and ROLL

this is a classic well worth doing it right . if you have check spark compression, timing and fuel flow ,the simple basics and it has not issued a solution . its time to dissasemble it and see what has changed.
iif it moves it wears out if somthing rubs on it it wears out so replace it and move on.

he's gotta point

if your as good as your first post indicates then maybe starting from scratch is a good idea

try andreas idea first though

It sounds like something is causing your bike to run lean - most likely a seal is going bad in the engine. That is why it seems you need to change the jetting. That "bogging" at high RPM is fuel starvation.

Also a bad coil can cause the same symptoms...

Why would you have to take the motor out?

Hello

Clutching at staws here, do you have a fuel filter or strainer in the line and does it do it at all tank levels.

Grumpy

To do the job right! why else. Hey are you associated with the shop , do you know any good mechanichs?

What the heck are "mechanichs"?

Is that like "Mike and the mechanichs"?

They sucked BTW.....

[quote="littlebluedisaster"] What the heck are "mechanichs"?

Is that like "Mike and the mechanichs"?

They sucked BTW.....[/quote

And so does my typing.

Still need some help getting this p motor to run backwards , so i can put it on this powered wheel barrow i invented.

Thanks In Advance

before going further need to determine if the bogging/cutting out is RPM related or throttle position related.

Sounds like it runs well at 3/4 throttle so try running it at 3/4 throttle and low load (2nd gear) up to high RPM. Does it still bog or cut out?

At WOT does it run well at lower RPM?

[quote="fastassgs"] Ah, I see. You're trying to be funny.

It has yet to be determined what issues this original poster is dealing with. You always troubleshoot easy causes before attempting difficult and expensive fixes. AND STILL, there is no reason to drop a motor in order to rebuild it.

But, please do continue being funny when someone is earnestly asking for advice.

We had a club meeting last night and one beer turned to too many beers. As a result, I did nothing yesterday Original SS coil is too expensive for trial. I hope I don't damage the Sprint coil. We have a meeting in Dubrovnik next weekend and Sprint is currently my only option for this 600 km trip. Original 8 mm ID from local Vespa store. This Vespa was crashed in 1982. and didn't run until two years ago when I did a complete rebuild. That means that 80% of the engine is new. Last winter I went on to replace the crankshaft and every time I open the engine I replace every seal and most of the bearings. Therefore I am 99% sure that everything is in perfect condition inside. The way SS engine is built, it's almost impossible. Anyway, there's no fuel in gearbox oil and, again, engine runs perfect up to highest RPM Everything is original so there's no additional filter installed.

It does it on all tank levels. Actually the fuel tap air pipe is a little short so I never fill it up above it. I think you didn't explain it right but I know what you mean. Good idea for ruling out mechanical issues (seizing as you say). Thanks!



Everyone, I can't thank you enough for your suggestions and ideas. I hope you can help me get this baby to Dubrovnik next weekend. Thanks!

judgeing ur smarter then me in maintenance ur ride all i can think is either timing nor bad electricty deliverence at high rpm normally i will blame my rotor if my bike can last for 10 km without overheated coil

good luck and cheer mate ;D

ps: can i see some pics

His is first one on the left, in first row

Its a damn seal ! and for the record I did say drop the motor after you exhausted all the basics . which from reading the posts it seams he had.
So the main reason i dont post more often with advice is basically everyone just wants the simple easy fix . Most people do not want to hear that they need to actually fix , inspect, or find the root cause of a problem .
exspecially when all everyone else keeps handing them is bandaids .

have fun fidling with your ss you will eventually fix it and teach yourself alot along the way , and that is the rewarding part !

thats awesome and i bet its a fun journey as well

That looks like the opera house in Zagreb? Gorgeous photo!

you beat me to it jake........everything.....building and bikes

hey kivno, put the original on the shelf and run the sprint coil, you can also contact "andrea at scooters 'o'" and have one shipped overnight

call them, they open at 11 but start calling at 10 and let the phone ring(i kid)

http://scootersoriginali.com/osc/?gclid=CLiSz5f3yp4CFRESawodamStrA

So don't post.

and whats wrong with easy if it fixes the problem?

yea, i did'nt quite get that one, but i think southpaw/ i mean southpark just gave em a new "guidline" to follow............see how that works for him

For me it's not a problem to drop the motor (and dismantle it) but I have to know why am I doing this. Which damn seal do you think it is?

Flywheel side has two seals, one on each side of crank bearing. Clutch side has one seal.

Remember, SS is a piston ported Vespa.

Thanks

Exactly! I think it's unlikely it's a seal. It could be, but it's unlikely.

If it's RPM related then I'd be looking at the ignition, and using that sprint coil would be a good start.

If it's throttle position then I'd be looking at jetting. Going to a HUGE main to verify that the tap, fuel line... can flow enough fuel to flood it at WOT. Then working down from there till it will run at WOT, then starting with plug chops to dial it in.

Reading the initial post I assume it used to run correctly with the current setup. So *something* has changed in the motor to cause the problem at faster RMP/load. If it seems that you need to be reaching for fatter jets then it is likely that you are getting a leaner mix, which means an air leak. Likely a seal, but could also be leaking at the head or cylinder base, or even a loose carb.

If the bike is stock then he should never need to change the mixer - only the main jet for altitude.

Again, a coil on it's way out could cause the same symptoms.

And, once again, I wonder: WHY would you advise to drop the motor if you think it needs a complete rebuild?

How long have you been repairing scooters professionally? You ALWAYS look for the simplest explanation first. Eliminate the easy causes and move your way through the system. What if the problem is his fuel line? You want the guy to disassemble the entire bike (witness your furtive cries to inexplicably drop the motor out of the frame). Where is the sense in that?

Any good researcher, doctor, mechanic follows this simple guideline: When you hear hoofbeats, think horses not zebras.

zebras are pretty bad ass though

not related to this thread at all, which is about time, did you know that the zebra is the only equestrian that will turn and chase down a large cat, cougars, jaguars, lions and tigers!!!!

i'm a bit of a nerd

My bet is still on the external coil, but if that does not help here are some more ideas ...

Have you replaced the condenser? A bad condenser can cause high RPM problems.

What float are you using? A lot of shops sell the regular si20 and si24 floats as si27s, but they are NOT the same. They do "sort of" fit but the clearances are not identical and they can cause problems.

You mentioned that the bike was running better with a "P style" plug, but now you have it running with the "standard" plug again. I don't understand this statement, as the SS is supposed to run with the same long plug as a P200.

Is your fuel line too long?

Did you try a 185 or 190 air jet yet?

ill put money on that it is actually starving at top end
check all fuel delivery points, lines, jets and sometimes theres a build up in the tank of crud quick check is disconnect line from carby and blow it back through on reserve as well then your needle and all the carby holes