Modern Vespa

After a few weeks of god fortune and 1st kick starting, my P almost whooped me...

Drivin home on PCH just now, doing about 35-40 in 4th gear, the power came down out of nowhere... The engine started to sound like it was running out of gas (it wasnt) and then immediately, the back wheel locked and I skid for a good 40-50 feet... then as the scoot slowed down, everything came back up and was well again...

I am leaning on ghost as the problem, but I am sure you guys are much more knowledgeable... help? please?

-Gmo

You seized your piston.

Basically, the aluminium piston and iron barrel expand at different rates. When the piston heats up too much, it gets stuck. That's how your wheel locked up.

Each time it happens, it damages the cylinder walls, making it more likely to happen again and again.

Seizes can be caused by inadequate lubrication, brought on by a lean condition.

Brotha Ian is correct, some time the oil injectors clog or oil jet, check your spark plug I bet its more of white beige color. Take it easy until you get that piston changed.
Ive changed my own pistons before, not too difficult. Or you can take it to one of the local Vintage shops, I hear the guy from OC, Mossimo is pretty good and reasonable.

Good luck and sorry to hear you seized

Manny

That's also why it's a good idea to always cover the clutch lever while riding. When you feel the engine start to lock up, pull the clutch and shut down the engine. Coast to a stop, let the engine cool down, then start up again.

Luckily, you SOFT sieized instead of HARD seized. ( i.e. the piston locked up TEMPORARILY instead of PERMANENTLY )

Nevertheless, rarely when you soft seize do you not lose some small amount of compression... the piston rings typically suffer some damage, the cylinder walls get scored a little.

So, it happened for a reason ( jetted too thin. autolube seized, too hot a plug, ran out of oil ... too high compression - though i doubt this for a stock P200. )

1) would be to figure out the reason

2) would be to pull the top end, check it for damage, and possibly run a ceramic ball-hone down the barrel to re-crosshatch it and smooth out any of those scores you might have put in it. ( we call the thing a "dingleberry" - the ceramic ball-hone )

thank you for the wisdom... sounds like a bigger problem than I had hoped for, thats for sure...

Is there any order of operation that you would suggest starting with? trouble shooting if you will?

My guess is plug first... If its too lean, adjust the mix jet?

also the oil... do you think that the two stroke line may be clogged somewhere?

As far as pulling out the piston, that seems like its going to be a job and a half, no?

Having recently reinstalled the autolube parts in a P motor, it's hard to see what would go wrong with an autolube, although anything is possible. I think I'd look at the other things Eric mentioned first, because they would seem to be the more likely...jetting and/or plug.

I agree with Len. First of all check your carb. If the jets are dirty less fuel and more air are coming inside your cylinder so you re running too lean, thing that could cause an overheat. Clean your carb well with carb cleaner!

I think most likely you probably have too small a main jet.

Is it a stock P200? What's your altitude? What's your main jet ?

etc.

its totally stock.. I just rebuilt the carb as far as cleaned and re gasketed. I am not sure what my main jet is, but, like said... nothing different...

ALSO

I redid it over a month ago closer to two... and have been driving it around fine for all this time just fine

I dont know if this helps u guys...

Thanks again

Might it be possible that you got a non-autolube gasket kit? That would cover the autolube hole, wouldn't it?

Someone check me on that.

If you have removed the autolube mechanism, this is a good thing. Covering the hole prevents air leaks into the engine. If you still have the autolube, then you'd have to cut a hole in it to put the carb back on the engine. Either way, you're going to notice.

The main jet is the big brass screw, on the tip of it, it has numbers on it that tells your the jet size..
roughly how many times have you gases up since rebuilding the carb. Also have you put in oil in the injector since then, that would be a good clue.
What did you follow for the rebuilding of the carb, i.e. online, Haynes manual, friend etc.
Did you adjust the rear air screw 1.5 out after tightening?


In the future, only fill the injector oil bubble a little above window, that way you can tell if the injectors working.

Just curious, what city do you live in?

Im off line until maybe Sunday, hopefully someone else can help you out in the mean time. .

Good luck.

Manny

Or, fill the oil reservoir as far up the nect as possible, measure the didtance between the level of the oil and the top of the neck and see if it drops after riding a reasonable distance.

Al

well, back after being gone for the weekend. To answer some questions


The oil system seems to pump the oil out fine. I go through two stroke about as fast as gas with no puddles under the scooter...

My gf's dad brought up the point that if the carb was not perfectly torqued when i put it on, that it may have warped just enough to cause the lean condition...


regardless, I have my work cut out for me. Tomorrow after work I will start opening things up... its just too late tonight.


And for the person who had asked, I live right on the border of san pedro and palos verdes...

Thanks for all the help so far and I will keep everyone posted and ask plenty of questions...

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theres the plug... runnin leeeaaaan


Also, I found the culprit of lean-ness... a little bit of leak coming from under the carb of 2-stroke oil... not even enough to make it out of the carb box, but enough to mess up my week or 2

There you go.

Might need to lap that carb if it's not completely flat on the bottom.

Honestly - that plug doesn't look lean at all to me. I've always tuned my scooters the way I tuned two stroke motorcycles - looking in the well between the electrode and plug casing for the color. The top of my electrodes are just the slightest bit tan. Everyone seems to be tuning vespas to be dark dark brown on the top of the electrode - and that just means the chamber is too rich or too cold to burn the excess color from the tip.

I.E. "When you look at a freshly removed plug from a two-stroke engine and make decisions based on the color of the oil deposited on the insulator nose you are likely passing a meaningless or incorrect decision. We all see plugs which are just wet and know that the mixture is far to rich but the real analysis takes place by reading the insulator deep inside the plug body. The insulator is coolest where it contacts the metal shell, which is where you "read" your mixture stetting. Look far inside the plug, where the insulator joins the shell,if your engine's mixture is too rich is a colored ring will be present. If
this ring continues outward along the insulator to a width of even a millimeter you can be sure the mixture is rich enough to be safe, and too rich for maximum performance.

In most engines best performance is achieved when the mixture contains only enough excess fuel to make just a wisp of a "mixture ring" on the plug insulator. "



From http://www.strappe.com/plugs.html :

A lot of amateur tuners, some of whom are fairly successful, will look at some plug freshly removed from a two-stroke engine and offer advice based on the color of the oil deposited on the insulator nose. In fact, if the plug is hot enough there won't be any color, and if there is that still has nothing much to do with air/fuel mixture. If you think about it you'll realize that the only color you can get from an air/fuel mixture is the color of soot. When the mixture trapped in an engine's combustion chamber has more fuel than can be burned with the available air, then combustion will be incomplete and the excess fuel will remain as soot, which is not brown or tan or magenta or any color other than black. And if your engine's mixture is too rich, the sooty evidence will be present on the spark plug's insulator, in a very particular area.

We cannot stress too strongly the need to give spark advance your closest attention, because excessive spark lead is the most frequent cause of detonation, which is a real engine killer. You can't stop advance-produced detonation with a cold spark plug, nor with anything but a wildly over-rich mixture. Also, excessive ignition advance has a bad effect on performance. We ran a 250cc road racer at the drags a few months ago, and found that retarding the spark about five degrees from the manufacturer's setting raised the trap speed from 106 to 110 mph. Similarly, there's a 125cc motocross machine residing in our shop which runs a lot stronger and cleaner since it has been retimed for less advance, jetted leaner, and been given a hotter spark plug.



My opinion - look somewhere else, that plug looks more than rich enough.

Very nice, thanks. I know I wasn't looking as deep myself.

P200 carbs if not torqued they will warp. Thats another reason I bought a GTS (fuel injection).



Eric, How would you determine if a carb is warped or level? I have three extra 24mm carbs for my rally.

Manny

Well, 2 things.

1) a badly warped carb can be dangerous as it will bind up the slide mechanism in a certain position - usually open - and you won't be able to free it when you're riding. That's scary. I've heard of people filing down slides and carb bodies to make them work correctly again after they've been warped, but i've never done it.

2) the physical bottom of the carb ( like other aluminum cast parts including your cylinder head ) can not be perfectly flat, and as such it can allow air to suck in between it and the engine cases. You can lap the bottom of the carb much the same as you lap a head ...with 300 grit sandpaper taped to a piece of glass, making figure 8 motions across it. Then there's some way of testing it with a paint or powder ( think : rubber stamping ) to see if there's any spots you've missed.

Cool thanks Eric, Ive had carbs in the past where the slider would stick. I almost rode my rally up a tree because of that carb sticking.

Thanks for Tech tips.

Manny

wow... yea, I noticed the same night of the incident, EARLIER the slide had gotten stuck... looks like the carb is definitely warped... That is no bueno...


so. the laundry list of things that need to be done- (feel free to add)

-Flatten out bottom of carb (via sandpaper)
-that will allow it to line up and not leak two stroke
-torque it properly this time (god I suck)
-Take off cylinder head and check out the scoring
- have it re honed
- purchase new piston kit
-head gasket (?)
-plug

what size carb would a p200e require? I am lookin on ebay just for prices... little bit confusing...

the guy on vespa maintenance was rocking a 24/24

they have a 20 on there that they claim fits p200's... I feel like you are the best people to advise me here

-Greg

Dellorto si 24/24 E
You dont want a 20mm unless it's all you got in the parts box and your friends are leaving for the rally without you

sean s

thanks for the response.

project update...

Opened up the head. I am guessing the thick vertical line of discolored metal in the cylinder is the scoring? i would imagine the inside of the cylinder should be uniform looking...?

unfortunately, the cylinder ALMOST comes off without removing the whole engine, but to complicate my life, it doesnt...

I think I am just gonna say F it and sell it to some sucker for more than what I paid...


kidding.


Baaaaack to the garage

as far as telling if the bottom of the carb is warped, any suggestions on what to use? assuming the kitchen table is not the best bet

remove 3 / 4 of the metal cylinder studs

( use the nuts that hold the head on - screw two on a single stud, tighten them together, and then use the INSIDE one to unscrew the stud from the case. Remove nuts from stud, put on next, repeat )

The head will come off without issue then.

you, my bearded friend... are a hero.

so post having it honed, that is when i will know what size piston to order, correct?

-G

You're having it honed or rebored? How deep are the seize marks.

You need to get a micrometer on the inside of the bore, check how deep the scratches/gouges are and how much material they'll have to take out.

Then, when you have the correct measurement, order the piston, taking into account if you'll have to go to the next oversize, or even more, depending on how much material they'll take out.

Always include the piston with the cylinder when you're getting a rebore, because they'll need to check tolerances.

You should have a piston there with a hone too to see how close to specs you'll be.

If you don't do it this way you're asking for trouble.

Andrea

the scratch is not deep at all, its more visible than anything

when i run my finger over it its not even really noticeable

Doesn't matter. Whenever material is taken off the cylinder wall you should have the piston there to check tolerances.

One of the potential problems with honing is that its very easy to take material off in an uneven manner.

Any machine shop thats worth its salt and knows what its doing will require the piston to be there before they'll even accept a rebore or hone job.

We see home honed jobs all the time where the cylinder tolerance specs are all over the place depending where you measure and the owner has been wondering why they've been having running problems!

Andrea

Thats good advice, Id purchase a one size over piston and have the cylinder machined to match.

As for the Carb, 20mm will work as well as the 24mm. The 20mm has a quicker takeoff but the 24mm will have a better top end. Match what came out of the scoot.

Id suggest not buying one from Ebay, you dont know if they are warped or not, PM Andrea and ask her if she has any and how much, maybe she has a good used one. Then try using our sponsors first, then try the sales threads on here before using ebay.

Good luck
Manny

so after a month of sadness, I am finally getting to work on my scoot. (long story involving shitty sales people)

Regardless, I should be getting my piston kit and a new cylinder ( surprisingly more economical) tomorrow... The bad news... While trying to preemptively take off the old piston, I realized that I cannot get to the rear circlip holding the piston head on..

I checked out VespaMaintenance and he did it with the engine out...

Can I do this project without taking the engine out of my P?

NVM... I got it


Modern Vespa... making me more intuitive

Probably not. It'll be easier to just drop the engine than to figure out a way to do it without.

oook.

i need help.

Frustration building.

I have the parts all set up. Attached new piston but the new cylinder is very resistant to sliding on. am i missing something? tool? trick? something?

It's hard sometimes.

Remember that the piston rings 1) need to be oriented the correct way. If you look, one side of the end of the rings has a notch for the orienting pin Make sure that's correct

2) focus on 1 ring at a time.. get the first one lined up, use your fingers to press it down and hold it tight, and slide the jug over the first ring... then do the same thing to the second.

Greg,

Can you take any pictures?

for those who are not sick of project updates...


everything is reassembled (thank you so much)

however


it is running SUPER hot... like... took it for a mile ride and came back... it was just unbelievable hot... also, ran sluggish

also, the attachment for the exhaust did not stay threaded and came loose... not excited about that.

SO super loud and super hot...

with a new cylinder and piston, is there something Im missing. something I could have (and probably did) screw up?

These were new rings, i take it. Were they properly gapped and all when you reinstalled them? Sometimes they are too big and need to be shaved down a hair at the tips.