Modern Vespa

Been chasing a high rpm stumble, haven't been able to jet it out. This is a stock p200, only mod is the sip road. Pulled the flywheel to have a look at the fly side seal and found the cylinder base wet. Could this be my issue? Can I pull the cylinder with engine in frame?

Can't tell you about the stumble, but IIRC you can't just pull the jog with the engine in place.

Which way is the swingarm bolt facing? Ive swapped all my front swingarm bolts so the nut is on the cylinder side (thanks JimmyB). That way I just pull the bolt in a bit and can wiggle cylinders off.

There's a couple of ways to get the cylinder off with the engine in. You can remove the shock bolt and tilt the engine, or you can remove the cylinder studs (double-nut method). I pull the studs... gives you more room to work.

I'll have a look, I've never checked. Seems easy enough. I'll have a look at it. I'm just thinking "that shouldn't be wet". There's 2 stroke spooge on my gear cables and such below that, so it seems it could be a part of my issue.

Not sure if I want to get deep into it yet, I have a Primavera with an air leak and a new selector to install as well. So which one is first? Tough call.

mine was leaking there and didn't want to to stop. Some hi-temp fuel resistant liquid gasket helped straighten it out.

I use MotoSeal down there, never had a problem.

did this a few month back,took a few snaps if your interested

PX Street Racer

Since when has the swingarm bolt ever kept anyone from pulling a jug off? That's the strangest thing I've heard in a couple days.

all things left alone, the jug on the P200 won't slide off with the engine on the bike. MJ was referring to the "workaround" of popping the bolt partway out so that the engine can rotate relative to the frame and give enough room to slide the jug off. Alternative to a full drop or the stud pulling approaches

Yep. Beat me to it. Thanks.

With the stud method do I need to rotate the engine down as well? I've not looked closely at that yet.

Btw thanks all for the input.

Nope. Just pull head, remove studs, get piston to BDC and the cylinder will slip right off.

Personally I'd rather leave the studs alone and do the tilt, but that's jet me. I suppose neither is painless

no,its just some people dont like to remove the studs because its a steel stud into a alloy thread

+1 on studs and motoseal. Not saying your problem is the same as mine, but I fixed high engine stumble with all new ignition. I had multiple flywheels, stators and cdi. But all new is what fixed it. Could have been anyone of the three. I'll never know.

I went out and stared at this a bit. The bolt flip around idea makes total sense now. I'll have to grab some rod of the same diameter to pull off the flip without dropping the engine, but I like this idea. I couldn't wrap my head around the fact that the engine was tipping out towards the cowl, not back and down, until I had a gander and the lightbulb went on. In the smallframe, the tip is always down, then you can do most stuff with the engine hanging down. But this is a different beast!

Now you're on the right track. This works well and here's the original tip from Jimmy as posted in tips n trix thread:

Words of caution from Bar Italia:

"... By pulling the swing arm bolt partway out in order to tilt your motor, you risk bending the actual frame at the bolt on the other side. We have seen this on quite a few bikes, unfortunately."

Thanks Socal, looks like care required!

Is that pipe on all the way up the cylinder stub? Looks to be a gap in the pic which may be the source of that high rpm stumble

I think so but definitely worth a check. Been busy with relatives in town, haven't moved on this yet.

it was indeed falling down a bit. Finished up my fly side seal and positioned this correctly and will see if I've got it. Will fix the base gasket leak next but I'm dying to isolate the cause so one item at a time. The fly side seal looked good but I changed it anyway for insurance.

Lap the head on a mirror/sand paper
Lap the barrel/head union of the cylinder too
One of my five scoots gets a high speed stumble every now and then. ..and its always a loose head
Conincidentally one just did it.
Starts normal..accelerates normal..and then stutters in the last few mm of throttle...not an electricsl miss..more like when its over jetted) which its not ...and Ive had this scoot for years (150 super...dr 177 sip road,24 delly,cut crank)

Noticed oil on the pipe ..head was leaking/loose

I Tweaked up the nuts..problem sorted. mental note to lap the head next time its off......for now tightening the head fixed the high end stumble
goodl uck

Thanks bluecati, will do when I pull the barrel. I pulled my smallie engine so it will happen after that, only one engine apart at a time is my rule.

That's like saying people don't like to remove the flywheel cover because the steel screws are going into an aluminum case.

Btw the exhaust and fly side seal didn't cure it...

this might though PX Street Racer ,few pics of what bluecati has advised

SFvsr,some people dont like to remove steel cylinder studs from alloy threads on a regular basis,I'm sure I dont need to explain to someone of your calibre why this is? its come from a well known uk tuner before you get going

Aren't the olio drain and fill bolts also steel? Seem to me most folks remove and replace them regularly with no problems.

Geez, why do you have to be such a trouble maker?


Yep - using shit slowly ruins it. Nothing lasts forever.

is the process of removing/fitting a cylinder stud the same for a oil change?

how do you fit a cylinder stud correctly?

how do you fit a drain plug correctly?

what can go wrong when doing both jobs?

what softer. alloy or steel?

what tools do you use to do these jobs?

I could link a lot more but you should get the point,also if you do a quick search you will find the drain plug is prone to leaking after being removed/fitted or over tightened

cylinder studs?

Casing - Stripped Cylinder Stud Thread

Same Cylinder Stud Keeps Stripping

Torqueing down cylinder head??

Yeah, you should not over tighten the Drain plug, but I've not seen it leaking just from being removed and fitted properly.

Two of the four example discussions you cite aren't even about what you are talking about.

Does your tuner recommend changing the oil in the case by using some sort of Star Trek transporter device? How do you service a clutch? How do you service the stator? Dude - it is all aluminum secured with steel hardware. Seriously - all of it.

And for god's sake if you are going to bother "researching" a subject at least cite credible sources and not a bunch of people you don't know and mechanical abilities are dubious. Modernvespa might be a collection of information, but as a reference it is not authoritative.

SFvsr,theres a clue in those links

torque settings? why do we have torque settings on different parts of the engine?

the point of posting those threads whether you think there credible or not was to show you can get problems when removing and fitting cylinder studs

now tell me why people strip the 'alloy' threads on a case when fitting the studs?

your arguing about a problem that exists,why?

just to help people if they do have problems stripping case threads

Engine case bolts and cylinder bolts

you make a good point mate torque settings are a very important guide to tightening,but most important is having a decent quality accurate torque wrench ,calibrated

this rather simplistic below

http://www.wikihow.com/Calibrate-a-Torque-Wrench

your accuracy is only as good as the tool your using and i,ve seen torque wrenches less accurate than a poor guess
george

Another reason why 'some' people strip threads when playing with studs

thats what i was getting at asking what tools you use for each job

who torques there drain plug?

To nudge back towards topic - SFvsr can I assume you are in the "remove the studs" crowd? Sounds like it.

AGAIN - that is a thread where the OP has started a conversation about nuts (steel) stripping the threads from bolts (steel). If you are going to continue to cite stuff to bolster your point at least read the stuff to make sure it supports your point.