Modern Vespa

Hi everyone

New to the group. Not that new to scooters but recently got my first in about 28 years.

I have a 2017 Vespa PX150 in the UK. It is standard except for a SIP2 road exhaust (with jet upgrade) and a (Zeus) unrestricted cdi.

It ran well except for fuel starvation at high revs. Checked fuel flow and it was poor, so changed fuel tap for a SIP fast flow version. Project went well and now have excellent fuel flow.

When I started the scooter up after the fit, it ticked over for two minutes then died. It would start again after a couple of minutes but not for long. Now won't start at all.

Suspected old fuel so drained and refreshed. It has a spark. Not fully stripped the carb but checked the two jets that unscrew in the top (clear) and float bowl (seems fine, bit of dirt in bottom but cleaned this).

Fuel is getting to the engine. The spark plug is wet with fuel when I remove it. But it is not even close to firing.

What can have gone wrong? I can only think of trying a full carb clean and/or changing the spark plug.

I've only changed the fuel tap and it is dead as a dodo.

Any advice gratefully received.

Rob

Wet plug it could be too rich to kick over. Clean the carb fully and try with a new plug. What are the jets that are in there?

I'm going to guess that your float needle is leaking, causing the motor to flood.

First, confirm you have spark by grounding a plug to the cases and kicking the bike over.

Once that's confirmed, shut off the fuel tap, kick the bike over a few times, then pull and either dry the spark plug or replace it, then try again.

Thanks for the help so far.

I had a spark the other day but thought it seemed maybe weak. Today no spark at all! I will order a new plug. NGK BR7HS it's what's currently in there.

The float assembly seemed fine when I took it apart, but I am warned of deteriorating tips on the needle so can also replace on the same order.

The big jet (apologies for terminology) is 160 and the small 45-140. Do they sound about right? I can get alternatives to try on the same order.

I think it was running rich before the tap change. The spark plug was black rather than brown. I understand increasing fuel flow can richen further. I have adjusted the mix screw to two full turns out (it is a Spaco carb - tedious job with electric start in the way). Again does this sound right as a starting point?

Thanks again for the advice.

I doubt that a standard PX150 with a SIP exhaust would suffer from fuel starvation, but you've changed the tap anyway which is a good move for future tuning. Try putting the original CDI back on to see if the Readspeed CDI is your issue.

The fuel was barely a trickle with the old tap (and surging) and the fuel starvation got worse the lower the fuel level - so pretty sure was faulty.

I've tried the old cdi with no improvement- so think that's ruled out.

Thanks for taking the time to respond.

I'm going round in circles (and disclosing the rank amateur that I am).

Swapped the cdi back to the original ang got a spark. I wasn't earlier. No sign of life from the engine though.

Swapped back to the Zeus unit and still getting a spark, so don't think the cdi is an issue.

But have fuel present at the carburettor (and in the cylinder) and a spark and the damn thing just will not fire.

So I can change the spark plug and the float needle and can strip clean the carb (a job for next weekend). Hoping (but not convinced) it is going to be the cure.

Sometimes you have a spark, sometimes you don't. The common denominator for both CDIs is the pickup coil on the stator.

Assuming the coil is working, and the magnets that trigger it are also ok, I would suspect the wiring. But to check it, flywheel must come off. Alternatively, you can measure the voltage on it with a true RMS voltmeter, by spinning the crank with an impact driver (battery or air powered).

With that said, testing the spark with the plug out of the engine, and with it in, is not the same. One way to properly test the spark would be with a spark tester. Spark should jump around 7-8mm distance if ignition system system is ok. Other way to test the spark is with a plug in the motor, and with the automotive test light. Clip the crocodile clamp on the HV cable, and bring the test light tip close to the plug. Spark should jump across the open gap if all is well.

The latest model of PX withe the Chinese ignition and stator are prone to failure

Its a VERY common issue on 2012 onwards models. I urge you to replace the entire stator plate.

Yours will most likely be this one - given its year of manufacture

https://ebay.us/m/AAHrlf

Thanks. I've heard that before.

But help me with this if you can.

How do I get it replaced? What do I replace it with? It's beyond my mechanical capabilities. The scooter is immobile. I live in south Manchester. The nearest scooter place (that I know of) is Ron Daley in Barnsley. Is it hiring a van to drive it over? There are a couple of local mobile motorcycle mechanics but not sure they'd be willing to work on a Vespa.

What do you think?

Any advice welcome.

Just seen eBay recommendation. Thanks

It seems intimidating if you've never done it, but replacing the stator is not that hard and probably a fair amount cheaper than getting your scoot hauled to a shop and back for fifteen minutes or less of work, half of which is feeding the stupid wires up to the junction box.

All you need to do it yourself are:

- Screwdrivers (to remove the flywheel cover)
- Flywheel puller
- 19mm socket wrench
- 17mm socket (I think, for the SIP flywheel puller) or an adjustable crescent wrench
- Flywheel holding tool -- You can also use a large screwdriver for this with a bit of practice, but maybe not a great way to start your Vespa wrenching career
- (Ideally) Torque Wrench

Scooterhelp has instructions, or you can find plenty of YouTube videos that show it, too, usually as the beginning of a motor teardown.

Short version so you can decide if you feel up to it:
1. Remove the flywheel cover
2. Remove the flywheel nut. If you have an impact wrench, it'll take it right off. Otherwise, you may need to fit the flywheel holding tool.
2. Screw the flywheel puller into the flywheel
2.A. tighten the center bolt of the puller and it will lift the flywheel off the taper.
3. Disconnect the output wires at the junction box.
4. Make note of how the stator's timing mark is aligned, specifically there will be a mark on the stator that aligns to (probably) "IT" stamped on the cases)
4. Remove the stator
5. Install the new stator
5A. Make sure the timing mark matches what you had
6. Reinstall the flywheel, realizing that you need to properly align the Woodruff Key (the little steel crescent that aligns the flywheel and crank) to get it on. You will feel it slide pretty solidly onto the cone when you get it right. Again, takes practice.
7. Reinstall the flywheel nut. Torque to 35 ft-lbs. You'll want the flywheel holding tool for this.
8. Reinstall the flywheel cover.
9. Reconnect wiring
10. (Probably) Test ride

My personal opinion is that for 30 quid worth of tools and shipping, assuming you have some basic hand tools around the house, why not at least try it.

Worst case scenario is that you're out 30 quid more than you would have been, best case is that you fixed it yourself, learned a little bit along the way, and saved a decent amount of cash in the process.

I would also suggest yoi try to do it yourself. Its a topic we'll covered on the intertubes and YouTube.

I can think of at least one place closer to you if you really dont want to do the work yourself.

https://parrspeed.com/
There are a good few others too but tnat one jumps to mind

If I wasn't booked solid with work I would offer to drive up and give you a hand

Thanks chandlerman and Gravelrash2004. Both very helpful posts.

Right! I'm going to be brave and replace the stator this coming weekend.

I don't use eBay due to previous bad experiences of being ripped off.

I've found what I am pretty sure is the same part Gravelrash2004 you recommended but from Buzzmotosolo - means I can get this, flywheel puller and flywheel holding tool from same place.

https://www.buzzsolomoto.co.uk/scooters-parts.php/id/002815

Gravelrash2004 can you confirm it is the same part? (eBay listing for it states Italian made and photo identical.)

Then just need to get a torque wrench. I've always fancied one of these anyway...

That's the badger

I've used Buzz many times - especially for some remade badges that he sourced for me, from his contact in Spain

Well that has not gone well.

Screwed the puller into the flywheel as far as it would go but the flywheel would not budge.

More force and it has stripped the threads off the inside of the flywheel.

Any ideas where I go from here? I'm at a bit of a loss.

3 legged puller on the edge of the flywheel?

I could try this:

https://www.screwfix.com/p/hilka-pro-craft-2-3-leg-gear-puller-8-/647hp#product_additional_details_container

Or am I throwing good money after bad and should get this to a proper mechanic?

Hmm...yeah...that's bad, but also surprising. The puller should be made of softer steel than the flywheel so that if something fails, it'll be the puller, which you can then curse at, throw in a drawer, and then order a replacement.

The three arm puller will break off the edges of the flywheel where you attach it. The metal just isn't up to the job. And I assume that your flywheel is stock (all one piece)?

If the threads are gone from the flywheel itself, I'm honestly not sure what your options are. How far in had you screwed in the puller? Can you share some pictures?

Pretty much every idea I have is going to either require tools you don't have; and/or be fairly destructive.

if you can get some tension pulling the flywheel off the crank, you might try hitting the tip of the crank with a hammer. That's the "usual" way of removing flywheels on smaller motors like lawnmowers, but I've never seen it work on a Vespa motor. It can also potentially knock the crank a little bit out of true, so it's a single, solid tap, not hammering on it repeatedly.

You could also try heating the flywheel around the crank with a propane torch (like...a lot), then hitting the end of the crank. The fit is established by pressure downward onto a taper, so if you can get the flywheel to expand with heat, that will release tension on it.

Maybe someone else has better ideas than I do at this point.

(The last time I ran into this situation, it was on a Lambretta and the crank were already trash, so I just went at it with an angle grinder. That's not what you want to do)

Are you positive you have the right puller with the correct thread pitch? The threads on the flywheel are pretty robust and shouldn't easily strip. The puller threads could be stripped - try cleaning it up with a thread file.

If it is in fact the flywheel that stripped, you've got nothing to lose by using a three arm puller. I'd apply heat - lots of it - where the flywheel sits on the crank as you put tension on it. It's an interference fit, so heating around the flywheel should cause it to expand and loosen.

chandlerman you are right! It is the puller that has damaged threads and not the flywheel. Having a proper look in broad daylight rather than half light in my shed (and not jumping to conclusions) are my two takeaways!

So plan is to get an new puller and try again but with some heat applied.

Not sure where to go regarding new puller as hesitant to buy the same again. Maybe I'll just try a different one from a different seller.

Expect another post describing further failure in a few days

As bad news goes, that's good news.

Like I said, the puller is softer steel than the flywheel so that if something fails, it will be the puller.

When you try again, make sure that you have the puller screwed all the way in. you can see there's about a centimeter worth of threads in the flywheel, so use a pair of large pliers or a wrench to tighten the puller until it seats, then back it off about 1/4-1/2 turn.

Tighten the puller down and it should break the seating of the flywheel on the taper pretty quickly. If it doesn't, you can try rapping the puller with a hammer to see if that will free it.

You can also try heating the flywheel center with a torch, then quickly install the puller and possibly try rapping it with a hammer. Make sure you're really comfortable with fully installing the puller before you try to do it quickly, though.

The first time I ever tried to remove a flywheel, the extractor bolt sheared off under tension and I had to cut the entire puller off before I could even remove it. That was an older design of puller with a narrow extractor bolt.

I wouldn't worry about that happening to you, but it's a good reminder that while these things can be (and usually are) pretty easy to work on once you start to know what you're doing, but can be incredibly frustrating at the most inopportune times, too.

Make sure the extractor bolt is fully unthreaded for the puller before you thread the puller into the flywheel so that the puller threads are fully threaded into the flywheel threads before the extraction bolt bottoms out onto the crankshaft.

I had a similar issue about 6 months ago on a bike I bought from evilbay. The crank and taper had never been apart or lubed in its 10 years, therfore it had rust welded itself together and I ended up removing the rivets tnat held it onto the boss with an angle grinder and ultimately cutting it off with a 1mm cutting disk... I lost the flywheel, crank and stator

If I had ro do this again, I would remove the engine from the frame and soak the flywheel et al in a container filled with rust remover for a long time - think a few days - then try again

Think laying it on its side into the solution and you get the idea

I can heartily recommend the following as a superb rust remover. Just clean as much oil and grime as you can from the engine first before you immerse tje flywheel side in the solution

This time with the link...

https://amzn.eu/d/b2F8lpR

This stuff is amazing!

Spanish Mk1 T5 Elestart - "Costa Fortuna" (Post 2746977)

Maybe Acetone + ATF, 1:1 ratio.

I don't necessarily disagree, but recall this dude had never touched a wrench before he took this on. He's doing great, even if he got off to a bit of a rough start.

Totally agree, the OP is doing well - albeit as you say.

Good luck!

O.P. - Im UK based, so feel free to PM me

I genuinely appreciate every bit of help and advice!

I've got a new SIP puller, knowing SIP stuff has a good reputation. It feels a bit more substantial than the wrecked one.

Positive: it screws in fully and feels totally solid. Seemingly haven't damaged the threads on the flywheel.

Negative. I've not really gone at it. (It's not the right time when I'm knackered and impatient after work.) But it's still not budging, even after a few taps on the bolt. So Friday/Saturday I'll get some heat on it and try some more.

chandlerman - can't I get heat on it with the puller in place and under tension?

Gravelrash2004 - really appreciate the offer to pm.

Sounds like probable progress.

You can absolutely try adding heat with the puller in place. Can't hurt, and the worst thing that will happen (short of melting it all into a lump) is that it doesn't work.

The hard part of adding heat with the puller in place is that there are already a lot of heat sinks going on there, making it harder to add enough heat to be effective.

I've done this method years ago before i knew any better. It worked on my 50. the only thing i would say, is put the nut back on loosely to protect the threads on the end of the crank.

So I bought a blow torch and went through two rounds of heating and allowing to cool (the second one with the puller in place tight - thinking as everything cools and contracts it could put some nice gentle pressure on it).

When mostly cooled for the second time I tightened the puller and PING! - the damn thing was off. What a satisfying sound. The cone and shaft were clean as a whistle - was expecting some corrosion or similar binding it in place.

Stator plate swapped out in minutes, reassembly only a few more minutes (using a torque wrench for the first time in my life).

And it fired on second kick! I almost wept with joy.

Might be idling a touch lean so will adjust in the morning and take for a longish ride, pull the plug and start quizzing everyone about jetting (which I wasn't convinced was right before this episode).

Thanks everyone who helped for their help. Confidence and knowledge both boosted.

HAHAHAH! This became a fun read... with everyone pulling for you and that damn flywheel to pop off. Way to keep your cool and see it all through.

Yes!

It was a long and painful journey, but you did it!

This is one of my favorite wrenching success stories in a long time.

You also now know why (if you've been reading along for a while) I love and always post/encourage First Start Videos--there's just something so satisfying about that indisputable "Yes/No" of kicking the motor and have it turn over.

Congratulations on your first successful Vespa repair. Believe it or not, while there's obviously a lot more to know, there's not much you might do to maintain or repair one of those motors that's more difficult than what you just accomplished, though there may be more moving parts and different challenges involved.

As to the idle's richness (or lack thereof), it should be within the range of the mixture screw. There's plenty of guidance both here and on YouTube about how to tackle that, but we're still more than happy to assist to the extent we can.

Enjoy your scoot this weekend. You've absolutely earned it! Maybe post a shot in the Vespa's That Have Left the House thread to celebrate.

Well done sir!

You did it and such a fantastic write up too. I believe we have a future mechanic with "golden hands" amongst us


I applaud your dedication and results both!

Well I'm running but it's still not right...

Ignition seems fine and lights are brighter and less flickery with new stator - or am I just imagining this?

To recap - the reason for starting this project was serious loss of power with consistent (more than say 5-10 seconds) 3/4 throttle or more.

So changed fuel tap for fast flow. Old one was slow and 'glugging'.

Then wouldn't go at all so with excellent advice replaced the stator plate.

But have exactly the same problem. Great at low revs or variable throttle but dies on 3/4+ throttle for anything but a short period. So if fuel flow good and ignition good problem has to be in the carb, right?

I plan to strip clean the carb. Watched many a YouTube video on this. And I'll replace the float needle.

But could it be the jetting? I'd like to order any alternatives with the float needle as I spend more on shipping than the actual parts. Stock barrel and carb with SIP Road 2 exhaust (fitted before I got it and told was upjetted accordingly).

Idle jet is 45-140 (though appreciate this does not affect top end of running). I read stock is 45/160 go guess this has been upjetted?

Main jet is 160 BE3 100. I read stock is 100 or 102, and that for SIP 2 exhaust should be 104 or 106.

Any advice continues to be very welcome!

You definitely need to up your main jet if it's still stock with the SR2. Now I worry about whether you've been soft seizing. When you say "loss of power," does the engine fully stop, or just cut out like it's hitting a governor? (And is your CDI rev-limited?)

For comparison, here are a couple videos. Is what you're experiencing like #1 or #2 (it's like going to the eye doctor, but for scooter symptoms )

Fuel starvation:
or seize (this was a lot more than a soft seize, but you get the idea):
Unfortunately (for you), I don't think I have a video of a motor running that's just too lean, but not full-on destroying itself.

If you can share video or audio of what you're experiencing, that will help a LOT with diagnosis.

Agreed totally with all chandlerman comments and observations and advice

A video is a really helpful thing to see and listen to


Heed well the advice of the Sage that is Chandlerman


Many an issue had been resolved with a well cleaned carburetor, new plug, HT cap and lead also..

Is it better with, or without?

Very much like video 1. I really think it's fuel starvation. Loss of power (but not a hard stop) that recovers after about 5 seconds off the throttle.

I had a proper seize once. On a horrible SIL GP200 on the M1 motorway in 1994. And it wrecked the engine. New crank etc. Bought that scooter from new and sold a lovely 1977 Primavera to part fund it. To this day I don't know why…

Can you explain a 'soft seize'? Heard the phrase a lot but don't know what it means.

But there is no lack of fuel at the carb with the fast flow tap. It's gushing out.

I don't have a rev limiter. I thought that was the problem as stock 2017 model does (so I'm told) so swapped cdi for a Zeus unit with no limiter.

The plug is box fresh, and the HT lead is as new as the cdi.

So plan is:

Strip clean the carb. Replace float pin. Get a 102 and 104 jet. Replace plug cap. Start up with 102 jet and see if there's an improvement.

Any better or other suggestions folks?