Cutting out and not idling. revving up and down on its own.

[sime66]

Since before Christmas my scooter has cut out on me a couple of times, which initially I put down to water getting into the electrics somewhere; it has been extremely wet here. Not having a shed to work in it’s been difficult to get a long enough dry spell to have a look at it.

This morning it started up fine, but cut out before I’d got to the end of the road.
I gave it a liberal spray around plug, CDI etc with WD40 and changed the plug and she started up, but won’t idle smoothly –

If I sit with no hands on the throttle it revs up-and-down as if I’m blipping it like a boy-racer.

I am now thinking it might be either CDI dying or carb, so I started with the carb (in-situ):

(When I took the top off there was plenty of fuel in the float chamber, so it’s getting that far OK)
(The choke mechanism and throttle slide both work smoothly from the controls)
I’ve cleaned main and idle jet, cleaned the filter and checked float and needle valve. (it's a new, red-tipped needle).
I’ve checked the carb is tightened down OK (not torqued; just hand-checked so far)
I’ve also checked my cylinder head bolts, and they are all OK too.

I could remove and service the carb completely, or I do have a 2nd-hand Dellorto 24/24, which I have overhauled, but never used yet (so I don't actually know that it's OK)

The symptoms before my attention to the carb are exactly the same now that I’ve put it all back together. It starts, pulls away, stalls, will start again, but won’t idle and is revving without my doing anything. – Not revving wildly high, but as if I was revving up and down.

I haven't touched the idle screw because it was idling nicely before this problem, and I don't want to mess it up, but it might be the next step; I don't know.

I’m now thinking it must be back to the electrics - along the lines of:

Wiring to CDI
CDI
HT lead and/or cap
Stator-related
Something to do with the new reg/rec, which is working fine, and I can't see they're related, or is that now putting a strain on the stator?

Does anyone think it might be anything else that I can check, before I start ordering and waiting for replacement bits?

I’d appreciate any input chaps, or a sensible order of testing it, given the symptoms above…..

[bsr65]

sounds like an air leak, check the condition of the carb & carb bottom gaskets to start with.

[bryno]

Ditto, air leak causes irratic running and reving up unaided, not an electical issue IMO..

If not carb leak, could be air leak at the flywheel side oil seal, they suck in air there which screws the fuel/air mix and makes it run lean and erratic.

New seal a couple of quid and easy to change without splitting the casings (on a PX).

[sime66]

Thanks chaps, both of these make sense to me;

From the odd self-revving I did think air-leak, but having checked round carb and cylinder head I was having a rethink back to the soggy electrics.

. I can do a bubble-check round the carb (sure I read it here somewhere, will find it again) to dismiss that one, can't I? Certainly needs a proper careful check anyway.

. I've just had a mate split the casings and change cruciform, selector-rod AND the hub-side oil seal and bearings, so as this has all been disassembled recently it has to be prime suspect. (I had looked for oil leaks, but didn't realise that air could leak here).
I suppose I should check the casings gasket too; could air suck in without oil leaking out?

Possibly on a similar note, since getting the scooter gears overhauled I've had a couple of sudden high revs when accelerating and changing-up through gears, which I was beginning to suspect was due to either clutch again, or poor shimming or something similar; but now I'm wondering if it is possible that it is this flywheel-side oil seal that's to blame; it might be the cause of both symptoms, which I hadn't linked 'til now.

In the meantime I'll have a read-up about changing this flywheel-side oil seal, no doubt I'll have a few questions before tackling it. I know for sure that I'll definitely be asking about brand, manufacturer, supplier, quality etc. because otherwise it seems to be a lottery getting something that isn't rubbish.

Thanks again for the replies, they certainly give me something to be looking into.

REVISED:

Just an afterthought - Can there be an air leak at clutch cover?

[mickymidas]

Shouldn't be air leak at clutch cover unless main crank seal has gone . If clutch cover O ring is leaking, oil would be seeping out .



I think

[bryno]

leak on clutch side will just leak oil, not suck in air, fly side seal is most obvious.

Damaged or poorly sealed casing up near the carb box would also cause a problem, but less likely.

Bent crank will also give a problem with keeping it air tight at the fly seal, again less likely.

If the fly seal was not changed when casings were split it could easily have got damaged then if it was not already gone.

Personally, I'd do this before anything else.

Oh, another leak culprit is the carb body, these can get warped if tightened down too much, so nuts will be tight, but it will still leak, sit the carb on a piece of glass to check it's totally flat.

But fly seal first I'd say.

[kru251]

A quick fix on the distorted (potential) carb base (if indeed it is after the glass test) is to use a couple of std gaskets one on top of the other to help alleviate the distortion factor. Not how it was designed to work, but it's a good, workable solution to the problem.

[bryno]

i'd perfer to put a piece of wet & dry on the glass and move the carb in fig of 8 until it's perfectly flat..

[sime66]

I appreciate all the suggestions; definitely looking at doing both jobs.

Think I’ll take the carb off and service it, and in the meantime put the 24/24E on, which is overhauled and waiting anyway. I can do those jobs this weekend, whilst I’m waiting for the flywheel puller and holder, which I have to order.

If the 24/24E solves the problem, then I’ll be happy to finally have it on.

If the 24/24E doesn’t solve it I can put the serviced 20/20 on to see if that solves it. I know what you mean about flattening it with wet &dry on glass; I did that with the 24. I’ve also got sheets of several different thicknesses of gasket paper, and we also discussed before about making them out of allsorts, rather than using bought, non-fitting ones.

If I’ve still got no joy with the serviced carb I’ll do the flywheel seal (my mate, who split the casings, reckons that would give high revving, rather than intermittent revving though?)

I have read-up about flywheel extraction and seal replacing, it seems pretty straight forward, but I have a couple of quick questions:

1.How do I take the stator plate off without mucking up timing; do I mark it or is it obvious how to put it back as before?

2.Can I do any useful jobs with the stator whilst it is out? New pick-up thingy, etc? I will renew the wiring out because it is very old and suspect around the CDI.

3.Do I need to drain the oil?

4.AND the obvious question – any particular make, colour, or reliable supplier of the seal? I know they’re cheap, but I still want to get the right one.

Thanks for your advice; at least I have a plan of action now…….

Latest:
I did a couple of films to try to show the revving and cutting out. These are both cold with choke, and I couldn't keep it running long enough to warm up or ride along for a stall. In the first one I'm just trying to keep the revs up enough to keep it running evenly, but the second film in particular shows it revving on its own.

s1290.photobucket.com/user/sime6954/media/P1110768_zps49cb84c9.mp4.html

s1290.photobucket.com/user/sime6954/media/P1110769_zps1c823687.mp4.html

[bryno]

1. There are marks on the stator and the casing it bolts to, you can't really go wrong, if the marks are not currently aligned (which is possible) just mark yourself with tippex and put back exactly as you removed. You dont need to remove the wiring, the stator can just hang on the wires whilst you lever the seal out, its really quick to do.

2. If the wiring is bad, freyed or rock hard yes change it, (with same guage of proper heat resistent automotive wiring and soldered ends not crimp ons) if it looks ok, I'd not mess with it. No need to change the pick up, its not a service item, if it was duff you'd be misfiring.

3. No need to drain oil, you are working on the dry side of the engine.

4. TBH, for the fly side I'd just buy what is convienient from a decent dealer like Beedspeed who will have sold thousands of them (though personally I'd probably go for their most expensive option), IMO there really is no 'best' when it comes to seals, premature failure is probably more down to how carefully they are fitted (dont forget to grease it)

I'll take a peek at the vids later..

[sime66]

Thanks again Bryno, you’re on top form with this one; I’m confident about doing the seal. I’ve put a Beedspeed order together for this morning.
Did the films show anything useful to confirm probable air leak? Did you notice the little back-fire at end of 2nd film?
Just trying to decide whether or not to do the carb whilst waiting for seal and tools; that tackles air and fuel, but complicates the fault finding it not the cure.

[bryno]

Sure you'll get there!

Having heard the vids, it does sound like it's misfiring, with an air leak it would not really misfire, just not hold steady revs or rev higher than usual and be very slow to die back down when you close the throttle.

Personally I'd stick with changing that fly oil seal first as its easy enough to do and check the carb base is flat, but maybe not spend time stripping with the carb.

I'd also go over the CDI connetors, HT lead, plug cap at same time, check the HT lead is not stuffed doen the back of the engine casing, they can short on the metal of the casing.

Have you checked the head is down ok? i'd back off the nuts and do them up again (in stages, diagonal)?

If none of that works, CDI would be my next port of call, maybe borrow one to try if you don't have a spare?.

After that, the pick up on the stator, then the stator itself...

[sime66]

Chaps – we have progress, of a sort:

. I cut-back and rewired the terminals to the CDI – no change, but it needed doing anyway.
. I ran it again with much misfiring, but I persevered and when it stalled it smelled strongly of petrol, so I took the top off the carb. When I removed the top off the carb fuel filter, fuel leaked out, and that chamber is full – I don't know if that's as it should be? (There is a film and photo below)
. As I was there I pulled out the HT lead and it was corroded both ends, so I cut it back 10mm each end and refitted it. I checked for a spark, which was OK (Can't say strong or weak, but definitely present).
. I started up and set off and did manage to have a good ride to warm it up. It feels nippy too because I've cleaned the air filter.
. When I got back I grabbed my camera to record it idling when warmed-up, which I think is pretty good. The throttle response seems good, and it cuts off quickly with the ignition OK.

So, fingers crossed, I'm narrowing it down I think. Still unsure about all that fuel in the carb, and whether my novice hands should still tackle the flywheel oil seal and the carb seating. I think I will, but I'm busy now until the weekend, so a couple of rides beforehand might indicate whether those jobs are needed.
It ain't finished, but there's definitely progress, and big thanks again for the excellent advice.

There's still fly seal, cylinder head, carb seating, CDI and stator to go at, but a bit of monitoring progress first I think. I'm still going to order all the stuff - something for the weekend.

A photo of carb top, and films of top removal (not sure if they show anything) and idling when warm, which I think is pretty healthy now. Tomorrow morning will tell:

s1290.photobucket.com/user/sime6954/media/P1110775_zps0c4dba18.mp4.html

s1290.photobucket.com/user/sime6954/media/P1110771_zps7615aaaf.mp4.html

i1290.photobucket.com/albums/b538/sime6954/P1110774_zps27727e3b.jpg

[bryno]

Better then!

Smell of fuel could just be because it's misfiring and not burning it, or it may be being fed with more fuel than it can burn..

Have you tried running it with the filter off?

If you do that and it is blowing back a lot of fuel through the top of the carb and/or you can see petrol hissing out of the brass tube even with the fuel tap off, then the needle valve in the float bowl has gone bad OR the float itself has a hole in it.

In which case remove the needle and clean the needle seat with carb clearer spray, cotton bud or whatever.

Shake the float and see if it has petrol in it, I've seen a couple of PX's with this problem, when the float gets fuel in it, it doesnt stay afloat, so the needle can't shut the fuel off when the float bowl is full.

Worth a check whilst you are waiting for the other bits

[sime66]

I did the float and needle yesterday, both are new, in good nick and moving freely. Worth another look though; what I didn't do this morning is check the carb after I'd had a decent run and got it idling warm. Now it's running those observations may be OK. If it still looks dodgy I'll follow the steps you said. I didn't expect fuel to flow out when I took the top off. As you say I can check that whilst waiting. There is no fuel in the carb box..

The other bits are as good as ordered, I'm just waiting confirmation that the cap I need is a resistor cap (NGK LB05F) I've queried it because mine is black and I have no reference for it. Other than that I'm ordering all tools, seals gaskets and HT stuff to do all jobs around flywheel, carb, and clutch cover 'o' ring, either to do them now (weekend) or spares for later.

How do you think it sounds when I've got it idling warm?

[bryno]

Can't seem to run the vids, probably just my home PC..

tell you what though, I've never seen the inside of a carb box and a carb so covered in crap, no dirt should get in there.

Can see you have no rubber seal around the fuel pipe which means you'll be taking in water/dirt off the back wheel area and do you have the hose to body flexy hose on? and also the 2 grommets in the box lid?

[sime66]

Blimey, didn’t realise. All others, including body to box flex, are there, I’ll order and fit the fuel one. Carb box is coming off on weekend, so will get it and the carb spotless and sealed.
Think the vids are OK, but changed the tickover one to .avi, which might help:

s1290.photobucket.com/user/sime6954/media/P1110775_xvid_zps999bc72d.mp4.html

(Looks like photobucket converts everything to mp4 anyway, so that probably didn't help)

[sime66]

Morning Update:

No need to worry about that warm tickover film because it's back to surging and misfiring again this morning - had to leave it at home.

It also took a lot of kicking before it started.

Funny how it was OK for a while when I eventually got it warmed up yesterday. Makes me wonder if the muck around the carb is blocking it somewhere, which clears after perseverance.

Anyway, as long as the stuff arrives it's back to plan A, which is fly oil seal and carb, and cylinder head bolts - I'll do the exhaust as well.

I've got a new cap and HT lead coming, and all carb gaskets in case I decide to strip it. (I might try the 24 whilst I've got the 20 off).

I'll sort and fully-grommet the carb box too.

I'm going to give the engine a scrub to see if I can see where the oil is coming from (suspect clutch, and have a new 'o' ring coming).

I suppose after that it's CDI, and then the pickup on the stator if not the stator itself.

Bit of a bugger, thought I was on the right lines yesterday, but I suppose it's just working through methodically when time and weather permit. (No shed as I said).

I'll update over weekend......

[rab]

get a shed built old pallets bolted or nailed together for frame then just ply the bugger on the outside and felt the roof

[sime66]

It's all stripped out and cleaned up.

It might not be the cause of the problem, but I reckon I’ve definitely found a problem with the carb. Although the slide moves freely, it won’t come right out, and you can see where it’s been rubbing, so I think the carb body is warped from overtightening. Looks like someone had trouble with air leaks in the past; there was loads of red gunk (liquid gasket) both sides of the carb body. Anyway I think the 20/20 is written off:



I have been waiting to try this 24mm out anyway, so that’s the plan. First obvious thing to note is the different size and shape of opening. I think it’s a Dremel job to do it properly isn’t it? Just one thought though – as the inlet on the engine matches this carb box, and I am not cutting the engine, I can probably get away with not cutting the carb box for now – just to get this up and running again and take the carb out of the suspects list for the ongoing problem? Or should I really open up the carb box?



All the other stuff came today, so I’d like to at least temporarily put this carb on to see if a clean carb with new gaskets in a clean, sealed up carb box makes any difference, so I can crack on.

Lastly – I’m not supposed to be using any liquid gasket am I?

(Rab, re shed: Ain’t got one, can’t have one, doing the best with what I’ve got: a manky old scooter and a bit of shared garden to park in).

[bryno]

Best to open up the carb box if there is an overlap, though you'll probably find the inlet to the engine is a restriction anyway, If you dont want to make the hole in the box bigger, just radius the edges so the fuel/air mix flow is a bit smoother where carb joins the box.

No liquid gasket needed... ever - Piaggio never needed it!

[sime66]

These are disgusting, and I’m embarrassed to show them, but here they are. Before and after shots:





A lot of careful cleaning needed yesterday.

Fitting the 24mm this morning went well; didn’t cut the box for now because it’s about the same as engine – can go back to it sometime, saw some bevelling and will improve on it when I get a Dremel.

Still a bugger to start, and still have the same erratic revving and cutting out when cold as before though, but when I managed to keep it going long enough to get warmed up she ran beautifully, and really nippy. I’m going to like the 24mm.

Got the warm tickover going, so I could adjust the idle; I’m part way through setting that up. Bit of bogging down to sort, but I think that’s going to be OK.
So, although it’s good to finally have the bigger carb on, and everything cleaned up, I’m still working through the possibilities we discussed before to sort the initial problem – ran out of daylight today. More of the same tomorrow………

Film: (ticking over, warm with new 24mm carb; good idle, but a bit of a delay in throttle?)

s1290.photobucket.com/user/sime6954/media/P1110872_zpsc479d611.mp4.html

Photo: Cleaned up and grommeted, and a lesson learned!

[pxguru]

Sime66, Did you check the gear box oil? Just to be sure, if you take the plug out under the gear selector just a little oil should run out. If nothing comes out put some in. If its really runny and squirts out, then we need to have a chat

[sime66]

You’re thinking no oil or blown seal?

I checked the oil and had a sniff just before Christmas, it all looked and smelled normal to me. I topped up a little to be sure; think at the time I asked here because I was worried about over-filling without draining it all and measuring back in.
I squeezed less than 50ml in, until I was certain it was coming back out, which seemed reasonable.
There’s no oil hanging off bottom of engine and no oil patches on floor. I think all is well there, but will check again.
Because, now the carb is done, and as I was going to look at my mates recent work for leaks/seals as my next area to check, he has offered to go back over it himself, so I don’t have my scooter now until the weekend.
If he hasn’t done it, I can do an oil change and check when I get it back.

Stripping and changing the carb was as ambitious as I've got for doing my own jobs so far, I’m doing more and more for myself as I pick it up, but I’m still leaving open-engine jobs alone.

[bryno]

Nice job on the carb

Have you done the fly side oil seal yet?

[sime66]

No bryno - I got the tools and seal to do it, but my mate wanted to check his own work, (all leaks associated with split casings including all seals, which I'd asked him to check before), so that's fair.
While he's got the flywheel off I've asked him to continue checking the electrics, which I'd have done at the same time, ie stator wiring/pickup/new CDI. I've done the HT on weekend.
The thing is it runs great with new carb when warmed up, but is a bugger to start and keep running cold, and did still cut out idling warm, (but that might be just setting carb up (or CDI?)).
I'm narrowing it down; He has it for the week now to go over his work, I'm confident good news is imminent.
Will of course report back when solved.

[bryno]

Good progress then..

Yes, you may need to tweek the pilot jet to suit your set up and probably the mix screw as well. Not sure that would have much bearing on the choke and cold starting though.

Be good to get the stator wiring checked over though, if it is still the original stator and wiring, it may be a bit fragile, mine is a 1985 and although genuine low miles and all original, the stator itself had gone faulty and some of the wiring a bit crusty..

[sime66]

There's two, probably fairly separate things now, setting up the carb, and still fault-finding the problem, (which wasn't the carb):

Carb:

Funny you should mention the pilot jet. When I got hold of this 24mm carb last Spring I made a note of jets whilst overhauling it:



At the time I did notice that the Idle (pilot?) jet was non-standard, but obviously didn’t know then if it would ever matter. I think I was cross-referencing a standard P200 set-up anyway – I’ll go back over it all when I get the scooter back; I read about it at the time and have forgotten most of it.

Anyway, now I have: SI24/24E - 160 BE3 118 / 48.160 / 60 / 04 (It's a PX150 with a DR177 kit & Sito+)

I reckon with a bit of practice I’ll be able to tweak the mixture screw. Initially I did 2.5 out on the idle screw and 1.5 on the mix, which seemed OK given the other circumstances affecting running. I fiddled with the idle on the weekend, but didn't get as far as the mix screw, but I’m happy tweaking the carb; just need to do a bit of revision about pilot jet if necessary. (I know it's something about the ratio of the two numbers being higher or lower corresponding to richer or leaner.)

------
Elec:

Given the good warm running (subject to carb being set-up properly), the poor starting, and the erratic revving/misfiring mainly when cold, the spotlight will definitely next be back on the electrics, after checking for any air leaks. Judging by the state of the old wiring around the CDI, the stator wiring has got to be suspect. I’ve already replaced the CDI wiring, and had to run a new green ignition wire thro’ body last year.

(Old photo of CDI wiring, since changed):



There's light at the end of the tunnel..............

[sime66]

Not an ideal outcome, because it appears to be resolved without being certain what the problem was.
My mate had it for the week, and returned it satisfied that there are no air or oil leaks at all, anywhere.
With some suggestions to point me in the right direction, I have changed down a jet size (now 116) and played with the mix on the new carb, which now seems to be splendid.
The stator readings I had already done were good, and a CDI change made no difference, so with the new HT already done, all electrical possibilities were covered.
As the main change was the carb, it must have been:
. Dirty carb blocking jets,
. Air leak on carb - sorted when cleaned up and changed.
. Previous over-tightening to sort old air leak causing slide to jam, which was evident when stripped.

So, not an ideal outcome, but probably sorted, and it meant I got some overdue jobs done as well, so not a wasted exercise.
Thanks for all the input.