Modern Vespa

Bike start Ok, but when put in gear & power applied starts to fade, tried cleaning petrol tank, carbi,, changed spark plug, CDI unit, changed rectifier measured resistance of the coils they are within range, only thing I can think of is the electronic pick=up point on the stator is faulty but cannot test, has anybody got any ideas ?

What's your timing like?

can you borrow a px stator off someone in the club len? then youll know the pickup


fodes wanted some wiring done and i think he has a stator collecting dust (in an engine)

Timing is OK, had a wire of come off windings recently did not realise as it was during the day & lights not working soldered back on but think the CT is shot, due to this problem, ordered a new one from SIP cannot buy just the CT box, have you got john number he wants me to wire his bike up but have tried to phone him a number of times but phone rings out

How long is your fuel line and have you checked that it's not pinched?

Yes checked that, the fuel line is heavy rubber type impossible to pinch

Accck......same symptoms I had on my old magnetic weirdo P range. Culprit= air leak= flyside seal..... Of . urse this is shitty worse case scenario.

Just remembered.....old scoot had a similar problem on his vbb wayyyy back when. Ended up being vapor lock. Did clear out the gas cap holes?

If idle isn't erratic, I would focus on condition of exhaust and cylinder compression.

I once had a P125 that ran great in the shop. But once I tried to drive it the motor would almost die and not have ANY power.

I pulled the motor apart and found that the clutch side bearing had lost it's ball retainers and the crank was getting bunched up.

I replaced the bearing and it fixed the problem.

Engine starts Ok no adverse noises when running, which I presume you would get if clutch bearing was shot , flywheel oil seal fine no deposit of oil in stator area, will check vapour lock scenario its bound to be something as simple as that in the end will let you know, if it is the problem at least the carbi/petrol area is clean, & have a spare CDI unit to boot.

Not the fuel vapour lock, only option left is the bearing scenario, that can be quite a pain, waiting for stator to arrive but once that option is cleared down to a workshop job.
Started bike earlier had it on full throttle but power was still just above idle speed seemed to slow then increase slightly then back to just above idle, it still seems & feels like its a a fuel problem.

On my P125 I had no weird noises from the bad bearing. It just had zero power and would die when I went to ride it.

You can check the bearing pretty quickly by just removing the clutch cover and clutch and having a look.

If you see all the balls next to each other at the bottom of the bearing.. then the bearing is shot. If not then put the clutch back together and try something else.

Another check on the bearings is to remove the flywheel cover and push the top of the flywheel in and pull the bottom out.. and then reverse the pushing and pulling. Do this in a very quiet place and see if you can hear the crank rocking in the bearings. Sometimes you can feel and see the rocking when it's really bad, but usually if you hear it rocking then the bearings are worn out.

A motor should run fine with somewhat worn bearings but it will be harder to start and eventually will have ignition issues - but they are usually just starting problems.

If the bearing is really really shot then it will visibly rock in the bearings. And if this is happening then you may have a worn rotary pad.

What's the condition of your exhaust? Do you know anything about the engine history? When you put it in gear does the engine sputter or does it just run weaker than it used to?

How good are your soldering skills? Wire could be grounding out somewhere

I had same symptoms after a soft seize. Checked compression, and it was right at 90 psi. I could start it fine, then put it in gear and it would die off.

To check the condition of the clutch side seal, remove the clutch breather. Block and unblock the hole while it's running. If the revs are affected then your seal is gone.

Some people fit a nipple and hose to the breather hole to keep things a bit cleaner... it would also make this test a bit easier. A friend used a rear brake cable adjusting sleeve thingy (right thread) and was able to fit a hose to it.

Checked clutch side bearing that is ok, next stage is the breather on the clutch, however this was only cleaned a couple of months ago, do not think I have had a soft seize, noticed loss of power (Slight drop down for very short periods) over the last couple of weeks.
Exhaust is only a couple of year old, do not think problem is in this area because bike starts OK after second kick, still come back to fuel or stator at this stage, the CT component tin the stator operates like a switch & my thinking is that when engine heats up the CT component tends to stick & not operate as it should.

if a baffle is loose and is blocking flow then yes as Chris said that can stop air flow and cause poor performance in anything above idle

remove it and put a bung over engine side of flange
then compress are it with as high as your compressor can do
if it flows fine then maybe it is fine

shake it
hear anything bouncing around

test another exhaust from a club mate
I would do this asap

The clutch breather is OK, only the exhaust pipe left, still coming back to stator, ordered new one which arrives on Monday, if not stator at least I will have a spare, running out of ideas at the moment, will be completely out of ideas if stator does not fix problem

how much compression do you have?

Bike starts OK, will rev up to full revs, however when I try to rev up again starts to die, can keep engine running on low revs but will not throttle up without dying, so think compression is fine, will check later today.

Compression is fine, I keep drifting back to the stator(Ct Box) even though all the electrics work, will have new stator on Monday so fingers crossed that is the problem.

you pull exhaust yet...??

sticky choke

+1 might be draino time.

(No offense to Nigel)



I will go on record again saying this is a bad idea. The mesh baffle affixed to the interior can come out and then get sucked up through the exhaust port, into the cylinder. This will fuck your shit all up. Draino can destroy the welds securing the mesh inside the exhaust.

If you are unsure as to whether your exhaust is in good condition, I would just replace it. Exhausts aren't really that expensive. In fact, a new exhaust is probably the least expensive thing to replace on your scooter (not on a Lambretta).

yuuuuuuuuup
8)

Huh. I've never heard of this being an issue and have never had an issue myself doing it. I'll keep that in mind in the future.

The exhaust is fine,(Sito Brand) only been on bike for 4 years cleaned once & do not it is think exhaust problem, plus it is a PIA to remove, when first started with choke out exhaust works fine with the standard fumes coming out the back which soon die out once engine is warm.
Checked stator CT have a 3 ohm resistance across the contact & to earth, not sure what the value is meant to but seems a bit low, any ideas on what value should be ?

He uses the feng shui type gauge, so it's "OK" and not an actual value. Same for his degree wheel.

if you don't check this then your not being smart... in that you should do the easy stuff 1st...

why is it a "PIA" to remove...??
mine come off easy

if it a tight fit on the barrel then all you have to do is use some oil to help it slip back on easy like. I always make sure those sealing flanges are smooth as possible so they come apart fast and go back on fast. A file works wonders as does some sand paper / emory cloth.

don't assume that it is OK
they can rust out and get loose baffles as short as a year and there are some out there that never fail... odds are odds.

good luck

what does this smart arse comment mean eh?



pearcy is an electrician and built the engine from scratch himself. it fairly flies too or it did the last few times i rode with him



ive got a good 200 exhaust you can have len, im home all weekend and finish work mid morning during the week

for all we know he thinks 90 psi and 10 degrees is ok?

fixed that for ya

I will try out the exhaust thanks, send me your contact number on pearceylrmp@optusnet.com.au,however I will go down this path only after I have fitted new stator which will arrive tomorrow (10/3/2014)
The reason I have kept away from exhaust is that my exhaust is very tight on the barrel with no air leaks last time it was removed it required a rubber hammer to remove, plus rear wheel & disc brake needs removal hence while this may turn out to be the problem I will exhaust (Pardon the pun) all other avenues first, however if it is the exhaust then I will strip down the barrel/rings etc & give it a good clean out
In saying that I still think is a stator problem the CT unit has only a 3 ohm resistance across the contacts & to earth that seems very small when you consider what the unit does.

All sorted turned out to be dirty fuel, dust was so fine even when filtered through four layers of cotton pads it just mixed with fuel, cleaned tank out with acid then washed out with petrol, discarded fuel in system also changed petrol station, since found out same petrol station gave problem to a friends car, contamination was like red dust but mixed with fuel.