Engine cuts out under load

[fyfer]

Hi folks, Fyfer here.

New Member (March 2021)



Have recently finished re-building my scoot, took it for its first MOT since 1992, on Friday there.

Vespa PX125e (1984) with standard T5 engine (1989)



MOT station not even half a mile away and the road is on a slight decline all the way to it, so never really got a chance to take it thro the gears.

She passed & I taxed her before taking her for her first run.

Got her into 3rd gear on a steady incline, stuck her into 4th and she died.

She started again no problem but continues to stutter & cut out when she’s under load in 3rd & 4th.



Initially thought it was a fueling problem but Spark Plug looks fine and she will start no problem then sit and tick over for 20 minutes without issue.



Got myself some new HT lead, NGK Plug Cap and Spark plug but this has made no difference.

Checked out the Trouble Shooting in the Haynes which suggests: it may be the Coil or Regulator.



Can any of you more experienced ‘Scooter Lads or Lassies’ give me any pointers please?



Also, Clutch feels Grabby/Snatchy when pulling away in 1st, with a slight rubbing noise as it’s released.

I did replace the Clutch Plates but never bothered with the Cush Drive.

Clutch & Gear Selection Cables are adjusted nicely. Any idea’s?



Kinda hoping it’s just the Newness of the Clutch Plates and that it will get better as the plates wear in.

Have only covered about 3 miles since the rebuild


Cheers for any help  

[adrian]

Does sound like a fuel issue, but I am no expert. Could the fuel pipe have a kink? Or another flow restriction?

[ironsloth]

Did you change the fuel pipe at all?

[fyfer]

New fuel pipe with no apparent kinks

Had to tighten banjo bolt after initially filling her up, as the garage floor ended up covered in fuel, which was leaking from hose end at banjo.
So didn't think it would be fuel starved.

Cheers

[ironsloth]

Was it the same length fuel pipe? Too long would give it a similar problem.

[fyfer]

Hi Ironsloth
I never compared the fuel pipe (old against new) lengths - several years between dismantling & rebuilding!
I slipped the new fuel hose (WD40 on the hose surface) through the rubber grommet in the frame as I was lowering the tank into position.
Only when everything was sitting 'nicely' did I cut the new fuel pipe 'to length'.
I will unbolt the tank and play about with the hose to see if there is any excess, just in case I have left it too long.
Does anyone know the length the hose should be?

Thanks in advance

[adrian]

24 inches springs to mind, but would need to go to the garage and measure to be certain 🤔

[adrian]

Just done a Google search for you and its 24 inches, even looked on Ebay and they are coming up at 24inches so go with that 👍👍👍

[fyfer]

Magic Guys
Many thanks!!

[alan34]

Hello there. make sure petrol pipe is the right size internal bore. I put a pipe on which was to small internal bore and scoot went like yours. petrol is gravety fed and needs to be right size bore.let us know how you get on cheers alan.

[fyfer]

Hi Alan34
I will order a new fuel hose for a PX, check that it is 24"/600mm long and try that for starters.
Will be sure to leave a post (or 2) here to let y'all know how it goes
I may not get a chance to tinker with her until the weekend

Thanks again guys

[fyfer]

Hi guys.
Just an update on my poor / non - running issue.

I got myself a new (fast flow?) fuel tap and new length (24") of hose.
Have to assume Hose is the correct internal bore as it fitted onto the Fuel Tap Hose Spigot and Carb Banjo Bolt, nice & neatly.
Scoot now appears to run & rev fine.

Old Hose was just over 25" in length.

Reckon my problem was a blocked Fuel Filter as there was some loose crud in the tank but may also have been due to the OLD Hose being a bit too long.

Thanks for all your help folks.

Much appreciated

[adrian]

Good to hear that you're all sorted 👍