Vespa MK1 T5 Nightmare(please Help)

Here’s the problem that’s driving me nuts!

Riding home from work almost a year ago my normally trusty T5 died after about 100 yards.

Tried everything to fix it and still no joy.

thought at first it was an oil seal so split the engine and changed oil seals, at the same time changed the cruciform,clutch plates and all gaskets.Also bought new exhaust(sito plus).

that didn’t work(bearing in mind that it’s got a very healthy spark and changed spark plug twice and made sure the stator went back in exactly the same place as before. Also it has good compression)

then thought it must be a fuel problem so changed petrol tap unit,fuel lines,cleaned petrol tank and carb completely, and it fired after a while and ran for 15 minutes with no problem.Next day it wouldn’t start at all.So then fitted complete new carb and it ran again with no problems till I switched it off.Next day it wouldn’t start again.

Then changed the piston rings and it ran again for a while but since then no amount of kicking it over and drying off the plug can get it to go again. There is fuel getting to the cylinder,it’s sparking fine…what can possibly be the matter with the bloody thing?..Please help as I have no idea what to try next.

Thanks all.


The plot thickens…

Right, so I changed the cdi unit and that did absolutely nothing sadly.

So last night in desperation i put the spark plug from my T5 classic into the mk1 and it fired up!..and it ran no problem. Bear in mind I used two different spark plugs before when trying to fix it. Result I thought!

this morning, I put the spark plug back into the classic and now that won’t start.How the fuck can the Mk1 blow up spark plugs? because that 's what it’s doing…can the stator plate be producing too many amps?

any ideas much appreciated…[:rotate:]


Thanks everyone…I was thinking it might be electrical but didn’t want to admit it! Electrics are a whole new ball game ain’t they…oh well.

It can’t be a re spray either because it has been…maybe it doesn’t like it’s new colour!

I’ll get my chum to lend me a spare stator and cdi and regulator…hopefully it’ll be one of those…the cheapest one with a bit of luck…once again,thanks.

Sometimes a blocked or carbon fill pipe can cause plugs to die… I had this with my T5 when i bought it. It wouldn’t rev out cleanly and the plugs would simply stop firing every few days. Replaced the pipe and its fine.
just a thought.


i had no spark in the end

Well here’s the final result. Slidingdog was absolutely spot on…It was the plug cap. All that aggro for the sake of £2.50.

I took the stator into work and put a meter on it and all the resistances were fine (as stated in the Haynes manual) so then thought, hang on,what did that geezer say about the cap?..put a new one on and it now starts first kick everytime!

a hell of a lot of effort to find such a small problem,still, I have now got a rebuilt engine for my troubles.

Thanks all and cheers mate to Slidingdog.[:drink:]

My feeling is its ignition as well. If you have a friend with a T5 swop stator cdi etc till you find the culprit. Also dosn’t sound like this but try it anyway, take the petrol cap off and run it without one. Its possible the breather is blocked.

i hope that you got your problem sorted if not try a different number plug ie an 8 instead of a 9 to make it a hotter running plug hope this helps

Howard youv’e swapped everything bar the item its most likely to be-the stator! Must admit whenever I have a customers T5 that gets through spark plugs at an alarming rate so I’ll be interested to see the outcome.
With regards timing the T5 should really be strobed but just put it where the old one was and if it pinks retard it(clockwise)

how you doing!
crawford on wednesday,I’ll bring that panel!!

I had same problem with the wifes T5. Kept breaking plugs. Changed everything - 3 coils, 3 stators, HT leads, caps, plugs etc etc. Was totally stumped. Problem instantly fixed and never came back when I changed the......................flywheel????



Thanks all…and Stubbsy mate, if you’ve had the same prob then god bless you,you know what you’re talkin about…it’s nearly made me even balder…new stator it is then, nice few bob again, cheaper to buy a new engine at this rate…oh well, thanks lads you’ve been a big help [;)]

Have you checked all the wiring?Go through the whole thing with a circut tester as it’s possible there’s a broken wire or a duff CDI or other ignition part in there.

I’m sure someone else will have an other option for you.

Hi Howard,
Wow! It seems like you’ve done everything humanly possible although in the reverse order.
Maybe you should re paint - it??? Only joking!!!

The only thing I can think of is electrics .It could be a broken wire or a loose connection. Check the loom with one of those Ampmetre things. If not re-spray it!


had the same problem on my t5 on the way to mersea rally turned out to be the black pickup box on the stator plate in the end .scooter would run ok for about 5 miles then stop wait few mins then start then stop had this for about 40 miles on the way to mersea on friday had the carb out and stripped still no change then was going to take the tank out when home so turned round to go home the scooter went ok for 20 miles then gave up 2 miles from home so had to push it home could not get a spark in the end changed the cdi no change so i took the pickup black box of my brothers p 2 put in mine then went to mersea on saturday and back no problem just got to get new pickup to put back in his about for £ 15

read me message above mate…it… (for some reason,and I’m an elderly trainee electrician)…destroys spark plugs…ie you can’t use em again in a normal running scoot…it won’t fire. I think my stator is now shorting out somewhere and producing an overcurrent ,which is directly supplied to the plug and burning out the electrode.Thereby causing a missfire…if you take your plug out and put the base of the plug on the engine casing above the flywheel cover, does your spark plug still spark between the gap (as it should)?..mine don’t…it sparks from the bottom electrode with no spark between the gap…therefore,fucked spark plug.[:roll:]

It’s got a brand new Sito pipe on it, but thanks anyway.;D

Awright guys… haven’t been on here for a bit but i gotta tell you about strobing my T5.

Mk1, Malossi 172, 122 main, cosa 21T, sito plus pipe…

So i finally got the strobe on it after fitting the kit several months ago. I had just reterded the timing by eye when i put the kit on and estimated about 14 degrees before TDC… how wrong i could be!!!

Under the strobe, the correct setting for 14 deg is actually the other side of the standard mark for 16 deg!! I hope this makes sense but i mean that if you belive the original casing marks i’m now running on about 18 degrees… but it’s actually 14 degrees as confirmed by strobing.

This only proves that the casing marks can be pretty out of whack and four degree on this motor makes a big difference.

heaps mor epower now and the bike is just really smooth and keen to run throuhout the range.

so… moral of the story is that a tenner for a second hand strobe unit is money well spent!

Cheers to all,

And also throw away the spark plug cap!
Don’t ask why, but had the same prob with cap,it just used to eat plug’s