Probs with Malossi 172 T5

Please someone save me from being sectioned!![:rotate:]

Are you sure that you are getting enough gas through? Maybe you have a partially blocked fuel tap or you need a faster flowing one. Next time it dies turn off the fuel straight away and see if the float bowl is empty.

Couple of things maybe :

  1. Is the fuel pipe kinked under the tank or is it squat between the frame and the cylinder cowl ?
  2. Is the carb gasket o.k and not drawing air (or maybe the crank seal is split and drawing air)
    Keep trying we’ll get there in the end !![:smile:] [:smile:] [:smile:] [:smile:] [:smile:] Keep smiling.

My lammy used to do the same thing with a K&N filter. It was getting wet from dew in the morning and restricting the air flow. Check to see that its not damp.

After a long and frustrating conversation with a Vespa „mechanic“, I still need help!! [:bounce:]
What should the timing be @ for malo 172; 14,16 or 19??
Wht reasons could there be for not being able to set tickover via the slide adjustment screw?
Is it really necessary to change or modiy the original head which is in pristine condition?
What could be causing the really rough feel to the engine between 3-4k rpm (as in feeling choked)???
Any help much appreciated.


Got the colourtune and have set up as best all the way through the rev range, but now the bast*** will not run. Feels like fuel starvation, hits powerband and cuts out!!! Also starting is not what it used to be, takes at least a dozen 'kin kicks from cold.
The set-up is 52/140 idle, 120 air, be4 tube and 115 main.
I can’t help thinking that the mix is wrong (3% exact) but i don’t want to dilute for fear of seizure.
I have checked all seals and there is no sign of leakage and the engineis pristine.
WHAT THE f*** IS UP£££££££££[:@]

The fella told me that it would need RE-PROFILING and that the job was well practised in making the original head suit the Malossi barrel,so i can only take him on his word.
I just hope i 'aint in for for more fkg grief, I’ve had enough of the b’stard.

where did you get the carb from? ihad similar problems to this with my lammy. I bought a second hand phbh 26mm dellorto which turned out to be a 4stroke carb the difference being the atomizer protrudes into the venturi on one and is flush on the other. But they are nearly impossible to jet up on a 2 stroke. Just a suggestion . Other reasons could be leaky gaskets or hairline cracks in crankcase.

Pleased to hear you are in business again.

Vespa… its not just a scooter, its a way of life!

Ive recently rebirthed my 89 Mk 1 T5 , ive fitted a mal 172 with a standaed carb but changed the main to a 120 , its got a mk3 mikeck. It runs sweet as a nut , although still running in it starts 2nd kick cold and 1st kick when hot . All the way through the gears is fine. Have you fitted a decent spark plug because it might be breaking down under load.
Ive been there with the bigger carbs etc , there ok when alls set up right but can be more hassle than there worth if not !

Cheers for the input Didge,
Since my last post things have gone from bad to worse!!
I am now unable to set up tickover from the pilot, only by adjusting the slide thus making the mixture screw redundant which i know can’t be right. Pickup from standstill is awful, having to get the revs up before releasing the clutch and bunny hopping off down the road. The plug is a decent colour, but i am not sure this a good indicator as i can’t really chop it. I am at a complete loss and fear damage might occur if I don’t get this sorted. Not having any decent vespa dealerships around Cambridge does’nt help either.

Totally p****d off Dave[:’(]

Try cleaning the filter in petrol or someink… when they are new they are often too heavily oiled…this will effect the amount of air getting through

hi there have you had the cylinder head modifyed i have the same set up and taffspeed had to modif my cylinder head . the air corrector jet on my T5 is a 120 . good luck should get there soon


Right Fella’s the latest in this long running poxy saga is that i have changed the slide and re-checked the timing which was ok. I now have a scooter that refuses to do f**k all above 3k rpm with the air filter on the carb. When i remove it the sound and feel of the engine change completely for the better, but i and the scoot get covered in petroil being spat out of the carb opening.
What shall i do next??
Before anybody suggests it, i have already done it this morning…twice


Changed the filter still no go, 'kin b’stard.
Thinking very much towards nov.5th and bonfires[:@] .
Alternatively i have ordered a new slide and re-profiled head from SIP and hopefully when i can convince them that such a thing exists i may be able to thrash my little baby so much that i have to start this 'kin project all over again!!!



WOW thats cheap, are they reprofiling the head or just enlarging it?

Dave i made a mistake with MB Developments website go to archives then magazine articles then sroll down to articles by and about Mark Broadhurst, its the second link down in that section.
Cheers Andy [[:O]]

The piston is defino in the right way[:D], done that back in '83 on a 50 special, did’nt like it much!
So much for the head, 3-4 wks then only a maybe. At this rate my insurance will be up for re-newel next year without any more than 3 miles on the clock, still can be sure of 1 yr ncb ;D

Get MB developements to re-profile the head, very efficent, in-expensive service