60 MPH Max!

Hi Everyone.

Ive just ran my bike with a new set up and I’m finding problems with top end. Its a Malossi 210 with ported crankcase, 26/26 carb, lightened flywheel, racing crank, cosa 23 tooth clutch. Simonini pipe & standard gearing. Timing at 125 mark.

I was running before stet up with a standard crank & Sito plus and the scoot pulled all through 4th up to 75 ish mph. The bike now with new set up pulls well & does 55 ish in 3rd then just 60 mph in 4th.

I’m presuming that this is due to the simonini pipe with the Malossi kit pushing the power band towards the higher revs & in 4th the engine cant pull though to this band?

I’m in 2 mind whether to fit a T5 4th gear or preferably increase the power band so I’m not reving the heck out the engine on the Motorway or am I wrong to think this?!

4 topic questions :

  1. Does an engine fitted with T5 gear rev v highly at motorway speeds 70 ish mph?

  2. Would fitting an upgrade pipe ie RZ or SIP pipe alter the power curve enough to pull through in 4th with the present standard 4th gear? Is it worth £200 getting a SIP pipe anyway?

  3. Would fiting a 28/30 PWK carb (ive got one on order) to standard gear set up & Simonini pipe also incease the power enough to get to the power band in 4th?

  4. Ive not checked the ‚squish‘ dimension for Piston./Head clearance. Im running a machined head from Beedspeed for the Malossi with a copper head gasket to be on the safe side - Would reducing this dimension to 1.8-2.0 mm as specified make much difference to the power of the 210 thus pulling it better in 4th standard gearing?

Excuse the ‚war & peace‘!

Any suggestions/comments greatly appreciated.

Thanks in advance,



Hi vespa doctor - yeah piston same way round as previous set-up.

If it was the wrong way up would the ends of the rings catch on the ports?

thanks Vespa doctor,

Do you mean 128 or 122 main jet seams right? - It does splutter a bit at low rev range.

Do you run a T5 4th gear?

Thanks Curare,

I was running a 120 Jet with my SITO PLUS so I’ll try a 122 and see what happens.

Yeah think its a good move to get the engine runing correctly & pulling in 4th before I fit PWK and treat myself to a RZ RH.

Ive been looking at Exhaust comparisons:


It appears that at 6,00 revs the Simonini gives less power than the SITO PLUS. I know the readings are for a reed valve set-up but the figures I presume should transpose the same. Therefore it makes sense the Sito will pull through 4th gear better. The Simonini at the end of the rev range ultimately gives more power so I presume fitting the T5 4th will bring me ‚on power‘.

Thanks again chaps

Cheers Boys,

I’m just about to order a 122 Main Jet.

Matt what was your squish dimension that gave you bad perfomance and what did you change it to?

did you put the piston in the right way up. this isnt as silly as it sounds

that seems about right, otherwise it would burble and splutter

Or also could it be Jetting?

I’ve just read that GP225TS1 is runningm a very similar set up the same carb with a 122 main jet and his is running like a dream.

Im running with a 128 main jet - If the mixture is over rich would this be very detremental to the power?

hello Jimmer,

before, when you when running with the SITO, what was your main jet?
I think you would need a main jet just next bigger size then the one you have used with Sito.

Any expansion ehaust that I know will have more or less some problems with your set up to pull the 4th, so you should consider getting a short 4 gear.

The SIP will give you more power from mid - high high rpm, the problem is that with your set up you won’t get there and it is very probable you will have even more hard time with the 4 then the Simonini you have. The RZ right hand less, but I would try to make your scooter right now and only then considering an exhaust of this price. …so at least if you spend money at the end it could only work better and not be the same.

The PWK would improve globally your engine, but it won’t be able to sove this problem all by its own.

I am not sure I understand the head question,
but with the Malossi 210 I don’t think you should need a copper head gasket, though I don’t know beedspeed head, but why don’t you give it try and see how it will be with more compression?

I would definately get the squish on the cylinder head checked out.

I had all sorts of problems with really poor performance on a newly kitted T5 and ended up spending a small fortune replacing virtually every part of the engine until I got the head re-examined properly using the correct equipment.

Here’s the thread highlighting all the things I had tried


it is a good thing you found these dyno graphs, so our friends can have a look a it.
The most difficult thing reading this sort of graph is that if you don’t have enough experience you are not going to understand the curve, but you are going to see the numbers.

As you can see there is not much difference in 5000 - 6000 range between a SITO plus and the Simonini. I don’t think this minor difference is the cause of the problem you have.
But… if you were running happily with a 120 main jet with the SITO, putting a 128 main to fit a Simonini is way too big.
Try a 122 and get a 125 so you are going to be sure you have the right one.

It would be easier and safer if you don’t have too much feeling with carb set up to try the 125 first and see how it goes and then if needed go down to 122.