135 Malossi Primmy

Hello everybody I have a little problem with my prim

here is the spec
full small frame primervera
135 Malossi with reed
25mm delorto carb still in the orginal place under the seat
ported / matched barrel and case opened up a little
standard gearbox
pk racing crank flywheel
12 Eletronic
Sip down and forward exhaust

Here is the Problem

I recently brought the Sip Evo Down and Forward exhaust WOW its like a differnt scooter a real pocket rocket BUT with performace you get problems the scooter now goes like s**t through 1st 2nd and 3rd unless you rev the nuts off it in 3rd when you put it in 4th is starts to slow down so you can do 65mph in 3rd change up into 4th and the sped goes down to 55mph. with the old exhaust it never pulled much in 4th but you would be able to go a bit quicker then 55mph Please Please help.

Thanks in advance.

So all was ok before you changed to the sip pipe? And what pipe was on it before you changed? The SIP smallframe expansion is sounding like the fault, but maybe only on your engine. Back to what a person wants from the pipe. If you are on 3.50x10 tyres, blag a 300x10 to lower gearing and try again. This should sort it as a temporary measure. If your on 300x10 then to use this exhaust you will have to use a lower primary gear ratio, which involves an engine strip, again. Alternatively, IF you dont mind cutting up a new pipe, get it modified by a scooter tuner. This type of pipe does have a very high rev range and also your barrel doesnt have the port duration to cope in „standard malossi tune“.

I dont believe its the expansion, at least your immediate problem isnt. I dont believe your over geared either. With what your saying, its on standard primmy gearing and yet a malossi 135 wont pull over 65 in top? First, where does your reed enter the engine, and what machining did you have done for it? What is the timing set at? What is the squish clearance? Did you check each of these when building it. Need more info to go further forward. Double check timing is first thought now.

The pipe i used to have on was a leovicni it pull through the gears but only did about 60mph but i did have a little acceleration in fourth. I am running 300X10 tyres on it at the minute if i lower the primary gear ratio will the acceleration still be there and i am guessing i would lose top end. would it be able to pull in fourth gear?

How much work would have to be done on the barrell to be able to use this exhaust properly.

Is there enything else i can do to allow the scooter to rev higher. so the exhaust is usable

The reed block is mounted on a standard malossi manifold on the cases I believe the work done to the cases was to open up the inlet in order to match the inlet maifold and barrel ports.
All ports have been polished and I’m hoping the crank has been machined in order to use the reed valve.
The exhaust port has been opened up to match the SIP pipe.

I have no way to measure the timing as yet as I have a timing gauge on order.
What would you suggest as a rough starting point in terms of degrees.

Do you have any guides on port measurements/requirements I can use to check my barrel.