Modern Vespa

Hello everyone.My Setup is;

-Malossi 210 Mhr kit (Ported and polish)

-57mm SeriePro Flowed Crank

-SeriePro 30mm Dellorto Carb Set

-Malossi reed valve

-Pinasco 1.8kg cdi with e-start

-Sip Fast flow fuel

-Malossi air filter E13

-Sip Performance 2.0 Exhaust

-Bgm Superstrong Clutch

And ı m thinking to swap my carb to Keihen 35 Air ,my question is;

Should ı buy this setup Fuel Pump and Boost Bottle? Is it really necessary? if yes,which product should ı go with the pump?

Thank you...

i have a boost bottle, but never fitted it, as its HUGE (compared to a compact Vespa)... still undecided if it will actually do much, but do wonder if it would stop 'blowback'

Boost bottle is intended for piston ported engines primarily. Yamaha designed them and found an increase of around 8% on their early dirt bikes. On a reed valve engine it is not a noticeable benefit and I really doubt that what's available on the market is sized correctly for specific cylinders (more of a generic offering).

Fuel pump is required whenever a large (height wise) carb is used. The reason is that when the tank falls below half full there is not enough weight to keep flowing. Fuel starvation is normal otherwise (seen as lean running etc).

I prefer to use the smallest of mikuni pumps that is rated at 17L/min flow. Some of the larger round ones are around 35L/min so make sure you get correct flow rate or the carb will get flooded too easily. Also, Keihin and Dellorto carbs don't have removable float needle and seat to reduce incoming flow so you will have to relieve the pressure in other ways.

I put a fuel pump on to fix the fact that I could not utilize the bottom half of my tank when I installed my PWK carb.

I use a low rate Mikuni pump with a low pressure Holley regulator to keep pressure at about 3.5 PSI. Works like a charm.

Go check out the Fuel Pump thread on here for lots of good discussion of that topic.

As to the boost bottle, I have to say it looks interesting. I have visible back pressure out the mouth of my PWK and have struggled to get the low end dialed in since I replaced my ported DR with a Malossi top end.

If you put the boost bottle on, please do before & after SIP Dyno app runs of the before and after so we can see if it made a difference or not.

Thank you for your detail answers

I wish ı could dyno before and after but we havent got any bike dyno in here

First step,ı will stay away from the boost battle.

Which pump should ı go with,ı m not still decided. 14lt or 50lt ı have no idea

was told by me mate thatdynos scoots that boost bottles are a waste ...... did know someone that had that malossi one painted with pink latex poking from under his panel .... made us chuckle on tickover

I run PWK35's on 4 out of 5 bikes.. One has a fuel pump (small mikuni rectangular type that I havent taken off because I'm too lazy)...with a good fuel tap ie: BGMFast Flow... I've not found a pump necessary... 1 is on a P, one is on a Super, one is one my RB Lambretta, and the 4th is on my M200 in my 50Special fame.

My v90(PoliniEvo130) uses a PWK33 with no pump.

If you have a reasonable flow line from the tap to the carb, the carb should do the work (assuming the float height is set correctly) to deliver enough fuel to satisfy a thirsty cylinder..