Down-tuning P210 Polini for better fuel economy
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Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Thu Nov 28, 2019 8:55 am quote
I bought a tuned P200 motor which I greatly enjoy, but I am struggling with fuel economy.

Motor is built around a heavily ported Polini kit, reed valve, Mikuni 34 carb, fuel pump, full cycle crank, JL expansion pipe.

What are good ways to improve fuel economy? Smaller carb? Different kit?

I.e. my friend has a Pinasco 225 with a SI26/26 and a BGM big box. That bike is just as powerful of a touring bike but uses half the fuel that the above mentioned does.
Ossessionato
2015 GTS300, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 4068
Location: San Diego, CA
Thu Nov 28, 2019 9:45 am quote
I bet your carb isnít jetted well, too rich. But Iím thinking smaller carb jetted well would help a lot.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1582
Location: London UK
Thu Nov 28, 2019 10:09 am quote
Full cycle I guess is full circle. This is not an ideal crank for the kit or pipe.

No reason why this should not be economical while crusing along.

I would say the same as John. The carb is probably set up badly. They are hard to do and most just get them so they don't seize and stop there. Normally rich, heavy and no economy.

The other thing is that if it was ported and you don't know the squish or port durations, this is something you should check and adjust.
Molto Verboso
Joined: 26 Oct 2015
Posts: 1875

Thu Nov 28, 2019 10:14 am quote
To start out, just what kind of fuel economy are you currently getting?...and what kind of economy are you hoping for?
Enthusiast
68 Sprint, 58 VNA
Joined: 21 Aug 2015
Posts: 57
Location: Nanaimo, BC
Thu Nov 28, 2019 10:18 am quote
whodatschrome wrote:
To start out, just what kind of fuel economy are you currently getting?...and what kind of economy are you hoping for?
Roughly 90-100 km / 60 miles before reserve (5 litres / 1.3 gal). When I fill up the Pinasco need to fill up about half.
Enthusiast
2007 Stella 150
Joined: 02 Nov 2019
Posts: 60
Location: Rochester, Minnesota
Thu Nov 28, 2019 12:01 pm quote
Miscellaneous ramblings and a little food for thought. Along with jetting, look at gearing. With the extra power you have, maybe you can gear higher to slow the motor down and use less fuel. I did this on a build on a 50cc scooter, I installed a 70cc BBK on. I set it up for better low rpm performance and was able to use an overdrive pulley. I was tracking 0-35 times to see if acceleration improved with every change I made. If it didn't improve I removed the change. I cut the 0-35MPH times by 50% from 13 seconds to 6 seconds. Gas mileage is just as good because I can cruise at a lower rpm.

My plans for my Stella 150 are a scooter that can cruise at 57mph reliably. If I can add an extra tooth and still cruise my 12 miles to work without issues I'm good. Small hills is all I have to deal with. Some people only tune for wot and high rpm as people have stated here.

As others have said, maybe ride it for 10 miles at your desired rpm, keep track of cylinder head temperature to see where it is and perform a few plug chops to see what the spark plug looks like. I also added a tachometer to see what rpm I was turning. Maybe your running rich at your cruising rpm.
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