Why is the Aero 50 so much faster than the Spree?

koelpien · Post by **koelpien** » Wed Jul 30, 2008 7:39 am

I was on my way to work on my Spree (at about 28-29 MPH) when a co-worker blew by me on a Honda Aero 50, which, for those that don't know, is the roughly same age and size (49cc) as my Spree.

I was jealous. I was somewhat able to keep up with him with superior cornering abilities, but it was obvious to me that his machine was faster. I asked him when we arrived at work if his Aero was modified in any way to explain the faster speed. He said no, and that on average, his top speed almost buried the needle (which would be almost 40 MPH)

Poking around online, one explanation I found was that the Spree DOESN'T have something called variable pulley, while the Aero HAS a variable pulley.

I'm a smart buy, but not much of a mechanic. Can someone explain this? Is this something that can be modified on my Spree?

I, like many others, I'm sure, would like to get a bit more speed, but without spending big bucks.

keithw · Post by **keithw** » Wed Jul 30, 2008 11:23 am

The Spree and Aero have the same size engine, 49cc. The porting, intake, exhaust, gearing, just about everything, on the Spree was built around going 25-30 mph. There are reasonably priced things that can push the Spree into the 35 to 40 mph range. They are covered fairly well here but the quick list is:

Drill the muffler baffles, this will increase noise and add power.
If you're really handy a tuned pipe exhaust, lots more power.
Grind and smooth the inside of the intake manifold, will add power.
Mill head .020" or remove the head gasket, more power.
1/2" drive belt rather than the stock Honda, higher gearing.
Front pulley mod, higher gearing.
3.00x10 rear tire, higher gearing.
Bigger main jet, learn how to select jets or you will burn up the engine.

Go for the power things first. Once the engine can make more power then start working on the gear ratio stuff. The stock engine wants to do about 8000 rpm. With the power mods it can hit 11000 rpm. With the extra power you can push the higher gearing. If you do the gearing things first you will kill your acceleration but will be able to go down hill faster, not real usefull.

keithw

SPREEtown · Post by **SPREEtown** » Wed Jul 30, 2008 5:51 pm

ive done the pulley mod on my bike, will the wider belt work in conjunction with this? and will this reduce my low end even more?

Kenny_McCormic · Post by **Kenny_McCormic** » Wed Jul 30, 2008 6:50 pm

A spree is pretty much "stuck in second gear" where a bike with a CVT transmission (aero, elite, etc) has all 3 gears and shifts through them seamlessly.

keithw · Post by **keithw** » Wed Jul 30, 2008 7:00 pm

The wider belt will work in conjuction and will reduce your bottom end even more. Check your exhaust port for carbon buildup. Check into porting the exhaust port on the cylinder and raising the exhaust port some. The Spree exhaust passage out of the head has a narrow area between the port and the exhaust flange. This is one of the built in HP limiters. Opening this up and raising the exhaust port about a ring width is supposed to do good things. I've got a cylinder with this done but haven't tried it yet, waiting for a piston. I have heard good reports though.

keithw