Honda Spree and Elite 50 Forums

I am upgrading my 1983 Honda Aero 80 with a new cylinder bored over by 1.5mm and ported to handle a 24mm carb, The base is also being ported to the max. The 80 has a 1984 Honda Aero 125 instrument package with tach. I need a true High performance exhaust like the NH 90 exhaust by Arrow, or the Peugeot 100 exhaust by Doppler, Peugeot Speed fight 100 by Endy or Peugeot Speed fight 100 by PM Tuning. Or the specs on a high performance exhaust so I can get one made.

Nothing by anyone?

LOL this board is slow slow slow and you're onto advanced topics.

Personally, I'd pull a single chamber design from a similar CC bike w/ same porting, and just copy the design. The cone design is similar for all of them, just the effective length changes, and you need the downtube and stinger diameter which is sized by the CC.

Frankly, anyone that can make a 2-stroke expansion chamber should know those diameters off the top of their head, and then they'll just want to know what RPM you want it to make the most power so they can set the length. That RPM should be the RPM where the variator starts shifting, or slightly below that.

Thanks for the info and am looking for a guy to make this pipe now.

Good luck. From memory: downtube cross-sectional area should match exhaust port. For 50cc, ideal is 25mm inner diameter. Stinger diameter is 50% of downtube. The tuned length (front of piston to front of stinger) is what sets peak RPM and is based on what RPM you want for peak torque.
The shape in between: bigger around is broader tuning than thinner.
There's some other guidelines in there, but the above will get you going. It's been many years since I looked into these design and the guidelines for them.

I am interested in this topic, I have two 84 80s one I'm keeping stock and one I'm looking to upgrade. Bear you seem to be the top contributor here, what have you done in the past or are doing now. I'd like to make it faster but I wanna change all the lines and filters and fluids first.

Until now all I did was add a 21mm carb and a CTC intake and reeds which gave me about 3 MPH on the top end but not much else. This change should give me at least 5 MPH or as much as twice that. We will have to see because I could die before I finish this.

Are there variator or gearing modifications for these bikes as well? That's a big part of getting any performance out of them.

Yes, changing the weights of the parts in the variator is a good thing to do and I don't know if there are any good gearing options.

Is there a special variator or weights. Also clutches, can any be used?