Ultra quiet 70 CC?

[prism]

Here's an idea:

 

[JemmaUK]

Jemma have you got some pics of the invention you were talking about.
Interested.
Doc

There are pictures on here under the GEBE exhaust thread on rack 'em up. very basically I cut the bottom off one can and flared it. I cut a square 1cm x 1cm exhaust port in the other can and fitted the flared part with the can opening at 180 degrees to the cut port, thus acting as a sort of baffle plate.

It does make the machine quieter and it also changes the character of the sound as well

Jemma xx

 

[Dockspa1]

Will redirect myself and thank you Jemma!
Doc

 

[Egor]

A 2 stroke engine is a very interesting bit of engineering. first it is a dirty running engine, a lot of the fuel is wasted in the exhaust as it is pushed out of the engine by the new charge. On the old 60's bikes if you took the baffles out they would fall on there face, but if you jetted them for the extra air you could now get the extra power, Hang On. The expansion chamber uses a shock wave produced by the combustion to create a pulling affect to pull extra fuel through the engine and them take that extra charge that has been pulled into the pipe and shove it back into the engine, all done at the speed of sound. This is why the engine has a narrow power band, or comes on the pipe then off. It is critical as to the shape and length. Look at some pipes and you will see there is a tube in the middle, and then there are some that have the cones welded together, the latter are for higher revving engines. If you are at high RPM's you need the shock wave quicker, sound only travels at 700 MPH. One thing that is interesting about a 2 stroke is you can throttle them at both ends. As an experiment start your bike and before the pipe gets hot take your finger and cover the tail pipe with the throttle wide open, roll your finger as a throttle and see what happens. this is how Honda and others used to make a small bike that would only go a given speed. Drill a small hole next to the tailpipe out of the way and your friend never knew why your bike was always faster. There is a lot of info out there for the 2 stroke now but back in the day as we experimented with our Hodaka's we eventually got them up to 15 HP, and thats 90cc. You could get 12 out of a 80cc, one of these engines would not last long but you could do it. Have fun Dave
PS: You want to get some HP! rig up a reed valve in the intake and run a 18mm carb, look at the Russians mods.