I Want My Tanaka Engine Ported

Discussion in 'Performance Mods' started by 5-7HEAVEN, Jan 21, 2012.

  1. 5-7HEAVEN

    5-7HEAVEN Active Member

    I have a 2.8hp Tanaka 47R engine on my 70lb. bike. It has an 8-speed shift kit with 46.32:1 low gear, a 17.72:1 seventh gear and a 15:1 highway gear. It's got awesome low and midrange. I need more power above the engine redline, about 8500rpm. The only high-performance equipment is the Tanaka-specific 3-piece pipe. The engine gets 125mpg, so I can afford to lose mileage for power.

    Any porters out there?

  2. HeadSmess

    HeadSmess Well-Known Member

    yes, but....

    small bore, hard to get into to change ports.

    single uniified cylinder-head designs...even harder, and almost impossible to measure port timings accurately!

    you dont just "port". you design the ports to work in conjunction with a pipe. very specific.

    what you gain on the top youll lose on the bottom and mids.

    better to gear it higher, and work with a pipe around the ports you have...

    the load therefore wear on parts follows a logarithmic scale. go over the stated redline, and expect lifetime to be reduced proportionately.
  3. 5-7HEAVEN

    5-7HEAVEN Active Member

    I bought a used Tanaka 47R a couple years ago. It was ported by someone on a goped site. It ran very well.

    so I'm looking for someone who can do a good porting job.
  4. jaguar

    jaguar Well-Known Member

    The porting mainly sets the peak rpm. Only when there is a mismatch does porting help with power when the mismatch is corrected. Otherwise you can raise the exhaust, widen the transfers and lower the intake (non reed valve) to raise the peak rpm of all ports. There are formulas for determining the peak rpm of each port on my web site.
    The pipe mostly sets the type powerband you have. You can emphasize mid range or peak rpm power. By using a dual cone baffle you can gain peak rpm power without hardly any loss of mid range power.