Detuning four stroke

Discussion in '4-Stroke Engines' started by simonjohnwilmer, Feb 10, 2010.

  1. Im trying to work out how I can get the power output of my Huasheng down to the Australian maximum which is a puny 200 watts . The first thing that comes to mind is limiting the throttles movement.this at least would be very simple and easily retrofitted . anyone know any other methods ?
    Cheers everyone .

  2. HoughMade

    HoughMade Guest

    Do it Nascar style- restrictor plate. Put a plate over the carb inlet to restrict the air intake, then adjust the fuel mix accordingly.
  3. Dilly Bar Rob

    Dilly Bar Rob Member

    Whoa! 200 watts?! And I thought we had it bad here....

    I am thinking that bringing a 4 stroke down to that power level might be tricky... I mean, what does it have stock? 1.5kw/2hp @ 6800 (sorry if that's wrong, just did a quick search)? You'd probably get 200 watts somewhere around idle rpm...just ride around at idle :)

    Like Hough says a restrictor could be used. How will you find out what your power is though? Dyno? Honestly I think that a 4 stroke "set" to 200watts would be next to useless...
  4. HoughMade

    HoughMade Guest

    I don't disagree with that.
  5. I agree with both of you , the 200watt limit is unrealistic , the legislation hasnt been thought thru at all , there is only one powerplant available that has a certfied 200 w , its a two stroke ,and that is a backwards step in my view, I may buy one for one of my other bikes tho .
    Thanks for the restrictor plate info, first step is to book some dyno time once I have sorted out the modification , all of this is to gain proof for the authorities . the onus is on the owner to prove the bikes power rating , measuring the output at the wheel may gain enough power to actually move the bike , pretty sure the drivetrain soaks up around 30% .
    onwards and upwards .
    Last edited: Feb 10, 2010
  6. professor

    professor Active Member

    Is there anyone available to dyno it? To me, that would be the most difficult thing.
    A limited throttle setting would be easiest to do. You would need a bunch of restrictor plates if you went with a restrictor plate- not knowing what size to use until you dynoed it over and over.
    I think it can be done, but you sure won't go fast.
  7. There are dynometers available , I tend to think limiting the throttle is the easiest option , and I could make it look permanent , and be able to put it back to normal as it were , the silly thing is , the bike is quite heavy and is comfortable cruising at around 25mph , so the whole thing is about jumping thru hoops to satisfy the law here .
  8. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    You might want to install a plate with a 6.5 MM hole [1/4"] in front of the carburetor. Bevel the hole on the carburetor side to smooth out the flow. This will allow the motor to run, but will work similar to installing a much smaller carburetor.

    I worked on a similar project 5 years ago but reduced +4HP to under 2HP or over 50% reduction. The final results produced a .375" [9.5 MM] restrictor plate.

    I don't know what the final results would net on the 49 CC, but should be a good starting point. I do know the I.D. of the hole in the restrictor is somewhat based on motor size, but not totaly. I would guess somewhere between 6.5 MM to 8 MM will still let the carburetor work reasonably well. It sure won't cost much to drill different size holes in a small plate and do a few minor tests, prior to actual DYNO testing. It is possible to look at the HP & torque charts on the motor and see what RPM produces the desired power. Using a tachometer and different plates it would be possible to get close before the expensive DYNO tests.

    I started with a small hole in the restrictor plate and just kept increasing the size until I found a good combination. Although the carburetor main jet had to be reduced about 15% to match the reduced air flow into the motor.

    We originally tried the limited throttle travel method, but it stopped the carburetor from working normaly [seldom if ever used the main jet] and created a lot of carburetor issues [passages easily stopped up].

    Sure looks like an interesting idea, and has captured my attention.

    Keep us posted on the results.

    Have fun,
    Last edited: Feb 10, 2010
  9. biketec

    biketec Member

    You could try using the rear mount carb, it has a super small hole! Not really familiar with Aussie geographic's but I know there's a few around. Ask fetter or Irish Or dude at MBB. I have some but with no real defined experience I cant tell you what your going to get and the price of shipping is just crazy talk so I would stick to someone around that side of the pond. I will take a quick pic to show size diff and post here soon just a suggestion.
  10. Biketec ,I didnt know there was a smaller carb , sounds interesting and usefull ,
    Quenton , thankyou for your detailed explanation , this will be a big help and its easy to do .
  11. biketec

    biketec Member

    Here is a picture kinda bad its from my phone but you get the idea :idea:

    Attached Files:

  12. Yeah thats tiny , so what model is that carb for ? I thought there was only one type of Huasheng ,or is that for a Honda ?
  13. biketec

    biketec Member

    That is a carb for the HS 142F it has the diaphragm pump and no bowl and will also fit the Hondas as well, BUT if you have a Honda it should have come with a pump and would let you use the same carb with float, so no need to neck down but thats a whole new thread on pumps.:thinking:

    When I get done here I will look for the articles on it and post the links
  14. looks like Id have to make an adapter to fit , I just checked out the 134f motor ,interesting
  15. biketec

    biketec Member

    Nah it comes complete as a kit the carb bolts to the adapter and then that whole assembly bolts up like normal.
  16. Oh right , Ill have to track one down , shipping wouldnt be that much to Aus , thats if I cant find the kit here of course , thanks for helping .
  17. biketec

    biketec Member

  18. HoughMade

    HoughMade Guest

    When you dyno, if your laws are not specific, I would suggest dynoing at the rear wheel...otherwise if you reduce power to 200 watts at the crankshaft, you will have well under that at the rear wheel. If you tune to the rear wheel output, you will preserve as much power as possible. Again, it depends on the law.
  19. Fabian

    Fabian Well-Known Member

    If it can be determined that 200 watts of produced power is to be measured at the rear wheel, there are a few nifty options for power down techniques.

    1) The calorific content and octane rating determin power potential of a fuel
    Suppling a high compression engine (with a billet cylinder head) and low octane & low calorific fuel will induce power robbing detonation, especially if jetted lean.

    2) Adjust the flower nut on the clutch so it slips just before 200 watts is produced.

    3) Increase exhaust restriction to lower power figures.

    4) Install a wide knobby tyre and run it at the lowest possible pressure on the dyno roller.
    It will induce significant friction and lower power output at the roller.

    5) Allow a percentage of exhaust gas to be recirculated into the intake air stream - this will hurt power production significantly.

    Last edited: Feb 11, 2010
  20. Hey Thanks ,all usefull methods that will help lower the power figures ,
    I have heard that roller dynos cant give accurate readings of small low output engines , this could work in my favor .
    Last edited: Feb 11, 2010