Detuning four stroke

[simonjohnwilmer]

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 .

 

[HoughMade]

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

 

[Dilly Bar Rob]

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...

 

[HoughMade]

...Honestly I think that a 4 stroke "set" to 200watts would be next to useless...

I don't disagree with that.

 

[simonjohnwilmer]

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 .

 

[professor]

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.

 

[simonjohnwilmer]

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 .

 

[Quenton Guenther]

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,

 

[biketec]

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.

 

[simonjohnwilmer]

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 .