stupid newbi question. Why do 4 strokes need gearbox and not 2 strokes?

D

dirtrider5001

New Member
is this simply because these engines arent tuned to run at 1000 rpm. I read something about the 4 stroke running at like 2k. So is that the reason for the reduction box. Dont tell me that theres no small 4 stroke that can idle at like 1200k. Couldnt that be cured with like a tighter springed clutch or engine modding. I dont know im an idiot someone school me please....xx.
 
The 2 strokes do need gear reduction. The china kit engines have a gear case built in, 4 stroke utility engines do not.
 
Last edited:
Yup, what Happyvalley said. The 2-stroke chinas have a 4.1:1 reduction built-in.
With a 44T rear sprocket, the overall ratio is ~18:1 with 26.2" wheel. 26MPH @ 6000RPM

As for idle speed, it depends alot on the design of the engine - mainly the reciprocating mass of the internals - and the rest is tuning.
Heavier engines tend to idle @ lower rpm because their mass enhances torque. Our smaller engines need to spin faster to compensate.

My HS 49cc's lowest idle is 1800RPM..and sometimes it will stall. It will run 2K rpm all day tho, and that's it's rec idle speed in manual.
These small engines make very little torque at low RPMs. They need to spin up to at least 4K rpm to do real work.
 
Thanks now one more question. What is better the grubee 4g transmission or the ezm qmatic transmission. Is one better than the other or are they just for different applications. I plan to use the honda gxh engine.
 
Well, I've ridden 100's of miles on both and I think the Q-matic is better for overall transportation. It's made for cruising all day long.

The 4G requires more work and maintenance, but it can outaccelerate a Q-matic. With a shifter kit, it's really quick off the line!
 
dirtrider5001 said:
is this simply because these engines arent tuned to run at 1000 rpm. I read something about the 4 stroke running at like 2k. So is that the reason for the reduction box. Dont tell me that theres no small 4 stroke that can idle at like 1200k. Couldnt that be cured with like a tighter springed clutch or engine modding. I dont know im an idiot someone school me please....xx.
Click to expand...

are the bike kits at bikemotorparts.com anygood? Do you know of any quality kits I can mount a honda gx35 or a gxh50 on....I was also interested in a kit that had different speeds through the bike shifter or any other means....thanks
 
You must log in or register to reply here.
Back
Top