Removing rev limiter on small two stroke

  • Thread starter Thread starter oldunion
  • Start date Start date
  • Tags Tags
    Rev
Click For Summary

Discussion Overview

The discussion centers around the removal of a rev limiter on a Zenoah G62PU two-stroke engine used in a scooter. Participants explore various methods to bypass or eliminate the rev limiter, considering the implications for engine performance and reliability.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the method to remove the rev limiter, mentioning rumors of burning it out but lacking concrete information.
  • Another participant discusses the complexity of rev limiters, suggesting that the motor may exhibit a specific sound when reaching the limit, indicating a potential method to circumvent it, though the exact mechanism remains uncertain without a schematic.
  • A participant notes that the physical construction of the engine may inherently limit revs due to power constraints, raising concerns about the stress on the connecting rod as RPMs increase.
  • One contributor mentions that Zenoah engines typically come with locked carburetor settings and that aftermarket solutions exist to allow higher RPMs, suggesting that the rev limiter is coil-based.
  • Another participant proposes that if the coil is designed to limit spark delivery at high RPMs, replacing it with an aftermarket coil might be necessary to achieve higher performance.
  • A historical example is provided regarding the rev limiter in the late 60s Boss 302 Mustang, illustrating a method to bypass it by cutting a wire, though the relevance to the current discussion is not explicitly agreed upon.
  • A participant expresses curiosity about what to expect when opening up the engine, linking to an external resource for further information.

Areas of Agreement / Disagreement

Participants express various viewpoints on the methods to remove the rev limiter, with no consensus reached on a definitive approach. The discussion remains unresolved regarding the best method to achieve this modification.

Contextual Notes

The discussion includes assumptions about the design and functionality of the rev limiter and the engine's physical limitations, which are not fully explored or defined. There are also references to aftermarket modifications that may not be universally applicable to all Zenoah engines.

oldunion
Messages
182
Reaction score
0
I have a zenoah g62pu engine on a scooter, about 62cc's. It has a rev limiter in the coil set at 12,500 i think. Id like to know how you could remove this. I have heard rumors of burning it out somehow, but no facts on it. It is a very small unit, maybe 1 square inch with a wire that goes right to the spark plug.
 
Engineering news on Phys.org
A rev limiter can be implemented different ways that could be simple or complex to circumvent.

Does the motor start cutting out when it reaches the rev limiter? Like whirrrrr rrrrr rrrr rrr rrrr rrrr rrr type running? If so this MAY be easy to circumvent but could still be complex because while there are popular methods a lot of different ones could be used. Without a schematic you'd have to test it and figure out what method it uses.

A lot of times the physical construction of the engine limits revs because it runs out of power extremely quickly near the top. Used on inexpensive edge trimmers and leaf blowers, but applicable to any two stroke.

As you increase the revs the stress on the connecting rod rises sharply by the square of the increase. Add 10% more revs and you have 20% more stress, 20% more revs and 44% more stress. How long can it handle that before failure?
 
im not extremely concerned with the connecting rod, the engine puts out maybe 7 or 8 hp tops, 5 stock. this engine, and all of zenoah engines that I am aware of, originally came with locked carburetor settings. currently the engines come with a coil based rev limiter. other people buy different limiters for other zenoah engines and retime the flywheel to allow for the engine to rev to 20k or so. so it is coil based, schematics...i don't know ill try, does anyone know how to get around it?
 
If the coil itself was designed to stop delivering good spark above that RPM then you will need a new coil. OEM puts reliability above performance, no one makes money doing warranty work and earning a reputation of engines that blow up. So aftermarket may be the only choice.

On the late 60s Boss 302 Mustang for example, the rev limiter simply cut off the ignition power source by interferring with the points/coil. It was a simple one wire to cut to eliminate it, as if the engineers had acknowledged that for warranty purposes it had to remain intact. But for owners who bought the car to use it, they cut the wire as soon as they could and they both win since the customer gets perf and Ford didn't have to warranty it.

Altering the ignition timing makes sense too.

If the connecting rod goes there isn't much of a point to the rest.
 
http://www.davesmotors.com/store/product404.html

What am i going to see if i open this thing up
 

Similar threads

Replies
7
Views
9K
  • · Replies 39 ·
2
Replies
39
Views
6K
  • · Replies 8 ·
Replies
8
Views
4K
Replies
4
Views
4K
  • · Replies 13 ·
Replies
13
Views
6K
  • · Replies 31 ·
2
Replies
31
Views
8K
Replies
5
Views
5K
Replies
12
Views
6K
  • · Replies 19 ·
Replies
19
Views
11K
Replies
14
Views
5K