Off set key

[45u]

Has any one tried a off set key to adjust the timing? If so input please.
Thanks
Jeff

 

[butre]

they exist and people have done it, but this is a better product

http://www.pistonbikes.com/product-p/mmatm.htm

combined with an aftermarket CDI like a Jaguar CDI can make for easily adjustable timing and a proper timing curve

 

[45u]

Thanks for the input. What do you know about squish? Been working on combustible engines none stop for over 45 years. Did a lot to my 1/5 scale gas buggy. Work on motorcycles just about daily including but not limited to all machine work. I had all ready plainded on getting a better CDI (capacitor discharge ignition)
Thanks
Jeff

 

[sbest]

Timing advance is a crutch to get over slow combustion. If you can speed up the combustion, you don't need so much advance. Pressure, heat and turbulence tend to speed up the combustion. RPM and increased throttle opening tend to increase these and help to pick up the pace, so less advance is needed. A tuned exhaust pipe increases the pressure substantially so often some sort of timing retard mechanism is needed once you go tuned exhaust. Improved squish will also necessitate less timing advance.

An offset key will do the job and has been used for years as a timing tool. Many of the CDI coil conversions for older engines come with a stepped key for the flywheel right from the engine manufacturer. Timing advance is normally conservative on a stock engine so a few more degrees advance will liven a stock engine. Raise the compression or otherwise modify it and you risk detonation.
Steve

Where detonation starts on a Happy Time motor:

 

[45u]

Thanks for the input. On the rotor in the link above they say to go the hole width of the key slot if I am not mistake a offset key only advance it about half that much. Being parts for these little engines are fairly cheap going to try one just to see.

 

[sbest]

Jeff,
Typical advertising stuff. More is always better.
The good news is detonation is very audible on these motors.
I am assuming you are using the key to advance the timing?

You know that rpm advance works opposite on 2 stroke engines from 4 strokes?
The efficiency increases immensely with rpm, so will pressure and burn speed, so less advance is needed at rpm.

Note in that drawing above there are little pockets in the squish out near the cylinder wall?
That is accurate on the stock head. The squish area does not go out to the cylinder wall.
Cut the squish out to the edge of the cylinder walls and you will have MUCH less detonation.
This is from my own experience with these engines.
You want it to look like this on the right (stock on the left):

I mention this because the increased burn speed caused from the squish turbulence acts the same as timing advance.
An offset key would still be a good tuning tool.

Steve

 

[45u]

Before I do anything I will check the timing with a degree wheel. I know on the many fixed timing motors I have messed with the timing is normally off at least some. Steve do you have any idea how many degrees before TDC the timing is suppose to be?
Thanks
Jeff

 

[Bufu racing#1]

Has any one tried a off set key to adjust the timing? If so input please.
Thanks
Jeff

Yes they work if you file them down right first.. depending on wat gas and compression you got ... it's only going to be little gain unless it's used in conjunction with other methods of tunning... mine is set very close to stock and we get the stock ignition over 14k rpm , what I'm trying to say is you stock ignition is beautiful China work lol

 

[45u]

Does anyone know what the stock timing is suppose to be? If I new this I could check it with a degree wheel. How many degrees before TDC? I have seen too many fixed timed motors that where not very close. I am going to run the motor stock then do upgrades to see just how much I can get out of one of these little motors. When doing a perfrmace up grade a little here and a litte there ads up.
Thanks
Jeff

 

[Bufu racing#1]

If I'm not mistaken it's somewhere in the ballpark of 30