Advancing Ignition

I think Norman was working on dissecting a CDI. I've been looking for a replacement CDI, but ours is not the traditional CDI. Most CDI's have a constant power source and constant ground, and it receives a "fire signal" coming from a secondary magnet/coil on the flywheel...in other words they use a minimum of 3 wires, unlike our 2.

Easiest way to advance ignition I would think would be to slightly adjust the magnet position in the magneto. But changing it just a couple degrees would be very difficult with the design.

Removing the base gasket won't affect ignition timing. The piston will be in the same spot in it's stroke compared to the magneto position. It will however, change intake/exhaust timing (i.e. when the ports open/close)

We've been working on this for a while...I have not found any components that would work to improve it and have found no way to improve what we already have.

Read more about it here........http://motorbicycling.com/f13/beefed-up-ignition-647.html

I have done some advancing, from just slight to a full key. I have now removed the advance completely and am just running the stock. The problem was that the engine got finicky and the other thing is that these engines will not last at high revs so for torque and low end power I like them stock. I have a lot of porting and a larger carb 18mm and I think for me that is enough, the bike will do 40 with a 39 tooth sprocket and climb some big hills around hear, I get the most out of the porting, I don't even change the intake tube. Let us know if you have any luck with the changes. Have fun, Dave

PS: I forgot to tell you how I did it. I file the slot in the rotor and then make a small wedge to fill the gap. You can then just move the filler over to the opposite side if you want to return to normal.

I would urge the inexperiencd to procede with utmost caution. Air cooled engines may not have as wide a latitude of tolerance as water cooled. For the small increase in power it may cost in a failed motor. If this is done enrichening the fuel air supply should be considered.

Yeah... I would say don't mess with the timing unless you REALLY know what you're doing!!
You could also end up making the engine run really hot!!!
You can get plenty more speed & power from gear changes, a good plug, wire & boot, & simple porting!!

I'm going to throw a monkey wrench into the soup.
To advance the timing and not destroy parts I take an over sized woodruff key and dremel it to make an off set key to advance or retard the timing a few degrees. I need to sit down some time and put my timing light in these engines to find where it's firing spot really is. then a guy would know if changing the timing would be of any use.
Any of you guys remember a bike called a Hodaka? I've wondered if the parts off the old hodaka would fit these china engines?! I remember the Hodaka would run like a scalded dog and were lots of fun.

I raced Hodaka's and thinking back, I don't think any of the parts would fit. There is a chance that parts from a chain saw would work. But the only reason to use them would be to in crease the quality of parts. I have used some of the porting skills I learned from the Hodaka on these engines. one thing about points is that it is easy to change the timing and see what you have. I am looking forward to hear what the timing is on these engines stock. Like I said I moved timing up about 1/2 a key and then a full key, but it wanted more fuel and got fussy I didn't like the way it ran slow. Have fun, Dave

Yeah those offset woodruff's will do it for advancing or retarding a 2 stroke flywheel or on a timing gear to advance or retard a camshaft on a 4 cycle engine.

I'd bet the expansion chamber would be the best route to go for performance tuning....and just keep the stock timing settings.

Norman said:

To advance the timing and not destroy parts I take an over sized woodruff key and dremel it to make an off set key to advance or retard the timing a few degrees. I need to sit down some time and put my timing light in these engines to find where it's firing spot really is. then a guy would know if changing the timing would be of any use.

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Hey Norm, Do you think a rocket key work?

Goped Rocket Key - Go Ped Rockit G23LH G43

that is what the keys I made look like but the problem with that key for sale is you don't know if it will fit the bicycle engines key ways. For that price you can make one form an over size woodruff key and some time with a dremel with a fiber reinforced cut off wheel for if you want to take a chance but that key and see if it will fit if its a little large then take the dremel to it. cut on the key and not your engine's shaft keyways.

eDJ said:

Yeah those offset woodruff's will do it for advancing or retarding a 2 stroke flywheel or on a timing gear to advance or retard a camshaft on a 4 cycle engine.

I'd bet the expansion chamber would be the best route to go for performance tuning....and just keep the stock timing settings.

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Yes the expansion chamber and porting on these engines is the best bet, I have the timing back to stock. I would still like to see someone put a timing light on one of these engines to see what they are from the get go. I have not fooled with the compression yet there are a few that have done that and claim that it helps. I am fearful that the tiny little bearings in the lower end of these things would just give out under pressure. I would suggest that if you are not good at carving on the inside of these motors, I would say carb and Pipe, and not over 18mm on the carb. Have fun, Dave

I've got a timing light I can point at the motor. But since there are no timing marks or anything, what the heck can I do with it?

I guess I could print out one of those degree wheels and make a mark at the tip of the magnet in the middle...

Over the years I've wrenched on lots of air cooled motors and I'd mention this
for what it's worth.

The air cooled are more sensitive to timing advance and the heat it generates.

Many of the air cooled had tech manuals that measured the BTDC with a spark plug bore gage and would state to set the piston 4 mm BTDC measured at the piston. Thus you TDCed the piston and marked the gaging rod and measured up 4 mm above that. Then moved the piston back and pushed the rod inward so when you moved the piston foreward it touched the rod and moved it up to where the 4 mm line matched to the point where you gaged the TDC from.

I don't know if these Chinese engines are doing something like that and tech manuals for them would indicate that or not. If I had one, as soon as I got it
I'd try to calculate this measurement before going any further. I'd write it down keep it in the tool box. I don't know how the ignitions are configured on these....whether with coil & battery with points and condensor or a unitized
mag with hall effect switch.

In most instanced I didn't use a timing light. The timing was set static. I had a small light bulb I soldered leads to and mounted this in a small empty parts box. When the leads were connected and I set the timing pully to it's mark all I had to do was move the distributor (or timing plate) to where the light just begin to glow. Then lock down the timing adjustments. Then it was good to go. If it was like the motorcycles........I made the spark plug being set X number of mm BTDC.....I purchased an adaptor for a sparkplug that was fowling due to excess oil in that cylinder. Then I took that to the hardware store and purchased a brass fitting that screwed into that sparkplug adapor that had a compression fitting. A simple piece of rod stock that fit snugly into that was purchased. When I got it home I'd use the grinder to slightly round the piston contact end and then cut the outside portion of the rod at about
four inches, so it wouldn't be too long and interfere with other parts of the bike when working.

Again, I don't know what kind of info these Chinese motors provide.

As for increasing the compression, I've ground (or milled) the base of the cylinder to where it sit deeper into the crank case. But it must be remembered that for daily use this makes the motor more tempermental, and will effect it's useful life expectancy. I doubt the Chinese are aware there are some old school American speed tuners around wanting to tweek these things as I see on the net.

I really think the free flow air cleaner and expansion chamber offer the biggest bang for the buck performance wise with the dependability the makers intended. If you're racing.....then anything goes.

If I adjusted my time ahead of the stated factory setting.......I'd be reading my spark plug often. Awhile back I posted photos of what good running 2 cycle plugs should look like and some photos of plugs that would mean the 2 stroke would be ready to fail soon.

Speaking for myself, I'd rather buy a larger motor than try to tweek a small one. It's just hard to argue with larger displacements.

Jason - I would take a rod and find TDC by placing it through the spark plug hole, move the crank till it is at top. Then put a line through the stator and the coil this will be your TDC. Start the engine put the timing light on the marks and you will see that the light will stop the engine look at the marks and try and remember the place that the mark is on the stator, stop the engine and then make a mark at that spot with a marker, then restart the engine and run the light on the marks again and see how close you are, if you are on then take a degree wheel and measure how many degrees the lines are apart, then we will all know what the advance for these engines is. Have fun, Dave

eDJ - I think you have been working on some interesting engines. Sounds like a Maico or a Husky! you bring a lot of talent to this forum. These little engines have CDI for ignition. I like them because they run lousy till we put some of the knowledge from the 60's in them, LOL. Have fun, Dave

PS: I still have my Buzz Box. Ill have to look for my degree pins.

Ive found there to be an insane amount of play in the stock key
you can move the rotor several degrees
I can get mine advanced enough to hear it ping with the stock key no problem
I would be careful with it
take care
JAK

Jak - That says a lot, what you just told me. I moved the one on my bike 1/2 a key and it did not ping. So what that tells me is, that as usual there is no common or standard timing. Mine has to be very retarded to not ping, I was not using high test fuel. I am going to try and borrow a timing light and check my bikes and see how far the difference would be between the engines. I have not messed with the compression at all you may have a higher compression. Have fun, Dave

jak stoll said:

Ive found there to be an insane amount of play in the stock key
you can move the rotor several degrees
I can get mine advanced enough to hear it ping with the stock key no problem
I would be careful with it
take care
JAK

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Egor said:

Jak - That says a lot, what you just told me. I moved the one on my bike 1/2 a key and it did not ping. So what that tells me is, that as usual there is no common or standard timing. Mine has to be very retarded to not ping, I was not using high test fuel. I am going to try and borrow a timing light and check my bikes and see how far the difference would be between the engines. I have not messed with the compression at all you may have a higher compression. Have fun, Dave

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I found out later that the head/ cylinder combo I was using was making the comp ratio way too high
I put on another head here with the same shape fins & the engine runs way better overall
I was reqorqueing after it coold down & pulled threads from the case for the nead studs so Ill be getting some helicoils tomarrow morning
take care

JAK

Hi
From personal experience with na and forced induction cars
Air and water cooled
Most power was made retarding the ignition
I asume these china engines come preset for fuel economy, not power
That means as much ignition advance as possible
I would try to retard it
Peace