"Racing" CDI modules...snake oil?

[forchetto]

The weather wasn't up to much here yesterday, so instead of my usual Sunday ride I stood in my workshop with nothing much to do. You know the saying "idle bikes are the devil's workshop"?, well I set about finding something to do.

I had a look at some of my old tool relics, the sort of thing that's not used anymore, like that OHV tappet adjuster, the stroboscopic timing light used to set the timing after adjusting the old contact breakers, etc, etc.

This last item is no longer used as today's vehicles have electronic ignitions and engine management systems that can not be adjusted, so the timing is set correctly for all eternity. For those who do not know how they work they have a Xenon lamp that is made to flash in time with the spark by a sensor attached to the plug HT lead and are then pointed at the moving rotor. As the flashes are at the same frequency as the plug firing, the rotor appears to stand still and the light iluminates the index marks. You can tell the exact point at which the spark happens as the marks are visible even though the rotor is spinning. The behaviour of the advance and retard mechanism can be observed by reving the engine and watching how the index marks move about.

I then looked down at one of my pitbikes with a Honda Cub clone horizontal engine and remembered that the magneto cover can be removed without any oil loss, as the magneto runs dry. Also there are TDC and firing point marks engraved on the rotor and an index mark on the crankcase. I then ran the engine and pointed the light at the rotor and observed that the timing "F" mark and the crankcase index mark were aligned exactly. Revving the engine produced no change, same as on the original Honda Cubs where the timing was fixed on full advance. No centrifugal or vacuum advance mechanisms were fitted.

But, wait a minute, I have a fancy anodised aftermarket CDI module fitted with "Racing" written all over it and the promise of oodles of extra horsepower by, and I quote: "an agressive timing curve".

Next I made the CDI plug accessible and lined up 3 more CDI units to try out this way: The factory OEM one, an aftermarket unit with the RPM limiter removed, and another "Racing" one from a different maker to the one tested already and ran the test.

Guess what: No difference whatsoever was noted with any of them. The firing stayed at the "F" mark at idle, midrevs and high revs. How then can extra power be claimed by these units?. The overall advance can not be changed as this is set by the position of the pulser or pick-up coil. The advance curve doesn't exist as the timing appears to be fixed on full advance regardless of what unit is used.

Is this all a scam?...snake oil?...a placebo?...thousands upon thousands of these units are for sale all over the world and eagerly bought by people (me, for a start!) and we seriously believe they're doing good, maybe because we rarely test the claims and are subjective about any improvements. What do others think?.

[TeamCheap]

Unless its wired wrong somehow (not likely).

I know the one I tried on my lf200 did make a difference but it was a negative difference so out it went.

I think they advance the release of money from people wallets.

Its sad that people are like that but it is the world we live in.

[knothead]

Good work Forchetto.
This brings to mind the debate about those Nology spark plug wires and the spark plugs that went with them.
It's a shame that people will try to get something for nothing by taking advantage of people, it happens all the time.
Like P.T. Barnum said, there's a sucker born every minuet.

[phil]

the only thing i think they MIGHT do is remove the rev limiter,but most chinese cdi dont have one anyway as that cost extra. they also should last longer as the heat sink built into the aluminum case but that just a guess i have seen some with a adjustable limit which would be a plus but overall i vote snake oil

[forchetto]

Does anyone know the recipe for humble pie?

After the disappointment with the CDI units when tested on one of my Jincheng Monkey bikes, I was left wondering why the POSH CDI module appeared to make such a difference when used on my Skyteam ST110-6 with a LIFAN 152FMH engine.
I wrongly assumed all Honda horizontal engine clones where the same but couldn't be more wrong: The magneto assembly and timing gear are totally different.

The Lifan engine has a far more sophisticated and powerful alternator-magneto and arrangements for varying the ignition timing electronically. The POSH CDI unit does advance the timing by a greater amount and a lot more quickly, as observed with my timing light.

This is a picture of the interior of the magneto housing. Unlike a normal monkey bike clone engine, the left hand crankcase cover is an integral part of the magneto. It carries the stator components, pulse coil, etc. It has to be accurately located to the main crankcase to ensure alignment with the rotor and its magnets, and for that purpose has two dowels that engage with holes in the crankcase. Watch out for these dowels dropping out and getting attracted by the powerful rotor magnets. They're only a loose push-fit in the cover.

The second picture shows the rotor with its firing and advance magnetic strip as described in my post on this thread:

http://www.chinariders.net/modules.p...ewtopic&t=8015





That the POSH CDI happens to work on this engine does not really invalidate the original premise. A huge variety of these devices are sold to be fitted to bikes with unsuitable engines with a promise of more power. They don't work on my Jincheng engines or on my Zongshen 125 cc engine either.

[SpeedSouth]

If I were a smarter man I'd understand more of this stuff...but I find it really interesting, nonetheless.


I appreciate the effort in testing these things and posting the results.
And with pictures, even! Well done, sir.



I bought one of the CDI units that was being discussed here last year. I never put it on the bike, and it's the only item I had for the Lifan that I did not give the new owner. In other words, I have one sitting on the bench in the garage, if someone is interested.

[SpudRider]

Dear friend,

Thank you for yet another superbly written, thought-provoking post. I must admit, I am largely ignorant of my bike’s electrical system and CDI unit. However, I am eager to learn. I do not wish to hijack your thread; however, I am very curious. Can you please help me with a few questions. :?:

Below is a picture of the rotor on my Zonshen Sierra 200GY-2. If you look closely, I hope your can detect the two faint marks inside the yellow circle. I assume that the rectangular mark on the left is the advance timing/firing mark, and the straight line is the TDC mark. In this photograph the Zong’s pickup coil is also shown inside the orange circle.




The next photo shows the timing strip on the rotor. For the sake of reference, the advance timing/firing mark is once again shown inside the yellow circle in this photograph.




The next photograph shows the stator and pickup coil mounted inside the Zong’s left crankcase cover.




The last photograph shows my Zongshen’s CDI unit.




In the link below, please reference the electrical system diagram on page 132 of the Zongshen service manual you so graciously posted. It appears that my Zongshen CDI employs seven wires.

http://www.mychinamoto.com/downloads...2EC-Manual.pdf

I assume that my Zongshen’s CDI unit is incompatible with the typical CDI units found on other Chinabikes; am I correct? Once again, thank you for yet another superbly written, though-provoking post.

Spud

[forchetto]

Thanks for your kind words. I do try to get my head around these things but it's not easy. I've always found car and bike electrics a nightmare, and I work in electronics... :roll:

You're correct. The rectangle is the range of advance the CDI unit can cope with. If you used a timing light through the inspection hole in the crankcase cover you would see the right side of the rectangle at up to about 1500 rom and as you rev up the engine you'd see the rectangle apparently "moving" clockwise and the other side becoming visible.

The CDI unit is physically incompatible with others sold for CG clones, pitbikes, etc. Electrically they could possibly be adapted but you'll need to go head-hunting at Cape Canaveral to find someone to do it...

[SpudRider]

Originally Posted by forchetto

...You're correct. The rectangle is the range of advance the CDI unit can cope with. If you used a timing light through the inspection hole in the crankcase cover you would see the right side of the rectangle at up to about 1500 rom and as you rev up the engine you'd see the rectangle apparently "moving" clockwise and the other side becoming visible.

The CDI unit is physically incompatible with others sold for CG clones, pitbikes, etc. Electrically they could possibly be adapted but you'll need to go head-hunting at Cape Canaveral to find someone to do it...

Thank you, my friend. I live a good distance from Cape Canaveral, so I will probably buy a spare ZS 200GY-2 CDI unit, instead.

Spud

[phil]

well i learnt something :?
a cdi might help but i guess its a hit or miss if its for your bike assuming your bike is what im also guessing is a ac cdi box i have found the lifan scooters will let the smoke out of a normal performance cdi box
i have never eaten spanish crow before but its the same as all the rest and i have eat a lot
spud, that cdi box is on my list if i get everything together quick enough

[SpudRider]

Originally Posted by phil

...spud, that cdi box is on my list if i get everything together quick enough

Stocking the Zongshen CDI is a very good idea, Phil. I was going to offer you that suggestion, but you "beat me to the punch."

Spud