125cc Lifan engine charging problem
 

Hi, all. New to the site.

I've put a Lifan 125cc engine (model 1P54FMI) in an old Honda bike (C100), and am having trouble with the charging/lighting system. In short, it doesn't provide enough electricity to run the lights and charge the battery, so the battery drains.

I've replaced the rectifier/regulator, and with the new one installed (yellow and white wires from stator on the lower-left and upper-right terminals, ground on the lower right, and the upper-left terminal is the DC output), at idle I get less than 4VDC on the output terminal even with nothing but the multimeter connected to that terminal. It's not much better if I rev the engine. And I measure between 5.5 and 7.3 VAC at the (yellow and white) stator wires coming into the rectifier/regulator.

Does this sound like a bad charging/lighting stator coil?

Thanks for any advice---I'd really like to get this thing on the street!

Mark

Welcome Mark!

I don't know the finer points of the stator in terms of output voltage, but I do know that there are different types. Does your new engine have electric start?

Thanks for the reply and the welcome!

It's kick-start only. The stator plate has two coil assemblies: one the magneto which powers the CDI ignition, and the other the alternator charging/lighting coil that is supposed to power a 12V electrical system. That latter coil produces a dual-phase AC output (two "hot" AC wires and ground), which go to the rectifier/regulator, which is supposed to turn it into something like 13V DC to charge the battery and run accessories. I'm only getting 3.7V DC out of the system...

Mark

Ok, the little that I know about these stators includes the fact that the electric start version is different. It has a dedicated coil for the headlight and another for the 12v accessories. Check out www.dratv.com

It may be that you got a weak stator out of the box. I do have a parts engine on my bench. It was an e-start model and I would be happy to send the stator and matching flywheel assembly.

Yes, I think there's actually a short (to ground) in the charging coil in my stator.

Cool of you to suggest the parts from your parts engine. Since my engine is kick-start only, would the plate from yours work? The pictures on the following web page make me think there is a difference in the center-hole diameter (33mm for the electric-start version versus 18mm for the kick-only version):

http://www.chinese-parts-canada.com/magneto.html

I suppose I could just swap in the charging coil from your plate?

Mark

Again, I'm not as knowledgable as some on this topic, but if the stator is from an electric start engine, I don't think it will bolt on to a kick-only. The reason that sticks in my mind is that the stator is mounted to the engine in the kick version, but it's mounted to the side cover with an inverted flywheel on the electric start style.

I spotted a stator that is the same, but it will bolt on to the kick-only version. it was either at www.dratv.com or www.scrappydogscooters.com

Weld is probably right. I may have the side cover yet too. The easier would be to just replace the stator. You will need a flywheel puller.

I tried installing the side cover from an electric start version onto a kick-only motor with no success. the details are fuzzy for me, but I think the bolt pattern was different.

I think this is the answer, but I'm not sure. I found it at Sachs MadAss 125cc & Monkey

http://www.scrappydogscooters.com/im...key-stator.jpg

Thanks, guys.

That stator won't fit as is into my engine, as mine is kick-start only. The stators for these look like this:

http://www.motopartsmax.com/images/Coil/387-003/500.jpg

It's a somewhat different plate with different mounting holes for the coils.

I could get one of those on a crf50 type mounting plate:

http://ep.yimg.com/ca/I/dratv_2202_61439985

That looks pretty similar and claims 90W. Anyone know if it would really mount in my engine? And would the Lifan stock rotor work with it or would I need to get an OEM crf50 type rotor?

I'm going to "float" the ground on mine and use a full-wave rectifier with it, which should double the DC power, but I'm suspecting that won't be enough for the lights.

So when that doesn't work I am considering getting a pre-made six-pole thing like that ($55 at dratv.com), or maybe monkeying with my two-coil stator by moving the coils together and putting a third one in there (there'd then be two lighting coils---wired together like the five coils in Weldangrind's picture), which might well be good enough, and cheap to boot. Plus it would give me that nice warm Frankenbike feeling.

Mark

It looks like you found the crf plate version that I was talking about. I don't know if it would work with your existing flywheel, but it's worth a try. A custom-wound coil sounds really cool! Please keep us updated as you make progress.

Just to follow up.

The charging coils on the Lifan horizontal kick-start engines are grounded at one end, and the two output wires (normally yellow and white) are from partway down the coil (yellow) and the other end (white). The rec/reg for these units is a half-wave rectifier, and an inefficient regulator, meaning it's not a good system for getting the most DC power out of that coil.

But there are pretty easy and cheap solutions if you want more DC power and are not running lights off AC. Cheapest and easiest is to "float the ground" (take the coil end that's grounded and attach it instead to the yellow wire), AND get a $10 full-wave rectifier off ebay (looks just like the half-wave ones, except it has cooling fins on the sides as well as on top; search for lifan rectifier). If you're really looking for efficiency and want all the DC power you can get out of that little coil, do the ground-floating trick and also find a Shindengen FH series rec/reg. They are kind of big, partly because they are made for three-phase stators, but they work as full-wave rec/regs just fine. They use MOSFET circuitry which is much more efficient than the stuff in the old school rec/regs. Unfortunately they're expensive, so expect to spend at least $50 on ebay. But there are BIG differences between the wattages you can get these ways. For instance, you get MORE than twice the DC power by floating the ground and using a full-wave rec/reg.

Mark

That's terrific information, Mark. Do you intend to move forward with a better reg / rec?

It runs fine with the $10 full-wave unit from ebay---the battery doesn't run down at all. But I ran across one of the MOSFET units for a steal, so I will wire that in and see what difference it makes and try to quantify the amount of DC power you get with the different options. Soon. As soon as I figure out my fuel/air problem

About that. The main jet on my "PZ22" carb is a strange little creature. 5mm diameter round, slotted head, 4mm diameter thread, 7mm overall length of which 2mm is the depth of the head.

My 125cc Lifan idles okay but give it any throttle (with no choke) and it halts and surges. Run it with the choke on and it's much better. So it seems lean. No air leaks past the carb. So I'm guessing the #83 main jet the carb came with is too small. But I have no idea where to find jets that will fit the carb. Will the Keihin 99101-116 work? At least they have 4mm threads, even if they differ in other dimensions...?

Mark

I don't have experience with the PZ22, but I'm betting that it's a Keihin clone. I've tried to find slow jets for the larger Keihin clones and was unsuccessful. I stick with Mikuni clones now. Jets are very easy to find.

Have you tried www.jetsrus.com ?