Author Topic: Piranha/YX 140 charging and ignition issues (Chinese clone engine)  (Read 1981 times)

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Offline Scott S

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A while back I resurrected a 1971 CT70 and installed a Chinese clone 140cc engine (Piranha/YX140).

It's NEVER seemed to charge correctly. I've since found out that there are several different styles of stators on the clone engines, and they all need the correct REG/REC. I probably don't have the correct one. I'll see if I can dig up the info on that.

I let it sit for a few months. It's ALWAYS been a booger to get started after sitting. When ridden regularly, it's a 1-3 kick bike.
BUT.... I seem to have lost spark. I ordered some new plugs (only takes one, obviously), but I dug into it to test out some other stuff.

I pulled the seat, tank and battery so I could get to the wiring. Someone said I could remove the coil that way, but not on my bike. The nut that goes on the coil stud goes on from underneath and I have to drop the engine to pull it. The coil sits under the tank mount (see pics).
I looked at the trouble shooting instructions at T-BoltUSA and they are pretty lacking. I can get 0.8 Ohms on the lowest scale between the two small wires on the coil. I haven't tested to the spark plug lead yet. Can someone give me the idiot proof test for that?
I found the stator wiring but, again, instructions aren't clear. I know I need to go between the two yellows and....something. Can someone walk me through that as well?
I see the REG/REC and it only has fins on one side (see pic). I read somewhere that the Piranha YX140 needs one with fins on three sides? (that is the stuff I need to dig up)
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #1 on: July 06, 2021, 02:24:17 AM »
Here are the stator wires. What's the procedure to check that it is good?
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #2 on: July 06, 2021, 02:24:51 AM »
Now, Vince Pale at TBoltUSA recommends wiring the Piranha 140 (which has a full wave charging coil) to a half wave regulator. The slight wiring mod needed is shown in the right hand panel of this illustration
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #3 on: July 06, 2021, 02:26:12 AM »
The bigger picture shows how the Piranha 140 charging coil is rewired slightly: one end of the charging coil is grounded, and the other is spread across the 2 AC inputs on a half wave regulator. Without this modification, if you are running a half wave regulator (fins on one side) the charging system will never work well.
 However, I have also read that I need a regulator with fins on 3 sides. Why rewire the charging coil if I can just change the regulator?
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #4 on: July 06, 2021, 02:26:55 AM »
The last two posts, I'd have to really study. I'm...eh, OK...with electrics. HOWEVER, why change the wiring of the stator of there is a REG/REC that will work? (Again, gotta dig that info up again).

Long story short:
-No spark
-new plugs on the way
-need to test coil and stator
- want to get better charging.

Can anyone walk me through this in really simple steps?

And here's the stator/regulator info (there's some more in detail, but I've already posted a million words):

There are 5 types or 12v stators out there for these bikes that generate electricity. Here is how you know which is which and what u can do with it.

1. Floating. You have two leads yellow and/or white. Measure resistance of zero at the ends AND measure open at the end and to the bolts of the plate. Here you need to purchase a full wave rectifier and run all voltage to the battery. This is usually a setup that is about 2.5x2.5" square and has 4 wires sticking off of it...yellow/white inputs, red to the battery, green to the battery split to ground. Then from the battery to your electronics. Typically this will provide 50-55watts DC power.

2. Split System. You have two leads, yellow and/or white. You measure resistance at the ends between them and they are open. You measure resistance between each one to the bolts and they are open. On this system you need a regulator/rectifier. This is usually the ones you see that have the 4 male prongs in a square pattern that a harness plugs into. One line goes to the rectifier line via the white input line and produces DC power and goes to the battery via the red line from the unit. The other line goes to an AC regulator side, usually yellow, and is tee'd and can be used to power your lights. Typically these result in approximately 13w DC to your battery and 35w AC to your lighting circuit as usually one line does produce more juice than the other (yellow usually makes more than the white on these)

3. Grounded style. You have two leads yellow and/or white. You measure resistance at the ends and it is zero. You measure ends to the bolts on the plate and it is also zero. This style means you need to actually ground one of those wires and then take the other wire and run it how you want. This can be either as a single line AC circuit producing about 50w and power your lights ( you get a stand alone regulator for this), or you can run to a rectifier and get 25w DC and run to your battery (same style as the split system, but you ignore the regulator prong. Some people will take this 50w AC single line and split it to a regulator to power AC things and also to the Rectifier to power DC things (single input, split to work on the same hardware as the Split system). It does work, but I would think it would tax the overall system components. If you do it, you can wire it just like the split system.

4. Single Line. Effectively the same thing as grounded style, but you only get one line, usually yellow. Typically this is seen on the smaller versions of the outer rotors and do not produce as much wattage. Usually the max wattage is about 30w. You wire it the same way as you would with the Grounded Style...you can run full ac via just a regulator, you can run full DC by using the rectifier prongs, or you can split it just like above.

5. 3 Phase. The three phase setup is the most powerful and most like big bikes. This will produce about 150w DC power. This setup has three yellows coming out of it and goes to a full wave rectifier and produces full DC power to the battery. This one also powers the CDI unit directly from the battery, and not from independent coils. However, this one also means that if your battery is dead, you do not get any spark, no matter how much you kick it. That extra coil that is isolated to spark your system on the other 4 setups is now integrated to produce more overall power and delivers better conditioned juice to the CDI unit. Relatively rare.
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline MauiK3

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #5 on: July 06, 2021, 08:38:58 AM »
I like to tackle problems one at a time unless they are connected.
Your no spark situation could be many things.
Check that no ignition wiring is shorted with an ohm meter
Check the spark plug wire is not burned with an ohm meter
Does the coil work?
Is it electronic ignition or does it have points and capacitor? If it is points make sure the capacitor is not dead shorted. New ignition capacitors are known for being junk
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #6 on: July 06, 2021, 12:46:25 PM »
 It is a CDI system.

 It should run without a battery, so I'm tackling two separate issues here: no spark and weak charging.

 I tested between the two small leads on the coil and got 0.8 ohms. I don't know if this is good or not. Remind me how to test on the spark plug lead/end of the coil, please?

 I think I have one of the first three systems on the stator (see above). But, to me, the instructions are unclear and they all seem to be the same for all three types. How do I know which type I have, as that determines which regulator I need
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline MauiK3

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #7 on: July 06, 2021, 03:45:40 PM »
On CB750’s the connector at the plugs is a resistor, if they read over 5k ohms they are toast (I think that number is right). See if you can check between your plug end and the coil, if it’s over about 5k the wire may be too high resistance. I don’t know much about your spark system so this information may not be helpful. Others here likely will know more.
1973 CB 750 K3
10/72 build Z1 Kawasaki

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #8 on: July 06, 2021, 04:17:25 PM »
 When I check between the two small wires, I get 0.8 Ohms on the 200 Ohm scale.

 When I check from either of those wires to the plug cap, I get 5.9 Ohms on the 200K Ohm scale.
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #9 on: July 22, 2021, 06:27:29 PM »
With help from a friend, we determined that the coil and CDI were bad. His theory is the coil probably crapped out and took out the CDI.
He actually had some parts on hand (from an old Hi-Po Grom build) and he got it to run.
The "Race CDI" actually makes it easier to start, too.

We tested the charging system and all seems fine.

I still have to put it all back together and neaten
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650

Offline Scott S

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Re: Piranha/YX 140 charging and ignition issues (Chinese clone engine)
« Reply #10 on: August 13, 2021, 05:21:03 AM »
OK, so back to the charging/lighting issues...
 Took the CT to a local bike night yesterday. About 12 miles each way. Ran great and my wife clocked me at 60+ at one point (and had more in it). Easily cruises at 55.
  When we left, it was dark. Both she and some random guy at a stop light told me that my tail light would fade away. Started out bright and would just fade out, like the battery was dying. The brake light was bright and would "recharge" the tail light, only to have it slowly fade out as I went down the road. I was keeping the revs up and doing at least 45 MPH or more during the ride home.
 I can't say if the headlight was fading out as well because I have auxiliary LED lights up front. I know the headlight was working when I left the parking lot.
 When I got home, I checked the battery and it was at 12.71 volts. Checked it this morning after sitting and it's still at 12.66 volts. When I turn on the key (engine off) the lights are on and bright.
 So what's going on? Why would the lights fade out? This is what I was seeing in the past, when I thought it wasn't charging. But we checked the charging when we replaced the coil/CDI and I'm getting plenty of voltage from the stator.
'71 CB500 K0
'17 Triumph Street Scrambler
'81 Yamaha XS650