Roketa 250cc-MC54- no Spark. By tinatinu (Read 12,346 times)

[tinatinu]

Yes sir, i did it, and connected. Can you send me some pic wire ground.?
Make sure i did it right. Thank you sir so much. Happy Thanksgiving.

[JR]

I'm sure if you have a good copper wire hooked up to the engine anywhere on it and hooked up to the frame where the negative battery cable hooks up you've got her grounded good.

Has there been any change since you're last check for spark?

JR

[tinatinu]

Hello sir,
Nothing change. So tired wit tha.

[blitztek]

would you happen to know what the static voltage to the coil should be KEY ON? I am getting 5vdc and it cuts out as supposed to when cranking but spark is yellow and weak. won't jump more than 1/8" or so. I tried another coil and same thing. I would assume the coil is 12v like the system has onboard

edit, I have tested all the items listed earlier here and swapped two other cdi's and a new coil.

[JR]

If this is the 250 with either engine the system has a DC powered CDI and it's voltage will be on the black wire and needs to be 12.5vdc or greater with the ignition key on. Now when you say 5vdc on the coil are you talking about taking a reading on the yellow black wire to ground from the CDI while you are turning the engine over? If so then that's not near enough to the coil to produce a good blue spark.

Here is the basics of the CDI syatem:

A CDI module has "capacitor" storage of its own and sends a short high voltage (about 250+ volts) pulse through the coil. The coil now acts more like a transformer (instead of a storage inductor) and multiplies this voltage even higher. Modern CDI coils step up the voltage about 100:1. So, a typical 250v CDI module output is stepped up to over 25,000v output from the coil. The CDI output voltage of course can be higher. So you'll see CDI systems claiming coil output capability over 40,000-60,000 volts!!? As you will see this is not exactly what happens at the plug but for math purposes it works out. The huge advantage of CDI is the higher coil output and "hotter" spark. The spark duration is much shorter (about 10-12 microseconds) and accurate. This is better at high RPM but can be a problem for both starting and/or lean mixture/high compression situations. CDI systems can and do use "low" resistance coils.


Also have you checked the spark plug cap and made sure it's getting goo connection to the coil wire? A poor cap connection can cause this too.

Get back with us and also Welcome to the forum and please do tell us more about yourself.

JR

[blitztek]

sorry i didn't introduce myself, my name is trent and I used to work for peace sports (long story, burnt bad) for two years. I even wrote all the new manuals and PDI's on the 50's and 150's. Anyways, I now work for Blitz Moped in Dallas, TX and have never been happier. We are a B&M small shop in the old "party" side of dallas, just east of downtown. We are one of the few shops around that will touch chinese scooters, and do it honestly. I keep gettting these dang 250's because nobody else will touch them. I currently have 4 in the shop now. One for engine death, one for no spark, one for cooling system, and one for situp problems. Back to the no spark one, I have 11.98v to the cdi and just measuring between the two leads of the coil I get 5vdc. I will check the rest tomorrow.

also, I changed the whole coil wire and all when I replaced it.

[blitztek]

I have full battery voltage at the black wire, ground at the green wire, and I retried the first test, from battery ground to yellow/black at coil, I got .3vdc got the same at the cdi pin to dismiss a fault between the cdi and the coil in the black/yellow. i get around (jumpy) .25v from the stator on red/white (cranking) and the grey/white is open key on and grounded key off.

[JR]

Very strange? OK lets go over the wiring set up. First of all here is the wiring diagrams for these scooters as in the 250A and B with the linhai and the YY250/t version with the vertical moto engine.

thescooterprofessor.proboards.com/index.cgi?board=250g&action=display&thread=430

There are also two other wiring diagrams to different vesrsions that I know about. Now the linhai vesrsion was carefully drawn by me because I own a 250A and B and the YY250T version was drawn up by myself and Cruiser as he owns one of those. There are few differences in the scooters but the spark system is the same as far as I know?

So on the CDI there are 5 wires;

Black = 12vdc feed from battery with ignition on
Green = ground
red/white = pick up coil from stator or pulse sender
black/yellow = power feed to coil
gray/white = kill wire from enigne kill switch and key ignition

So lets review you got nearly 12vdc on black wire which is enough to produce a good spark

You have .25v on red/white wire and you need to measure it as AC voltage and the most you'll see here is around 1.5vac and as little as .01v will send a message to the CDI to fire as the flywheel spins, that is all this wire does, send a message to the CDI as to when to fire.

You said on the gray/white you have ground(continuity) with key off and open with it on which is correct. This wire is for killing the CDI when you do one of two things, turn the key off and/or put the engine kill switch located on the right handle bar in the engine not run position. You need to do the same test on the engine kill switch.

Green is ground and the CDI MUST have a good ground and you need to check the ground cable to the frame from the battery, check the engine to see if it has the ground jumper from the frame where the negative battery cable hooks up AND check the green wires out where the ground wire to the CDI hooks up.

The Chinese do lots of putting the wires together especially the grounds with little crimp brass connectors and they are very poor connections, my self I soldier mine.

ALSO make sure the frame where the negative battery and grounds hook up is bare clean metal with no paint under it for a poor connection. If it's one thing the Chinese are not shy on is paint!

Now the black/yellow wire check each end as again these are crimp on cheap brass connectors many a person has had weak spark or no spark from this area. Sometimes they don't even peel the wire good and they will be crimped on the outside rubber insulation. The plugs that plug into the CDI the wires can be removed by inserting a tiny screwdriver in the end of the plug with the small slot. Once inserted this will release the one way locking pin and one can pull the wire out repair if necesary and then bend the locking tab back out and re-insert. Again myself I put a tiny tad of soldier on all of mine.

There is one more thing to check make absolutely sure the gray/white wire with the engine kill switch in the run position and the key switch on has no continuiyt at all NONE. Also make sure the engine itself is grounded.

If after all of this you still have a weak spark I'll say bad or weak coil and/or CDI.

I don't believe in just throwing parts at a problem like this, I check the cost nothing and easy to check poor Chinese electrical first.

Also on that engine check with my pal Chance at Killer Motor Sports in Ft. Worth, they still sell 250's from the JCL warehouse and at one time he had some Moto stuff they scrapped for parts and he might have a spare engine?

.killermotorsports.com/Scooters_50cc_scooter_150cc_scooter_250cc_Gas_Scooter_s/405.htm" rel="nofollow" target="_blank">.killermotorsports.com/Scooters_50cc_scooter_150cc_scooter_250cc_Gas_Scooter_s/405.htm

Again ask for Chance and tell him JR sent ya!

Keep me posted on this and we'll figure it out.

[blitztek]

i actually know chance personally. He is a good guy. I will give him a ring.

I have 3ohms resistance from the negative battery post to the green pin at the cdi. i get .3-.4vAC on the red/white wire

this scooter with no spark is a JCL MC__ with a horizontal engine.

[blitztek]

also I have tried the a new (known good) coil, and two other CDI's form the other 250's. and one confirmed running has cooling system issues.

[JR]

You should have full ohms resistance from the negative wire to the green pin on the CDI. I will go verify that right now on my scooter, I own two linhais a A and B bought one from Chance on a trip tp see my grandkids in Dallas. I'll get back.

JR

[JR]

OK here is the readings. your red/white wire is fine again it's only purpose is to tell the CDI when to fire the reading is perfect. mine read .25v or higher depending on the rpm.

On the ohming of the green wire on the CDI to the negative post of the battery my reading is .001ohm. Now when you said 3 ohms did you mean 3.0 ohms or as I read .003? That is vertually full continuity whereas 3.0 is a different story and I would consider that a poor ground. My meter was set on the 2M setting.

With the scooter idling the black/yellow read 150mv. And when revved up it would hit a lot higher. I measured this on the the 200m setting on my meter.

At this point I believe it to be a poor ground if in fact you have a full 3 ohms resistance on the green wire to the CDI. Also again check to see if the engine is properly grounded with a jumper wire. Had a fellow once ready to push his off a cliff and the engine wasn't grounded at all but would spark sometimes.

I'll wait for your reply.

JR

[blitztek]

It was 3.0 ohms. I will run a jumper from green to battery ground tomorrow and see what I get

[blitztek]

hot blue spark... dang harness ground... thanks for the help

[JR]

Awesome!! Glad you got it! Now you can check the motor thread as Cruiser may have located a engine!

Yes the grounds can be a pain! I would find the splice point of where the CDI ground wire ties into and for sure fix that if you haven't already.

We are here for you and was sure glad to help!

JR