Budget Bike: Roketa Resurrection

[criggs]

Hey guys,

I have a 2005 Roketa 125cc pit bike that I recently purchased in terrible shape for 100 bucks (you know the story if you've seen my SSR budget bike thread). It needs a ton of work, not the least of which is a clutch diagnosis/replacement. However, since I've yet to hear the bike run, I'd rather not spend the money on a clutch, in case it needs other, more important stuff first. The bike came with a stripped kick start lever and kick start shaft with pretty severely rounded teeth. However, I was able to get a new kick start lever to grab on the shaft, and with the help of a hammer I tapped it on fully and tightened the bolt as much as possible. So, earlier this afternoon, I gave the carb a good, thorough cleaning, tidied the bike up a bit, got some gas in it, and gave the kick starter a try. It kicked over fine so far, and seems to have good compression, however it would not start. Tried to spray some starter fluid in the carb, and still nothing. I pulled the plug to check for spark, and it has none. So, at this point, I have a few questions:

- This bike has the on/off toggle style kill switch (picture below). It is in bad shape. If I want to delete this switch, do I simply unplug it? Or do I have to connect its two wires together? Neither of these gave it spark, but I want to make sure for later.

- Where and How should I check voltages to figure out what has failed? I have a basic knowledge of how ignition is achieved on these bikes, but I have zero knowledge of how to diagnose it. Should I be checking signal from the stator? Or should I be checking voltages in/out of the CDI? The coil?

Here are a few (crappy) pictures of the system on this bike.

In the first picture, you can see the style of coil on the bike, as well as a lot of the melted insulation in areas that the PO allowed the wiring to get too close to the exhaust (including the top corner of the CDI).

In the second, you can see the wiring that comes from the stator, wraps over the top of the frame, and ends at that connector. In the middle of the picture you can see a section of one of the wires is missing insulation, and the wire there is an ash gray color, not copper. That could be my problem right there =P.

The third picture is just for reference, in case there is something there that I can check or test.

So, are there wiring diagrams or something that can help me out here? I have no idea which wires do what, but if I know what to check and what I'm checking it for, I have the capability to put two and two together =P. Any help on this would be much appreciated, I really wanna figure out the specific problem before I start buying parts (this is as much about learning as it is about a cheap budget bike). Thanks in advance =].

 

[my67xr]

To disconnect the kill switch to trouble shoot it, just unplug it, you dont need to bridge any wires.

The black w/red stripe wire that has the broken insulation is from the source coil on the stator, it sends power to the cdi.
If you have a multimeter you can test it, first set the meter to 2000 ohms
Put one lead from your meter to the cdi earth (green), and the other lead from the meter to the black w/red stripe wire
You should get a reading around 380 ohms

If that is ok, then you can test the pulse/trigger coil too.
Set your meter to 200 ohms,
Place one lead from the meter to the green from the stator, and the other lead from your meter to the blue w/white stripe wire
You should get a reading around 130 ohms.

If there is no reading from either ^^, then there could be a broken or corroded wire, or a contact issue with the terminals in the plug/socket where thee stator wire's connect to the main loom.


Another place to check for a bad connection is the spark plug cap, a new one is cheap from a bike shop, you need one that has a built in resistor 5k ohms.
the cap just screws onto the end of the lead, same at the coil end, it just screws onto a thread inside the coil.
You could try pulling yours apart, there is a flat head slot inside the cap, unscrew it, and a small spring will come out after you remove the brass end that clips to your plug thread.
If that spring is corroded it may not let the spark travel through the cap to your spark plug.


To test the ignition coil, set your meter to 200 ohms and place one lead from the meter to the black termial on the coil, and the other lead from the meter to the green terminal on the coil
You should get a reading around .7 ohms.
Now to test the secondary reading of the ignition coil, first unscrew the spark plug cap off the end of the coil lead.
Now set your multimeter to 20,000 ohms
Place one lead from your meter to the black terminal on the coil, and the other lead into the end of the coil lead (touch it against the solid copper wire)
You should get a reading somewhere between 3k to 5k ohms

 

[criggs]

Thank you so much for the info, I really appreciate it. I am looking forward to testing this stuff to find out what is wrong.

Would there happen to be a basic wiring diagram (or something similar) available for reference? I know that you have to "power down and isolate" the specific circuit to be tested, so I want to know where in the wiring I should be testing. For example, how do I access and properly check the wiring at the stator? do I need to remove it, or is there a connector I can get at?

 

[my67xr]

Follow the wiring up from the stator cover on the left of the bike, about 8" up there should be a few bullet connectors where it join's to the main loom, just unplug them to test them.
This is a pic of the stator, you can see the black cover's on the bullet connectors.

This is a basic wiring diagram

 

[criggs]

Oh, I see, I didn't quite understand the circuit to be tested, but I think I get it now. I actually intended on working on the bike a bit today, but I got caught up installing new tires/tubes on the SSR, and accidentally forgot my meter at work. Needless to say I didn't get much done on the Roketa. I took the plug wire and boot apart and checked it out visually, but not much to see other than the melted insulation and some minimal corrosion. I think that even if they aren't the reason I'm not getting spark they will still need to be replaced. Are CDI's specific to make/model/year of these bikes? Or are they all pretty much universal? The CDI also has a lot of melted plastic on it, I think I'm going to end up re-doing most of the ignition on this bike.

 

[my67xr]

The cdi's that are used are just generic china 5 pin cdi's, and can be picked up cheap from any pit bike shop or off ebay etc.
We can get a new stator, new cdi, new igniton coil, a new main loom, and a spark plug for under $50 the lot off ebay here.
Magneto Flywheel Stator Plate 90C 110cc 125cc Kick Start PIT PRO Trail Dirt Bike | eBay
Ignition Coil Spark Plug CDI FOR 50cc 150cc Quad PIT Dirt Bike ATV Buggy | eBay
Wire Wiring Harness Loom 90cc 110cc 125cc 140cc 150cc PIT PRO Trail Dirt Bike | eBay

 

[criggs]

Ok, I spent some time on the Roketa today and found some interesting/confusing things. Firstly I repaired the Black/Red wire where the insulation was gone, and in another place near the CDI connector where the insulation had been melted through. Afterwards, I checked resistance of the source and pulse coils at the stator wiring connector. Here is what I found:

Source coil (checked between Black/Red wire and Green wire) - 422 ohms.
Pulse coil (checked between Blue/White wire and Green wire) - 130 ohms.
Coil, primary side (checked between black and green terminals) - 0.1 ohm.
Coil, secondary (checked between black terminal and coil lead) - 3.1K ohms.

After checking these readings, repairing the two wire sections, and substituting a known good spark plug cap, the bike still has no spark. So I decided to check voltages at the CDI connector while pushing the kickstarter by hand. This is what I found:

Source coil (Black/Red wire) - Approx 5v
Pulse coil (Blue/White wire) - Approx 0.3v

I also checked ground (green wire) at every available connection, and got 0.0 ohms each time (just to verify that the ground circuit did indeed go to ground).

To make things more confusing, I got a lot of weird readings at the ignition coil itself. I know that the stator generates AC voltage, but I don't know if the coil is ignited with AC, or does the CDI convert it and send DC voltage to the coil? I checked it for DC volts first, and got a constant 0.5v at the Black/Yellow wire when unplugged from the coil, but then 0v when plugged back in. Kicking the bike changed neither. When checking for AC voltage, I got a constant 0v at the Black/Yellow wire when unplugged, up to 0.3v when cycling the kickstarter. When I plugged it back in, I would get nothing there at all.

So I am definitely getting a source and pulse signal to the CDI, but I don't know if the CDI is sending a pulse to the coil or not. I checked the two wires from the CDI to the coil and got 0 ohms on both, so I know they are ok. Any idea what these readings mean? I'm starting to lean towards a CDI problem, but I want to be sure before I replace it.

Here's a few pictures of the bike, just for fun =].

Here's what it looks like with the seat and plastics (no gas tank)

Thanks again for all of the help, I really appreciate it. Looking forward to getting this bike going.

 

[my67xr]

The source coil reading on the stator is a bit high, normal is around 380 ohms.
It should still run, but i would be replacing it when you get a chance.

The reading for the primary coil on the ignition coil is a bit low, it should read around .7 to 1 ohm
The ignition coil work's by getting power from the cdi in through the primary side, and as it travel's through the winding's in the secondary side it amplify's it
If your coil has a winding ratio of say 100 to 1, and it's only letting in 1/7th of the power it could be that will be a huge drop in the coil's output to the plug.
Eg, if your coil normally has 7 volt's running to power it, times that by 100 by the time it comes out the coil lead to the plug there's 700 volt's.
But if your coil can only accept 1 volt into it, time's that by 100 and you only get 100 volt's out to the spark plug

I would be getting a new replacement ignition coil for it, they are pretty cheap $10 and up
If the wiring terminal's on your other bikes' coil are the same, you could alway's swap them over to see it it get's a spark then.

 

[emmo1980]

while its all good and well to stuff around testing everything and the advice given above is excellent,

but did you do the most basic thing first and start with a known good plug to check spark?

or did you just assume there is no spark because the plug that was in the bike when you got it didnt spark?

im not having a go or trying to be a smart arse but whenever you are trying to diagnose electricis the first step is to use a known good spark plug [well provided you have one that is] and if you dont have one when you get the bike running take the plug out and put it away for future reference and buy the bike a new plug [and never assume that a new spark plug is good either you would be suprised at how many are duds].

 

[my67xr]

At least he know's the stator reading's a bit high so that will need replacing soon
And the ignition coil won't work with a reading that low either.

But yeah fit a new NGK C7HSA plug in it too.
I haven't seen that many faulty new spark plug's though (not decent brand plugs that is).
But i do remember having a set of Bosch plug's in the early 90's that wouldn't let my car rev properly though.
I took them back to the shop where i bought them and swapped them for NGK's, and have used NGK's ever since.
I reckon the plug's in my car now are still the original plug's that i put in it back in 1992 as well

 

[criggs]

Quick update on the Roketa:

Got the Coil/plug wire in the mail today, so I went over and installed it on the bike, and still no spark. Just in case, I substituted a known good spark plug and still nothing. Didn't have my meter on me at the time to check the coil and make sure it's good, I'll have to try that over the weekend.

This is the one I bought: Link

I know it says Honda, but the coil is identical in appearance to what was already on the bike, so I figured they'd be the same. Hopefully they are? I also have a CDI on its way to replace the beat up, melted one that's currently on the bike. Hopefully the CDI takes care of it, because if it's not the problem I don't know where to go from here, haha.

 

[my67xr]

Try the power wire to the coil to the green terminal
Black terminal to earth

Are you just looking for spark at the plug tip with the plug thread's earthed to the head ?
You can hold it in your hand with you hand against the head too, you will feel a small zap but can't alway's see one

 

[criggs]

Yeah, I'm holding the plug threads against the head, same way I checked for spark on the SSR originally, was able to see one just fine. Do you mean reverse the two wires going to the coil? Attach power to green terminal and ground to black terminal? Or attach power to green terminal and then chassis ground the black terminal?

The CDI was supposed to be here today (California, USA), but according to the routing number hasn't even left its seller in Texas, yet. A little upset that I'm probably going to have to wait until next week to get it.

 

[my67xr]

Yeah swap the green and black around at the coil and check the spark then
With it wired one way the spark will be small , reversed it will be a lot better.
Make sure its wired to give the best spark

 

[criggs]

It's ALIIIIIIVVE!

http://vid25.photobucket.com/albums/c53/CRaSAfe/roketa warm_zpsg2nko3it.mp4

My suspicion was correct, it was the CDI. The bike now produces a strong, consistent spark. Started up on the third kick.

For the first few minutes it would only run with the choke on. It smoked out the exhaust pretty badly, but slowly dwindled off as it warmed up. Once it warmed up (as it is in the video), it seemed to run quite well. It revs strong, and idles decent (although the carb probably needs a bit of tweaking still). For some reason the throttle was stuck in the carb, I actually had to wet it with a bit of gas to free it up. No idea why it did that, I cleaned the carb pretty thoroughly a few weeks ago. Maybe the moisture from the rain we had a few nights back? Either way, starts up quick and runs strong. The only thing I noticed is that the lower end seems kinda loud. No knocks or rattles, just... I don't know, just loud, haha.

Next hurdle is the clutch that still will not work. I was kinda hoping that getting it nice and hot would help free it up, but it's still stuck solid, pulling the lever in does absolutely nothing. Guess it's time to order a new one. I'll probably pull it apart on my day off this week to make sure I order the correct part.

 

[my67xr]

That noise sound's like the bash plate is vibrating, either that or an exhaust heat shield

 

[criggs]

Yeah, it sounds external whatever it is, just gotta spend some time and find what's loose =P.

Thanks so much for all the info and help in getting this bike running, feels good to bring it back from the dead, haha. Anything in particular I should know about replacing the clutch? I'm going to try to get a complete clutch, since I'm not sure what is binding. I already pulled the clutch plates apart and sanded/cleaned/lubricated them to no avail. Wondering if I need to soak the new clutch in oil, or is it safe to put it in dry as shipped? I'd rather not disassemble a brand new clutch unless it's really necessary/recommended.

 

[my67xr]

Have you tried an adjustable wrench on the clutch arm to see if moving it more will disengage the clutch ?

Otherwise there is an adjuster under the round cover on the clutch cover.
You might be able to loosen the locking nut, and turn the stud in more to take up most of the play, then do up the nut again.
Make sure there is a little play there

 

[criggs]

That's the first thing I tried, since the clutch was very loose when I originally picked up the bike, anyways. I have that adjuster set so that it has just the slightest bit of play, and I have the lever adjusted so that it has a few mm's of play as well. Just to see if it did anything, I ran that adjuster as far in as it would go just for fun, and it made no difference. The part I have trouble with is what kind of play should it have? The plate that actually presses in on the clutch can move up and down as well as back and forth. How tight does that have to be?

 

[criggs]

So the Roketa is finally mobile. I ordered a new clutch last week that came in today. I spent the majority of the evening installing the new clutch. Got everything put back together and adjusted, and I still could not roll the bike in gear with the clutch pulled in. Needless to say I was a bit upset. So I decided to start the bike and get it warmed up. Once warm, I worked the clutch in and out for a bit, then gently attempted to shift to first. The bike immediately jumped forward, but kept moving and running as long as I kept the throttle on it. I took it up and down the street a few times, and after about 5 minutes I could sit at a stop with the clutch in, but the bike struggled to idle. So, I don't know if the clutch is just sticky or something because it is new or sat on a shelf for a while or whatever, or if maybe it needs to be adjusted more? I have it set So that there is just the smallest amount of play at the bottom adjuster, and there is a few mm of play at the lever. I'm thinking if the clutch isn't disengaging all the way I might have to adjust the bottom one in more, or should the clutch loosen up as it is ridden more? I'm leaning more towards the latter, but I didn't have enough time to ride it much tonight, so I guess we'll see this weekend.