CDI help needed... Please

ahdunno

ahdunno

New Member
EDIT:
If someone could look at my second post and check my readings I would be grateful.
Thanks

Right from the initial install, I've had what seemed to be a weak spark. I could turn the wheel with the plug laying on the head and would get spark but it appeared weak.
Recently, the motor has been hard starting. I thought the clutch may have been slipping so I replaced the pads, which didn't help.

The motor does start, but now with the plug laying on the head and turning the rear wheel, there is no spark.

Doing further diagnosis, I disconnected my kill switch, which in turn lead to re-soldering of the leads between the mag and CDI. I also removed the mag and cleaned/sanded the contact points of the mag and the engine casing where the screws are inserted as well as the terminal on the black wire. I also removed the white wire. All of this has had no effect on the poor starting.

I started to believe the CDI is the issue and was searching for multimeter readings so I could check it, which leads to my question.

In this post (http://motorbicycling.com/showthread.php?t=35058) fishyfish777 was getting a reading on his old cdi of 2.4k. The new one was in the 6.8k range which was confirmed good in the thread.

Mine is reading 2.4k, however, that is with the CDI and mag wires still connected. Do I have to unsolder the wires to take this reading or is the 2.4k accurate as is?

Thanks in advance for any help.
 
Last edited:
Thanks for the response Legwon.

OK, tested cdi with just black wire disconnected and then blue wire as well. All readings were the same 2.4k. I then tested the mag and it reads 305 ohms no matter which way I have the leads. As I understand, one way is supposed to tread infinite. Is this correct? Now it seems both have bad readings.
Can anyone confirm this?
Thanks again

Further test of cdi
I read in another thread:
Black to + Blue to - should read 130-150k
I have to set meter to 2000k to get any reading and then it starts at 1900 then continually counts down.

Plug Boot to+ Blue to- should read 135-155k
I get no reading on any range.
 
Last edited:
You're gonna get impedance thru the plug wire by itself. For an accurate reading of the coil you're gonna need to remove the plug wire and test the coil again. Good luck with that, as a lot of them come glued in from the factory.

Have you considered replacing the plug wire? The stock ones from China are junk, notorious for going bad. I replaced mine with one I "recycled" from my last tune up I did on my Chevy, I used an Accel wire (cut short of course), had to srtip off 1/2 an inch of insulation to get it to fit into the coil, but I also used shrink wrap to seal it and make it water resistant. A lot of folks here on these forums have used auto plug wires with success. Just don't use a resistor plug with an automotive wire, car wires are RFI shielded (Radio Frequency Interference) and coupled with a resistor plug, there may not be enough voltage from our HT ignitions to overcome the impedance of both.
 
I got replacement mag and cdi. Before they arrived, I had better results starting it with a fresh plug. I have replaced the stock wire.
It started better with the replacement parts, but after a few mile ride tonite, it was hard starting again.
I'm starting to suspect the cheap 2 stroke mix I'm using. It was the econo brand from O'Reily's. Really thick and dark looking compared to Penzoil or Advanced Auto's econo stuff.
I run 32:1 and I'm probably on the 5th or 6th gallon using this oil. It may have lead to fouled plugs.
 
I looked at the thread,. I have disconnected my kill switch and my tests are in proper ranges with the exception of the cdi. I was getting 2.4k on my original one whichis close to normal that I've read until I saw the thread I posted that showed a 6.4k reading of one member which was verified by another. My new cdi reads at 6.4k.
I had also seen plug color charts on the forum. I was running aBH5S and it was a nice light brown color. No dark build up like a fouled plug would have. Maybe it was damaged in some way, I'm not sure. I went to a 6 but still had weak spark. Then I threw in the kit plug that had a smaller hex size that made it easier to loosen.(I would have to loosen it to lower the compression just to get it started.) All the plugs had a nice color to them, just weak spark. It does run rich though. Even at the meanest setting I had low end sputter which is worse now since I reinstalled a second head gasket, again to lessen the compression for easier starting. I need a smaller jet but have been putting out off thinking I would try a speed carb, then I put that on the back burner thinking of upgrading to a scooter.
So, yeah, better oil is a good call.
 
Last edited:
How do you start your engine? Are you pedalling fast before you pop the clutch? Leaning back over the rear tire for traction?
I've never seen a ht that had THAT much compression...
Looking at the spark is not a good way to diagnose a problem.
Generally, if it sparks at all, it will run (if other conditions are met (air&fuel))
 
I'm pedalling fast and traction isn't an issue. I'm 300+... lol. It's starting good now with the replacement parts. Plus I installed new clutch pads when this all started.

I need to check my air filter. I needed a new petcock and before I got the new one, the carb flooded a couple of times. It was pretty major, to the point that I had to pull the plug and pedal with the clutch engaged to clear the fuel mix from the cylinder just to start it. It was around then that the hard starting ensued, I thought mix may have drained into the crankcase and contaminated the clutch plates and pads. That's why I installed the new pads. I broke a couple of then trying to remove them for cleaning.

I also need to solder my wires up. They're just wire nutted right now. I've been holding off on that to make sure it was starting OK. When I do the soldering I want to reconnect my kill switch too.

All that and better oil and I should be good to go.
 
Last edited:
You have a carb float problem, that's why its hard to start when its hot. You either need to adjust the float so the needle closes earlier or you have debris keeping it from closing. You should never have to remove the plug to blow out fuel, fuel on top of the piston can cause damage to the engine under compression if it's enough to lock up the rear tire.
 
Thanks for the tip Greg. I haven't checked the float adjustment in quite some time and the bike has fallen a few times as well as being dumped pretty hard when I hit a curb one night. That spill left me banged up and immobile for over a week.
I just attributed the flooding to not being able to shut off the fuel flow because it only happened intermittently and only when the bike was left sitting over night. Plus it hasn't occurred since the installation of the new petcock. Still worth looking into, especially now that you've mentioned it. I won't have peace of mind until I do.

Sometimes you put things off or let them go because you're thinking upgrades. I was indecisive on whether to buy a $7 jet or just getting an NT speed carb for $17. That coupled with a recent forced pay cut has lead to postponing a few things when it comes to expenditures.

Besides the carb, I've been wanting to upgrade to some 10x thick tubes and I've been thinking of those 12 gauge wheels over on the rat rod forum ( because of my weight, I could use some heavy duty wheels.).

When I start factoring the costs of all that I become hesitant, thinking that those funds could be used towards a purchase of a scooter, which is what I ultimately want anyways. I love my motor bike but I need more dependability for everyday use ad well as the lighting (brakes, turn signals,etc.) that a scooter would have.
 
Last edited:
Well, Greg's call was right, the float was off and letting too much fuel into the bowl. Set it at Norm's recommended 21mm and now we'll see how it goes. Seemed to start OK after stopping once it was heated up. Feels like it runs smoother at 1/8 to 1/4 throttle too. It was sputtering in that range before.

Thanks again Greg.

Edit: I read somewhere that the measurement from the gasket surface to the bottom of the float is supposed to be 21mm with no gasket in place while measuring. I thought it was in Norman's carb thread but I searched and couldn't find it. It's here somewhere for anyone who wants to know what it should be.
 
Last edited:
You must log in or register to reply here.
Back
Top