650sx no spark

[tweeka13]

Hello;
I'm new to this board but i need some help.
I had the motor rebuilt on my 88 650sx, ran ok before the rebuild. After i installed the motor and double checked all the connections. the rear plug has spark (kinda weak) the front has no spark. I cut a 1/4 inch off both leads but didnt help. Not sure what to check next. I have a parts boat that i can swap parts from.

list of mods
westcoast head 170 lbs
westcoast pipe
44mm carb

Thanx in advance

[Dan DePardo]

Hi;
It sounds like you either have a bad set of wires or the secondary coil is winding is fried. Remove the OEM resistor plug boots from the wires, connect an ohmmeter across the two plug wires and you should measure around 3K (3000) Ohms of resistance through the coil winding.

If you read a very high resistance or an "open" you have one of more breaks in the wires or winding. Use a sharp meter probe to poke through the wire insulation along each wire to narrow down where the wires are broken.

If you find that the coil is good, but your wires are broken at a point that won't allow trimming to remove the damage, I recommend either replacing the coil assembly or using "solid core" (multistranded copper) Moroso motorcycle wire kits to replace the OEM wires on the coil.

The OEM wires are "potted" or epoxied to the coil, but you can carefully remove the epoxy, replace the wires (the coil winding terminates in two large "spikes" which the wires push onto) and then use a good quality epoxy to reseal the wires to the coil.

Dan

[tweeka13]

Okay i checked the coil and got a reading of 2.5k.
I also checked a spare coil and got the same reading 2.5k. Checked for spark agian had no spark at either plug !!!!!

[Dan DePardo]

Hi;
If the engine cranks over at a suitable RPM, your erratic ignition could be a problem with either your wiring harness, or the ignition trigger coil behind the flywheel.

Open your electrical box and unplug the black wire with a red stripe from the CDI module. You should be able to measure from around 250 to 400 Ohms of resistance between the engine harness side of the black / red wire connection and ground.

You should measure close to the same resistance measuring the engine harness side of the black / red and black / yellow connections (the two wires should lead to the trigger coil).

If you read a very high resistance, you'll need to open the flywheel cover and inspect the trigger coil. It's not unusual to find heavy corrosion if water has made it's way into the flywheel cavity.

It's also possible that your CDI (Capacitive Discharge Ignition) is on it's way out.

If the engine cranks strongly, chances are your primary DC system is in decent shape, but if the engine appears to be cranking slowly, you should take a hard look at your battery and other connections.

Dan

[ April 28, 2002, 12:42 PM: Message edited by: Dan DePardo ]

[tweeka13]

Hey Dan;
Thanx for the help so far this board has a lot of good info and help. I dont know what i did but i have a strong spark now. But it still will not start??? The engine is new, it has good comp. ,spark, and their is fuel on the plugs so it has fuel. It should fire but it dont him????????? Is their anything i can test to see whats up i have a manual but the trouble shooting isn't much help. The shops around here dont want to work on a ski that old, all they want to do is sell you a new one. [img]graemlins/spit.gif[/img]

[Dan DePardo]

Hi;
Did you set the ignition timing correctly?
The mark or notch on the stator should be lined up with the mark on the top case half.

Did you install the crank key when you bolted on the flywheel?

Dan

[tweeka13]

Dan;
The engine was rebuilt by "playtime powersports" i sent the flywheel still on the engine and they set the timing. the reason the motor blew was the woodruff key had worn. the engine has a new crank and pistons etc. is thier any way i can check if it's timed correctly. i dont have a flywheel puller.

Thanx dean

[Dan DePardo]

Hi Dean;
Well, you can use an automotive timing light to check your ignition timing through the front cover inspection plug hole, but if there are no visable timing marks on your flywheel, you'll need to "degree" it in order to get a reasonably accurate measurement. There is a reference timing mark cast into the inspection plug hole on most 650 front covers. To degree your flywheel, you'll need a dial micrometer and a degree wheel to find TDC. Use white paint to mark the flywheel in one degree increments from 15-20 degrees BTDC. The OEM timing spec is 17 degrees BTDC at 6000 RPM.

You might find it easier to pull the flywheel and visually check that the crank woodruff key is in place, and the that stator is properly aligned with the timing mark on the top case casting.

The 650 flywheel can be pulled using a flange type gear puller that you can find at most automotive parts stores for around $30.

Dan

[DatOldGuy]

Did ya get it running yet? I had a similar problem, went through tons of grief, parts and money, and found out in the bitter end that I had a weak starter. The new rebuild upped the compression a bit and made it just a little bit harder for the engine to spin fast enough to give a good hot spark. The plugs would spark out of the engine weakly, but not under compression. I hooked a Sears Die-Hard auto battery to the starter to see if it wanted a taste of amperage. It fired up right now! Sounds radical, but desparate times sometime require desparate measures. Don't know what Bryan would think of this technique? [img]graemlins/uts.gif[/img]

[kidscost]

I may be out of my league as I am a yamaha man. but I just bought a 750 ss xi and it was running great. and then not at all I had great spark at the plugs and gas in the carbs. believe it or not I replaced the plugs and it cranked on the first spin. simple but can be a pain you said you had spark but no start? try some plugs cheap and can't hurt

[tweeka13]

I'ts still not running i checked the timing and it was okay. i tried new plugs, hooked it up to a batt. charger and tried to start it that way it spun fast but still wont start. i'm gonna pull my hair out soon!!! know one around here (Boston MA) wants to touch a 88 650sx.