250sx Weak Spark-----Help.....

[ewalker302]

Ok I just finished getting my sx ready for summer.
I had to heli-coil the drain plug. Put on a new seat cover, new fork seals.
Thouroughly cleaned the carb, and the starter brushes.
I replaced lots of bearings--rear axle, front wheel, steering stem.
New spark plug.

I took it out yesterday for its first test run, and it ran beautifully.

Today, I was just driving it around a little to mix up the rear end oil so I could change it, and it just quit on me. I was just thinking it was feeling weak, when it died.

Now I am getting a very weak spark.

Where is the first place I should look?? Since I am still getting a weak spark, I am hoping it is just a loose or corroded connection somewhere.

I have already cleaned the 2 connnections going into the coil. I know the ground on the engine by the starter is good, and the ground at the top left rear of the bike is good.

Is there another ground somewhere for the coil??

Or other connections I should check before testing the coil, CDI----etc???


Thanks

[Dirtcrasher]

Weak spark, why do you say that?? Many times when a motor runs crappy I have blamed the spark. Lots of times I did this outside in the light and thought it was definately the spark but I just couldn't see it all that well and the sun made it "appear" weak. I find the carburetor to usually be the culprit. There is a pulse generator in the left side cover, not sure if the gap is adjustable but there could be a problem in there or check the coil for OHMS and as you mentioned - all the connections and grounds etc are a good place to start. Just don't condemn the electrical stuff just yet but you can check it all out with a multi meter.

[MTS]

uhhh first of all try a new spark plug

[ewalker302]

Ok, I'm taking out the spark plug and grounding it on the jug in a dark shop, I can barely see the spark bridging the gap---it is very weak....I know what it's supposed to look like. I checked it when I was redoing everything else, and it had a nice fat spark.

I'm 100% sure it's not the carb, I just put it back on after completley tearing it down, soaking, cleaning. The plug was damp after I tried to start it when it quit on me, its getting gas, just very little spark.

It was running fine then quit, after that, I checked it and, almost no spark.


My trike sucks---Please read the fifth line of my initial post, -----New spark plug.

[Dirtcrasher]

Then all you can do is check all the electrical components and grounds. Make sure the lead back to the coil itself is in good shape especially where it snaps onto the plug. Let us know what you find.

[MTS]

My trike sucks---Please read the fifth line of my initial post, -----New spark plug.
sorry, i thought you ment you just put a new spark plug in before going to ride it, not after it had died. :beer

[ewalker302]

Ok, I found the problem.

After cleaning every electrical connection on the bike (I even took off the left case cover to check the stator connections), I started testing all the components according to the chiltons manual.

The coil checked out, as did the regulator, so I figured the only other thing it could possibly be was the cdi unit, I had already looked at the connections on it (the cdi) and they were very clean.

Luckily I have an 86 trx250 sitting in the shed waiting to be revived, and the cdi's were identical. I swapped them, and she fired up on the first hit.

I guess the orig cdi just crapped out while I was riding.


Anyways---I got the SX new in November of 85', but its been sitting up since I got a 400ex about 3 years ago, so maybe she was just getting back at me for neglecting her.

Here's a pic
http://www.imagestation.com/picture/sraid165/pde0a382276fe90c4509d4d1f27f02525/f4717c01.jpg