Honda NX250 Ignition Problems

[alphacheese]

I'm having trouble keeping my Honda 1989 NX250 running. Some days it will start just fine and run all day with no problems. Other days it will never crank or stall while I'm riding.

Here's what happens when it wont crank:

• Starter motor is good and turns over
• Sometimes it will fire and rev when I crank with throttle open and choked but immediately dies
• Sometimes will backfire (yes a real backfire through the air intake) sometimes "backfire" (impropper fuel burn) through exhaust pipe

Here's what I've done and know:

Battery is new and charged

• The fuel is fresh, clean, and has a new inline filter to carb
• Carb has been completley broken down and cleaned, all jets are unclogged, all o-rings are good, accelerator diaphragm is good, throttle needle is not damaged, float is good no leaks
• Spark plug is new and has been tested, gives nice blue spark
• There are no leaks from the air cleaner to the carb (new air filter) and there is good air flow

I originally thought it was a fuel problem - carb bowels were empty. One day when I turned fuel on it started pouring through the overflow. I took apart the carb and cleaned out small patch of goo that I think was causing the float needle to stick (both open and closed). After that it never overflowed. I cleaned the carb spotless even though there it was already very clean. I thought the problem was the carb because some days the bike runs just fine and other days it will never crank. When it is running sometimes it will die when I'm riding at speed (throttle open 3/4), I've noticed mostly when I'm going uphill. I'll pull off the road and it will turn over a few times than crank, other times it won't start unless I let it sit for a few minutes sometimes it take hours. As I said, I can't find any fault in the fuel delivery, no blockages or clogs (that I can find in fuel line, tank, or carb). I was wondering if it's a valve clearance problem, but it runs perfectly half the time. It never overheats after 30 mins of riding and there is not ratteling sound or rough running. I'm kind of lost from this point forward as to what to try and what to test next. Any thoughts or suggestions

[Johnj]

The only thing I can think of is fuel tank venting.

[alphacheese]

The only thing I can think of is fuel tank venting.

Breather tube is clear. I've even tried it with the tank lid completely off just to be certain.

[pchast]

If its so unpredictable its more likely electrical, A bad switch or short to ground somewhere.... ?

[HYPERR]

Here's what happens when it wont crank:
Starter motor is good and turns over

Not sure I quite understand this....

If the starter motor is good, how can it not be cranking?

The starter motor's job is to cranks the engine until the engine ignites and starts up.

[alphacheese]

Here's what happens when it wont crank:
Starter motor is good and turns over

Not sure I quite understand this....

If the starter motor is good, how can it not be cranking?

The starter motor's job is to cranks the engine until the engine ignites and starts up.

I guess that's just my misinterpretation of the terms. I always took "turn over" as the starter motor turning and "cranking" as firing up. So what I mean is that it will turn over, crank, what-have-you, but will never fire up. Some times a get a few sputters of ignition but it won't start.

[alphacheese]

Ok! Here's an update. I got it started today and here's what I have to add: My spark plugs aren't fouled but they are sooty. After attempting to start the bike and couldn't I took out the spark plug and it was wet. I cleaned it off put it back in and still couldn't get it started. I took it out again and the chamber dry out, cleaned the plug and put it back in and vaaaaarooooom!

So I think my mixture is too rich? It has a new/clean air filter and there is good air flow. My floats aren't leaking but I don't have the tool to measure that they are at the correct level. I've read that if my float lets too much fuel into the carb this can result in too rich mixture? The float valve and needle are good. It seals well and is clean. So if my bowels have too much fuel in them could this be my problem?

[Murdoog]

hi
I've got a problema similer in my nx250
sometimes it never start. The starter engine always roll but the engine no
I see very times that I have no spark in the plug wen this happens, but like you say, sometimes it works very well..
Right now, i can make it start any way, and i think that the problem is on the cdi.
All my measures are similar the manual service - the alternator, the pick up and ignition plug, but i can't test the cdi.
Other think and is one that i can't understand is if the regulater can have anything doing about it.. that i think it do not.

If you have any sugest, thanks a lot

[BRUMBEAR]

that sounds like a coil to me?

[Murdoog]

I am sory... i wanted to say that I have measured the ignition coil and i said write ignition plug, but i mean that that the ignition coil have the rigth measures in the primary and in the secundary.
sory and thanks