cr125 -2006 loosing spark...

[morgangdfp]

Hey,

I've got a Honda CR 125 -2006 with a weird problem... I start the engine up and it runs for a few minutes but then dies suddenly and I can not start it again.

I take the plug out and test it but I can not get a spark from it.

And here is the weird thing: I try the same plug on another CR 125 and can not get a spark from it there either..

The spark plug starts to give off sparks again if I let it rest for a few days.

I have two theories:

1. There is something wrong with either the coil or the CDI box that somehow destroys spark plugs.
2. There is something wrong with the fuel/air mixture that makes the spark plug seize to work for a while.

I'm leaning towards alternative no. 2 but would like to know if this is something that has happened to someone else or if anyone has any other theories regarding this.

It might be worth mentioning that this has started to happen about the same time as winter arrived here and I have not adjusted my carburator at all. Should I buy a bigger main jet and see if that solves the problem?

Thanks and a happy new year!!

 

[sharky243]

Try a new spark plug. Make sure the fuel is fresh and mixed properly. Avoid trying to rev the engine with the choke out. Don't leave the choke out longer than it needs. Check the strength of the spark by holding the new plug about 1\2 an inch away from the cylinder head and kicking the engine over. You may want to get someone to assist you with kicking the bike while you watch for good spark. If the spark is weak (won't jump the gap consistantly), check the generator coils for proper resistance. If they are good, check the main ignition coil for proper resistances. Is there gas constantly leaking from the overflow tube on the carb. ? Maybe it's flooding itself out.

 

[2strokerfun]

Sounds like your plug is fouling. Does it look black or wet when you first pull it out after it stops running?

 

[addie]

Do you oil your air filter when cleaning it?
I recently had the same problem - a mx mechanic told me contrary to belief, not to use oil at all as it constantly kills the plug. Since taking his advice I havent had the problem since but it might be worth making sure the filter hasnt been oiled too much.

 

[morgangdfp]

Thanks for all the help!!

I 've tried doing as sharky243 suggested:
I took a new spark plug, filled the tank with fresh petrol premixed with high quality two stroke engine oil (ratio 50:1).

(I did have a low quality mineral 2 stroke oil in before and it was a higher ratio as well...)

I also took the carburator apart and cleaned it properly.

While I was at it I lowered the jet needle one step to get the engine to run leaner.

After I had put it all back together again I started the engine up (with the choke pulled out) I let it run on idle for a few minutes until I could push the choke in. I then did a few laps around the house and she seems to go fine now.

I need to test it out properly on the course this week, but it might have been that I had too much oil in the fuel in combination with not revving the engine high enough..

I'm a beginner so I don't let the engine run on as high rpm as it should.

Sounds like your plug is fouling. Does it look black or wet when you first pull it out after it stops running?

Yes it does look black and wet. I will look at it after a few laps the next time I go out on the course and see if it did help.

Actually I should really buy a couple of main jets and do a proper tuning of my carburetor since I have never done it and I bought the bike in the summer (we get about 20 degrees C in the summer and -10 degrees C in the winter...)
Anyone know a good set of steps for tuning in the carb on a mx bike?

Do you oil your air filter when cleaning it?
I recently had the same problem - a mx mechanic told me contrary to belief, not to use oil at all as it constantly kills the plug. Since taking his advice I havent had the problem since but it might be worth making sure the filter hasnt been oiled too much.

Yes I oil the filter... Everyone I know oils their filters.. Are you sure about that? sounds strange.. What about sand and dirt coming into the carburator?

Thanks for all the help!!

 

[Rich Rohrich]

- a mx mechanic told me contrary to belief, not to use oil at all as it constantly kills the plug.

That might be the dumbest thing I've ever read out here.

If that's any indication of his skill as a mechanic, you would do well to look elsewhere for advice in the future. ;)

 

[Red Pinger]

Check the strength of the spark by holding the new plug about 1\2 an inch away from the cylinder head and kicking the engine over.
That may be the second dumbest thing I have heard in a while.

 

[sharky243]

It may sound dumb to you, but thats how you check the strength of the spark, if you don't have a proper spark tester. If you look at a proper spark testing tool, note the gap bettween the 2 points. That is where i'm getting the 1\2 inch from.

 

[Red Pinger]

Without getting into spark plug physics, the spark you see is current jumping from the center electrode to the tang, which is GROUND. The tang of a spark plug is the same as the threads of the plug so when you screw it into the metal of the engine you give it a ground to jump to. Without it screwed into the head or at least touching some metal part of the engine no spark plug is going to spark. Especially one a half inch away from the engine.

 

[sharky243]

Pinger, I've been working on bikes for over 15 years. If you want to test the strength of an ignition system, you have to put it under a load. Again I say look at a proper spark testing tool. The gap between the 2 points in the tester, is far greater then a normal plug gap. A weak ignition system will fire a plug when grounded to the head, but it will have trouble firing the plug under compression. This can lead to hard starting, poor performance, and wet fouling of the spark plug. An ignition system that is making a good strong spark WILL jump a large gap. Go ahead and try it, you'll be suprised.