I have a 2009 Wildfire 250cc Atv that is almost impossible to get it to start. I think there may be a starter problem or maybe a valve adjustment problem. When the atv is cold, the starter turns the engine fine without the choke on. The minute the choke is engaged, the starter will turn the engine over a couple of times and then will stop abruptly with a loud banging noise. I am not sure what choking the engine has to do with the starter stopping and making this noise unless it has something to do with the valve adjustments. It is like compression is building up in the engine when the choke is engaged. I have got it to start a few times by bumping the starter several times with the choke engaged until it starts. After the engine has warmed up, it starts easily without the choke. It has been like this since it was new. Does anyone have any suggestions. Wildfire Tecs sure don't. They said it wa the cdi which I tried and I knew that was a joke and then they said it may be the carb but I would have to remove it and send it to them. I have set the valves at .002 and .004 like they said to do but that didn't help. HELP PLEASE!!

 

This is a very weird problem, and I'm not sure I have any answers. But here are some thoughts and things to try:

Turn on a kill switch (so now you cannot have spark generated combustion). Crank the engine and fiddle with the choke. Do you ever experience the engine stall and loud banging? If it cranks fine without spark then perhaps spark is happening early and driving the piston backwards on the compression stroke.

Try using a timing light to check ignition timing. Many quads have an access plug over the flywheel that allows you to shine the timing strobe light down onto the flywheel. Mine does, but I don't know about your quad.

The timing trigger pulse that fires the CDI is a plus/minus pulse pair that happens in rapid succession once per engine revolution. On all the CDI's I've taken apart the plus pulse "arms" the CDI, and the negative pulse right behind it "fires" the CDI. If the CDI were to (mistakenly) fire when armed, the spark would occur about 18 degrees too soon. Based on your description, and my lmited knowledge of 250cc engine mechanics I would suspect the CDI - the same as the Wildfire Techs.

In any case it might be worth the effort to look at the ignition timing to see if it sometimes fires early when cranking.

Also, maybe the choke thing is pure coincidence. Jump the quad battery to your car or truck and try cranking. Does the quad still stall while cranking? Maybe your battery volatge is the thing that is stalling. I don't know what the banging thing would be though.

I may be way off base. Other ideas are welcome.

 

Welcome to the forum kmejr09!

Id try jumping from your car battery...(with the car engine off)

My other thought it the timing is off. sheared flywheel key maybe?

 

I have tried jumping the thing off with a car battery and all that does is heat up the wire going to the starter. I changed the battery out and went to a larger battery and even beefed up the wire going from the starter solenoid to the starter. The thing still stalls when the choke is engaged and the banging noise is still there also. I own a outdoor power equipment business and we sell the chinese quads, scooters, dirt bikes and go carts. We have worked on hundreds of these things and believe me we have had some stump us for awhile but noyhing like this one. I had this one sold and when it wouldn't start the first time on the initial service, I refused to sell it until we could get it repaired. That was right before Christmas of 2009 and it is still at my shop. I see it everyday sitting in the showroom and I refuse to give up. I am rreally starting to think that maybe the cam was installed a couple of teeth out of time or either the starter is weak. The starter wire gets very hot when trying to start the quad if I try and use the choke continuously to start. The only way I can get it to start is to pulse the starter with the choke on for a couple of seconds at a time till it starts. After it starts, I leave it choked for a couple of minutes until it warms up, release the choke and the thing runs and idles fine. That is what is so puzzling about the whole thing. If the timing was off, it should affect the running of the engine after initial warmup right? By the way, I tried a new CDI that Wildfire sent and that was no help either. Same problem. I am thinking of ordering a new starter and trying that and maybe checking the timing and valves again. I am baffled with this one. I am open to any suggestions. Thanks!

 

and...

This is interesting new information. Normally jumping (or changing) to a larger battery doesn't change anything in the way the quad operates (on a working quad). The small quad battery is supposed to be more than capable of powering the starter motor. And the fact that adding a larger capacity battery causes the battery cables to get hotter indicates:

1) That the small quad battery voltage is collapsing under the starter load (this is not right if the battery is charged and good). Do you have a meter? Can you verify this? Measure the DC volts from the starter input lug to the starter frame ground.

2) The hot starter cables with a bigger capacity battery indicates that when the battery voltage is forcefully held up to 12 volts while cranking the starter draws *way* too much current. This is not right either.

But let's make sure of one point: Does the starter cable(s) get equally hot along its entire length? Or does one section or point on the starter wiring path get hotter than other points or sections? Heat coming from one point indicates a bad connection. Heat distributed evenly along an entire wiring path indicates too much current.

If the problem is too much current then it must be a bad starter motor or the engine is too hard to turn. If it is a bad connection then focus on the hot spot.

I'm still curious as to whether the cranking symptoms (stalling and banging with choke) occur when cranking with the kill switch engaged (spark disabled).

I certainly agree with this.

If you don't get anywhere with the above tests I would change the starter also. You've already changed the CDI. Valve timing and adjustment aren't on my "most likely" list but it doesn't hurt to try.

 

Thanks Lynn,
To answer your question about the wire getting hot, it was geting hot along the entire length of the wire which indicates to me too much current draw on the wire itself. This was happening before I changed the battery or the cable. That makes me think that the starter motor is not strong enough to turn the engine. But, why does it only do that with the choke engaged? It will turn the motor fine unless you try and choke the engine to start it. I haven't tried to start the engine and choke it with the kill switch engaged but I will. What would that tell us if it doesn't stall the starter and make the loud banging noise. Unless that would tell us that the timimg is off and the engine is trying to fire when it shouldn't and causing back pressure in the engine that stalls the starter? I am thinking the banging noise is from the starter disengaging and trying to reengage. I may be wrong. What do you think?

 

The only reason that I can think of for the starter motor stalling with the choke on is that it makes the fuel mixture right on a cold engine, and it mixture ignites. That is why I'm wondering if disabling the spark will have any effect on this problem.

Many decades ago when I was a teenager I had a small go cart powered with a chain saw motor. It started with a pull rope. To start this engine I had to grit my teeth and pull hard with all the gusto I had. If I did, it would start right up and run great. But if I hesitated at all on the pulling part the pull rope would stop dead about half way out, rip the rope out of my hands, and I would swear my arm was broken. The memory of this is what makes me think pre-ignition is what is halting the engine. In the case of my go-cart the engine had been modified by the previous owner to advance the fixed magneto ignition timing to improve top end performance.

Your quad uses a one way 'sprag clutch' (google that for more info) to connect the starter to the engine. As long as the starter is trying to spin faster than the engine, the clutch seizes and connects the starter to the engine. If the engine starts it runs faster than the starter and disconnects. But think about this for a moment. If the engine tries to fire too early on the compression stroke it tries to force the piston back down going backwards. This locks up the starter clutch and tries to spin up the starter motor backwards- which it can't do becaue the starter motor is geared way up when driven backwards from the engine. Everything grinds to a sudden halt. (Or in the case of my go cart, this is where I hold my arm and yell expletives).

Can you use a engine stethescope (or even a short piece of hose held to your ear) to find out where that "bang" is coming from?

My title says I'm an "electrical expert". I specifically asked for that title rather than just "expert". I'm hoping that this distinction conveys the fact that I'm not the best around when it comes to engine mechanics. Anyone is welcome to challenge my ideas. I won't take offense, and hope to learn from any new ideas.

 

I will try the kill switch theory on Tuesday since we are closed on Monday. I will post the results Tuesday night. I will also try to find out where the banging noise is coming from.

 

OK... Tried starting the quad today with the kill switch activated ( no spark ). Got the same results whether it was activated or not. But something different today from previoud times. The starter didn't stall as it did previously. There is a slapping/banging continuously as I was trying to start the engine. It sounds like the noise is happening on every revolution of the engine and the noise is coming from the starter mechanism in the engine and not the starter itself. I removed the 3 screws in the side cover and removed the cover. There is a large gear that engages the starter motor to the engine. All of the teeth on both gears looked fine to me. Now I am lost. I have never torn into one of these and was hoping that someone could have some idea of what is cauing this noise. The quad did start once and there was no usual noise while it was running. It stalled and by then the battery was about drained and I had to put it on charge. Any ideas?