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EX500 Looses power then stalls...

2350 Views 3 Replies 2 Participants Last post by  magnum_5150
My EX500 is doing something strange. I'll get up to about 50 mph or so and start to feel the bike loose power (FYI- this always happens at the beginnig of my ride, before the engine is totally warmed up, say 3-5 minutes after being started). Twisting the throttle has no effect and the bike starts to slow down and the engine comes to stop as it stalls. After a few attempts to restart, it finally starts up, sluggish then clears its self up and seems fine for the rest of the ride. I have replaced the fuel filter, plugs, air and oil filters recently, I have also removed the emmisions control system (its a CA bike). This problem doesn't happen everytime I ride, but often enough to worry me. I've checked all the fuel lines and they are fine, infact I replaced them recently too. I have no idea what could be causing this and I'm too poor to take in to the shop. Besides, it does'nt do it enough and I'm afraid the problem won't repeat it's self if I take it in.

Any thoughts?
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First go with fresh 91+octane, change back to another set of plugs (seriously). From there I would see if you could do a compression test, a leakdown test.. also how is your battery? Batteries can cause wierd problems when they start to go...After checking your ground points to make sure that they are clean, and doing the plugs, I'd eplace the next cheapest part, the battery...also befor you try any of this make sure that your tank is full and instead of running on your "ON" position turn your petcock to "RES". there is a screen in your tank that may have some gunk or corosion built up on it inside...

Just wondering if you figured it out...YOu could also turn off the petcock remove the gas line an dthen blow with some light pressure into the gas line as you turn the petcock on...this might remove any crud that would be lodged in the microscreen in the bottom of your tank...let me know...I'm still curious...
I think I've got it figured out! I was discussing this problem with a friend who I respect as having a better understanding of engines than I do, and I think he nailed the problem.

It's flooding. Which makes sense. The problem only happens when I really lay on the throttle. If I cruise it and keep the revs down this problem does'nt happen. I can get it to repeat when ever I twist the trottle. This problem coinsides with the removal of the fuel evaportation system and replacement of the fuel and vacume lines.

Here are some more details on the symptoms for anyone who cares. After one of these stalling episodes, I can smell a different sort of smell from the engine, not oil, not rubber, not exactly like exhaust but similar to burning fuel (this is what keyed my friend in). The excess fuel in the engine is burning off which can be smelled at a stop light or when I finish my ride.

So here is where I need some help from some experienced EX500 owners. How do I correct this problem without reinstalling the fuel evaporation system. Does anyone have a diagram of the petcock or know why at higher reves too much fuel is getting into the engine? It is being sucked back down the vacume tube in to the engine? Is there a small check valve I can add or some sort of vacume control valve?

Any advice is welcomed.


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