ec 300 sudden power loss, wont rev

[wrench]

I'm sorry that you are stuck with a new ECU but we did try to get you to check the things that were free and cheap first.

You will most likely need to fashion up a couple of jumper leads to use the KX coil, by remember you're just trying to figure out what's wrong before spending money.

You said that it goes flat on the top of the rev range in each gear causing you to short shift, correct? This is what is leading me to the coil. You said that you were in a rocky section and hauling the mail before the problem started. Again, this leads me to the coil (or other electrical part) because of the high demand that you were placing on the system.

As cylinder temp and pressure rises, the demand on the ignition system also increases or there will not be any spark to ignite at the plug. When a tired coil gets hot it cannot meet this demand and the spark gets weak resulting in a loss of power.
It could be a corroded connection in the plug cap, a small crack or burn spot on the plug wire (HT lead) or a crack in the plug insulator (porcelain).

Now to throw another thought into the mix. Someone else mentioned stopped up vent hose on the carb. What about the air bleeds in the intake throat of the carb. Have you made sure that they were not full of oil from an over oiled filter? That gets overlooked a lot.

[Fastboysparky]

Just tried 2 simple things. Changed the fuel, just in case it got double oiled by mistake and also ran it with a known good plug. No difference. Going to try coil now.


Sent from my i phone whilst doing a tail whip.

[Fastboysparky]

I just fitted the coil off an old contact 250 I have in bits and guess what!! No difference. I was getting to the point of stripping the engine when I thought I'd take a closer look at the pv. I removed the exhaust and pv cover and moved it manually whilst looking up exhaust port with a torch. It seemed ok. I decided to see if I could remove it and clean it. As I removed the centre bolt that holds the actuator to the spindle, I noticed that it had not been located in the notch and was just tightened onto the spindle. I located the actuator correctly and fastened everything back together. Just took the bike for a ride and it took off like the wind, wheel came up in fourth. It's never been like that since I bought it. The guy who had it before me must have assembled the pv incorrectly and it must have slowly slipped around the spindle. Thanks to everyone for their help and support and if anyone needs a brand new ECU for 2005 inwards with dual map then I will sell it for 90 pounds plus post.


Sent from my i phone whilst doing a tail whip.

[barossi73]

awesome!glad you got a result finally,and what you found is bound to help another person from ripping out their hair!bet your pleased you didn't flick that match in the tank now!

[wrench]

Originally Posted by Fastboysparky

I just fitted the coil off an old contact 250 I have in bits and guess what!! No difference. I was getting to the point of stripping the engine when I thought I'd take a closer look at the pv. I removed the exhaust and pv cover and moved it manually whilst looking up exhaust port with a torch. It seemed ok. I decided to see if I could remove it and clean it. As I removed the centre bolt that holds the actuator to the spindle, I noticed that it had not been located in the notch and was just tightened onto the spindle. I located the actuator correctly and fastened everything back together. Just took the bike for a ride and it took off like the wind, wheel came up in fourth. It's never been like that since I bought it. The guy who had it before me must have assembled the pv incorrectly and it must have slowly slipped around the spindle. Thanks to everyone for their help and support and if anyone needs a brand new ECU for 2005 inwards with dual map then I will sell it for 90 pounds plus post.

Sent from my i phone whilst doing a tail whip.

Great result, good on you for going back and double checking!