EC300 - No top end power

[aardouzie]

I have a 2005 EC300 that runs fantastically at low rpm, huge torque, but falls on its face when "giving the the beans", so to speak. At full throttle, it almost feels like a rev-limiter that wont let it spin past 5000 (estimated) rpm.

So far, I've cleaned the carb jets (which I suspected was the obvious problem, but didn't seem to help). I've pulled the power valve cover and visually verified that the valve is opening with rpm, and also pulled the muffler and checked for blockage.

I was wondering if anyone has other ideas what might cause this, or what to check next.

One thing to note is that when this running condition first started happening, it was intermittent- like one minute it was pulling strong through the rev range and the next minute it felt choked up at open throttle.

Thanks!

[(F5)]

Its probably time to repack the muffler to keep you amused. While you are in there, check the perforated tube hasn't collapsed or broken.

New plug and plug cap for giggles.

Presumably it used to rev out ok in your ownership?

[SS109]

Originally Posted by (F5)

New plug and plug cap for giggles.

This!

Plus double check all your wire connections are clean and tight and especially so on all ground connections.

[Zman]

Pull off the power valve cover behind the exhaust pipe. Check to see if the weld broke on the actuator linkage pin. That was a semi common problem for that era bike.

[(F5)]

He said he'd done that. . . . Oh, and I I read properly I'd see he did muffler check. . .

[Gasser Nate]

Did you actually pull the muffler apart though? If it is the long two section muffler as F5 said the perforated core can break in the middle. My 04 did. Very similar intermittent problem.

[aardouzie]

Thanks for the suggestions. I've been out of town, so just now following up...

Yes, the bike ran/revved great until recently. The electrical items (plugs, wires, ground) I've not explored, and definitely a good idea.

I checked the power valve by pulling the cover and watching the arm move the lever while revving the engine, and also checked that manually moving the lever moved the valve while peering into the exhaust port. I suppose the timing of when the valve starts moving could be off somehow though.

When I inspected the muffler (FMF turbine-core), I pulled the end screws and pulled the packing wrapped center tube out of the aluminum shell. The center tube did not appear to be collapsed, and the turbine-like piece in the end cap looked ok from shining a flashlight through. Is it possible that the expansion chamber would get plugged?

The carb still seems suspicious to me, but not sure what else to do short of shooting carb cleaner through the jets again.

[gasgasman]

Check the fuel tank vent hose