Need to Mellow WOT Power at high revs

[stay_upright]

All,

I would like to mellow the power at WOT and high revs on my '05 EC300 - is it best to lean or richen the main jet?

 

[poelinca]

If you lean the mixture you risk damaging the piston and cylinder. On the other hand, if you richen it you might foul the spark plug more often.

If you want to mellow the WOT power, then i'd suggest pre-loading the spring on the power valve governor slightly. There are washers you can buy for this (i think they are 0.4mm thick).

 

[Zman]

You can richen the bike one size in the main jet and or try a different needle.

You can retard the ignition timing but that will make a difference across the rpm range.

You can go to the 2k3 ignition or add a fly wheel weight.

You can install the dual map ignition and run it on rain mode.

You can add the reed cage spacer. There are two sizes and they make a big difference in slowing the response of power delivery.

You can reduce compression by adding more base gaskets.

You can start the triple cheeseburger and milkshake diet.

 

[(F5)]

D
Doesn't the 05 have the rain setting option on the cdi but you need to add the switch? Do a search.

 

[Davehuge]

No, definitely don't try to soften the power by making the fuel/air mixture bad....as mentioned previously a lean mixture could damage your engine.

Best way is to alter the way the power valve opens...

Closed power valve = Lower Exhaust Port = Increased bottom end/lower RPM power = Reduced high RPM power.

 

[Jakobi]

I'll nibble..

Use your right hand..

...or perhaps a throttle stop?

I'm sorry, I just don't see how you can have too much power at WOT and upper rpms. That is exactly where you should be making peak power.. If it's too much gear it taller and/or use less throttle.

 

[Zman]

I'll nibble..

If it's too much gear it taller and/or use less throttle.

Good answer

 

[rvktm]

some how had a 300 reed valve and spacer on my 05 250 from new ,fitted one of a 98 as the 300 valve did not fit without the spacer made a big difference maybe the way to go iv still got the 300 setup

 

[stay_upright]

D
Doesn't the 05 have the rain setting option on the cdi but you need to add the switch? Do a search.

Yes I have the switch - need to remount on the radiator hose as I keep knocking it when riding and inspect the wiring as it's a bit mangled -

 

[stay_upright]

I'll nibble..

Use your right hand..

...or perhaps a throttle stop?

I'm sorry, I just don't see how you can have too much power at WOT and upper rpms. That is exactly where you should be making peak power.. If it's too much gear it taller and/or use less throttle.

It would be fine if I were racing for shorter times but its coming out of corners revving up I need nearly all the power I'm getting I'll be WOT and as the revs build to 3/4-max (at a guess) there's a hit and the acceleration makes it difficult to hang on when you've been racing for 2 hours already also makes precise throttle control difficult i.e. I need would WOT but then as it takes off and I'm hanging on trying to stay forward I need to precisely take 1/8 throttle off? Very difficult I end up staying WOT and hanging on but would be nicer to tame the top end a bit. (but only at higher rpm's ideally)

 

[stay_upright]

No, definitely don't try to soften the power by making the fuel/air mixture bad....as mentioned previously a lean mixture could damage your engine.

Best way is to alter the way the power valve opens...

Closed power valve = Lower Exhaust Port = Increased bottom end/lower RPM power = Reduced high RPM power.

But at WOT and 3/4-max rpm I assume the power valve will be fully open and will have been fully open for quite a long time? (does any-one know rpm's the port opens as std?)

 

[Zman]

What pipe and silencer are you running?

 

[Davehuge]

The power valve (or exhaust valve) opens up proportionally with the engine's RPM.

I haven't seen the mechanism properly but seen photos of it. I'm pretty sure you'll be able to add some washers or spacers to limit the travel of the mechanism, thus preventing the exhaust valve opening fully and in turn softening the power at higher RPM.

You could also experiment with disconnecting the linkage and locking the exhaust valve in it's closed position. In effect this lowers the exhaust port giving more power at lower RPM and less at higher RPM.

These are a bit expensive, but might be exactly what you're looking for...

http://www.enduropuro.it/shop/en/gasgas-racing-parts/1055-adjustable-powervalve-cover.html

Good luck, Dave.

 

[Brian]

That scenario sounds like it could be solved with some clutch.
Other than that you got lots of suggestions, seems like you will need to do a bunch of experimentation to find the right trade off.

 

[Jakobi]

That scenario sounds like it could be solved with some clutch.
Other than that you got lots of suggestions, seems like you will need to do a bunch of experimentation to find the right trade off.

Few variables. I know on the 250 (which has more pronounced surge as it comes onto song in the mid to upper rpm) that I tend to clutch it onto the pipe all the time. I couple it up with a quick pull throttle cam which means it takes very little effort for me to have poor 'throttle control', and very easy to twist it wide open. The clutch is where the control comes from and it modulates how much power gets to the ground.

Again, you face issues with clutch control as fatigue builds throughout the duration of a race, but imo that becomes more to do with conditioning (and gassing our from poor technique/line selection) than with the engine and setup itself.

Last couple hours I've been riding with my stock expansion chamber kinked at the header, coupled with a nice big dint on the backside where it's been pushed into the frame. It's definitely moved the power down and where it used to pull like a train in the upper rpm you can easily feel the power drop off as the revs climb on. For 90% of my riding it hasn't slowed me. The point being I wouldn't discount a change of pipe either.

Port/deck height changes can move it around too.

 

[Jakobi]

And in relation to the original jetting side. Richer. You can go rich till she starts to blubber. It might soften it up some, probably suck some more juice too.