EC300 07 - breaks down over 7K RPM

[Hamish]

Took the gasser for a ride today and she refused to pull above 7000 RPM
It idles fine and goes well in the midrange, but just refuses to rev. Even if you hold it WOT for a few seconds it just wont rev out. Sounds like a 2 stroke that is about to foul a plug.I tried a new plug - same.
It was fine last time I rode it.
Does anyone have any ideas? Blocked main jet springs to mind as I have had the fuel tap out since the last ride. On the subject can you get a longer fuel pickup for these bikes to increase the reserve capacity to something remotely useful?

thanks

 

[Eric K]

Here is where I would start looking...

Check your fuel system and carb for blockage.

Check to make sure the power valve is opening. Take off the left side power valve cover. I suggest putting a visible mark on the power valve shaft with a marking pen. Start the engine and rev the engine. As the RPM increases the shaft should rotate, opening the valve. If the shaft does not rotate, the power valve is likely stuck shut.

You may have an electrical system fault. I had my voltage regulator go bad earlier this year and it did the same thing you are describing. The lights went dim at high RPM as well. You could check the voltage as you rev the engine.

In very rare instances new plugs will be bad.

 

[GMP]

Also check the coil HV wire where it threads into the coil and cap.

 

[Dave]

...On the subject can you get a longer fuel pickup for these bikes to increase the reserve capacity to something remotely useful?

thanks

You can fabricate one. The '03s fuel pick-up is a plastic tube supported by a mesh filter that is threaded in to the petcock. A longer piece of 5mm brass tubing (or 3/16" with the end tinned) can be used instead of the plastic. Cut off the top of the mesh filter and use an external fuel filter. The mesh filter has to remain - it keeps the petcock o-ring in place.

 

[Hamish]

Thanks for that Dave, will have a look at doing it one day

Problem with the bike was the HT cable connection into the coil, thanks guys

 

[wence]

Thanks for that Dave, will have a look at doing it one day

Problem with the bike was the HT cable connection into the coil, thanks guys

What did you find with the cap? was it loose, broken or just old?
My bike seems to be doing the same thing.
Cheers Mark

 

[Hamish]

What did you find with the cap? was it loose, broken or just old?
My bike seems to be doing the same thing.
Cheers Mark

the cap was fine, the problem was where the coil wire enters the coil. The plastic support was broken and the coil wire wasnt completely screwed into the coil screw. Give this wire a tug and if it comes out easily it may be your proble, also do this at the cap end. If it is loose, cut the HT lead back so the screw has fresh cable to dig into

 

[wence]

Cheers Hamish I'll check it out and let you know.
Thanks again,
Mark

 

[wence]

Hey, Hamish,
Checked the coil wire at both ends..... all seems ok???
Rinsed carby and cleaned with fuel and air compressor.
Haven't checked lights and voltage reg at higher revs, could anything else be the problem?
I have come from riding anRmx 250(98 model), and the 300 seems to sign off or stop pulling at about 7 or 8 grand. Is this normal for this bike 07 gg ec300?
Cheers Mark

 

[Hamish]

I am no expert, as only new to the gassers myself, but compared to the kato it does sigh off early. I check the 'max rpm' on my speedo after i reved it out (past where it stopped making good power) and it said 9600, so I would imagine useable power is up to about 8500-9000rpm. Mind you my barrel has 9K km's on it, and the piston has about 3500km's, so it isnt exactly fresh

Mine is slightly better since I leaned out the MJ 1 size

 

[Eric K]

The 300 with the stock GG pipe and proper jetting will pull very smoothly to high RPMs.

My '06 EC300 max RPM will go up 10200. It pulls hard very close to max RPM when jetted correctly.

On most of my trail rides max recorded RPM is around 9000.

As a note I have the LTR head mod.

 

[wence]

Thanks guys, I thinkI am expecting a pull like the 250 Rmx but from what I am told the 300 will not be like that.
I like the way you can feel the torque in the motor on the 300 whereas on the 250 it was revs and wheelspin.
I will definitely have to have a look at the jetting and I know I will get used to this different type of power.
Bring on the enduros....

 

[Hollywood]

Thanks guys, I thinkI am expecting a pull like the 250 Rmx but from what I am told the 300 will not be like that.
I like the way you can feel the torque in the motor on the 300 whereas on the 250 it was revs and wheelspin.
I will definitely have to have a look at the jetting and I know I will get used to this different type of power.
Bring on the enduros....

My 07 pulls fine all the way to the top 9.8-10k. That same 250 hit is not there because the tq is so much more linear. The power definately is more trackable up hils vs a 250. It's a considerable difference.

But getting the jetting right can be tricky to maximizing your hit on these bikes.

 

[Warwick Simpson]

07 ec300 wont rev

Hi Hamish. I have identical bike with same problem. Did you pull the fuel tap apart or just out. The rubber gaskit in my fuel tap wasn't cut out properly restricting flow. I am aware of another bike seizing because of this problem. Easy fix.

 

[Hamish]

Warrick, I am back to problem 1 with the bike breaking down at 7,000 rpm. It was really shitting me as it cost me a weekend of riding in perfect conditions
It was fine last week, but back to its original games this week, so I'll order a new coil and see what happens. Fuel flow seems fine, not that it would be the cause of this particular problem. I rode down, up and then down a hill the other week with the fuel turned off before I realised there was a problem

My KTm may have handled and turned like a mack truck, but it was super reliable.. had more ride with problems than I have without with this gasser

 

[Hamish]

Update

Got a new coil, check MJ was clear (replaced) problem remains.

Removed pipe and marked PV settings with cable tie on LH side, refitted pipe and checked PV operation, PV opens fully.

Removed carby and reeds block, all reeds ok, not cracked and sealing well

removed flywheel and inspected stator, appears ok.
Does anyone have any stator ohm readings?

 

[stay_upright]

As a suggestion to find out if it is electrical you could try closing up your plug gap say from 0.7mm to 0.4. This means it requires less voltage to fire so if your electrics are compromised this may indicate your marginal condition. It may not run as cleanly right off the bottom with this spark plug gap but don't worry about that for a quick test. Let us know how you get on.

 

[Eric K]

Have you checked/replaced the voltage regulator?

My '06 EC300 acted very much like your description. Replacing the voltage regulator fixed the problem.

 

[Hamish]

Have you checked/replaced the voltage regulator?

My '06 EC300 acted very much like your description. Replacing the voltage regulator fixed the problem.

as in that blittle black box that mounts on the coil?

 

[stay_upright]

The voltage regulator should be a smallish device with metal (normally silver) fins on to dissipate the heat. Can't remember where it is on the GG's