Engine won't run at high revs

[motopsycho87]

Sorry I'm moving my post to this section as it is a bit more active.


Hi, I recently purchased a GasGas EC300 2006 from 'greenlane motorcycles', a dealer with whom I suggest you avoid like the plague due to many lies in the sales process and general bad customer relations.

The bike
Since purchase I have
Changed oil
New oiled air filter
Rejetted for best performance (40pilot, 180main), running 32:1 fuelil


The bike ran great, in which I decided to ride on the local motocross circuit, half way through the second lap, suddenly the bike refused to rev high;
https://www.youtube.com/watch?v=4e_H_ogPWx8 - video showing the bike running badly.

This problem is now constant, I have checked the following;

Spark plug, replaced - BR8ES
Ignition coil, HT lead and plug cap replaced
Stator coil replaced - Electrex
Carb has been cleaned
Reeds are in good condition
Power valve is operating correctly
Piston appears clean and ring are in tact
Engine has very good compression on the kick start
All earth points have been checked
All wiring has been checked and re-shielded

The bike starts first or second kick every time, idles very strongly, but will not rev past approximately 5000-6000rpm. The bike can be ridden and still pulls at full throttle below this rev range.

At this point all I can think is that I have a faulty CDI? I have tried running the bike with both 'maps', bypassing the switch etc, but to no avail. Is there any way to test the CDI or anyone I can send it to for testing? Or are there any other possibilities you think I should consider?

[davedunaway]

I had the very same issues with my 06-300,it finally got to the point where it run crappy for a few minutes than die. You had to wait about 10-15 minutes to restart than it would repeat the whole process. I checked out the basics just as you have and finally put the cdi on off of my 550 husaberg. It ran a little weird,strange powerband but it never quit running. After that I borrowed a cdi from a friends GG and tried it. Bike ran perfect. Bought a new cdi and haven't had any problems since. A bit pricey however.
From what you're describing I'll bet that's the issue.
Dave

[motopsycho87]

I can't imagine it being anything else no excess money till next month too as the car has it's MOT. My mate is coming over in a couple of weeks and has a 250sm so will try his cdi, fingers crossed!

[Coop]

I read on here you can check between the ground wire and the kill switch wire on the CDI and if it's not at least 100K ohms it's bad. I did check my working CDI and it's 137K ohms but if that is a valid test or not I do not know.

[bonkeye]

Originally Posted by motopsycho87

Rejetted for best performance (40pilot, 180main), running 32:1 fuel

just out of curiosity what slot is your needle clip set at?

[motopsycho87]

I'll check next time I take the carb off.

Fitted a CDI off of a RM125 and the problem is exactly the same

So electrical wise, it has had a new spark plug, new ignition coil, new stator coil and new cdi.

[gasmonkey]

Pull the muffler and disassemble.The inner may have broken causing a blockage ime.
Repack it while your there.

[Jon250]

Powervalve working ok?

[motopsycho87]

I've looked through the exhaust, it appears to be actuating correctly, no slack.

[motopsycho87]

Starting to think it is head gasket... will report back soon...