Engine won't run at high revs

M

motopsycho87

New member
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?
 
Faulty cdi

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

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

So electrical wise, it has had a new spark plug, new ignition coil, new stator coil and new cdi. :confused:
 
Pull the muffler and disassemble.The inner may have broken causing a blockage ime.
Repack it while your there.
 
In my Opinion is the Main Jet 180 mich too Rich.
Check a smaller One.
Have you checked your squish? What is it?
Also i would Check a mixture of 40:1 or 50:1
 
What temps/altitude are you in? 180 main sounds way rich for anything above freezing/sealevel.
 
OH MY ****ING GOD IT STILL DOESN'T WORK!!!!!

Just put in Wossner piston and obviously new gaskets (head gasket was going slightly ad piston was worn)?!!?!? WTF CAN IT BE?!?!?! It literally will not run above half throttle?!?
 
Like others have said I think trying some less rich jetting is the next step. 180 sounds pretty rich.
 
Phone decided not to record... eurgh.

My only thoughts now are crank seal or carb... how easy is the crank seal on these? Split cases or can it be done without?

The bike seems to be smoking more than it should when trying to rev, but very hard to pinpoint whether rich or crank oil. I have drained the crank oil before and it came out black, which says to me contamination with combustion gasses etc...? When holding at about 1/4 throttle (before it gets really crappy) it will rev for a bit, then sputter and hunt for a bit..? Still, the bike ran absolutely fine with this configuration beforehand...
 
Last edited:
Ok, bike has had,

New stator coil assembly (ign, pickup and lighting)
New HT coil, HT lead, HT cap and spark plug (3x spark plugs)
New piston and rings (gapped 0.004" per 1" bore), obviously head and base gasket at this point
Tested different CDI, bypassed all of the bike's own wiring
Have cleaned carb, gone to standard jetting (appears worse at top, and won't idle)
Have run without spanny, and with spanny without muffler
Have run with power valve fully open and closed
Reeds are in good condition
Great compression
New fuel



I am really, REALLY confused, something happened to this bike SUDDENLY, it seems to have gotten worse every time I run it, low down is fine, but high revs just kill it, BUT, the plug comes out wet?
 
Both crank seals appear fine, replaced anyway, can't run it until I get the new gaskets though... it does seem to me like it is incredibly LEAN on full throttle, but with a clear main jet, how could this be? The base gasket is brand new, so no leaks there, reed gaskets have come off in-tact... wahhh :(
 
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