6 replies to this topic

[Gary5173]

Hi everyone. I own a 2005 Gas Gas TXT280Pro thats making a metallic clinking sound at mid revs upwards in every gear. Is this pinking. I've heard that using a higher octane fuel can help but can anyone advice what the carb settings should be. I.E fuel / air screw etc. I tried to download the user manual but apparently its not available for the 2005 model for whatever reason. I bought the bike second hand so would like to know what the base settings for the carb are in so I know if they've been altered. Advice much appriciated

[motomerlin]

First off, check jet sizes in carb.
You might be able to tune this out with the pilot screw.
Possibly a de-coke is needed.

[Lowbrow]

If its something that's started recently and you haven't changed anything check for leaks on the intake side; particularly the face between the crankcase and the reed block/intake stub. The rubber intake stubs can also split, but always at the back, next to the exhaust, where you can't see! I always use super unleaded fuel too.

[dschigoda]

Some guys mix in ~ 1/3 race gas (~110 octane u.s.) with their premium unleaded, in their trials bikes.

[dschigoda]

Also, if the Premium contains 10% ethanol, I get pinking. But most of the pinking goes away when I use the 100% gasoline premium.
When I've added 1/3 race gas, the motor seems to loose some of its power, and some of its "snap".

I ride a 2002 GG 280 Edition.

[JSE]

dschigoda, on Jul 28 2009, 09:45 AM, said:

Also, if the Premium contains 10% ethanol, I get pinking. But most of the pinking goes away when I use the 100% gasoline premium.
When I've added 1/3 race gas, the motor seems to loose some of its power, and some of its "snap".
I ride a 2002 GG 280 Edition.

The race fuel will give you less "snap" due to it's slower burning properties (kinda like retarding the static timing a little, it changes the "Indicated Mean Effective Pressure" ie: there is a little less pressure buildup between when the plug fires and the piston reaches TDC). I use it in my 02' 280 Pro to smooth out the lower RPM power delivery (I'm a slow, old geezer) and it can be used by riders to adjust the power output in wet, sloppy conditions when traction is marginal (softer power delivery off-idle) and the radiator may get plugged with mud (the higher octane is a little insurance to resist detonation due to higher engine temps).

Jetting on the 05' Pro (sea level) should be in the neighborhood of:

MAIN: 116/118
PILOT: 36/38
NEEDLE: D36 (3rd, or 2nd CLIP POSITION DOWN FROM TOP)
FUEL SCREW: 3.5 TURNS OUT TO START (adjust for ambient conditions)

I run my 280 with a 118/38/2nd-clip combo with good results and never a "pink".....

Jon

[Stork955]

Gday, Give it a good decoke (head off) and while you are at it, check your Carb as Jon said above, and clean the pipe from front to back. It should run like a beauty afterwards. It is a 2-stroke, burning all its oil after all.

Cheers,

Stork.