[yzeefoureight]

Hi everyone,
i was just wondering if I advance the ignition on my gas gas 125, will it give it a bit more bottom end?
thanks
Sam

[JSE]

yzeefoureight, on Jul 26 2010, 04:30 PM, said:

Hi everyone,
i was just wondering if I advance the ignition on my gas gas 125, will it give it a bit more bottom end?
thanks
Sam

It can, but for issues related to combustion, it can reduce power at higher RPMs, much like raising
compression too high.

Jon

[bobtlr]

if you advance your timing your propably loose bottom end power and gain top end,
better try to turn it the other way but you will loose top end power and revs

best regards bob

[JSE]

bobtlr, on Jul 27 2010, 11:26 AM, said:

if you advance your timing your propably loose bottom end power and gain top end,
better try to turn it the other way but you will loose top end power and revs

In the case of the two-stroke engine, that's not been my experience. Advancing the static
ignition timing from the factory setting tends to move the torque curve downwards, not upwards
as it changes the IMEP (Indicated Mean Effective Pressure) and at lower RPMs provides higher gas
pressure on the piston (and therefore the crank) after TDC.

To test this, an engine at idle setting will gain RPM when the static timing is advanced.

Jon

[Stork955]

Gday, further to the above, get it wrong and melt your piston in about 5 seconds. My advice is leave it be and get a larger bike if that is possible.


Cheers,


Stork

[JSE]

Stork955, on Jul 27 2010, 03:37 PM, said:

Gday, further to the above, get it wrong and melt your piston in about 5 seconds. My advice is leave it be and get a larger bike if that is possible.
Cheers,
Stork

Boy, there's truth to that. There is a point of very rapidly diminishing returns when it come to spark lead. It should only be
used very carefully as a tuning tool by the experienced and most of the time the stock setting is the most overall effecient setting.
Incidently, the more effectively an engine uses it's fuel, the less spark lead it needs. In evaluating port/chamber modifications on a dyno run,
the less static timing needed to produce good results was a good indication I was going in the right direction.

In most 125's, proper factory recommended maintenance and tune-up proceedures will most likely yield better overall results in the power
department than a degree or two of advance.

Jon

[Stork955]

Gday, Further to Jon's post, you might clean the exhaust front to rear, especially if the bike has had a few years service, and that may well be all you need do to get it running well. A quick check will show if there is a build up of carbon in the header pipe, this is normal for all 2-strokes, and will effect performance greatly. There are many threads on exhaust cleaning for you to peruse if this is the case.

Cheers,


Stork

[JSE]

Stork955, on Jul 28 2010, 07:00 AM, said:

A quick check will show if there is a build up of carbon in the header pipe, this is normal for all 2-strokes, and will effect performance greatly.
Stork

That's especially critical in the smaller two-strokes. The first 5-7" in the exhaust port (from the piston crown edge out) is probably the most important area in the whole exhaust system in terms of performance. The Trials exhaust system is unique among competition engines that usually run close to full throttle and maintain high temperatures in the port/tubing walls, which keeps carbon buildup to a minimum. The area where the cylinder port meets the header pipe has a high differential in surface temperature and it's common for there to be a thick buildup of carbon just inside the header pipe (right in the middle of the most critical area in the exhaust) so taking the pipe off and cleaning it out now and then is a good way to maintain performance.

Jon