carb jetting questions, again...

Return the timing to the "stock" position. Put your jetting back to
where you found it. Install a new spark plug. Take it out on a long
straight road and open it all the way in all your gears. Pull in the
clutch and kill the engine, coasting to a stop. Pull the plug out and
read the color. If it is dark and sooty go down one main jet size.
Repeat the process. If you get a plug reading that is whitish go back
up one size until you see a nice tan or gray color. If your timing is
correct and you still hear "pinging" it may be too lean. That is the
sound it makes just before everything melts. Use the needle to fine
tune the main and the seat of your pants to identify the proper pilot
jet. OF
 >> Stay informed about: carb jetting questions, again... 

"oldfart" <adavidg RemoveThis @peoplepc.com> wrote in message
news:1122329138.818756.89850@g43g2000cwa.googlegroups.com...
> Return the timing to the "stock" position. Put your jetting back to
> where you found it. Install a new spark plug. Take it out on a long
> straight road and open it all the way in all your gears. Pull in the
> clutch and kill the engine, coasting to a stop. Pull the plug out and
> read the color. If it is dark and sooty go down one main jet size.
> Repeat the process. If you get a plug reading that is whitish go back
> up one size until you see a nice tan or gray color. If your timing is
> correct and you still hear "pinging" it may be too lean. That is the
> sound it makes just before everything melts. Use the needle to fine
> tune the main and the seat of your pants to identify the proper pilot
> jet. OF


Unless you are using leaded fuel the above advice is not going to be much
use, as unleaded fuel makes it impossible read plug color in the way
suggested.

Before messing around altering jetting or timing, make sure the air filter
is clean, and freshly oiled, strip and clean the carb, then repack the
exhaust back box, and fit new plug. After you have done this fill the tank
with a 50-50 mixture of pump gas, and race fuel, using good quality fully
synthetic oil, mixed at 80:1. then see how the bike runs.

If its ok then you have nothing more to do............if its not then the
next step is to look at the timing and jetting, but only after you have
looked at everything I outlined earlier.

ken
 >> Stay informed about: carb jetting questions, again... 

>On Mon, 25 Jul 2005 14:17:31 -0700, "Peckham" <peckhammer.TakeThisOut@ROTMAIL.com> wrote:

>
>"Peckham" <peckhammer.TakeThisOut@ROTMAIL.com> wrote in message
>news:dc3jlq$q16$1@gnus01.u.washington.edu...
>
>> I've been playing with the carb on my GG280. It had very rich jetting...
>
>Another thought: The previous owner had mentioned that he advanced the
>timing. With the jetting changes, perhaps the advanced timing is adding to
>the issue. Not sure I understand the "why" behind advancing the timing?
>
>>--
>Peckham
>

He probably advanced the timing to give the engine more snap off the
bottom.

Considering the advanced timing and leaner needle clip position,
and the knocking, I feel that your engine is suffering from
pre-ignition or detonation. If this is the case, you are on the way
towards engine damage.
I'd move the needle clip back to the original position and retard
the timing that one degree.



Jim Cook
'04 Gas Gas DE300 Woods Pilot
Team LAGNAF
SMACKOVER RACING
BJEC/SERA/TSCEC/AHSCS
 >> Stay informed about: carb jetting questions, again... 

On Mon, 25 Jul 2005 14:17:31 -0700, "Peckham" <peckhammer.TakeThisOut@ROTMAIL.com>
wrote:

>
>"Peckham" <peckhammer.TakeThisOut@ROTMAIL.com> wrote in message
>news:dc3jlq$q16$1@gnus01.u.washington.edu...
>
>> I've been playing with the carb on my GG280. It had very rich jetting...
>
>Another thought: The previous owner had mentioned that he advanced the
>timing. With the jetting changes, perhaps the advanced timing is adding to
>the issue. Not sure I understand the "why" behind advancing the timing?
>
If at all possible I would try and get the timing back to the stock
position. It will be hard to determine if the knock is from jetting to
lean or to far advanced timing if it's not right.

General rule on the pilot screw.

2 strokes are air screws, so "in" is less air, or richer.
4 strokes are fuel screws, so "in" is less fuel, or leaner.

This is my experience anyway, I have no experience with a GG280's
carb so just be careful. If the knock gets more pronounced go the
other way.

Murray
>>--
>Peckham
>
 >> Stay informed about: carb jetting questions, again... 

"Murray" <Murraynolonger DeleteThis @work.com> wrote in message
news:l6kce1hrd8fgortl0ofu0eh74khsjqn54h@4ax.com...
> On Mon, 25 Jul 2005 14:17:31 -0700, "Peckham" <peckhammer DeleteThis @ROTMAIL.com>
> wrote:
>
>>
>>"Peckham" <peckhammer DeleteThis @ROTMAIL.com> wrote in message
>>news:dc3jlq$q16$1@gnus01.u.washington.edu...
>>
>>> I've been playing with the carb on my GG280. It had very rich
>>> jetting...
>>
>>Another thought: The previous owner had mentioned that he advanced the
>>timing. With the jetting changes, perhaps the advanced timing is adding to
>>the issue. Not sure I understand the "why" behind advancing the timing?
>>
> If at all possible I would try and get the timing back to the stock
> position. It will be hard to determine if the knock is from jetting to
> lean or to far advanced timing if it's not right.
>
> General rule on the pilot screw.
>
> 2 strokes are air screws, so "in" is less air, or richer.
> 4 strokes are fuel screws, so "in" is less fuel, or leaner.

I think this depends on the carb. If the screw is at the back of the carb,
it's an air screw. At the front of the carbs it's a fuel screw. The
Dellorto carb on this bike is at the front, so I am assumings it's a fuel
screw. Thus, according to your description, I should turn it in to lean the
pilot circuit.

>--
Peckham
 >> Stay informed about: carb jetting questions, again...