jetting

[macho comacho]

Hi all
I have been trying to get rid of a sputter at small openings on the throttle and have tried 45 and 42 pilots,but with these pilots the air screw had no effect either in or out.Then i tried a 40 pilot and the air screw now worked but only at 3.5 turns out.
My jetting is 178 main,40 pilot,CEK needle 4th clip,sea level and the temp is around 9 C. Reeds ok.
Could i use a 38 pilot or am i too lean at the moment with my current settings,also is there anything else that could cause this type of setting.
Many thanks Macho

[2 strokes 4 life]

Well best bet is the RBD carb mod. Best money you can spend if you can not get rid of the sputter.

[Eric K]

What carb slide do you have?

What year is the MC?

[macho comacho]

As i'm in the uk the rbd mod is out.The slide is a 7*.would a 38 pilot be too lean.

[iancp5]

Originally Posted by macho comacho

As i'm in the uk the rbd mod is out.The slide is a 7*.would a 38 pilot be too lean.

What bike is it - 300? How are you using it?

I used to have a 300 and best jetting I found was 40, CCK and 180. That was in cool temp. I would go to 38 & 178 in summer. That's for tight woods. If I was doing lots of fast stuff I'd probably have it richer to be safe after a bad experience! I tried going very lean once and it was great in the woods but seized on a fast bit. That was on 35p & clip 1 on an N1EF - a lesson learned.

I don't think you can completely eliminate 4 stroking if that is what you mean by sputtering but the bike shouldn't hesitate when you open the throttle after slow running. If you completely eliminate 4 stroking on tiny throttle you will be so lean you are going to seize.

[macho comacho]

Ok cheers iancp5 yes its a 300 and i use the bike for trail riding so i will stick with the jetting i have until it warms up.

[ferguscawley]

Clip 4 on that needle is very rich. Try clip 2. My 300 runs too rich with CCK needle in clip 3 but sweet in clip 2. (178 MJ, 40 pj, num 7 slide, CCK on 2). Sea level approx and Ireland cold.

[rpduc]

Here is a great thread on jetting. Pobit supplies some great info in post #27 about page three...

http://www.gasgasrider.org/forum/sho...?t=1414&page=3

Also see post #14 regarding setting squish to get a cleaner burn.

[stay_upright]

I run my bike quite lean and the jetting is sweet - no 4 stroking pulls like a train nice and linear and plenty of top end seems to outdrag 400 and 450 4 strokes. Hardly uses and fuel but my bike never has. I have never changed the main though it appears it's possible to go upto 2 sizes leaner than stock without problems but as Ian mentions you don't want to seize the bike and my 300 makes enough power at the top end so I've left the main alone.

I've got a 35pilot, 9 slide, N1EF though not sure what clip - either standard or more likely 1 clip lean. I've been running this for a couple of years and it's really nice because once it's dialed I dont really need to touch it again in summer or winter. The lack of 4 stroking does make the bike run hotter though and I used engine ice for severe events to stop the bike boiling which has worked really well.

As with most 2 strokes the lack of throttle response - blubbery feel and plug fouling and high fuel consumption all comes from 4 stroking as low throttle openings. This can be improved (or in my case eliminated) by leaning the fuelling at low throttle openings - the pilot and slide cutaway and needle type and clip position are all factors.

[stay_upright]

Originally Posted by iancp5

What bike is it - 300? How are you using it?

I used to have a 300 and best jetting I found was 40, CCK and 180. That was in cool temp. I would go to 38 & 178 in summer. That's for tight woods. If I was doing lots of fast stuff I'd probably have it richer to be safe after a bad experience! I tried going very lean once and it was great in the woods but seized on a fast bit. That was on 35p & clip 1 on an N1EF - a lesson learned.

I don't think you can completely eliminate 4 stroking if that is what you mean by sputtering but the bike shouldn't hesitate when you open the throttle after slow running. If you completely eliminate 4 stroking on tiny throttle you will be so lean you are going to seize.

Ian - what throttle opening did your bike seize at? 3/4 or WOT? or more like 1/4 to 1/2..

As you read from my post below I'm running my bike a lot leaner than yours and have eliminated the 4 stroking, have ran this jetting for a couple of years and it works great. Mine is lean at teh bottom end and gets richer - back to stock at the top end. I would not worry about seizing the bike at low throttle openings only 3/4 throttle onwards but it sounds as if you have had other problems... Were the rings definately welded to the cylinder?