Originally posted by BaxterC
I am having a problem, the low-end needle is not set correctly, but I cant get it right, it just revs high, the idle is set to 1mm and it idles, for a bit, but then the revs climb, if I rev it, it revs, settles to idle, but then the revs climb again, I thought the low end wasto lean, so I turned it out, but then it dies when you rev, I am lost with this, any ideas?
I've been through these kind of problems, too. Set your carb back to the factory settings, i.e. as they were when you got the engine. This will give you a starting point.
Do a few laps and then come in. First I would set the idle screw, as I found when I got this wrong, the engine kept dying and therefore I couldn't tune the HSN.
After you've done the few laps, your engine will be nicely upto operating temp. Now use the pinch method, to see if your LSN is correct. Pinch the fuel tube right next to the carb inlet.
If the revs increase, then the LSN is rich - if the engine dies without the revs increasing, you're too lean.
Adjust the LSN until the revs increase for about 0.5 to 1 second and then the engine dies.
Your HSN should be a bit rich at the moment, so when you hit the track at first it should probably four-stroke, but as the engine gets upto operating temp, it should run aok. Really I would use a temp gun at this point - my experience of engine tuning is not so great, so I prefer to stick to the safe side. Getting the HSN leaned out until you're seeing about 105 C is a good point to get to - after a fast 3 lap run.
Once you have your HSN set correctly use the pinch method to get the LSN tuned again. Also when you're on the track, when you enter a slow corner after a flat out section and your revs remain high when you come out of the throttle, then your LSN is still a bit rich.
Hope this helps, Mark.