Im guessing this post mainly goes out to the buddha but any help would be nice...
Ive just installed new air filter pods, and so installed new main jets. After a bit of trial and error and tweaking bits i think ive got the idle mixture just right but as far as the rest goes...
1. how long do have to leave it before the plugs will change to show how it is in there? I.e. if leave it idling for 5mins wil the plug chops reflect the fuel mix at idle or do i have to leave it longer?
2. What are the best things to look out for as far as the mix at other throttle positions? Or when i take it out tomorrow how will i know what needs changing (if anything) when i get back?
Stats:
00' with stock exhast and Universal air filter pods
40 pilot 137.5 main
I'm no guru by any means, but I do know that leaving it to idle will only (mostly) show effects resulting from the pilot jet. Your main jet comes into play at other throttle positions. If you want to do a plug chop do assess your main jet choice, you need to do it at speed. Here's an explanation I found at http://justkdx.dirtrider.net/printcarbtuning.html. It's for a dirtbike, but still applies here:
Checking the Main Jet– Warm up the engine and go for a short ride letting the engine comes up to its normal operating temperature. Install a brand new plug that's been properly gapped. With the new plug installed aggressively accelerate through the gears until you reach 4th or 5th gear. For best results you should accelerate up a slight up hill section to place additional load on the engine. Continue to run the engine at WOT for 20 to 30 seconds longer if there is not fear the engine is running lean. If you suspect the engine is running lean 15 to 20 seconds to give you an indication. At the end of your full throttle run simultaneously push the kill button, chop the throttle and pull in the clutch. This procedure is often refereed to as a " plug chop". It is important to perform a plug chop exactly as described. If you allow the engine to run or leave the throttle open for even a few seconds after the plug chop the plug reading will be invalid. Now remove the spark plug and carefully look at its color.
For what it's worth, I think you're at a pretty good starting point for the setup you have. I think you should be pretty close to having it jetted properly. Good luck!
-Mike
Quote from: crazyfish on April 16, 2008, 04:50:09 PM
Im guessing this post mainly goes out to the buddha but any help would be nice...
Ive just installed new air filter pods, and so installed new main jets. After a bit of trial and error and tweaking bits i think ive got the idle mixture just right but as far as the rest goes...
1. how long do have to leave it before the plugs will change to show how it is in there? I.e. if leave it idling for 5mins wil the plug chops reflect the fuel mix at idle or do i have to leave it longer?
2. What are the best things to look out for as far as the mix at other throttle positions? Or when i take it out tomorrow how will i know what needs changing (if anything) when i get back?
Stats:
00' with stock exhast and Universal air filter pods
40 pilot 137.5 main
Reading the plug at idle - 30 seconds is plenty. A few cycles is all it takes.
Jet it by feel, now that is rather deceptive at first, leaner jet setting make more power and accelerate harder when you whack it open, but will surge at steady throttle.
If the bike behaves at steady throttle but feels soggy when you open the throttle its too rich.
If the bike accelerates well when you open the throttle but surges (wandering rpm, misfiring when you open slightly from the cruise position etc) that is lean.
If the bike accelerates hard when you open throttle slowly, but falls on its face when you open fast that = slide comming up too fast.
The bike's acceleration depends a lot on float level, especially form 1/2 to 3/4 throttle. Make sure that is set to the exact top of the float bowl.
and as a side note ... with 137.5 mains, 40 pilots, stock pipe and uni pods and assuming you have washer under needle and have mix screws at 3 I'd be surprised if you are rich. You may be 1-3 main jet sizes away from ideal depending on how cold/humid/high it is where you are.
Somewhere 140-145 is my guess. But try it unbiased from here and post back, set floats first, else it will totally screw your observation.
Cool.
Buddha.
I took it out today for a bit and...
On the plus side i took the plugs out after leaving it to idle for a bit and it looks like ive got the idle mix just right, plugs looked great...
On the less good side when I open the throttle more than about 1/4 (ish) the engine tone changes to a kind of deep bwwwooooaaaaaaarrrrr (note technical language), i couldnt tell much performance wise because i was riding in traffic most of the time. Is that a good noise or a bad noise, or at least it sound great :icon_lol: but is it supposed to sound like that? I dont think I got it up to WOT because it was raining on the way home so i dont know what its like up there yet... any ideas?