Timing adj.

[jmutiger]

Hey guys,

I've been having some problems recently with spark plug simply dying on me. Recently I have installed a new lighting coil, and I think I might not have the timing set exactly as it was before. There are 3 marks on the stator plate, which one of the 3 do you guys have your KDX250's set at? I believe I aimed for the middle one, but the bike really isn't liking it (assuming this is why I keep on killing plugs)... I think if my bike sparked earlier, I could have a more complete burn, and less fowling of the plug.. So which way advances the timing?

ps. I'm running a BR9ES plug now, got a new NGK race wire installed, new plug cap.. and the only fault is the plug dies after around 150-200km of riding, which is excessive even for this bike, as I didn't ruin one last year.

Jon!

 

[Yobedoc]

I think the best thing to do is sell this bike and get a KDX220...much lighter and much better for woods riding.

Yobe

 

[canyncarvr]

This is the bike with the wrong coil swapped...yes?

Otherwise there would be no reason to wonder about the timing, cuz you don't have to take the ring off OR loose to change the lighting coil....anyway...

So, it's running different than it did? Presumeably....

Anyway, be VERY careful on the advance thing. That (advancing) is much more likely to kill (seize) a 2-stroke than it is to make it run better.

Given that your flywheel turns CCW (looking at it), you move the stator ring CW to advance the timing.

As I recall from an eric gorr 'white paper' on the subject, he said that ring should be moved no more than .040" from spec. I don't understand this, personally...maybe misremember?? Considering the diameter of the flywheel, .040" doesn't seem like much at all. Point is, advancing a 2-stroke is iffy, and it doesn't take much to cause a problem.

That said...what does '..spark plug simply dying' mean? It fouls out? A new one looks great but still quits? Doing nothing other than changing the plug makes it run?

Keep in mind that 'changing the plug' means you also re-place the plug cap. Maybe the install of that new hi tension wire needs to be checked? The re-install of the sparky coil went perfectly? It's connected perfectly? No junk crimp connects?

A lot of questions :( The history of what's happened I think is going to be important in sorting the problem out, though.

 

[jmutiger]

Thanks for the info.. I won't go nuts :)

Okay, some background.. When the plug dies, it doesn't appear fouled, just dead.. it happens sometimes after fast running, and other times after slow running.. I can feel it start to die on me, and it's the typical plug fouling symptoms.. Just doesn't run right at high RPM, and isn't responsive. When I pull the plug out, it doesn't look totally ruined, but I know it's not about looks.. I'm assuming it's gas fouled, as it's always wetter than it should be.. That's why I think advancing the timing will help.

Yes, this is the same bike that I swapped lighting coils on, and had screwed up on the lighting vs. the ignition coil on. The new wire wasn't monkeyed on, it's properly threaded into the coil, and the plug cap came on the wire, and seems to be as it should, not loose.. The cap to plug junction also seems nice and tight now. The bike runs as it should when it does, but the plug issue makes the ride less fun than it should be.

I think that's it... I think..

Jon!

(Thanks for the info)

 

[canyncarvr]

Still...this is something that was NOT an issue before the spark coil was 'replaced'??

Obviously, given that a situation is apparent AFTER a given action, the action is the cause of the apparancy (new word!!). I understand it COULD be something else.....'stuff' DOES just happen.

I'm having a hard time moving off this having something to do with the spark coil, though.

How were the connections re-done?

 

[jmutiger]

The new wire off the coil was threaded into the wire, as the stock one was.. (this is the coil up by the gas tank, which I added a new wire there too).. The wire on the ignition and electrical coil under the flywheel were crimped and shrink wrapped together. With a blast of solder at the butt end of the crimps.

Jon!

 

[canyncarvr]

Have had this discussion in another thread..but a good crimp is better'n a bad solder job. But...solid wire doesn't crimp too well, either. With both (crimp and solder) you should be good to go.

Oh..that .040" is good for ABOUT 2º (figuring the stator ring to be around 5 inches in diameter). That may be a bit large on the measurement.

Take the diameter of the ring, multiply by 3.14, divide by 360 to get a result in inches that relates to 1º of timing change.

Oh..general rule (another input from a 'white paper' of mr. gorr): It's RETARDING the timing that will increase the upper revs (overrev), and ADVANCING the timing that will help bottom end, at the expense of the top.

I have to say (cuz this is the way it is) that I found that to be a bit different on my kdx....which is to say opposite ;). I retarded the timing on my bike (moved stator ring CCW) and found the bottom end much improved..and a head to head run against a kdx that I had stayed neck-and-neck with had me falling behind @ 2-3 mph! Change the timing back to where it was (middle mark) and it was even-steven again.

I started my 'experiment' by moving the ring a WHOLE mark..was aligned to the middle, changed to mark to the right. THAT would have been OVER 10º!! Then I read EG's comments, moved it BACK to approx. 2º retard. Topend was still a bit short of what it had been..but there was still a noticeable bottom improvement.

That should give you some guidelines as to which way to go...and how MUCH 'going' to try.

Good luck!