Timing curve?

[SSCHOEMAN]

Hi Guys
When the manual states that the timing is 21 degrees before
TDC at 6000 rpm, does that mean it is at full advance or will the timing be advanced even further with the revs climbing or is the timing already on a retarding curve when it hits 6000 rpm?
If the timing is already retarded at 6000 rpm, then is there anyone out there that knows what the full advance is and
at what rpm this happens?
From reading some posts, it seems that full advance happens around 3000rpm at about 25 degrees and then retards to 21degrees at 6000rpm and then progressively retard as the revs climb.
Is it safe to say that 8 degrees before TDC is the timing for
idling speed (1000-1200rpm)?
The info I need is for a 98 KDX 200 (normal not international)
I would appreciate all info

Cheers

Stephan

 

[tedkxkdx]

According to Eric Gorr's book, Jap ignitions have specific timing curves for two strokes. So your kdx falls right in this logic. idle 6 btdc, advances to 20 btdc at peak torque, at high rpm it changes back to 6btdc. So this tells me that testing on a stand with no load is 6 btdc and you would not be able to test degrees when riding.

 

[canyncarvr]

The timing is supposed to be retarded when the KIPS hits. The two systems aren't directly related, the KIPS running on centrifigal force against a spring, the ignition system running on impulses from the excitor and the charge on a capacitor in the control box.

So, with timing set to 21º @ 6000rpm, will it be advanced more at 6050rpm? Maybe. It depends if the timing circuit cap is completely charged, yet.

Is the KIPS open at 6000rpm? ...or 6100rpm? Maybe. It depends on the force of the spring and the resistance of the KIPS mechanism itself.

The control box is a discrete device beast..capacitors, resistors, and such. It isn't at all programmable in the way of processor controlled devices that do the same thing. Sure, you can change advance curves by changing the discrete components, but that is far from the programming of curves you can do with processor controlled devices. Jaguar did a lot of work on spark curve timing by changing components inside the control box. He ended up with something he thought ran a lot better than the oem configuration.

 

[cicone]

I was waiting for you to chime in, Carver!!! BTW---haven't continued my CDI from scratch project since acquiring a working version from Yoplait for $29 including shipping--such a deal!

 

[SSCHOEMAN]

Thanks for the reply guys.
Is there anyone out there that has used a timing light in conjunction with a rev counter to see degrees advanced at specific rpm's?
I spoke to a local guy that is willing to experiment in building a programmable CDI unit for a kdx 200. He needs a timing curve for a standard kdx 200 in order to modify it.
He says he will need to install a pickup next to the flywheel
like all the "new" bikes, and apparently its not as difficult
as it sounds.

Stephan

 

[cicone]

Stephan----Some good info can be found here:

http://www.dirtrider.net/forums3/showthread.php?t=93166&page=3&pp=20

 

[SSCHOEMAN]

Thanks

 

[canyncarvr]

Nothing you know how to do is difficult. If building CDI boxes is what you do, building one for the KDX wouldn't be much if any different from any other bike.

If he has the ability to build one, he surely has the tools to map an existing curve. Well, I'd think so anyway.

If not...make your own.

Timing lights with tachs are available. Don't now that they run to 8000RPM, though. Other RPM tools exist..like the units they use at HS for tech..to check your bike for db @ a certain RPM.

Find TDC on your bike. Measure the circumference of the flywheel, figure the 'length' per º, make your own timing tape, let the mapping begin!

It's not as difficult as it sounds. ;)

Your 'guy' knows the electrical system is AC? Not too usefull for most electronic wizardry.

cicone: I have yet to wire in the box I got from Jag. I have yet to work up the desire to cut into my existing harness to wire up something with unlike color codes...

I'm sure it's not as difficult as it sounds!!