CDI or Sparks key

[ballisticpb]

what would run better with my piped and k&n will i see a diffrence going to the GT thunder CDI or will i get the same results out of the sparks advance key??. i have no other engine mods other than the pipe and filter.

[EvilJester400EX]

You'd gain more with the advanced key. the CDI allows you to rev more, but you don't really have any engine work where you would need the extra RPM's.

[DirtDevilBT]

WHITE BROTHERS CDI!!!!!!!!!!

[JOEX]

I heard the GT Thunder CDI advances the timing....:confused:

[ballisticpb]

the gt thunder is said to advance the timing as well. so just spent the money?? what kind of programable ones are there i will be doing more engine work. i just want an engine mod for more power that i dont have to tear down my entire engine

[SHADETREE101]

get the rev box, you can switch to the stock one when it gets cold so it will start easier. if you just change the key, you will have to get someone to pull start you if it gets cold. this way you can let it warm up and just change them again.

[EXerHonda400]

I live in the upper penninsula of michigan, so it is cold a lot of the time. I have a sparks timing key in, and it don't start any harder than before. The CDI is obviously easier to install, because if you put the timing key in you have to buy a starter cover gasket and a flywheel cover gasket. Because most likely you can't get them off without ruining them. Plus the key is only $20 and you get a flywheel puller.

[muddy400EX]

sounds stupid but what exactly does a advance key do?

[cals400ex]

the timing key will advance your timing so your will get crisp throttle response and may feel a very slight low end gain

the aggressive curve gt thunder box advances timing from what i read too. i run this box and the throttle response is much greater than the stock box, if you know your bike well. i would get this box over the key. i realize the price difference may not be worth it when comparing power outputs, but this box works wonders on a modified motor. you will need a higher rev limit with a high revving cam if that is in the future for you.

don't get the white brothers or sparks boxes, been there done that.

the programable ignition boxes are nice for the adjustments and providing a better spark. from what i read, the msd is the best but i have never been a fan of msd quality. i don't hear of too many problems but i haven't cared for them on cars. i would run one on my bike though.

[400exrider707]

TC or GT thunder rev box!

[TORO1968]

You guys do know that advancing the valve timing will have a different effect than advancing the ignition timing, don't you???


Cals, so far so good with my MSD setup... I've had it installed for about 9 months now with not one problem.

-Jordan

[JOEX]

Originally posted by TORO1968
You guys do know that advancing the valve timing will have a different effect than advancing the ignition timing, don't you???

-Jordan
Would you mind explaining the difference for everyone? I think it could be some very useful and interesting info for many of us. And please don't use too many big words:p

[Xenu]

Originally posted by TORO1968
You guys do know that advancing the valve timing will have a different effect than advancing the ignition timing, don't you???


Cals, so far so good with my MSD setup... I've had it installed for about 9 months now with not one problem.


Any chance you have some wiring diagrams of exactly how you did this install? I'd be curious to hear more about it.

JOEX, Valve timing is the relationship between the angle of rotation of the crank and when the valves open and close. This affects the airflow into and out of the engine.

Ignition timing is the relationship between the angle of the crank and when the spark plug fires, starting combustion(hopefully).

They both affect how the engine runs, but you can view the valve timing as affecting airflow, and the ignition timing as affecting the spark.

[ballisticpb]

so witch can give you more throttle response?? valve timing or spark

[F-16Guy]

Originally posted by TORO1968
You guys do know that advancing the valve timing will have a different effect than advancing the ignition timing, don't you???


Cals, so far so good with my MSD setup... I've had it installed for about 9 months now with not one problem.

-Jordan
The advance key and the CDI BOTH affect ignition timing. The key affects base (initial) timing, and the CDI controls how far the timing advances to compensate for RPM. As the piston moves faster, the spark plug has to ignite the mixture sooner to keep up. Valve timing controls when the fuel and exhaust enters and exits in relation to piston position. Moving the valve timing (which you can't really do on the 400ex) basically moves the powerband higher or lower.

[TORO1968]

Okay, so I just realized I made a complete idiot of myself...It would help if I thought a little bit about what the advance key you guys are discussing does. Why I had the idea that it indexed the cam gear, I don't know. But I apologize for the misinformation I may have stated...

I think F-16Guy summed up the differences quite well. I guess you learn something new every day! :)

Why do you say the valve timing on a 400ex cannot be changed? Jumping a tooth forward or backward on the cam gear would alter the valve timing quite a bit, though it might be detrimental or even damaging...LOL

It's too bad no one manufactures an adjustable cam gear...now that would be pretty cool.


Xenu, I might be able to scan in the wiring diagram from my MSD install manual... It's not too difficult, although you do have to cut the factory harness in several locations. In addition to that, the instructions are somewhat vague in certain areas.

It took me about 3 hours to do everything, including soldering and heat shrinking every connection. So far, I think the MSD ignition box and coil were well worth the money.

-Jordan

[cals400ex]

gt thunder does make an adjustable timing sprocket for the 400ex.

[TORO1968]

Hmm...I might have to look into one of those. :)

[cals400ex]

here is a link on his website:

http://www.gtthunder.com/400ex.html


i just wouldn't know how to adjust that thing. i bet it would be major trial and error which would be a PITA somewhat because you need to take off the valve cover each time.

[TORO1968]

Yeah, I was wondering the same thing... It would definitely be a pain to dial the timing exactly where you wanted it.

I suppose if you knew what timing you had at both extremes of the adjustment, you'd be able to guess fairly well...

[JOEX]

What about a degree wheel? I'm don't know exactly how they work or if one is available for these motors..... are they even an option?

[DirtDevilBT]

WHITE BROS!!!!!!!!!!!!!!!!!!!!!!!!!!:D :macho

[UglyMotha™]

Originally posted by cals400ex
here is a link on his website:

http://www.gtthunder.com/400ex.html


i just wouldn't know how to adjust that thing. i bet it would be major trial and error which would be a PITA somewhat because you need to take off the valve cover each time.



you use a degree wheel to set the timing, they do make them small enough

[wes350x]

Could you run both together? Anyone here does???

[kilabeez0]

that's what i want to know, both for under $100 combined is cheap. but is that TOO much advancing causing detonation and requiring higher octane gas?

[UglyMotha™]

depends what cdi you go with, some out there will also advance the timing electronically, if you run both you will advance the timing too much and cause engine damage

[F-16Guy]

Originally posted by DirtDevilBT
WHITE BROS!!!!!!!!!!!!!!!!!!!!!!!!!!:D :macho
Yeah, those things are great!! I think they come with a free set of jumper cables now. :chinese:

[Fortman_400]

about the cam timing..
generally aftermarket cam companies change the timing of the valves slightly, such as advancing the intake and holding the duration longer to increase the ammount of fuel intake. if u look at all of the specs of a cam it should have the lift, duration, and degree of advance... thats why 2 cams that have the same exact lift and duration can make a quad or a car run completely different, just with the different degree of advancement