misfire at full throttle

[HondaRaceReady]

I recently installed a sparks racing +6 timing key and now my bike has a bad misfire from 3/4 to full throttle. Im positive its not jetting related because I tried the next 2 main jet sizes richer and leaner and there is no difference at all and it was running fine before. Is it possible that the timing key could be doing this or should I be checking the ignition coil, trigger coil, stator, etc?

[honda400ex2003]

what kind of gas do you run? 91?

my guess is that its pre-detonating from the advanced timing.

steve

[quadracer556]

Originally posted by honda400ex2003
what kind of gas do you run? 91?

my guess is that its pre-detonating from the advanced timing.

steve

this goes against the whole reasoning behind running a six deg. timing advance key as the sole significant mod on a stock motor.a 6 degree advance key should not be able to up the compression enough to cause pre-ignition/detonation unless other mistakes were made.

[honda400ex2003]

once again over here too... boy we are lucky to have your help tonight...

advanced timing requires more octane and if hes running 89 or 87 octane it will definitely pre-detonate. even with poor 91 it will pre-detonate.

if he is sure that its not jetting and such then theres not much else that can be wrong with it other than timing. if it is running fine any other time, its pre-deto when the engine gets warmer and is running at full compression at WOT.

steve

[quadracer556]

he stated he was achieving a "mis-fire" at WOT.there is no relative power being produced at wot.all i'm relaying are my experiences in pre-ignition and they all occur in the 1/4-3/4 throttle category when pouring on the power not running wot.regardless i'm not sure that with the info provided anyone can give an accurate reply at this point so take it easy and we may just be able to help this guy.barring any other timing changes should he be able to achieve detonation with only a 6 degree timing advance??and for fu*** sake its pre-ignition and or detonation.pre-deto?pre-whatoh lol

[honda400ex2003]

well you are the first one ive seen to have any issues with anything less than full throttle. just cause its not making power doesnt mean that its not running full compression. maximum pressure is still when the engine is running the fastest, it also builds the most heat when running at WOT. this combination of pressure and heat at WOT results in knocking.

pre-deto referring to igniting before the regular detonation of the spark plug. pre-ignition if you want to call it that. pre-detonate is not the correct term but thats what i call it.

steve

[quadracer556]

heat,as you stated can cause this but also ones weight in conjunction with traction being forced back through to the piston can dictate compression as well.

i was the first one to see a spring steel wiseco circlip break off at about 1/4 inch,pass forth and back through the wrist pin and gouge the clyinder severely but it happened.the point is there are so many variables to any situation,lets focus on helping.

[honda400ex2003]

exctly, just the first in the long list of stuff to start looking at with an engine. lots of good variables in these little engines

gotta take care of the common stuff first, we still dont know if he is running 87 or not. LOL

steve

[suspension101]

How did you remove your flywheel?

[JOHNDOE83]

To me, 1 or 2 jet size changes is meaningless.

I jet in incriments of 5, 1 or 2 incriments is so minor its not worth doing.

But I have a similar prob when I run to lean and the motor gets to hot, its like a pop when accelerating at about 3/4 throttle to WOT right? Almost at the shift point when in lower gears?

[dxcody]

Originally posted by suspension101
How did you remove your flywheel?


Flywheel puller.

[suspension101]

Ok. I was just curious because Ive had a couple of 400s with a bad flywheel. It acts just like being too rich and cuts out only at WOT.

[dxcody]

I thought you were asking How to remove a flywheel. I dunno how he did it, im guessing a flywheel puller.

I dunno how else you can do it.

[suspension101]

If a 2 or 3 jaw puller was used you can damage the magnets in the flywheel. The OEM flywheel remover that pulls from the center should only be used

[HondaRaceReady]

Im running fresh 93 octane gas. I used the flywheel puller that was included with the timing key. I dont see what I couldve done wrong installing it for this to happen. Surely sparks racing has done their research on whether 6 degrees could cause pre-ignition right? Oh and when I said I changed jet sizes I mean 175 was in there so I tried 178 then 180 then 173 then 170.

[suspension101]

Sounds like you're too rich if those are hex keihen jets. I'd say around a 160 would be closer.

[HondaRaceReady]

Sounds like you're too rich if those are hex keihen jets. I'd say around a 160 would be closer.

Idle to 3/4 throttle is great but once I get to full throttle its like someone is pressing the killswitch. It feels like its either running out of gas or it has no spark at full throttle. If I hold it at full for too long it will stall but if I let off a little it will run fine. I checked the trigger coil and exciter coil output and both are in spec. I thought it wasnt getting enough fuel so I removed the fuel filter from tank. I checked fuel tank vent hose. I cleaned carb. Im stumped.

[dxcody]

what does your spark plug look like?

Im gonna agree and say you are too rich.

[HondaRaceReady]

The 400ex has a full exhaust and k&n air filter with the airbox lid on. With these mods would a 175 still be too rich or did you guys mean on a stock bike.

[dxcody]

Originally posted by HondaRaceReady
The 400ex has a full exhaust and k&n air filter with the airbox lid on. With these mods would a 175 still be too rich or did you guys mean on a stock bike.

With the airbox lid on, yea thats still a pretty big main jet.

Pull the lid off and see how it runs at WOT.