Re-reading Bernie's first post here, it sounds like he modified the ignition on his son's 2007 KLX and got 29hp. Rather than him talking about that HP gain being something he saw on a bike years ago

Looking at my options, I think the easiest for me is to see if there's someone with a TIG welder in town and try adding the 3mm on my extra flywheel.

The idea of bolting on the flywheel without a key sounds like asking for trouble, though I suppose it'd be good enough to take a test ride.

I am going to be working on my bike anyway this weekend, and may take a look inside the flywheel cover to see how it all looks if the flywheel is rotated forward 3mm

 

While looking up what the lug on the rotor is called, I ran across this web page that part of the way down says:

Take a look at the new rotor. On its circumference you will find a protrusion (nose). This will trigger the ignition impulse. The system calculates the ignition advance by using the time the nose needs to passing the sensor's core. So the ignition happens after the complete nose had passed-by the sensor.

If the ignition happens after the complete nose has passed by the sensor (pickup coil) why would the suggestion here be to make the leading edge of the nose longer? Seems like the rotor should be rotated CCW on the crank to make the end of the nose rotate by sooner..

Maybe the ignition happening 'after' is unique to this engine

I also noted that the rotor on this particular engine doesn't seem to be keyed to the crankshaft, as they talk about moving into position to set timing.

 

Hey Richard, I just stumbled onto this thread and am stoked that you seem up to Guinea Pigging. If this works, then it is the most exciting thing since Marcellino and sliced bread. With bated breath we await your report, o brave one.

 

Well I'm into it, but I think Bernie's been put off. Now I am stumped as to which end to modify or which direction to reposition the crank after reading that bit on the webpage I sited

I'll surf around some more and see what's to know about these rotor nose-triggered ignitions.

 

I don't understand, why nobody in this forum can check the details...
if there is anyone with a little bit of knowledge about four stroke engines..and checks out the factory details of a KLX250R and KLX250, then it becomes pretty clear, the only difference is ignition and carby diameter.
the fact, that the carby is smaller, gives a higher gasflow at lower revs. that might explain the 30 / 32hp at only 500rpm higher. the major difference is in the ignition.
the KLX250R exhaust system doesn't make any change or difference to the stock silencer of the KLX250. these are facts. I've done more testing on a dyno then anyone else ( I assume) in this forum. I know what works or doesn't work .
and to change the static timing be a few degrees.. if you know how to do it, can't be such a big deal...only other problem can be the different cdi units used , but that can be sorted out easily..
again, its not magic tuning, its just going back to a standard factory setting.
the result with that will be, that the engine keeps reving past 8000 and produces more power.. just use a diagram of a dyno result in this forum, and extend the line from 8000 to 10500, and you'll see (roughly) at what hp it ends..

 

Bernie, why then does this page part way down, talk about ignition happening after the rotor core passed the sensor? Seemingly in conflict with your instructions to add 3mm up front?

Powerdynamo, Installationsanleitung für Horex Resident

Just trying to get the facts straight before I hand any parts over to the TIG welder guy that's turned up here in this small town

 

listen :

DON'T DO THIS. Do not change your timing or the CDI, the engine might explode instantly. You are better off investing more money into these super high tech exhaust system !!!!! or even better, but a TM 40 on your bike.
I'm just a bored idiot and tried to stir up a forum.

 

Well I won't. Not without positive information. I'm on your side, but there isn't much evidence online about going as far as welding bits onto your rotor or where to add it.

(MX bikes run big carbs btw..but thanks for the encouragement)


Anyway, quoting from what I have found on the internet:

(1)

"I mean we advance the ignition all the time without a serious problem. we also cut the nose shorter and increase the advance and cause it to peak earlier. It can take it just fine"



(2)

" as quoted by Eric Gorr.. it's a wee bit long but,,,it should help

AFFECTS OF THE IGNITION TIMING
Here is how changes in the static ignition timing affects the power band of a Japanese dirt bike. Advancing the timing will make the power band hit harder in the mid range but fall flat on top end.

Advancing the timing gives the flame front in the combustion chamber, adequate time to travel across the chamber to form a great pressure rise. The rapid pressure rise contributes to a power band's "Hit". In some cases the pressure rise can be so great that it causes an audible pinging noise from the engine.

As the engine rpm increases, the pressure in the cylinder becomes so great that pumping losses occur to the piston. That is why engines with too much spark advance or too high of a compression ratio, run flat at high rpm.

Retarding the timing will make the power band smoother in the mid-range and give more top end over rev. When the spark fires closer to TDC, the pressure rise in the cylinder isn't as great. The emphasis is on gaining more degrees of retard at high rpm.

This causes a shift of the heat from the cylinder to the pipe. This can prevent the piston from melting at high rpm, but the biggest benefit is how the heat affects the tuning in the pipe. When the temperature rises, the velocity of the waves in the pipe increases. At high rpm this can cause a closer synchronization between the returning compression wave and the piston speed. This effectively extends the rpm peak of the pipe."


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Research reveals Mr Gorr is regarded to know what he's talking about


NGK says: Advancing ignition timing by 10° causes spark plug tip temperature to increase by approx. 70°-100° C


Lots of serious consequences to getting it wrong Bernie, so we're just asking.



So far the meager online evidence shows that the spark and timing happen at the back of the nose, not the front


Drag cars typically want to retard timing at high rpm (look it up)

 

Bernie, please don't let naysayers put you off.

There were a lot of naysayers initially regarding Marcelino's cam mod as well and it turned out to work fine.

Some of us have wondered about ignition timing for a long time, but haven't had the knowledge to do anything about it. I for one, am glad that this subject has been brought up again and I hope someone will replicate what you are saying. Indeed, it would be cool if our KLX could once again make power in the upper revs.

I hope Richard gets this thing sorted and report back the positive results

 

good one,
my suggestion now is, you call or write KHI in Japan and tell them what you researched on the net, because they don't know that, and they have made the terrible mistake and changed the static timing and advance several times from 1993 til today....
and isn't it funny..that there isn't hardly anything on the net from the 80's and 90's... I bet you had the net in the 70's and wrote in all forums....