I'm with Wildcard on this. RayCours advanced total timing in increments and did a series of dyno runs with no improvement. Why did he not get gains? Don't get me wrong Bernie - I want to believe I can get 5 hp out of an hour or two of work... but RayCours has dyno charts saying I won't. What are we missing?

 

Hi guys,

Bernie, I assure you that advancing the timing with the adjustable cdi can do the same as rekeying the rotor or adding some metal in front of the teeth. From 5000 to 10000 rpm the oem cdi does a constant timing advance, 25 deg. Your mod would add a constant value everywhere, from idle to 10000 rpm, something which could be done with the adjustable cdi too. Our usual practice is to keep the idle advance the same and add more and more from idle to 5000 rpm. Then add a constant value again above 5000 rpm.

Anyway, the most interesting part is from 5000 to 10000. To our great surprise, we did not find appreciable benefit by adding 10 degrees over that band. It was also surprising to the highly skilled mechanics we shown this.

Was this lack of results due to our experimental setup? Maybe. We had a 800hp wheel dyno for measuring something in the range of 22hp... Or was it due to the fact that other engine parameters like cam timing is what restricts the power anyway? I'd like to know...

Your story makes me feel like we should do our homework more deeply. We had the intention of going to a motorcycle dyno back then, but did not have a chance yet. It's still in the plan though.

 

[QUOTE=RayCour;510374]Hi guys,


Anyway, the most interesting part is from 5000 to 10000. To our great surprise, we did not find appreciable benefit by adding 10 degrees over that band. It was also surprising to the highly skilled mechanics we shown this.

this just shows, there was something total wrong in the system.. any normal engine would response on 10 degree different ignition timing.. or do I see that wrong ?

 

May be there was something wrong, but that would be on the measurement side. We double checked that the cdi was indeed doing what we intended it to do...

 

we are not getting anywhere with this...
lets try this...

we agree.. KLX250R and KLX250 any model has exactly the same parts.
difference is ignition and timing..
there where a few different ignition box and rotors used over the years..
lets go back to 1994.. KLX250R 5 deg. BTDC and 40 deg. advance. that's the rotor and the ignition box.
now take any KLX250, set the static timing to 5 deg, and get the adjustable ignition box (and assume, there will be a useable advance curve in it), and the output will be around 30hp. Or buy rotor and box of a KLX250R.
then put the 36TM carby in the bin, and try a 32mm.. and we get to 32hp out of 250ccm. this is not magic tuning.. this is just going back to standard !!!!
after this..we can add more ccm... and then play with camshafts...and carby

 

It does seem strange that Ray's tests did not indicate any changes. The HP should increase, then fall off after the advance is too far, or at least cause engine ping or difficulties at various rpm's that should show up on the dyno.

On the post by Ray I see only one test, where he said they did about 7 or 8 runs, I would like to see all the test to observe any variances.

I think it would be pretty easy to re-adj the pickup, but I dont have access to dyno. The only down side is that at the lower rpms the timing my be a little too advanced for 1, and if you get pre-ignition, that would be hard on the piston 2.

 

It's just a small 2mm thick piece of metal, 3mm long and 8mm wide if it's as wide as the piece above the surface of the OE rotor. JB should hold it fine as long as you degrease the area where you are going to glue it and let it dry thoroughly..

I might lean towards having a machine shop chuck mine up in a lathe after I glue a piece on and make sure it's no higher than the original piece next to it.

But I'll look at running the bike with the rotor advanced/no key just to see how it responds to the change. I"ll have figure out a way to make sure the move is 3mm once the rotor is off. Looks like afix a pointer near either the F or T mark and move the rotor to a new adjacent mark 3mm away made with a line in some magic marker you've applied to the top of the rotor.

The key way appears to be 3mm wide, so an offset key or machining the Kaw key seems to be out unless half a key's worth adds up to 3mm at the OD

It could be hard keeping the rotor at 3mm advanced while tightening it..?



this rings a little bell seems familiar somehow

 

should be fine, when rotor in position, give it a light tap..and it should sit tight on the shaft, then put the bolt it.

 

And enjoy your instant and free 36% increase in horsepower !

Sorry, couldn't resist.

Let us know how it goes Richard - let's say I'm skeptical but sure as hell would love to be proven wrong. Any idea when you might be giving this a go?

 

I think this might shed some light -

Kawasaki KLX250R

Have a look at the horsepower specs - 30HP.... at the crank.
23.5HP at the rear wheel.

So, just about what a decently jetted and uncorked KLX250S makes - which I just noticed was noted in the second post of this thread - lol

Also y'all be careful if you glue stuff on - anything glued to the outside of that rotor is going to pulling about 7,400 g's at redline.