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View Full Version : changing timing with off-set keyway



h1dave
01-24-2005, 06:20 PM
hello all

i have a 04 cup bike with lomas pipes and high flow filter. after the change
to the pipes the butt dyno showed a big gain..... :micah: my ??? is it worth
the 50 bucks to put a off-set keyway for 3 to 5 degrees more advance??

i'm doing mods as i can afford them....next will be the o-ring heads with
new pro-x pistons......

thanks

dave

h1dave
01-25-2005, 08:08 AM
bump :confused:

colinskillicorn
01-25-2005, 09:25 AM
You can file 1mm off the side of the woodruff key that sticks up from the crank then turn the flywheel clockwise on the taper to get the same effect without any expense done this to quite a few motors with good results

h1dave
01-25-2005, 09:01 PM
hey colin

is there any chance that the key will break with 1 mm filed off it ???

i was going to do that but af1 said it might shear...............

thanks for the reply

dave

Racer XXX
01-25-2005, 10:36 PM
It would have the same strength as the off-set key which I believe AF1 sells.

Colin, I am confused about the rotation. If the flywheel rotates counter-clockwise with the engine running then you would want to move the flywheel counter-clockwise to advance.

h1dave
01-25-2005, 11:15 PM
racer x

moving clockwise will advance the timing( spark earlier ) for a better burn :cigar:

Racer XXX
01-25-2005, 11:24 PM
Dave, which way does the flywheel rotate when the engine is running?

VinCBR900
01-26-2005, 04:23 AM
H1Dave, it is the quality of the taper that holds the flywheel in place, thats why you need a puller to get it off. The Key just positions the flywheel for you to tighten the nut up, so as long as the tapers are good then the filed keyway isnt a problem.

I sometimes use fine grinding paste to lap my flywheels on if they keep coming loose - you often find some monkey has knocked the flywheel with a hammer to get it off instead of using a puller, and no matter how you tighten the nut it still comes loose. Grinding and restoring the taper solves this problem.

Cheers, Vincent

Vincent

colinskillicorn
01-26-2005, 04:23 AM
Won't shear as once the flywheel is locked up on the taper the woodruff is under no stress

The motor turns anticlockwise when runing & as dave say you want to advance ie start the burn earlier so you turn it clockwise

Regards CS

h1dave
01-26-2005, 07:46 AM
all i can say is you guys are the best!!!!!!!!!!!!!!!!!! now, how do i get that

damn flywheel off without that special tool ?? my puller wouldn't budge it.

thanks
dave


deal's gap 2-stroke meet is may 11 thru 15 !!!!!!!!!!!!!

www.tailofthedragon.com

Racer XXX
01-26-2005, 12:58 PM
You could get a monkey to knock it off with a hammer.


Moving it clockwise would retard the timing!

twocycler
01-26-2005, 02:49 PM
EXCELLENT advice guys about the filing of woodruff keys and crankshaft/rotor taper. All right on the money.

On the RSV, the output shaft for the ignition does not even use a key. You position the rotor and lock it down. The taper holds it. Yes, I also use fine valve grinding compound to achieve a non-slip fit.

You HAVE to file keys to allign the dual crankshafts on the RSV. It takes alot of time to get them perfect and I have filed alot of keys. You can simpy hold it with vise grips and file away. And yes, more advance would mean movement away from direction of engine rotation.

Rocky Stargel
Team Stargel Yamaha

Racer XXX
01-26-2005, 04:55 PM
If the metal strip on the rotor passes the pick-up later(turning it clockwise) how does this advance the timing?

h1dave
01-26-2005, 08:16 PM
you might be right. moving flywheel to the left will advance timing......i think


with motor running, it turns counter clockwise....so remove material from the
right side of keyway when its on top 12 o,clock position, and rotate to the left will advance timing, spark earlier than before for more balls :nutts:

Yard Sale
05-08-2007, 12:32 AM
I got the Factory Pro FZR400/600 advance kit, complete with useless flywheel puller and lame instructions. The poor directions say to insert the key with the offset to the left.

OK, for starters, let's assume we're on the left side of the bike, looking at the rotor and crank, with the woodruff key insert at 12 o'clock.

With the key inserted, is the wider part of the key supposed to be on the left or right?

(Kinda worries me that some of you don't agree on which direction advances and which retards...)

sameshoz
05-08-2007, 05:02 AM
If crank rotation is anti clockwise, to achieve spark advance you would need the flywheel turned in the same direction as crank rotation.

Otherwise you are retarding it as the crank will have to spin that 1-5 degrees more before firing.

evenace
05-08-2007, 08:18 AM
I agree with Sameshoz, for anti-clockwise engine rotation you would want to turn the flywheel to the left for more advance so you would file off the woodruff key on the right so you could rotate the flywheel a little more to the left hence making the spark earlier because it would reach the pick up point that small degree earlier.

I agree only because that seems the most logical explanation. I dont see how turning it the opposite direction to the direction of engine rotation could possibly advance the timing. It would retard it wouldn't it?? I am a bit confused myself now... Please help!

sameshoz
05-08-2007, 08:24 AM
As above^^^^

File right hand side of woodruff key, to shift flywheel anticlockwise for anticlockwise spinning cranks.

mikemx50
05-08-2007, 08:33 AM
what are the pro's and con's of advancing the timing? as i got a advancing key with a race pipe i bought for my 125.

sameshoz
05-08-2007, 08:36 AM
If it was an arrow pipe and it was for an RS or MX125.

Don't bother putting it on. You will only end up blowing it up. The one that comes with the Arrow pipe advances it way to much.

mikemx50
05-08-2007, 09:38 AM
:cheers: thanks 4 the reply, just out of intrest though what are the benefits of advancing it on the rs250's ?