Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: bower100 on April 28, 2013, 05:37:38 AM

Title: 1980 YZ250 ignition timing.
Post by: bower100 on April 28, 2013, 05:37:38 AM

 Finishing up my rebuild of this vintage bike, I realized I'm a little stuck on ignition advance setting. Unlike an RM, the YZ has no match marks between  the O.D. of the stator plate and the engine case. Instead the yz  ROTOR has a dash mark as does the ID of the stator plate  . Obviously they are to line up at some piston position. Hoping some old YZ owners might just be able to give me the spec and procedure. Are the hashmarks to line up at TDC or a "x" demention BTDC ?  No guessing here please .... only out of your manual or your experienced brain.

Thanks much guys, dave

Title: 1980 YZ250 ignition timing.
Post by: SachsGS on April 28, 2013, 08:04:05 PM

I use the stock timing marks for reference only. Dial in the ignition advance until the motor is "happy", pinging and excessive kickback at the kickstart will tell you that you've gone too far. I've worked on Euro bikes with no timing marks or flywheel keyway, everything is done by ear and seat of the pants.

Title: 1980 YZ250 ignition timing.
Post by: 2T Institute on April 28, 2013, 10:54:22 PM

Is it a Hitachi ignition with a inner rotor? If not your timing will be around 2.2 to 2.4mm static.

Quote from: SachsGS on April 29, 2013, 03:04:05 AM

I use the stock timing marks for reference only. Dial in the ignition advance until the motor is "happy", pinging and excessive kickback at the kickstart will tell you that you've gone too far. I've worked on Euro bikes with no timing marks or flywheel keyway, everything is done by ear and seat of the pants.

Try a timing light they tend to be a bit more accurate 

Title: 1980 YZ250 ignition timing.
Post by: SachsGS on April 29, 2013, 03:44:42 PM

Factory timing is always conservative - dial in a little more advance. 

Title: 1980 YZ250 ignition timing.
Post by: bower100 on April 30, 2013, 01:35:32 AM

It is a  Hitachi ignition, an internal "button" rotor. ('80 YZ250).
     Playing around with different possibilities looking for clues to what's possibly right.... when I set piston @ TDC and then line up dashmarks on rotor and stator there happens to be a punched dot mark on the stator plates O.D. that also lines up with a edge of the engine case. This might be some P/O's attempt to mark where stator goes,( or it might be a factory punch , I dunno).

Any 1980-'81 YZ owners out there that are familiar with Yamaha's marking methods? dave

Title: 1980 YZ250 ignition timing.
Post by: 2T Institute on April 30, 2013, 02:27:17 AM

All the Hitachi ignitions are similar on the rotor 1 mark will line up with TDC and the other will be close to the manual stated  "X.XXmm BTDC" figure. There will be an number on the CDI and on the rotor. Check they are correct as the same ignition did 80,100.125 and 250 (400 maybe even) the keyway slot and the numbers seem to be the only differences

Title: 1980 YZ250 ignition timing.
Post by: riffraff on April 30, 2013, 03:29:48 AM

Check the guys at yamahait.com.au somebody there will know exactly what you need

Title: 1980 YZ250 ignition timing.
Post by: 2T Institute on April 30, 2013, 03:53:57 AM

80/100/125 is 1-1.2mm, 250 is 2.2 to 2.4 and 360/400?? is 3.4or 3.6mm btdc static across the Hitachi ignitions.

IT forum fell over is it back up now?