Tech Info: Detonation & Pinging

[Bigbird]

OK here are a few of the heads I have laying around my garage, have a look at the differences between the three squish areas...

1983 YZ490K


1992 WR500Z


1982 IT465J


You can clearly see why the IT465 doesn't ping, the squish area is a lot more open chamber than the other 2.

BB  

[Jock]

KUDOS to Bigbird on this post. All you big bore owners out there should take note on this one. 

[Jasonit490]

Have done head mod to my 490 that BB posted a while back but have not finished putting bike back together yet to see if any different, also rejetting carby as well, just a quick note you can not get a 3.5 slide for 490 stock carb unless its right hand idle screw.

[b490]

 Did the head mod to my IT490K ,played with jetting (was too lean) & run BP 98 oct fuel  ; big improvement