Can electrical parts cause detonation?

[252wheelieking]

Seen issues with some of the CDI boxes around the same year as your machine. Yamaha released a few that had an advanced timing curve

thanks brandon...that makes a whole lot of sense right there as to whats happening to my engines. There is a reason why they only made them for two years & I always wondered why...This must be the reason. Do you know where I should set my timing plate if I have one of the advanced timing CDI box's? how much timing was advanced on the 95-96 year CDI box's?

Edited April 9, 2012 by 252wheelieking

[Mustang_Gay81]

thanks brandon...that makes a whole lot of sense right there as to whats happening to my engines. There is a reason why they only made them for two years & I always wondered why...This must be the reason. Do you know where I should set my timing plate if I have one of the advanced timing CDI box's? how much timing was advanced on the 95-96 year CDI box's?

 

 

So wait!!!

 

Youre running a cdi with an advance in the timing curve already as well as the timing plate advanced?That would definately be a source of detonation.

 

However if you had 2 cranks done by reputable builders id say your cases would have to be the issue.At the very minimum id have the cases lapped so they matched.

 

Also it could be a rare one off issue maybe the mold shifted a little when it was casted and offset the crank?Cranks do flex under loads.

 

when you assemble the engine does the rotating assembly spin freely?Does it drag any where when you spin it over.

[Larry's Shee]

So wait!!!

 

Youre running a cdi with an advance in the timing curve already as well as the timing plate advanced?That would definately be a source of detonation.

 

However if you had 2 cranks done by reputable builders id say your cases would have to be the issue.At the very minimum id have the cases lapped so they matched.

 

Also it could be a rare one off issue maybe the mold shifted a little when it was casted and offset the crank?Cranks do flex under loads.

 

when you assemble the engine does the rotating assembly spin freely?Does it drag any where when you spin it over.

Lapping cases and mold shift would have nothing to do with it. The two halves are assembled and then the shaft bores are bored into cases. Don't know about that particular run of cdi, but I could see where a box could get "stupid" and not retard timing after midrange advance.

[Coupelx]

Lapping cases and mold shift would have nothing to do with it. The two halves are assembled and then the shaft bores are bored into cases. Don't know about that particular run of cdi, but I could see where a box could get "stupid" and not retard timing after midrange advance.

 

ding ding ding!

[blowit]

I did not make it through all the responses but thought I might throw some hints out. A stator has nothing to do with detonation at ALL. However, the pulse generator does. The PG timing is VERY relative to the clearance gap it has. The main issue here is the assumption that if you set your stator plate at X degrees timing, you think you have X when you have Y. The wind of the PG makes a difference in the voltage rise of the PG pulse back to the CDI which then determines the advance.

 

As with all digital ignitions, there is mechanical and electrical advance. The CDI advances ignition relative to TDC regardless of stator plate adjustment. The plate moves everything up but the CDI is constantly changing the advance.

 

Detonation can still occur at a plate adjustment of 0 degrees if things are not built or adjusted quite right. Somewhere around here we have the CDI timing curves relative to RPM but IMO, the timing light is the magic tool to end the madness. It does not care who did what, all is cares is when the plug fires, I fire my strobe and that strobe will tell you where the crank is when it fires. And because the Banshee did not know what 3D mapping was, throttle position does not care at all, just RPM.

 

As always, I recommend you all customers to start with 0 degrees plate timing and move up from there in 1 degree incs. Just because one bike is set at 4* and another at 8* does NOT mean the actual plug timing is that different. The PG is a rather stupid device. They are proven rugged but IMO, there are much more accurate ways to relate crank position to the CDI like optical. I was really surprised to see the new EFI wave in ATVs follow with the PG ignitions. I figured they would be a little cockier than that.