None FJ content (Pinging)

[gumby302ho]

 My 2000 XR650L one lunger has been bumped to 670cc. The piston was a 10 1/2 comp piston. My issue is pinging only on wide open throttle. In the thumper forum guys have ran these pistons with zero issues but others do suffer from the ping curse. I was advised to fatten up the main jet which I did. The bike starts great, idles great, the plug looks more like a copper brown color with no evidence of running lean and did not show any black carbon at all? On these bikes there is no adjustment for timing control unless going aftermarket or butching the pickup which I hear there is not much room for error. The bike only pings on wide open throttle, its like the last quarter throttle when you roll on that it does it. Not sure what to do. Should I go fatter main jet and see, would shimming the needle help at wide open throttle, trying a brand new cdi, what do you guys think? Ps Thank god for my FJ, at least when I go to him he is solid like your best friend from early childhood.
           Don

[fj1289]

Have you tried a cooler spark plug? 

If you can't back off the ignition timing easily you really only have a couple choices - fatten up the main a bit more or maybe stack 2 head or base gaskets to drop the compression some.  (Problem with doubling up the gaskets is it can make the pinging worse sometimes if the quench height was right where it needed to be and then you open it up a bit.  BUT it is rare for the quench height to be right on in a production engine unless you had it machined to set it up that way.)

I wouldn't mess with raising the needle if the mid - upper mid range is good -- just focus on the main jet.  Then you may actually have to lower the needle depending on how much you increase the main.   

[a.graham52]

Make sure your running high quality, high octane fuel as well.

[FjLee]

I don't know if you've increased comp. on this thumper engine. 

NGK sez this:
As compression increases, a colder heat range plug, higher fuel octane, and careful attention to ignition timing and air/fuel ratios are necessary. Failure to select a colder spark plug can lead to spark plug/engine damage.

FjLee

[Flynt]

I'd recommend you go bigger on the main...  it's pinging (going lean) near WOT means you need more fuel for the amount of air the engine's moving.  That's a bigger main.  You can detune to compensate, but you need to get the AFR right before anything else in my opinion.  It all starts with getting the right main.  Hell, you might be able to crank in more timing if it's not pinging at low RPM...

Frank

[gumby302ho]

I'd recommend you go bigger on the main...  it's pinging (going lean) near WOT means you need more fuel for the amount of air the engine's moving.  That's a bigger main.  You can detune to compensate, but you need to get the AFR right before anything else in my opinion.  It all starts with getting the right main.  Hell, you might be able to crank in more timing if it's not pinging at low RPM...

  So what your saying Frank is maybe my motor could possibly handle a little more initial timing advance in the lower range rpm for some more hidden steam in my single thumper! Its the honda RFVC motor, my motor comes factory 8.3 to 1 comp, they are air cooled tough motors but do not like to be modified. There is no timing ajustment for these motors and they are reliable dogs, dogs as in zero hp, they have tractor like torque but are still dogs so there is a series of mods they do to them. Some are running higher comp piston with same setup as I with zero ping. I will take your advice and open up the main some more and keep my fingers crossed. Thanks again for all the suggestion from all of you gents.
                                   Don