cr ignition timing

[hartwill]

hey guys, I have a 92 cr 250 ignition on my 330, the thing runs great on idle and anything past 1/3 throttle but from 1/8-1/4 you can hear detonation. I thought maybe it was jetting but it runs good down on idle and I have only blipped the throttle real fast up to WOT. I am running a 52 pilot and a 200 main with a CEL needle in the richest clip position. I then machined my adaptor plate to retard the timing even more, found TDC with a dial indicator, scribed a line on the fly wheel and on my case outlined it with soap stone and ran a timing lite. the timing was showing up about 8*-10* before TDC at idle and would move counter clockwise as you reved the motor which if im correct would be retarding the timing at higher RPM? The only time you hear the detonation is under load, if you rev it in neutral it seems to run perfect. I think tomorrow I am going to switch back to my stock ignition and see if that solves my problem. I also have a 2002 cr250 Ignition but I am kinda hesitant on using that one also because the 02 doesnt seem to have too much research done with it.
any help you guys might have would be much appreciated. thanks in advance guys.

[efi2]

This is not going to help you at this time .
I ran a cr 2002 ign, had a lighting wiring .
I was running v-force the 1st style,I smoked the reeds on that .
I do not know if it was caused by the ign or not. people on the forums said they were v-force 1 and they had reed breaking problems
I had a race so went back to stock .later found out the adapter I bought was not made correctly. Just had it machined down so the adapter would not push the seal to far in. 5MM TOTAL DEPT.
HAVE A RACE NEXT WEEK 4-22
Hope to have it done in time ,it has been a very bad year for me.the people around me are not helping-personal problems .
So I going try using the 2002 ign and time like you did with a dial indicator.
I'LL LET YOU KNOW WHAT HAPPENS.

[hartwill]

thanks man, keep me posted.
Anybody know the timing difference between 2001 and 2002 cr250 ignitions?

[wilkin250r]

Originally posted by hartwill
8*-10* before TDC at idle and would move counter clockwise as you reved the motor which if im correct would be retarding the timing at higher RPM?

This is standard for 2-stroke motors. At low RPMs below the powerband, you get a very inefficient filling of the cylinder (duh, that's why you're not in the powerband), and there's often a lot of exhaust still in the mix as well. This poor mixture and low pressure doesn't burn really well, so you need a significant timing advance to start the burn early.

When you get into the powerband, you have a better mixture and significantly more pressure, which will burn faster. As a result, you need to retard the timing to compensate for it.

As RPMs increase even more, you need to start advancing the timing again to compensate for faster piston speeds and get the combustion to occur at the proper piston placement.

So the end result is that you have a lot of advance at low RPMs, very little advance in the meat of the powerband, and then a lot of advance again at higher RPMs.