Ignition settings for cb750 4 cyl wasted spark 2 tach inputs

750essess · Post by **750essess** » Mon Feb 04, 2008 5:29 am

Thanks, I'll try it out and report back

750essess · Post by **750essess** » Wed Feb 06, 2008 6:30 am

I set the offset to -320 and the ang offset to 0 and it doesn't work. I tried calculated and trigger rise. What else could I be doing wrong? It loked like it worked for a few revs then went way off. It did fix channel 2, but i couldnt get 1 to fire correctly

Post by **grippo** » Wed Feb 06, 2008 10:38 am

If it looked like it worked for a few revs and then went off, we may have another problem, which can best be solved by posting a short datalog. When you say it wandered off are you saying that the timing remained good on the second channel, but started wandering off on the first channel ?

750essess · Post by **750essess** » Wed Feb 06, 2008 10:42 am

Yes, channel two seemed fine, but I would get a few pulses on one that where correct then it went way off. If I switched the light to channel 2 it was ok. I will log it tonight.

750essess · Post by **750essess** » Thu Feb 07, 2008 5:38 am

Here are the logs with -320 offset and advance table set to all zero's. The sensors are at approximately 35 degrees BTDC. With it set to calculated 1/4 was way off looked to be more than 90 deg. 2/3 was at TDC. With it set to trigger rise, it fired a few times correctly on 1/4 then went off. 2/3 was at TDC. Rpm readings were both aprox. 300 RPM's. The offset for output number 2 didn't seem to have any effect. I think maybe something is strange with my sensors, or it is not applying the same settings to both channels. My reasoning for this is, if I change input capture from rising edge to falling edge the problem switches channels. It appears that channel one pickup likes rising edge and channel 2 pickup likes falling edge. Would it be possible to make a change so I can set the input capture separately for each channel? Another strange thing is I can physically move the sensor that is off about 10 degrees and it has no effect on were it fires.

Post by **grippo** » Thu Feb 07, 2008 4:40 pm

The deltaTs are all within 1 ms out of 200 ms or < +/- 2.5% variation. There is absolutely nothing wrong with the input captures. So the problem must be in the spark outputs. There is no sense changing the outputs. What you can do though is to repeat the trigger rise run exactly as you did, but change the cranking rpm to say 350. What is happening is that your rpm is a shade over 300, so the processor takes it out of cranking mode and therefore automatically reverts to Calculated, so there is no difference between your 2 runs. (I can tell this by the fact that the 'engine' column stays at 13 in both datalogs.) By setting the cranking rpm to 350, you will keep it in trigger rise mode. Do a datalog just as before and time both channels and tell us what you see.

750essess · Post by **750essess** » Fri Feb 08, 2008 5:09 am

Well, I thought I set that to 500. That very well could be the problem. I'll give it a shot.

750essess · Post by **750essess** » Mon Feb 11, 2008 5:28 am

Moving up the cranking rpm did not help. No matter what i do both channels dont spark at the correct time. What else could be wrong?

Post by **grippo** » Mon Feb 11, 2008 4:30 pm

What did you see when you up the rpm. Was channel 2 still correct and channel 1 wandered off ?

Can you try switching the leads on the first sensor - the one that doesn't work ?

old guy · Post by **old guy** » Mon Feb 11, 2008 7:28 pm

I don't know if this will help or not. Don't do like I did and assume that the shield on the coax in the wire harness is VR-. The inner wire is VR-.