Motorcycle Repair: Honda 1200 SE 1985, crankshaft sensor, camshaft sensor

Question
Subject: Honda 1200 SE 1985


Sir,
I have the above mentioned Bike and am having a problem that I thought you might be able to help with.


1.      The bike starts like a charm
2.      It idles well although not in advanced idle when starting cold as the book says and slightly erratic from 850thru 1000 and then settles about 950
3.      I have changed the Cam shaft angle sensor as it was way out of Hondas limits and changed the leaky seal.
4.      I have changed the crankshaft sensor as it had a open circuit. Prior to changing the bike would start but fired right away when changed.
5.      I have checked most everything else but my problem is that when trying to snap the throttle it hesitates and then the RPM ramps up, The same thing happens when         taking off from a stop, it hesitates and then takes off. After getting up to any speed when you hit the throttle it seems to be fairly decent but not what I think it used      to be. I have checked the timing with the light and can see the marks advancing, but because of the position of the hole and angle of looking I may not be reading      it well.
6.      When my problems first started the computer gave me a fault for the crankshaft sensor and after changing it the computer then said the camshaft sensor. After   changing both of these units the computer goes through it's self check and then gives no lights or faults, so it appears to be working OK. I hope!


I am just about at my wits end and as we have Honda dealers here in Ottawa, Canada, we do not have anyone who is really knowledgeable on the SE and most can only go through the Honda faults check list to which I get the feeling applies mainly to a new bike and not something that's been on the road for awhile and that the factory could anticipate.


Sorry for being long winded.


Jack Johnson
Ottawa, Canada  

Answer
Jack, I got out of the business before FI came into being for motorcycles. I checked the web briefly and found few references to this bike, as it was a one-year only edition.

If all the electronic concerns are covered in the self-test mode, then you have to look for mechanical issues, assuming that this was not an inherent problem with these bikes. I don't know if there is a way to reprogram the computers on this model. When you crack the throttle open, there is a huge lean condition that has to be instantly corrected by the FI system. Some early FI systems, even for cars had limited mapping and conditions could not be corrected if you changed a component like mufflers or air cleaners.

I would look at the linkage between the two banks of throttle bodies and see if you can determine that they are both opening at exactly the same time. If there is an adjustment in the linkage, perhaps you can fine-tune the linkage.

One of the fuel injectors could be partially plugged (no different than a car). Perhaps they can be removed and cleaned individually, or some FI system cleanser can be inserted into the fuel rail system to facilitate this issue.

Verify fuel injection line pressures. There is a pressure regulator that controls line pressure.

Check every vacuum line and vacuum-operated component for diaphragm failure or leaks. If you can find someone with a dyno, perhaps you can check the air/fuel ratios when you are going through this transitional air/fuel ration period.

Bill Silver