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no timing advance


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my '84 xvz12 won't rev past 2500rpm and the timing isn't advancing. It backfires out the carbs. (this bike was sitting for a while and dead when I bought it). I tested the vacuum sensor and it was 2.3v at standstill but wouldn't go below 1V with up to 26in HG vacuum. One interesting thing was the voltage source to the sensor was 2V lower than my battery (which was only about 12V running). I replaced the pressure sensor with an ebay used part and this part will only go to 0.8V at 26 in HG vacuum. (supposed to go to 0.5V). I've been working on clearing this problem for a little while (already did plugs and fuel and carb cleaning) and during that I have tried the bike with a good battery and it was backfiring the same when reving it. It idles very smoothly. I'll try it today with my truck battery (since I haven't tried it with a good battery since the carb cleaning) but suspect I'll find the same thing and that my problem is electrical with the timing advance and TCI and that low pressure sensor voltage.. does anyone know where that connector is between the pick up coils and the TCI?

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Yup!

You are getting some sort of advance out of your pressure sensor so I doubt it is the problem. Now one remote possibility is someone put an '83 TCI in which works 180 degrees out of phase with the rest of the years. Check the part number, it should start with 41 and not 26...

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  • 2 weeks later...

thanks Both!

 

anyone know how to get my TCI out?? looks like I need to remove the side fairings to hit the battery box mount.. My electronic factory manual is crap. any suggestions ona manual? Clymer or ebay CD from TechSpark?

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thanks Both!

 

anyone know how to get my TCI out?? looks like I need to remove the side fairings to hit the battery box mount.. My electronic factory manual is crap. any suggestions ona manual? Clymer or ebay CD from TechSpark?

 

I removed (and relocated) the TCI on both my '90 and '91 by first removing the airbox, the lower fairings, the radiator "triangular mesh covers" and the black plastic cover over the front head and then using a #3 Phillips bit (one inch insert) in a ¼" socket inserted onto a short handled ratchet, I removed the two "Phillips" head screws holding the TCI. I also removed the two "Phillips" head screws holding the boost sensor. I returned the boost sensor to its factory location after I had removed the TCI. Removing the boost sensor gave me a bit more room to remove the TCI. When I replaced the boost sensor, I used conventional hex head bolts, instead of the OEM Phillips.

Slide the black plastic head cover out the left side of the bike.

One does not have to remove the battery box.

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