Timing curves for XJ750 ? (it's an 84 model - 45T)

Does anyone have the timing curve for this engine? (ie. advance vs rpm) A friend has offered to build me a programmable ignition module to replace the TCI and I'd like to keep the timing stock. He needs the figures to put into the chip. Any assistance appreciated.

 

I don't think there is any advance on the timing on these bikes. If you look at the pick ups and coils inside the left engne cover nothing moves. (at least on mine). Does your bike advance timing? You could put a timing light on it and see what it does through the RPM range. I would be interested to see what you observe on your bike.

 

They most certainally do have an advance. It's done electronically by the TCI.

 

Yes, MiCarl that's what I am trying to find out, by how much and at what rpm. Older IC engines used mechanical weights which flung out with centrifigual force to move the points plate around but my XJ does this with the TCI, which we want to replace. If all else fails we might have to rig up some sort of bench test to find out what it's doing.

There doesn't seem to be any vacuum (ie. engine load) sensor anywhere. The TCI can't possibly be aware of engine load then, is this correct? It would be quite easy to fit an automotive MAP sensor to one of the vacuum ports to compensate for load. We will be able to run a three dimensional timing curve, ie. advance against rpm and a different curve for each load condition, but what values to use????? I don't want to reinvent the wheel, just want to replace troublesome old electronics with something far more reliable.

 

Iandmac.............what is the ID code on your TCI? It should say something like TYPE TIDXX-YY. From that ID code I might be able to provide you with the advance specs, if I have it in my database..........

 

From the top cover:

IC Igniter
TID14-21
29R-10 300

Hitachi, Japan etc.

Hope that helps

 

Here you go:

TCI:
TID14-21 Hitachi
Initial Timing: 7* BTDC @ 1050 rpms
Total advance: 37.5* BTDC @ 6000 rpms
7* +/- 1* at 1050rpms
9* at 1600 +/- 225 rpms
24.5* at 2600 +/- 300 rpms
30.5 +/-2* at 3500 rpms
37.5 +/-2* at 6000 rpms

 

Thanks Len, just what we need ! I think the biggest challenge will be fitting it into the available space.

 

awesome info!!!

 

Hi
I have a 45T as well & I got a great aftermarket TCI unit off these guys in NZ. Bike goes like a rocket

http://www.erd.co.nz/products/xjfj.html

 

Hey, G'day from BrisVegas, lol ... since putting up this post I found the curves in the factory manuals ... I didn't know about these guys back then either but they look like they have a good product, do you think it's stock tuning though? I'd like to see some pics of your XJ when you get a chance, cheers, Ian

 

Hi Ian
I got my TCI unit a few years ago now & in discussion with them I believe its an improved timing curve.
The guys I ride with keep asking if my bike is really a 900 ?? Just reacently we rode to Brisvegas , while travelling up Thunderbolts Way the guy on a Blackbird with us didn't want to come past me he said I was sitting on 200ks.



I'm actuall going to restore the 45T back to original & make the 900 the chopper.
Cheers Andrew B