TCI Timing Tweak

[5twins]

I like to retard the timing on these bikes a little bit, just a couple of degrees. On the points equipped models, it's no problem, you simply adjust the timing plate. On the TCI models, there is no adjustment provided, but that doesn't mean it can't be done. And it turns out, it's pretty simple. To change the timing, you have to move the pick-up a little. It mounts with 2 screws, one on top and one on the bottom. To move it, you only need to slot the top screw hole a little, maybe half a hole width. You do nothing to the bottom hole, the pick-up just rotates on it.

The idle timing for the points bikes is given as a range, 13°-17° BTDC. The timing marks on the alternator show this range. The actual "F" mark is in the middle of it and would be 15° BTDC .....

I set mine up so it fires over by the right slash mark, so about 12° to 13° BTDC. The idle timing spec for the TCI bikes is not given as a range, just a single 15° BTDC value, probably because there is no means to adjust it. But, the "U" mark for idle timing on the TCI timing plate does indicate a range. If you check your timing, you will usually find the rotor mark falling about in the center of the "U" mark, or at 15° BTDC .....

So, to retard this a little, get it to fire over on the right "leg" of the "U", we need to rotate the pickup to the left slightly, away from the direction of engine rotation. This makes the magnet on the rotor contact the pick-up a little later as it's spinning, and that retards the timing. Here's my modded pick-up, rotated slightly to the left. You can see how the top mounting screw is now off center slightly in relation to the 2 little tabs on top .....

To slot the top hole in the pick-up, I used a Dremel #194 1/8" high speed cutter .....

https://www.amazon.com/Dremel-194-High-Speed-Cutter/dp/B00008ZA00

You slot the hole to the right so the pick-up can be rotated left .....

And here's what my timing looks like now, firing over at the right "leg" of the "U" and slightly retarded .....

Besides warding off possible pre-ignition and pinging, I think these bikes run better like this, slightly better performance at high speeds and RPMs. The idle speed will drop off slightly but it's a simple matter to just turn it back up a little with the idle speed adjusting screw. The idle will also sound a bit more "lumpy", but that's OK. I like it, lol.

 

[Jim]

Nice write-up. I'm curious, what year are we looking at? On my 80SG, there isn't a "horseshoe" mark... just a single fire mark.

 

[5twins]

Mine is an '83.

 

[Jim]

Seems to me that retarding a few degrees would also make life a little easier on the starter. You notice any change in ease of starting?

 

[5twins]

Now that you mention it, maybe I do. But that could be due to more carb work (another cleaning) and/or me just better getting the hang of starting this one. It acts a bit differently than my '78. It likes throttle rolled into it almost immediately after you start cranking.

Checking shop manuals, it seems the "U" mark on the timing plate came along in '81, along with normal screws replacing the "tamper-proof" ones on the pick-up.

 

[Paul Sutton]

Nice document 5Twins - Thank you.

Note: I did not follow this route because I had easy access to higher octane fuel close to home. But if I lived my life again I would follow this guide of yours and stick with Regular unleaded which is more easily obtained a distances farther from home.

 

[xjwmx]

Some pickups are already slotted with a nice long slot. Don't know what years or if it's random. If you have to slot it yourself, use something fast like a diamond burr in a dremel, so it doesn't heat up so much. My '81 is retarded to the max within that horseshoe and it solved preignition, sounds a little throatier maybe, feels the same. No downside I know of.

 

[aldo5468]

Now that you mention it, maybe I do. But that could be due to more carb work (another cleaning) and/or me just better getting the hang of starting this one. It acts a bit differently than my '78. It likes throttle rolled into it almost immediately after you start cranking.

Checking shop manuals, it seems the "U" mark on the timing plate came along in '81, along with normal screws replacing the "tamper-proof" ones on the pick-up.

Did you happen to check full advance to see if it pul

led back slightly from the left edge of the notch?

 

[xjwmx]

Yes, everything goes back the amount of the slot.

 

[5twins]

No, I didn't check it at full advance, but as XJ said, it should show the same amount of change that was made at idle. The advance on these is a set amount, 25° I think, so where you set idle timing will determine where full advance timing ends up.

The timing specs on these were slightly different on the very early models, a little bit more retarded. Idle timing spec was 10°-15° BTDC instead of 13°-17°. Full advance was 38° BTDC instead of 40°. So basically, we're just reverting back to the original specs. Here's a tech bulletin about the change .....

The bulletin mentions the change was done to improve idling but honestly, I kinda like the lumpier idle, it sounds cooler, lol. But also as I mentioned, I think the bike performs a bit better at higher RPMs like this too.

 

[aldo5468]

No, I didn't check it at full advance, but as XJ said, it should show the same amount of change that was made at idle. The advance on these is a set amount, 25° I think, so where you set idle timing will determine where full advance timing ends up.

The timing specs on these were slightly different on the very early models, a little bit more retarded. Idle timing spec was 10°-15° BTDC instead of 13°-17°. Full advance was 38° BTDC instead of 40°. So basically, we're just reverting back to the original specs. Here's a tech bulletin about the change .....

The bulletin mentions the change was done to improve idling but honestly, I kinda like the lumpier idle, it sounds cooler, lol. But also as I mentioned, I think the bike performs a bit better at higher RPMs like this too.

I'm probably just being obsessive-compulsive about it. I had slotted the top hole in my TCI pickup many years ago after reading some of XSJohn's musings about retarding timing a bit back from 40 degree full advance, seemed pretty desirable and straightforward to do. Later on, I had to replace the original rotor in my '82; installed a Racetech, which worked fine; sometime after that got motivated to do a piston-stop TDC check and found that at true TDC, the TDC indicator mark on the Racetech was mis-aligned with the TDC mark on the timing tab by several degrees. My timing tab is movable, so that was easy to re-align - I was just concerned that the effect of trusting it when I first installed the Racetech was to put me back at or possibly over 40 degrees full.

 

[xjwmx]

Here's a pic I had of one with a slot from the factory, FWIW. No idea why I took a picture of it...

 

[5twins]

Wow, that's one heck of a slot, lol.

 

[xjwmx]

Yeah, longer than strictly necessary. To get it (for a spare) I bought a stator with it attached. The screws were different than in my non-slotted pickup/stator I already had. I don't remember any detail at all, just that they were different (and looked original).


P.S. I think I remember a mod, or maybe I'm full of it, where you can grind off the left cover a bit of just the lip the circular cover goes on. That lets you get a screwdriver on the upper screw without removing the left cover.

 

[nj1639]

Yep, grinding a bit of the lip that the alt cover sets in, XSJohn mod.

 

[Bushyeyed1]

@5twins have you done this on any of the tamper proof CDI units? I am curious if it has threads under the tamper proofing.

 

[azman857]

Yes they do have threads. The SG had a tamper proof fastener on the pickup and I ground off the head. There are threads in the hole.

 

[Bushyeyed1]

Yes they do have threads. The SG had a tamper proof fastener on the pickup and I ground off the head. There are threads in the hole.

Nice thanks for the info

 

[gggGary]

They are screws with "tamperproof" heads, guess I'm a next level "tamperer". Grab a dremel with a cut off wheel, cut a slot in the head, done, it's now a normal screw.

 

[xjwmx]

My picture of the factory-slotted pickup above, I must have taken the picture right before I put it on the bike. No reason for taking the pic that I remember, but I wouldn't have had it out just to take the pic. I went out one morning and the bike wouldn't start, just backfire like a rifle, and I traced it to an open pickup coil. Interesting thing is she has never ever left me stranded -- amazingly the pickup was just broken in the morning when I went out. On the other hand, it caused me to miss a date to go to a concert that afternoon.

She is faithful but she is jealous.