TCI Replacement 2020 It Works

Before I start filing my pickups, what would the downsides be with running with low advance for a while to continue the experiment?
With it not advancing to 35° you're gonna be slightly down on power and your mileage will be down. But.... it's not gonna hurt anything to run it like that.
I would definitely not do any re-jetting until you get that 35° advance.
 
You can bias towards the advance position and be a little advanced at idle, long as you don't get to "kick back" idle timing it'll be fine.
Exactly. How far you can advance the idle is still an unknown. I have bum knees and can't use the kicker. We could use a little feedback here on how the kicker behaves when you get the full 35° advance. I've filed the trigger to where I'm getting 34° advance and the elec starter handles that just fine. We need feedback on how the kicker handles it.... anybody?
 
So I have some preliminary success with the GN250 module for my 81. Wired exactly as Jim shows (above.) Starts and Idles. Timing exactly on the idle mark. So far so good.

I am jetted for my exhaust and K&N filters in stock airboxes. I haven't mounted the module yet, so was running with the bare carbs. It won't idle without enricheners (choke) without the airboxes. I fooled enough to get some center stand races going and saw that the advance kicked in.

So the GN250 module only has a limited amount of advance. (30 degrees?) Before I start filing my pickups, what would the downsides be with running with low advance for a while to continue the experiment?

Thanks, guys for all the hard work!

Matt

Hey so I was having the exact same issue and I switched the pick up (+) wire and pick up (-) wire around and now my bike runs fine. Worth a shot!

Update on my bike from today. I put about 20 miles on my Gonzo box and the bike seems to be doing great. I have some break up issues but I believe it’s the crappy K&N pod filters that are on there. I’m waiting on a set of UNI pods to come in to see if that helps and if not I’ll be sourcing a set of stock air boxes.
 
So I got the airboxes on and was able to take a short ride today. It runs, but not quite right. Bad bogging between 3-5k rpm under load and throttle. Once it gets to 5k it opens up. My son asked: "How much of the time are you between 3 and 5k when riding?" Almost all the time, buddy. :-/

The module I ended up with has neither side of the crank pickup grounded inside the module. I'll get on switching the crank pickup leads. More to come.

Matt
 
Well, I got the wires switched, and it seems different. One thing is now I have a kick-back problem. Almost to the point I am concerned about kicking it. The other is that it is really advanced. Here is idle: (looks right to me)
upload_2020-9-12_16-59-29.png

Here is 4 or 5k:
upload_2020-9-12_17-0-31.png


What am I doing wrong?

Matt

PS - My son says the pictures are worthy of an art gallery. ;-)
 
The left side of the drain slot is the 40° mark. Try retarding the pickup 3-4°. Rotate it to the left... ccw.
40° is acceptable (that's the original spec) but if it's kicking back, try to retard it. Might mean filing the slot in the pickup.

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Yes, that 10/35 spec for the GN250 is showing that the ignition is giving 25° of advance between idle and full advance (35 - 10 = 25). The stock 650 gives the same amount but it's idle/advance settings are 15/40. Where the firing happens depends on where the pick-up is located. Obviously the 650 pick-up is mounted in a slightly different spot than the GN250 one.

So, your pics seem to indicate the GN250 box is acting as designed, giving 25° of advance between idle and full advance. But many of us feel that the full advance setting of 40° is a bit much. It can cause pinging. So, we like to retard it a few degrees, set the idle timing at 12° or 13° to give a full advance of 37° or 38°. That's easily accomplished by slotting the top mounting hole on the pick-up a little bit. You only need do the top hole. The pick-up will just rotate on the bottom screw to the new position. It doesn't take much. You only need to slot the upper hole about half a hole wider. That's enough to change the timing that 2 or 3 degrees required .....

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So I decided to run the module tests I found in a GN250 manual on the module today. (Page below. Yeah, it's hard to read.) Every resistance (except open circuit) test came up bad. One interesting thing did happen. When I applied power to (2) and ground to (6,) 4 went to ground. Not sure what that means, but it's a data point. Perhaps I should re-do the resistance test with power to the module?

Any thoughts? (Other than get another module...)

A side thought is about the resistance test on the GN250 is 160-240 Ohms. XS pickups are 700 +/- 10%. Perhaps we need a resister in parallel?

Matt
2020-09-14_GN250_ignition_testing.JPG
 
That may be due to the slightly less full advance setting. The early bikes had a few more horsepower and one of the differences between them and the later models was that their full advance setting was a few degrees less. I think my bikes run better with the timing retarded like this. They seem to run stronger in the high RPMs and at high speeds.
 
I'm new here and just joined up because of this info. This is all fascinating. I want to try this on an sr500. They already use a magnet in the rotor and a trigger coil, along with a very rare and expensive cdi unit. I'm curious though, did you try one of the gy6 cdi boxes? I understand they give around 20 degrees advance.
 
A side thought is about the resistance test on the GN250 is 160-240 Ohms. XS pickups are 700 +/- 10%. Perhaps we need a resister in parallel?
Pickups produce voltage.I would think a 700 ohm coil would put out a fairly high voltage compared to something in the 200 ohm range. Maybe it cooked it?
 
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