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I had a pretty advanced plan for a gear indicator on the Bandit, using a few colored led's in patterns so they'd be obvious in peripheral vision. But I wrecked that bike before starting on it. The current ride has a gear display... its fine, but not as useful as it seems, I guess because I...

Heck I can't even give my '82 Seca away and I've tried twice; 2600 original miles, thoroughly overhauled and everything working. I suckered myself into buying it, not the faintest hope of getting even a quarter back of all the money I've sunk into it. Doesn't matter tho- I was given my old...

Every part you remove adds risk of damage (eg breaking a trace or an adjacent part), so its helpful to focus on likely sources of failure. 30+ yr old electrolytic caps are somewhat prone to failure, but its interesting how many don't. I have seen a just a few cases of failed resistors, but...

No sign of heat damage on the bottom of the board. Those caps don't look failed- that goop on them is the conformal coating which helps prevent vibrations from fatiguing the solder and when properly applied, helps prevent moisture intrusion. If the caps leaked electrolyte, it would be big...

C20 doesn't look like its swollen OTOH electrolytic caps can fail in a variety of ways- a closeup definitely necessary to tell more. Same with pin 2 of the IC- that does look weird. The oxidized resistor leads don't bother me, assuming the solder joints are good.

Nothing looks blown up from this perspective- that goop all over is conformal coating. If something did burn out I'd be expecting burns/melting on the inside- more than a spot. The move would be to remove the screws and lift the board to check the back side.

Yeah, like he said :thumbsup:

Measure the resistance of both pickup coils- both should be between 100 and 600 ohms or so, measured to ground. If either is open or shorted there will be no spark. You can do it at the end of the harness that plugs into the TCI.

Your latter point is approx correct. The shared throttle screw sets idle, with the AF screws set reasonably and the carbs synced. The AF screws tweak the air/fuel mix mostly at idle but they do account for maybe 10% of the mix with the throttle open; so they have an effect over the entire rpm...

here is the thread I wrote on the pickup coil drama I had with my '82 Seca https://www.xs400.com/threads/air-lock-in-fuel-line.20919/page-2

Check resistance of crank position sensor coils- orange and grey leads on the TCI. They should both be in the 100 to 600 ohm range. If one or both are shorted or open then there will be no spark. My '82 had one that would fail open once the engine got warm enough, causing the engine to...

My '82 Seca is supposed to have different main jets but when opened them up they were identical. I drilled out the left one and it made no discernable difference. What did help was balancing the carbs, getting the AF screws set reasonably and cleaning out the enrichener fuel passages. The...

The pistons etc were OK in mine but I did replace the hoses on your recommendation- it made a substantial difference 👍

The old brake fluid on my '82 had solidified to something like old crusty maple syrup, took ages to clean that garbage out.. and ethanol gas left in the carb bowls thoroughly plugged the start circuit holes to the point i had to drill them out... so I'd say all kinds of crazy stuff happens when...

Leaking float valves will drench a carb in fuel... When you take the bowls off note the passage which the brass tube dips into, there is a hole in the bottom of the well leading to the bottom of the bowl; that is the starting circuit. Its super easy for that to clog up.

Could always go for a ride with the tank lid loose- maybe secure it with masking tape so it doesn't flop around too much.

That could be a vacuum leak- make sure the diaphragms are in place and not torn, springs intact and they slide properly. Vacuum line ports on both intake boots should be plugged- usually the left one has a hose up to the fuel petcock.

only one "bb" on my '82 Seca. Not similar to this case but on one occasion after sitting for a while the clutch pads got stuck to the disk, took a bit of back and forth shoving of the bike to get them loose. The symptom made me think that the clutch actuator wasn't working. In the course of...

Probably worth testing the trigger coils also- one of mine had a problem where it would open when the engine was hot leading to no spark. A lot of the signals worth checking are on the TCI connector, as shown in the service manual.

I had good luck with an xs400 petcock "rebuild" kit from ebay- same kit as used on a bunch of other XS series bikes. The kit consisted of replacement gaskets and rubber bits to go into the petcock. It wasn't hard to take the old one apart and swap in the new stuff.