Coil voltage drop

[Squisher]

So, I have a project Kat (who here doesn't?)

I know my wiring harness is a little ugly, but it seems like the 'core' of it is alright.

I've figured out enough to get it to crank over (yay, good starter solenoid relay thingum!) but it's got no spark.

Voltage at the coil with just the ignition switch is a fairly healthy seeming 12.3-12.5v but drops to ~5v when cranking, so that's no good.

I know I've just hooked up to my other motorcycle for testing (no battery in the kat) so that's part of it, but are there any tricks to having extra grounds or what-have-you for better voltage on these bikes?

I have seen the coil relay mod, but in my case the volt drop seems a little extreme so I suspect other issues.

[05RedKat600]

Yeah, put a battery in it and test again. No battery with jumper wires tends to not provide enough amperage, which will cause a voltage drop.

Until you put a good battery in it and try again, you won't know for sure.

[Kreylyn]

Agreed... You need a fully connected actual battery in the bike.

If you have that and are seeing that low of a drop, then it's probably a bad battery issue.

Krey

[Squisher]

Will do

Hmm.
Well, the Honda can do w/o its battery for a few minutes

I will say this, I wasn't using jumper cables, I was able to use the Kat's main battery cables directly, but the negative was hooked to the Honda's frame instead of the battery, so I will try a more direct connection and report back. I just remember from the Honda that I was able to get enough stuff going on it before I bought a battery for it to get the mechanicals accomplished. Granted it's a 1983 single instead of a 2000 inline 4

[05RedKat600]

Put the battery in the Kat, and then try and start it. Don't add any length of wires, this will reduce available amperage and hence voltage.

The other issue is that the battery for your smaller Honda may not have the same amperage rating as the one for the Kat. Physical battery size means nothing. Get the right battery, or electrical tests will be null and void.

[hardlydangerous]

you will quickly kill the charging system on any bike running it with out a bad or low battery. nevermind no battery.
too much load for the system

[Squisher]

you will quickly kill the charging system on any bike running it with out a bad or low battery. nevermind no battery.
too much load for the system

Redkat's probably right on the Honda's battery being too small, I hooked it in directly and still only get about 6 v at the coil while cranking (granted that's 1 better than before but still too low). I won't know for certain until I get a correctly sized battery in there. I was just wondering if there was something Katana specific that I needed to look for, like in the way of upgraded or problematic ground (or otherwise) connections, etc.

And no, I wasn't going to run it sans battery; it has yet to run under my care in the first place. I'm just trying to get the spark in the air/fuel/spark/compression formula for a running engine...

Long term, this bike is getting a new main harness and RH control set (absolute MINIMUM, realistically also looking at head and tail light harnesses). If any of you saw what it looks like now you would understand and probably wonder why I'm messing with it before doing that. Main reason is that I LOVE to tinker with stuff, and was hoping to hear the engine fire up before I spend much money on it.

[Squisher]

Fire in the hole!

I got a new main harness off Fleabay from an '06

'00 and '06 are not exactly the same, but there are only a couple differences and with some solder and heat shrink tube you can adapt the 06 over (mainly connector differences).

After hooking it all up, the voltage drop at the coil while cranking was SIGNIFICANTLY improved (like 9.5-10v while cranking off my Honda's battery).

So, I put the tank on with some fuel, and after much fiddling I got it to fire up!

The idle is too low currently (just cold?), but as long as I use the throttle or hold the choke a little bit it runs and revs up. Stunk up the garage though

I tried messing with what I though was the idle set screw knobby thingy but it didn't seem to do anything, so I'll be messing with that bit in more detail later.