Where to start?..

A bit of a disappointment today (though I really didn't expect too much):
-- but, the 1975 kz400 noted here kzrider.com/index.php?option=com_kunena&...w&catid=10&id=397142 died on me on my first attempted foray outside my immediate neighborhood.
I'd adjusted valve clearances, points gap, and changed spark plugs, and had gotten a short-term idle (and a couple of successful kick starts) without the choke yesterday, so thought maybe it was ready for 'real' testing. Wrong. It barely pulled the hill 3/4-mile from my house in third gear, and died when I throttled back at the light at the top. No attempt to fire at that point. I pushed it back to the downhill portion of the ride home, when I tried a kick start, and got fire for about 3/4-mile, enough to coast within 25 yards of my driveway.
During its initial shutdown, the engine/carbs seemed to gurgle and pop, much like there was fuel not igniting. Then, when the battery 're-charged' after an idle quarter-hour or so -- which I've known to happen many times -- I got spark and managed to shift through the gears downhill, only to die again when the bike began to pull itself on the flat.
Now, I fully expect to have to rebuild the carbs on this one later, but I really don't think this was a fuel-delivery problem today. I assume I'm looking to change/repair the regulator, rectifier and/or stator, at this point. But, I welcome your thoughts...

If you haven't done so, clean the carbs thoroughly. If the bike was sitting more than a couple months without running it is VERY likely that the carbs are gunked up. I would start by cleaning them, making sure I had fresh gas, changing the oil, and installing a fuel filter. Ed

Just because I have to ask:

When you reset the points, you also reset the timing, no?

If you haven't done so, clean the carbs thoroughly. If the bike was sitting more than a couple months without running it is VERY likely that the carbs are gunked up. I would start by cleaning them, making sure I had fresh gas, changing the oil, and installing a fuel filter. Ed

I agree....you did all the good stuff you could have done, execpt a good carb cleaning! you didnt mention an oil and filter change, but id assume you did that. Id bet a good carb cleaning and adjustment would do this bike alot. Im talkin good gaskets, clean jets and carb orifices, float adjustment...ect..get a manual man. sounds like a fuel problem to me.

hell, get a new set of plugs for the fuck of it....check the ohms of the wires and coils....And you can probably find a manual online. I have for every bike ive owned, and they have all been free.

good luck

650ed wrote:

If you haven't done so, clean the carbs thoroughly. If the bike was sitting more than a couple months without running it is VERY likely that the carbs are gunked up. I would start by cleaning them, making sure I had fresh gas, changing the oil, and installing a fuel filter. Ed

Well, okay. I can always revisit the electrical/charging side later.
The bike was represented to me as 'running', but it plainly wasn't -- so, I don't know how long it sat. The gas tank looks good internally, and it started without too much hassle once the battery was charged. New fuel and oil change is accomplished, an in-line fuel filter is on 'to-do' list already.

sparkn wrote:

Just because I have to ask:
When you reset the points, you also reset the timing, no?

Actually, no -- because, in reality, I only checked the points gap, which was fine. No adjustment was made. Frankly, I don't have a timing gun/light available, since I'm about 25 years post-points on my automotive side, but priced one just yesterday. Will get it when absolutely necessary.

550A2 wrote:

...I agree....you did all the good stuff you could have done, execpt a good carb cleaning!..

You guys have convinced me (well, okay, maybe 75%; I STILL think it may well be a charging/re-charging problem, but I hope not!) -- my problem may well be in fuel delivery. I'll start with a thorough carburetor cleaning only -- since I don't have carb kits in hand, at the moment -- and hope I can reuse O-rings and gaskets, as I can likely accomplish it over the coming weekend. But I will do a thorough refurbishment as soon as practicable.
Thanks.

I would check the timing anyway. No timing light necessary (although it can be more accurate). Just measure the exact spot the points open and check the timing mark (either a voltmeter or light bulb connected appropriately should do the trick). As the points wear, it will retard your ignition. That bike was sitting a while? The lobe for the points could be rusty and like sand paper to the points (not the contact points, but rather the other end that makes contact with the lobe). The gap might be .012 now, but was it .016 the last time the timing was checked? Only takes a couple minutes to check. I like to do it with the plugs out so I'm not fighting compression while manually turning the crank.

I'm just saying 'cuz if the timing is off, you'll never get the carbs quite right and your plugs will never read correctly on a retarded ignition. Quick check, quick fix, and you'll know you're healthy enough to move on to the carburetor. If you use the voltmeter method, check the volts while you're there and make sure the voltage isn't dropping off, too. The points to ground when open should be within one volt of the battery. Any more and I'd start looking for reasons why it isn't closer.

And then I'd check the charging system to make it's output is OK. Idle, quarter throttle and full throttle all going bad at the same time? And it ran going downhill and died on the flat? I'd definitely make sure the electrical was healthy before pulling the carbs off the bike. This bike is an unknown. If you get the carbs perfect and have an electrical problem, you'll be screwing with the carbs again after you fix the electrical problems.