Bike Slowly Dies after 20 Minutes of Use

I was assuming the cams were taken out to check the valve clearance but im guessing the 400 engies have the shim over lifter design then? It'd still be a good idea to verify that all the timing marks (intake/exhasut cam and crank) all line up and the tension is good on the chain.

I'm really starting to think its electrical,... you could use some aluminum foil to create a heat shield between the electronics and engine (cuts down on radiant heat quite a bit if i remember heat transfer right).

I bought a compression tester on ebay that has the three adapters for common spark plug hole sizes.

Saablord wrote: I was assuming the cams were taken out to check the valve clearance but im guessing the 400 engies have the shim over lifter design then?

No shims. No buckets. Two types of adjusters were used on 400's. 1976 uses eccentrics.

Saablord wrote: I'm really starting to think its electrical,... you could use some aluminum foil to create a heat shield between the electronics and engine (cuts down on radiant heat quite a bit if i remember heat transfer right).

There isn't much in the way of electronics in the '76 KZ400. The coil will be up under the tank, so as long as the bike is moving there should be enough air passing through to keep the coil cool - as long as the coil itself is operating properly. Even if the bike were to sit and idle for a long time, the radiant and convective heat should not be enough to make a good coil fail.

The reg/rec will be (IIRC) under the right-hand side cover. There isn't much heat over there.

The OP mentioned that the failure has happened twice in rather different ambient temperatures. I am leaning toward an overheating issue that is internal to some component, e.g. there is excessive resistance somewhere and the temperate rises because of that.

I'm leaning towards fuel since the plugs aren't fouled or wet.

I am thinking back on the day this happened... the bike worked fine before the 2.5hr ride where it first developed this problem. Halfway through that ride the bike randomly cut off on me. I was on the side of the road and kicked it for literally 30 minutes (with a few rests every now and then - I actually wore a hole in my shoe from this.) Turns out the ground for the coil/points came loose. I connected it it and it started right up. 1 hr later this problem started.

Point of that story is I wonder if kicking the bike for 30 minutes without the coil grounded damaged the coil? I'm thinking that's the issue. I'm about the recheck the float valves, and probably just order a new coil. Any recommendations on a low-budget coil?

k1z947060 wrote: I am thinking back on the day this happened... the bike worked fine before the 2.5hr ride where it first developed this problem. Halfway through that ride the bike randomly cut off on me. I was on the side of the road and kicked it for literally 30 minutes (with a few rests every now and then - I actually wore a hole in my shoe from this.) Turns out the ground for the coil/points came loose. I connected it it and it started right up. 1 hr later this problem started.

Point of that story is I wonder if kicking the bike for 30 minutes without the coil grounded damaged the coil? I'm thinking that's the issue. I'm about the recheck the float valves, and probably just order a new coil. Any recommendations on a low-budget coil?

If the wire moved to a position where it would stay grounded, then the coil could have been damaged from heat. Does it look burned or smell burned? If not it is most likely ok.

Based on your other thread, the problem seems to be the installation of a non-compatible kill switch.

loudhvx wrote:

k1z947060 wrote: I am thinking back on the day this happened... the bike worked fine before the 2.5hr ride where it first developed this problem. Halfway through that ride the bike randomly cut off on me. I was on the side of the road and kicked it for literally 30 minutes (with a few rests every now and then - I actually wore a hole in my shoe from this.) Turns out the ground for the coil/points came loose. I connected it it and it started right up. 1 hr later this problem started.

Point of that story is I wonder if kicking the bike for 30 minutes without the coil grounded damaged the coil? I'm thinking that's the issue. I'm about the recheck the float valves, and probably just order a new coil. Any recommendations on a low-budget coil?

If the wire moved to a position where it would stay grounded, then the coil could have been damaged from heat. Does it look burned or smell burned? If not it is most likely ok.

Based on your other thread, the problem seems to be the installation of a non-compatible kill switch.

The original issue happened with the stock kill switch. But last week, 2nd ride over 10minutes since original issue, the problem did happen with the faulty kill switch wired in - which may have accelerated the problem. I will likely be buying a new coil today - everything I've read leads to a faulty coil. I checked the regulator and rectifier and battery yesterday and they all check out.

Presumably the coil physically appears okay, and has no bubbly black goo oozing from it.

If not already done, could try reproducing the symptoms more quickly by using a hair dryer to heat the coil while the engine is running at a high idle (tank removed; auxiliary fuel supply; transmission in neutral; bike on side-stand or kickstand).

Would also assure a good ground connection where the negative battery cable attaches to the engine.

Good Fortune!

Uh oh. I just went to play with the idle and fuel screws after adjusting the float height. That went good - but I noticed it's bubbling fuel from the head/cylinder gasket :ohmy:

That would explain my low compression, and maybe other issues?

Now to figure out how to resolve that.....

Just an update...

Since I'm really particular about things, and the bike wouldn't start with the choke in this 40 degree weather, I went back and leaned out the float heights. It started and idled better with the "leaner" float height, and required the chcoke like I wanted.

I ended up taking the spark plugs out after playing with the idle for about 10 minutes (most of it without choke). They were very black! Much much darker than the previous pictures posted of when the bike died on me.

Bubbling fuel from the cylinder head gasket?

You might want to fix that before looking into coils or carbs.

Kidkawie wrote: Bubbling fuel from the cylinder head gasket?

You might want to fix that before looking into coils or carbs.

I've already taken the engine apart and ordered the parts. But isn't this unrelated?

Also - it's extremely hard to find a coil that has the correct secondary and primary resistances - and half the sellers don't even know what they are selling!