Sudden power loss.

I have a problem whit my Z650 -81.

After running fine for about five minutes the bike loses power. There is no misfire, but the engine seems to struggle hard to keep on going. It seems that the noise from the top end increases at the same time (could be imaginary due to the muffled exhaust note during the power loss).

After a minute or two it fires up whit full power again but can loose power at any time there after.

Otherwise the bike runs great.

Faulty ignition (CDI) or fuel starvation?

How can I find the fault?

/David

It can be fuel starvation or electrical problems. This won't work as a normal troubleshooting as the problem is internmittent. I would suggest tackling one set of potential issues before jumping to the next. I think you should look at fuel first.

1. remove petcock and clean petcock screen
2. check fuel line for kinks or very sharp bends
3. ensure vacuum line to petcock isn't kinked or pinched
4. install inline gas filter

Do this stuff and the next time the problem occurs, pop your gas cap open as it is occuring to see if there could be a vacuum set up in the tank and fuel just won't flow.

If the fuel flow fixes don't resolve the problem, electrical is the culprit. Check ground and hot connections coming off the battery to ensure they are tight. Take a look at electrical connectors that feed your coils and igniter. Check the electrical connectors for the ignitor from the pickup coils and to the ignition coils. Check for excessive play in the kill switch mechanism. If a previous owner used the kill switch a lot, it may be worn a bit and you are just killing the power to the coils through a faulty connection.

I bet one of these things above is the culprit.

Dave,

Everything WG says is right on. Also, if you have the stock electronic ignition, note that a number of us have experienced an intermittant fault in one side of the pick-up coil, leading to a period of time running on 2 cylinders instead of 4. If you do a search you should find the threads that discuss this.

If you post your bike year and model in in your signature, we can generally help you out better.

Pictures of your bike are appreciated by all.

I've been doing some looking into my bike ('82 KZ550C LTD) and have found that the ignition cycliner on the bike is called a pulse coil. Since I'm having the same problems (power cutting out after its run a while and then kicking back in after its cooled off a bit) do I need to buy a Dyna-S replacement? Also, is a pick-up coil another name for what my local Kawasaki dealer called it (a pulse coil, which cost thru them $340 for a new one :blink: ).

Thank you for any information. I'm new to owning a KZ and have found that I very much so enjoy the one I have.

I would'nt spend a cent until I had done what the guys above suggested. The best and cheapest way is to take it a step at a time. Logical and methodical. No point spending big money until you are sure.
Pulse coil and pickup coil are the same thing - at least I think they are the same

On a bike that old it could be the smog control reed valves located on top of the exhaust cam cover. The reeds could be sticking open at times. Also, there is a vacuum operated smog valve under the tank that connects to each side of the exhaust cam cover that can stick open once in awhile. Maybe when it gets hot.

These areas are often overlooked during routine maintenance and never get cleaned or checked. It can cause all kinds of symptoms including back firing, hard starting, loss of power, etc.

Plugging the line that goes from the valve cover to the control valve could likely cure the problem. I plugged mine and threw the valve away after plugging the vacuum lines going to the carbs.

Anyway...its worth a try. It won't cost you a penny...

Bob

I've checked the fuel system as much as I know how. The bike is currently sitting in my back yard with the tank and seat off of it to let me see everything. Also, when I bought it it already had an inline fuel filter (which is still good) and was doing fine for the first month or so of riding it. Even took it out on the highways a few times and it did fine up to around 70 (as far as I was willing to push it). The only thing that I know that is wrong with the bike is one of the carbs is in need of tuning. However, whenever this happens (and it happened yesterday on the highway :blink: ) I can only go around 35 mph (not safe on a highway with a 65 mph speed limit). Needless to say I limped up to the next intersection and jumped onto back roads. Stopped and let it sit for a bit and when I got back on it was doing fine for a bit. I can recheck the fuel system (has to wait til tomorrow) but in the mean time, any other ideas as to what may be causeing this problem? :S

duke_hall wrote:

I've checked the fuel system as much as I know how. The bike is currently sitting in my back yard with the tank and seat off of it to let me see everything. Also, when I bought it it already had an inline fuel filter (which is still good) and was doing fine for the first month or so of riding it. Even took it out on the highways a few times and it did fine up to around 70 (as far as I was willing to push it). The only thing that I know that is wrong with the bike is one of the carbs is in need of tuning. However, whenever this happens (and it happened yesterday on the highway :blink: ) I can only go around 35 mph (not safe on a highway with a 65 mph speed limit). Needless to say I limped up to the next intersection and jumped onto back roads. Stopped and let it sit for a bit and when I got back on it was doing fine for a bit. I can recheck the fuel system (has to wait til tomorrow) but in the mean time, any other ideas as to what may be causeing this problem? :S

Helloooooo....did you read the message above about the smog valve possibly being the problem. Don't dismiss the idea till you've tried it. Been there, done that.

Bob

If you are happy with the fuel system then next would be to check the electrical/ignition. Check all the connections like WG said. I had similar problems once caused by corrosion of a connector when my battery breather fell off.
Check the leads to the coils and check the ignition wires from the coils to the plugs. Are the plugs old ? Do the plug caps fit snug ?

Bob_79KZ - seems like what you suggested is simple and worth a shot. We were lucky up here in that we never got that anti smog stuff. Sounds like it was a PITA.

I just noticed. David asked the first question and I think I'm answering Duke_hall.
I must be getting old - i'm to easily confused LOL

Post edited by: JR, at: 2006/09/28 17:30