Vacation is over... bad acceleration

Since the problem occurred just after filling up the tank it's possible the gas you put in was bad. I had that happen with my BSA. The fuel a was so bad the engine quit a few miles past the gas station (i think the gas has water in it). I dumped the fuel, put in fuel from a different station, and the bike ran fine. Ed

Drain one float bowl into a container and see what's in it.
Steve

650ed wrote: Here are a couple images the show how my KZ650-C1 fuel cap was oriented when I disassembled it. Ed

I'm going to question this in order to understand the engineering. The relationship of the backplate to the washer is fixed by the 2 smaller bumps in the backplate. Let's consider the air route on the backplate like a snake, air coming in at the head/hole and spinning around to the tail/no hole.

1. air enters the hole on the backplate (from the gas cover side - top side of tank) and spins around the route in the backplate
2. The hole in the paper washer aligns to the tail of the route in the backplate.
3. air goes through the hole in the paper washer.

Up to this point I understand the relationship - there is only one way to assembly the backplate and the paper washer.

4. Air coming from #3 enters the tail of the faceplate route (because there is an equal route lenght on the faceplate)
5. spins around the faceplate route
6. enters the tank through the faceplate hole/mouth.

Based on Ed's photos. His faceplate is not aligned to the tail of the faceplate route. There is only about 1/4" distance from the paper washer hole to the final exit. Meaning his faceplate got spun around at some point in the last 40+ years. So I question the remaining route length?

I'm way over thinking this but believe it's important. Because both the backplate and the faceplate have equally routed air chambers, i will assume air is suppose to travel the full distance before entering the tank. This may be a way of stabilizing airflow or because of the rotating route actually force it into the tank.

Good Stuff Here! (I'm losing it)

After thinking about it further I am going to answer my own question regarding the gas cap assembly. The orientation I have shown is correct in my opinion. It generates the longest path of travel for air to flow from outside to inside the gas tank.

Why?

It was engineered that way by Kawasaki Heavy Industries to keep water/moisture from entering the tank.

LineArtist wrote: ......................Based on Ed's photos. His faceplate is not aligned to the tail of the faceplate route. There is only about 1/4" distance from the paper washer hole to the final exit. Meaning his faceplate got spun around at some point in the last 40+ years. ...)

Please believe me; that is not the case. The photos I posted show the fuel cap as it was delivered from Kawasaki to the dealer in 1977 prior to the bike being sold. I bought the bike new in April, 1977. When I took the photos in May, 2007, the cap had never been disassembled since it was originally installed on the motorcycle, so the photos show how it was originally assembled. I know this to be true since the bike was never outside my immediate possession, and I had up to that time never disassembled the cap. I took the photos at that time simply to ensure that I could reassemble the cap exactly as it had originally been made. Ed

650Ed, no disbelief here. I knew right away you posted original documentation. I'm more interested in the design/engineering aspect of the cap. It seems someone sat down and really designed the air channel thoroughly. The faceplate has 3 possible mounting positions, and they may all work fine (even from the factory). But I believe the design was intended to take advantage of the full length of the air channel.

Poor man's leak down test (starting at 100 psi) indicated ring problems across all 4 cylinders. Could hear plenty of hiss coming up through the center abyss shaft and through the oil plug. Compression readings are low at 130 110 105 110 (cold). And also found a leak on the #4 intake valve. I ordered a couple tools to help with the job and will be going through the valves thoroughly. And plan on replacing the rings if that's the only found problem once the block is pulled. Going by the FSM and taking my time.

Thanks for all the help along the way. I plan on starting the work this week. If the cylinder walls are damaged and boring is required there might be a 700 Wiseco kit in my future.

OFF TOPIC: went to a swap meet this weekend and scored a complete Kerker baffle for $15 (new in the package). I have an original good condition Kerker 4-1 exhaust in storage. And after I sort my bike it will most likely get some use.

It's been awhile but are there any updates? Thanks Tim

My KZ is still offline mostly because of lack of time to work on her. I have all the parts and several contacts in the area if I need help. I'm planning on starting work again this month if all goes well. Sometimes life gets in the way.

I'm glad to have documented the problem here and was able to re-read all the comments - ty.

As of 2 weeks ago my 79 KZ650 is back on the road like never before. However I did not do any top end work or ring replacement at 11,972 original miles. The culprit turned out to be faulty coils. I replaced the points setup with a new DynaTek EI and 3.0 coils and problem solved. I later added a new set of carb boots and thoroughly went through carbs with an ultrasonic cleaner, replaced every o-ring and rebuilt the accelerator pump. Tuned the air mix screws using a Colortune device and performed both a bench and a stick vacuum sync. She runs like new!

Have you redone a compression test/leakdown test?