Vacation is over... bad acceleration

It will run on 3 1/2 cylinders. I've done it but power and overall performance would be down too. Don't wait, you may burn the seat beyond repair.
Steve

That's is exactly the problem!

I'm going to button up the carbs and start looking at the top end. Based on my history with the bike, I'm hoping for the best - that I will find carbon build up, valves not closing tight, low shim clearance and a bad oil seal on #2. If it's worse I'll deal with that too. I am holding off on piston rings until getting the top end sorted and being able to see the top of the block.

Steve - as always thanks for the words of wisdom!

You might get away with a valve job. Make sure you get all the carbon out of the cylinders and in between the pistons. If not you can ruin the bores. Pics of your progress?
Steve

Just went through the carbs today. The carbon was limited to the slider on #2. I rebuilt the accelerator pump (1979/B3) and noticed both old diaphragms were missing springs. This is my second time going through a complete carb clean and the first time around I didn't peal the diaphragms off to take a look (mistake).

Next up is a bench syn, I can visually see one slider has more aperture than the others. May even do a clear tube test off the bike. And then I'm pulling the head to take a look at the valves.

My bike found me, but if I had a choice a B1 or B2 is a better option without the recovery features. Word.

LineArtist wrote: . . . I'm pulling the head to take a look at the valves. . . .

Before pulling the head, would suggest:
Assuring valve clearances are within specs;
Compression test (both dry and wet);
Leak-down test (the poor man's version is sufficient).

Above procedures might avoid any need to pull the head, and will enable better diagnosis of top-end conditions if and when the head actually needs pulling.

If the head is pulled for whatever reason, would replace the valve stem seals.

Good Fortune!

Patton wrote: Assuring valve clearances are within specs;
Compression test (both dry and wet);
Leak-down test (the poor man's version is sufficient).

I will certainly be doing those tests before the head comes off (really prefer not to). What exactly is the "the poor man's version is sufficient" of a leak down test - just leaving the gauge hooked up for a few minutes?

While ruling out the obvious, I decided to look at the fuel cap today. I believe the paper washer was installed backyards (with all 3 holes lining up). This seems to be the logical assembly, but after looking closely I noticed the backplate has 2 small bumps to collect the 2 smaller holes in the paper washer.

A. with the engine running I can hear air being sucked through the cap - like a bad whistle noise, whine
B. while draining the tank through the PT with it in the Prime position, I noticed about a 50% decrease in flow with and without the gas cap open.

So if I'm correct, the assembly spins air travel in 2 directions before entering the tank. This is my effort at explaining the assembly (not covered in the FSM):

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

LineArtist wrote: . . . What exactly is the "the poor man's version is sufficient" of a leak down test - just leaving the gauge hooked up for a few minutes?

As known, a leak-down test injects air pressure through the spark plug hole to pressurize the combustion chamber.

Can perform a poor-man's leak-down test by introducing compressed air into a spark plug hole and listening to where it escapes from the combustion clamber. This may be done at TDC or any other cam positions where both valves are fully closed. Top dead center (TDC) is when the piston is at its highest position. An easy way to tell TDC is by alignment of the T mark with the case mark when viewed through the timing window.

May introduce a spurt of compressed air by using a rubber cone-tip blow gun (rubber air nozzle) held into the spark plug hole. And of course keep holding it in position to keep air from coming back out the spark plug hole while listening for escaping air at other places. The air compressor should not be running while listening because the noise will likely drown out any sound of escaping air. Or just use a portable compressed air tank.

Air heard escaping from exhaust port indicates exhaust valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from carb intake indicates intake valve not fully closing (perhaps too tight clearance or damaged valve or valve seat).

Air heard escaping from crankcase breather indicates loss of compression past rings into crankcase (perhaps worn piston rings or cylinders).

Air heard escaping from head gasket area indicates loss of compression past head gasket (perhaps due to a blown head gasket).

A leaking valve may sometimes be resolved by adjusting the clearance to within specs.

A leaking head gasket may sometimes be resolved by torquing the head fasteners when the engine is stone cold (such as after sitting overnight).

Good Fortune!

If fuel starvation hasn't already been ruled out ---

Patton wrote:

wallie2785 wrote: I have a kz1100 a2 I had my carbs cleaned and I also released them and it still bogs down when accelerating. I also need to know more about the position of the peacock if anyone can help with these two issues I'd appreciate it

The reported symptoms might result from fuel starvation due to inadequate fuel tank venting.

If not already done, would test ride with the fuel tank cap ajar (i.e., not snapped down), which assures ample venting, and to rule out inadequate fuel tank venting as a possible cause of the bogging when accelerating.

A similar cause could be crud of some sort (such as paint over-spray or whatever) suspended inside the fuel tank that collects around and clogs the filter screen on the petcock intake that protrudes up inside the tank.

The better fuel tank "flush" is imo a fast flush which entails tank removal in order to turn the tank upside down and fast dump out the contents through the filler hole.

There are also additional causes of fuel starvation, such as petcock malfunction, clogged petcock, clogged or pinched fuel line, water in the tank, etc. . . . Good Fortune!

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

Yes, that's how I put it back together. Once assembled you will see the paper washer through the hole. Aligning all 3 air holes is not correct.

Thanks Ed

fuel starvation

The problem manifested itself as a "bog" around 40mph on a steady throttle. Felt like I was getting hit by wind or I was running out of fuel. So I thought carb blockage or air leak. Bike was running amazing in the last few days and about 300 miles. Problem happened about 5 miles after a fill up.

Last time I started her it took a full choke and a few twists of the throttle - fuel starvation is certainly on my list. The carbs were "clean" but I found a few bits in the #2 bowl. Fuel pump diaphragms were shot and each missing a spring. i have all that back together now.

Before pulling the head
1. compression tests (ok without carbs on I'm assuming)
2. check valve clearances
3, check top end for any sort of damage (likely on the intake side)
4. check vacuum system hoses at petcock and recovery system (1979 B3)
5. install new air hoses at carb intake (old are hard, have a new set)
6. check carb holders or replace
7. test/replace condensers , replace points if condensers are bad, not getting a dwell read on the 2-3 side. I'm having trouble setting timing on the 2-3 side with a strobe, but can set it statically.

It's a good thing I'm a patient man at 46. Ruling 1 thing out at a time.