Kawi2strokes.com Forum

The Z1A that I ride most of the time seems to run very well, pulls strong all the way to 9000rpm's and starts instantly. I pulled the plugs yesterday just for the heck of it and the #1 and #2 plugs are very black and sooty while the #3 and #4 plugs are nice and tan. The valves are set, the carbs were cleaned and all set the same, the fuel system is clean, the intake manifolds are new, the air cleaner is new(stock air box)and I am running it on 91octane avgas. The air screws are all at 1 1/2 turns out. Did I set two of the carbs wrong? What should I do to fix it? I figured if it was one of the coils it would be affecting either #1 and #3 or #2 and#4.

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1969 H1, 1971 G3SSA, 1974 G5, 1973 H2A, 1975 S3A, 1975 H1F, 1973 Z1, 1988 HD FLTC, Captain America chopper, 2000 Excelsior Henderson, 1965 Bridgestone BS90

How are the piston rings and valves? Checking compression might provide some clues. And air screws aren't necessarily all set the same at 1 1/2 turns out. I can understand why you might not want to mess with them if the bike is running nicely.

balance the carbs

The spark plug caps should have plug sockets that unscrew out of the caps. Behind them are resistors that can carbon up and lose spark efficiency. Might take a resistance test and see if there are the two that are rich, that have high resistance. Stock factory resistance is 1K ohm.

Float levels are critical in those early carbs, and should be checked, and the needle/seat assemblies as well.

As far as the air screws, they should be in the sides of each carb, and if you look closely, there should be some sort of punched line in the boss around the screw. The adjustment goes, 1 -1/4 turns out from lightly seated, then line the slot in the screw up with the punched line on the boss.

I will advise that if all the carbs are relatively close in balance adjustment, LEAVE THE ADJUSTMENT AS IS, those particular stock Z1 carbs can make a serious nightmare because of their adjustment linkages. Also, if possible, DO NOT USE THE 4 INDIVIDUAL VACUUM GAUGE ADJUSTERS, they don't always read the same for any given vacuum level, if possible, use a manometer like Carb Stiz.

Also make sure all valves are set to .003/.004, that is the correct setting with the cam lobe nose 180 degrees from the shim flat in the tappet.

Compression test would show one head gasket if issues between those two cylinders, could be a gasket that has blown between the cylinders, but that is VERY rare.

I put new Mikuni needles and seats in when I cleaned the carbs. I was very careful when I set the float heights(but that doesn't mean they are right)and the .4mm gap on the back of the slides. The slides are mechanically set to what looks like the same, they all top out at the same time. The compression is low but even, right at 130 across the board. The reason the compression is down I believe, is because the bike spent it's life west river, on a lot of gravel roads and the engine probably ate more dirt than normal. It doesn't smoke at all and runs great(which is why I am surprised the compression figures are low although I have only checked with one compression gauge that is 40 years old)and it even idles perfect. Do compression gauges get old? I should buy a new compression gauge and check it again. I will check the spark plug caps and wires and test them like Dave said and see what happens.

I have checked the compression 4 times in the last 300 miles and it is always the same, within one or two pounds variance between all four cylinders.

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1969 H1, 1971 G3SSA, 1974 G5, 1973 H2A, 1975 S3A, 1975 H1F, 1973 Z1, 1988 HD FLTC, Captain America chopper, 2000 Excelsior Henderson, 1965 Bridgestone BS90

Did you remember to hold the throttle all the way open, WOT, while doing the compression testing? If not, the r3eading will be lower than the actual pressure build up.

130 psi isn't bad, some Z1's had that level and ran extremely well.

Just for grins, after doing the valve clearances, timing, check the balance with manometer.

AS I SAID, lots of balance problems with the linkage on those first series carbs, if good, leave them alone, if not, good luck with them getting even close, and saying there, most of them steadfastly refuse to stay balanced..

Yup, I held the throttle wide open. The valves were set when I got the bike running, a little over 300 miles ago. I have a full box of BMW shims so I had all the sizes I needed to do it right and I set the timing with a timing light.

Here is the old Z1A, an original survivor except for pipes, I just put new ones on it last week, it had a 4 into 1 Kerker on it. It has 19,000 miles on it.

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1969 H1, 1971 G3SSA, 1974 G5, 1973 H2A, 1975 S3A, 1975 H1F, 1973 Z1, 1988 HD FLTC, Captain America chopper, 2000 Excelsior Henderson, 1965 Bridgestone BS90

That is a really good original, nice! Hope you get it sorted soon!

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"One day, your life will flash before your eyes. Make sure it's worth watching." : anon.

If the tappets, shims and retainers are still stock, and haven't been converted to KZ650/750 shim under buckets, they'd be 29 mm diameter, same as Yamaha. Even my Toyota 2.5l 4valve Yamaha V6 uses them.

I use a dwell meter and timing light on the points, 192 degrees, on the 8 cylinder scale, 24 degrees. I then time it to the last full advance mark. From then on, as long as you do not move the timing plates, restoring the point gap with the timing light brings the dwell and timing right back.

Best electronic ignition, Dyna S, stock coils good NGK or stock resistor caps, B8ES spark plugs. No Iriduim plugs needed, nor wanted, better is B8EV Gold Palladium.

Cam chain tensioner is simple, cold engine, turn to 1/4 TDC, let the lock nut and bolt loose, tap the tensioner a couple of times, tighten the bolt and nut. Later model KZ1000 self adjusting ramp and ball bearing tensioner works better, no adjustment. Cross tensioner is icing on the cake.

If you ever find the need to pull the exhaust am out of the head, remove the tach drive gear and its holder first, put it back last. This is the single biggest reason we sold tach drive gears, broken when they didn't match up on cam reassembly, especially on shim under bucket exhaust cams.

We also used to turn the cam bore end caps 180 degrees, and position the lip inside the head, not outside, then we also used Three-Bond 1104, no1w 1194, to seal them into the bores.

20W-50 oil works best (I always used Castrol GTX), 10W-40 is too light, NO synthetics.

For the carb issues, adjuster problems, we were close to American Turbo-Pak, and bought all those 1978 Z1R carbs new, never run, that they took off when they turbo'd those things, 100 bucks later, and it was golden, they worked better than the stock carbs did, real world balance adjusters too, less money thn a set of 29 smooth bores.

Funny how all this stuff comes back like it was yesterday...oh, wait, I did one of these for a fellow in Reno, after the dealer there did it very badly, just last week.

That's a lot of great information Dave, Thanks a bunch.

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1969 H1, 1971 G3SSA, 1974 G5, 1973 H2A, 1975 S3A, 1975 H1F, 1973 Z1, 1988 HD FLTC, Captain America chopper, 2000 Excelsior Henderson, 1965 Bridgestone BS90