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Repair pictures

This page are for pictures taken during repairs and restoring.

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Carb Balancing

Balancing KZ400 1974-1976 and 1977 A1 carbs with a Morgan Carbtune

To be able to balance the carbs you will need a carb balancer, I have got a Morgan Carbtune II, and a tool for the balance adjustment screw and locknut that is located between the carbs. (Picture to the right). You will also need to connect a fuel tank to the carbs. An easy way is to buy a couple of long fuel hoses and use the fuel tank for the bike by placing it on a step ladder next to the bike, and then use the long hoses between the carbs and the fuel tank. When you have learned how to balance the carbs, you should be able to do it with the fuel that is in the float bowls only.
When you balance the carbs, you will have to warm up the engine for 4-5 minutes. Then stop the engine and unscrew the vacuum cap screws on each side of the carbs (Picture to the left), screw in the adapters and connect the vacuum hoses for the balancer. (Picture in the middle) The balancer should hang on the handlebar and be levelled. The vacuum hoses should be routed as on the pictures below.

Then start the engine and let it run at fast idle, adjust the idle speed to approx 1400-1500 rpm, and check the readings on the balancer (Picture in the middle).The difference should be less than 2 cm/hg between each carb. The actual reading is not that important. If the difference is more than 2 cm/hg you should balance the crabs. I try to balance them to the point where the difference is less than 1 cm/hg. I have made my own tool for the balancer screw and lock nut. (Picture to the left.) You can also buy a tool that is made for this purpose. And remember that the carbs are sensitive, and altering the balancer screw only a small amount will make a large effect on the vacuum meter. And securing the lock nut can be enough to upset the balance between the carbs. On the picture to the right you can see the reading on the balancer after I have balanced the carbs. Then blip the throttle to see that the balance is stable. When you are done, stop the engine, disconnect the balancer vacuum hoses, unscrew the adapters and reinstall the vacuum plugs. Then install the fuel tank, start the engine and readjust the idle speed to 1100-1200 rpm.

Note:

The engine should be tuned before balancing the carbs. Cam chain, valve clearances, points and ignition should be adjusted. Also the idle mixture and the idle speed must be adjusted. And the spark plugs should be cleaned, or replaced, and the air filter should be in good shape. And be careful not to overheat the engine during the balancing. An electric fan to help cool the engine down is advisable.

Here you can read more about the Morgan Carbtune. And you will find the instruction here.

Home made tool for measuring the fuel level in the float bowl

And this is how I made it:

The hose is a clear plastic fuel hose and the length is approx 15cm, and the inner diameter is 5mm, the outer diameter is 7mm. The highest mark, that I'm holding level with the bottom surface of the carb body, is at approx 7cm from the lower end of the tube. And it is 2mm between each marking. I have used a fine permanent marking pen when I made the markings.
The tube that is connected to the hose is 14mm long, and has an outer diameter of 6mm, and the hole through it is 2,7mm. On the other end of the tube I have used a nut and made threads that fit with the threads for the drain plug in the bottom of the float bowl.
And, as you see from one of the pictures, I'm using a piece of a steel wire to secure the hose to the carb body when I measure the fuel level. But it is no problem holding it steady with your hand.
I have also found that the 6mm nylon adaptors you can buy from Morgan Carbtune , can be used as adaptors for the float bowl drain screw hole for at least for the 1974-1976 model carbs:

A seized piston

This is how one of the pistons in my D3 engine looked when I opened the engine. It's hard to tell the reason for a piston seizure like that, since there can be several causes. But for this piston it is most likely caused by a too small piston to cylinder clearance after the cylinders was re-bored. When I measured the cylinder bores, and the piston that was still good, the clearance was a bit tight, so I assume it had been tight on the seized one as well.
This is what I believe is a "four wall seizure" since the piston has got scorings on 4 corners. When a piston looks like that, it might be saveable, but the scorings has to be polished and the piston has to be measured carefully to find out if it is worn passed the service limit. Also the cylinder has to be lightly honed, and there also is a risk that the piston to cylinder clearance will be to large to reuse the old piston, and a new piston has to be installed. This piston had to be replaced btw; the scorings were too deep to polish them away without exceeding the service limit.