1976 KZ400D3 Engine

This also covers the other KZ400 engines between 1974 and 1977, plus the 1978 A2. The only difference between the S model engines and the A and D model engines is the lack of a starter motor in the S model engines.

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Top end oil leaks. Kawasaki service bulletin

This is the service bulletin and the parts list Kawasaki sendt out to their dealers about how to repair the oil leaks that was a problem with all the 1974-1977 KZ400 engines:

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Replacing balancer chain and cam chain in a KZ400D3 engine

In the middle of October 2004, I started the work with replacing the cam chain and its guides, and the balancer chain and its guides in my KZ400D3 engine. During this process I will take pictures and try to tell a little about what I'm doing.
Have in mind that I'm not a professional mechanic, and this is not an engine overhaul. The top end was overhauled a couple of years back, and should be in good shape.
I have also been collecting parts for a long time, so I have got all the parts needed for this job. Some of these parts can be hard to find though.



1. The first thing I started with was the breather cover. Then I unbolted the valve adjusting covers on each side of the cylinder head.

2. Here is the valve cover with the rocker arms and rocker arm shafts removed from the cylinder head, after the cylinder head nuts are removed.

3.The cylinder head with the camshaft, cam chain and valves.

4. Before I can remove the camshaft, I must remove the cam chain tensioner unit from the front of the cylinder block. Before I loosened the bolts holding it, I took of the tensioner cap and backed out the tensioner as much as possible..

5. Here I have unbolted the cam chain sprocket from the camshaft and I can remove the camshaft and the sprocket.

6. Even if the cam chain will be replaced, I have secured it from falling in to the crankcase with a screwdriver that I have placed behind the cylinder studs. The cylinder bores looks very good, with a good cross pattern after the last honing.

7. This is how the cylinder head looked in the combustion chambers. This engine has been running to rich. I have made a note about adjusting the carbs to a leaner mixture. This cylinder head will be cleaned, or replaced with a new one that I have got, during the assembly processs.

8. Bad things are due to happen when you are wrenching on old engines. One of the cylinder studs broke off during the reassembly. This one broke off 1 cm above the gasket surface. That should make it a bit easier to remove.

9. It is a good thing that I opened this engine. This cam chain guide had split almost all the way.

10. The pistons seem to be in good shape.

11. Here I have unscrewed the bolts and taken off the generator cover with the stator and the field coil. The generator seems to be in good shape. And I did some measurements before I took the engine out of the bike, so I know that the generator works as it should. The starter clutch is bolted to the back of the generator rotor.

12. The starter motor. I will have to remove it to be able to take off the starter sprocket and remove the starter chain from the starter clutch.

13. The clutch boss and the primary drive. The clutch is easy to remove since both the clutch boss and the primary sprocket are held in place with circlips. Here I have removed the pressure plate, the clutch disks, steel disks and the springs that go between the clutch disks and the steel disks.

14. The gear selector, the kick start spring and the oil pump.

15. The only thing that is necessary to remove for splitting the crankcase for the job I'm planning, is the gear selector. It is held in place with two Philips screws. When they are removed, the selector has to be freed from the selector drum and pulled out.

16. Here I have split the crankcase. There are 6 bolts that had to be unbolted from the upper crankcase, and then I turned the crankcase upside down and unbolted the rest. This is the lower crankcase with the oil screen. It was full of remains from the different chain guides.

17. The transmission. I will not remove the transmission this time.

18. This is the chain driven crankshaft balancer. It will be removed later on, but from a first look over, the chain seems to be stretched, and the chain guides worn. There is a great amount of free play in the chain.

19. And I was not finished with the misfortune. Two of the bolts holding the crankcase together broke off. They were heavily oxidized and broke off very easily. It will be a problem to remove them. I'm spraying them with penetrating oil every day, and will do so for a while till I'm sure the threads are soaked. Then I will have to drill a hole in the bolts and try to remove them with a bolt extractor. Not what I had planned to spend my time on and it will slow down the rest of the process.

20. Here I have removed the crankshaft bearing cap and the balancer chain guides.

21. Crankshaft bearing cap and the balancer chain guides. All the crankshaft journals and bearing shells seem to be good. The balancer chain guides have got signs of wear.

22. The crankshaft balancer chain sprocket has got signs of wear, but at a first glance it looks usable. I will inspect it closely later. Hopefully the first impression was correct. If not, the entire crankshaft has to be replaced.

23. Crankshaft and balancer mechanism.

24. The front cam chain guide is worn, in addition to the split. To remove it, I had to lift up the dowel pin A, and push the guide shaft B, to the left and take out the guide.


Sorting out and assembly

1. Here is the crankcase half’s after I have cleaned them. I have also drilled through the broken crankcase bolts and tried to remove them with a bolt extractor. I did not succeed. So I will have to drill out the remains of the bolts.

2. The broken bolts are sorted out. I have drilled out the remains and cut new threads. I have also chosen to use 8mm Allen bolts as replacements. And the salesman in the machine shop advised against using stainless bolts for aluminium threads. He told me that there will be a chemical reaction between the aluminium and the stainless steel. Anyway, no I can go on with replacing the chains and their guides and the crankcase oil seals.

3. This is the chain guides that I am replacing. They are all well worn. I have also inspected the crankshaft balancer sprocket closely, and it is worn uneven. Hopefully it will last for a while longer with a new chain and guides. Also the balancer chain was stretched to the service limit. Normally I would also have replaced the main bearing shells, but since this is a running spare engine and with the wear on the balancer sprocket in mind, and the fact that the bearings and journals looked good, I decided to reuse the old ones. Maybe not the wisest thing to do. That I will find out soon enough. The rear cam chain guide sits in the cylinder block and it is easy to replace. Just push the guide upwards, take out the dowel pin on the top of the cylinders and then pull the guide down. The new one is installed in the reversed order.

4. The lover balancer chain guide is attached to the bearing cap by bending the "ears" on each end around the edge of the cap.

5. Same cap from another angle.

6. Here I have removed the dowel pin and pushed the cam chain guide shaft to one side.

7. Here the chain guide, the guide shaft and the dowel pin is in place. The guide shaft has a groove on one end that the dowel pin fits in too for locking the shaft. The dowel pin is locked in place by the bearing cap.

8. Here I have lined up the punch mark on the rear balancer sprocket with the index mark on the sprocket axle cap, and I have looped the chain around the sprocket with the chromed plate aligned with the markings. Before it is put in to place, the crankshaft should be turned till the oil drain holes on the journals aligns with the gasket surface, and the counterweights should point upwards. Be sure not to turn the crankshaft during the assembly of the balancer mechanism.

9. The rear balancer is in place.

10. Here are the front balancer in place. When it is mounted, it should be with the same markings aligned as on the rear balancer, and the second chromed plate on the chain should align with the markings on the front balancer. I have also placed the upper balancer chain guide in its position.

11. Rear balancer correctly aligned.

12 This is how it should look when both balancers are correctly aligned.

13. The balancers, the bearing cap and the upper balancer chain guide are bolted down. Remember that the upper chain guide must be placed before the bearing cap is placed and bolted down. And there is a significant difference in the amount of free play in the balancer mechanism with the new chain and chain guides. The free play is virtually gone.

14. I have also replaced the oil seals on the outgoing shaft and the clutch push rod before I joined the crankcase half’s. The crankcase must be split to be able to replace the push rod oil seal. Also the oil seal for the gear selector shaft has been replaced.

15. The crankcase halves are joined and bolted down. I have used a liquid gasket, Hermetite Gold for sealing the crankcase.

16. Here I have fitted the gear selector. And I have put on the gear lever and tested that the gear changing works.

17. And here is my next problem. The broken cylinder stud.

18. The cylinder stud has been replaced with a new one! I tried to file the broken stud to fit a 5mm socket and remove it that way, but it was no way it would come loose. I then put on a thin washer on the remains of the stud and filed it down till it was 1mm above the gasket surface. Then I punch marked it and started to drill it out with a 6,5mm drill bit. When the stud was drilled out, I cut new threads for the new stud. After testing the threads, I was not pleased with them. I have now drilled out the hole to 10,5mm and used an expanding brass insert for the stud. This seemed to work fine when I tested it. I could also have used a Helicoil, but it was interesting to try this method out firstt.

19. The starter motor is bolted on, and the also the starter chain and sprocket is reassembled.

20. The wiring for the generator, the power wire to the starter motor, the wire for the neutral switch, the red wire, and the wire for the oil pressure switch, the grey wire.

21. The generator cover with the stator and the field coil, and a new gasket, is back in place, ready to be bolted down.

22. After the generator side is ready assembled, I have started with the clutch side. The first thing I do is to measure the free play in the primary chain. I have installed the chain and the clutch housing and the primary sprocket temporarily for this. The free play should be less than 20 mm measured in the middle of the upper chain run. This chain had a 16 mm free play and is still useful.

23. I also inspect the damper springs on the rear of the clutch. There are no broken springs, but they have lost some of their tension compared to the springs in a new clutch basket I have in my spare parts shelf. I will still reuse this basket since it otherwise seems to be good. To the left is the clutch hub.

24. This is the parts for the primary drive. The clutch housing, the primary chain and sprocket must be installed as a unit. There is a trust washer that must be installed before the clutch hub is installed. And there is a shim that should be installed between the clutch hub and the circlip.

25. Here the clutch housing, clutch hub and the primary drive are installed and secured with their circlips.

26. Now the friction plates, the steel plates and the steel rings can be assembled. I have checked the steel plates for warpage, and I have measured the friction plates for wear. They are all within the service limit. I install the plates in following order: I start with a friction plate, then a steel ring and last a steel plate. I alter this till all the plates and rings are installed. The last to install is a steel ring.

27. After installing the rings and plates I install the clutch push rod form the generator side. Then I install the steel ball and the pusher.

28. Then the pressure plates should be installed. The notches on the pressure plates should align with the notches on the clutch hub. I then install the clutch springs with their bolts and washers. I try to screw them in even, and I try not to overdo the torque used when I fasten them. It is very easy to strip the threads in the clutch hub.

29. The clutch springs, bolts and washers. I have measured the clutch springs and they are well within the service limitt.

30. The primary cover. I have cleaned it and replaced the kick starter shaft oil seal. The crankshaft oil seal, and the primary chain guides was replaced only a short while ago. When the cover is installed it is important to be careful when entering the crank shaft oil seal on the crankshaftt.

31. I have also installed a timing advancer. I will need this when I'm timing the camshaft later on.

32. The bottom end is ready assembled.

33. I have started to reassemble the top end. A new cylinder base gasket, and new o-rings for the oil ways that runs through the cylinder block to the cylinder head is in place and I have cleaned the piston heads with a wire brush and assembled them to the rods. Before I did, I oiled the small ends in the rods and the piston pins. And before I assemble the cylinders I will also oil the piston rings.

34. Here the cylinders are entered to the studs and lowered down to the pistons. It is important to secure the cam chain to prevent it from falling in to the crankcase. Before I entered the cylinders I have covered the bores with engine oil. I don't have a piston ring compressor, so I use a small screwdriver for compressing the piston rings while entering the cylinders.

35. The cylinders are in place.

35b. From another angle

36. I have cleaned the cylinder head and the combustion chambers. The combustion chambers have been cleaned with a wire brush. At the same time I also cleaned the threads for the spark plugs. I did consider replacing this head with a new one I have got, but it seems to be in good shape so I saw no reason to replace it.

37. The cylinder head is ready for installation.

38. I have installed the new cylinder head gasket and the two oval o-rings for the oil ways. It is important to install these o-rings correctly with the flat side against the cylinder head. Also make sure that they don't slip under the head gasket during the assembly of the cylinder head.

39. The cylinder head is installed and I have secured it to the cylinders with the two 8mm and the two 6mm bolts.

40. Before installing the camshaft I will clean up the rocker arm cover, also called the cylinder head cover, and take a closer look at the rocker arms. I will also replace the oil seals on the rocker arm shafts and the oil seals for the cylinder studs. And also the cover gasket, called an o-ring in the parts list, will be replaced with a new one.

41. The valve adjustment screws. The rocker arm shafts are eccentric and when you adjust the valves you loosen the lock nut and turn the rocker arm shaft with a screwdriver. When correctly installed the punch mark on the end of the shaft should turn against the +/- marking on the washer.

42. This is how I removed the rocker arm shafts on this cover. They were very easy to remove because the oil seals are worn. They can also be removed by taking off the washer plate and then screw the lock nut back on the shaft and pull them out one by one with a pair of taped pliers.

43. From here I can pull them out with my fingers.

44. When the shafts are pulled out the rocker arms are loose and can be taken out and inspected.

45. This rocker arm has got signs of wear. I have got a set of used rocker arms and shafts that are in good shape that I bought from a breaker here in Norway and I will replace all of them if necessary.

46. Before I start to clean up the rocker cover, I have also removed the tachometer gear. This is very simple to remove by using a pair of pliers and just pull the gear out. If the tachometer gear is leaking, the oil seal in the front end and the o-ring on the guide must be replaced.

47. The camshaft and the cam chain sprocket are in place. The only way to get these parts in place is by following the manual. The sprocket should be slid on to the camshaft with the arrows on the right side, the clutch side, and then the camshaft should be manoeuvred in to place from the right to left through the loop in the cam chain.

48. Before the camshaft can be timed the engine should be turned to its TDC, the T mark on the timing advancer should align with the index mark. Then the engine should be turned exact 90 degrees counter clockwise with the 17mm nut on the end of the crankshaft. This can be confirmed by the position of the timing advancer. It should align like on the picture.

49. Then the camshaft should be turned till the notch on the right side points upwards. Now the sprocket can be turned till the arrow without any letter points to the front and are parallel with the gasket surface. The chain can now be installed on the sprocket. When the chain is on the sprocket, check that the arrow is in the correct position. If not move the chain on the sprocket till it is.

50. When the cam chain is in the correct position, hold the camshaft in position and turn the engine with the 17mm nut on the end of the crankshaft till the bolt holes in the sprocket and the bolt holes in the camshaft align. You can only screw in one bolt at a time. The engine must be turned to be able to screw in the other bolt. I have applied a drop of blue Locktite on the bolts.


51. After the cam chain sprocket bolts are torqued down I check that the camshaft is correctly timed. I turn the engine counter clockwise till the T on the timing advancer aligns with the index point. Now the arrow on the cam chain sprocket with the letter T next to it should point towards the front of the engine, and it should be parallel with the gasket surface.


52. Now I can install the cylinder head cover with the rocker arms. I have replaced the gasket, and I have applied a thin layer of non hardening gasket sealer to the cylinder head gasket surface. First I bolt the cover down till it is tight to the cylinder head.

53. The next step is to torque the cylinder head cover, cylinder head and cylinders, down. I do this in three steps. First I torque them down to 15 Newton following the pattern in the workshop manual. Then to 20 Newton, and at last to 25 Newtonn.

54. Next I install the cam chain tensioner unit. I have replaced the gasket and the bolts. When it is installed, I adjust the cam chain tension and install the tensioner cap whith a new o-ring.


55. Before I start to adjust the valves I check that the rocker arm shafts are correctly installed. If the punch mark points the wrong way, release the lock nut and turn them 1/2 a turn with a screwdriver till the punch mark faces the +/- marks.

56. For adjusting the valves I screw off the adjustment caps and watch the rear (intake) valve on the right side cylinder as I turn the engine counter clockwise with the 17mm nut on the end of the crankshaft. After it has opened and closed, I turn the engine till the T mark on the advancer aligns with the index mark. Then I adjust both valves on the right hand cylinder. When they are correctly adjusted I turn the engine counter clockwise exactly one turn till the T mark aligns with the index point again, and then I can adjust both valves on the left hand cylinder.

57. I set the valve clearances to a loose 0,10mm by loosening the lock nut and turning the eccentric shaft till the correct clearance is achieved. Then I hold the shaft steady with the screwdriver and fasten the lock nut. I always recheck the clearance after I have fastened the lock nut.

58. The engine is ready assembled and I have put on a set of newly cleaned and rebuilt carbs for this picture. Hopefully this engine will run for several more years.



1975 KZ400S engine rebuild

This is the pictures taken during a tear down and rebuild of my 1975 KZ400S engine in the fall 2006. The only difference between the 75 S and the D engines is the lack of an electric starter and a complete starter clutch.

Tear down


1. Cylinder head cover with rocker arms.

2. Camshaft, valves and cylinder head.

3. Cylinder head. The picture shows the combustion chambers and the exhaust balancing chamber that is integrated into the cylinder head/cylinders.

4. Cylinders.

5. Cylinders off.

6. Cylinder bores.

7. Pistons and piston rings.

8. Front cam chain guide. This one has split and needs to be replaced.

9. Generator.

10. Clutch and primary drive.

11. Generator rotor and starter sprocket. The 75 S engines have got the large starter sprocket installed because of an integrated collar, but not the starter clutch. This sprocket was dismissed on the later S models and replaced with a collar between the flywheel and the crankshaft oil seal. As you can see I have also cleaned the engine case. And since this engine doesn't have a starter clutch it is no need for taking off the rotor from the crankshaft.

12. Right hand side of the engine with the clutch, primary drive, shifter shaft and oil pump removed.

13. Clutch, oil pump, shifter shaft and pushrod.

14. The oil screen that is protecting the oil pump by preventing large fragments from entering it. This one should be taken off and cleaned from time to time. It is accessible from the underside of the engine, and the cleaning can be done together with an oil and filter change.

15. The oil pressure relief valve.

16. The kick starter gear and the inside of the oil screen.

17. One of the reasons I'm rebuilding this engine. I had a free play in the outgoing shaft, and when I split the crankcase I found that the bearing on the outgoing shaft from the transmission has been spinning in the crankcase.

18.The inside of the bottom crankcase half. As you can see there are a lot of fragments from all the worn chain guidess.

19. The transmission.

20. The sprockets for the cam chain and the balancer chain located in the middle of the crankshaft. The sprocket for the balancer chain is the one that should be inspected closely for wear.

21. The complete crank balancer. This is the second reason for the rebuild. I suspected the balancer chain and chain guides were worn, and they were so they need to be replaced. Typical signs of a stretched balancer chain and worn chain guides are increased vibrations and a grinding sound at a certain rpm. On this engine it was around 4000rpm.

22. Inside of the upper crankcase half with the main bearing bushings.

23. Crankshaft with con rods and a close up of the sprockets on the crankshaft. And a picture that shows the difference between the new and old bearing bushing. At this stage I measured the con rods and the journals for the con rod bearings to find out what size bearings I have to order. For the crankshaft main bearings on the 400, only one size was used by Kawasaki.

24. And finally I have cleaned the lower crankcase half.


At this point I have started to measure parts and decided what parts that needs to be replaced during assembling.

1. The first thing I have done is to clean the oil pump and installed it. Before I install it I have primed it with fresh engine oil.

2. Then I have replaced the oil seal for the shifter shaft since the old one was leaking slightly.

3. Replacing the front cam chain guide. This must be done before the balancer system and the bearing cap for the middle crankshaft main bearings are installed.

4. Replacing the clutch pushrod and the outgoing shaft oil seal. Note the outlet for the oil way next to the pushrod oil seal. This is for lubricating the roller bearing, and then oil is also forced through the main shaft and through an outlet that is lubricating the clutch house bushing. On the 400 A, D, S and the early 400 C and B engines you will have to split the crankcase to replace the push rod seall.

5. Cleaning and checking the clutch parts. Here I have cleaned all the clutch parts and measured the thickness of the trust washer and the friction discs, and checked all the discs for warpage.

6. Checking and measuring the primary chain guides inside the primary cover, and the crankshaft oil seal. The screws for the chain guides must be secured with a thread lock.

7. Replacing the con rod bearings and installing the con rods to the crankshaft. To get the correct bearing size the hole in the con rod and the crankshaft journal must be measured to find the difference between the diameters. Then the table in the workshop manual can be used to pick the correct size.

8. Replacing the crankshaft main bearings and the balancer chain guide that is installed on the bearing cap. Then I installed the crankshaft into the top crankcase half and torque down the bolts for the con rod bearing caps. The crankshaft main bearing comes in only one size, unlike the con rod bearings, and as long as the journals are within the service limit they will work fine.

9. Installing the crank balancer and the second chain guide. It is important that the instruction in the manual is followed to get the timing right.

10. Then I took out the outgoing shaft to prepare for locking the bearing to the crankshaft halves and joining the crankcase. The last picture shows the needle bearing on the the other end of the outgoing shaft. I took it off just for the photo.

11. For locking the outgoing shaft bearing to the crankshaft preventing it from spinning I have been advised to use Loctite 648. And I'm using Threebond 1104 liquid gasket, applied sparely with a small paint brush on the lower crankcase, for the gasket mating surfaces. But first I have cleaned the outside of the bearing race and all the mating surfaces with thinner to make sure all the old gasket sealer is removed and that all remains of oil are washed off before applying the Loctite and the Threebond.

12. Then something happened that I might have been able to avoid. When I bolted the crankcase halves together two of the M6 bolts broke off. I remember that two of the bolts were hard too loosen when I split the crankcase, and I should have checked all the bolts more carefully. They probably started to crack when I loosened them. The way I have fixed the broken bolts are probably not the way a workshop would have done it, but it worked. I used the hole in the lover crankcase half as a guide and drilled out the bolts with a 5mm drill bit. Then I re-tapped the hole and cleaned out the remains of the bolts with a M6-1.00mm tap. One downside is that I rubbed off some metal of the crankcase with the drill when I drilled the first hole.

13. Installing the gear shifter shaft.

14. Installing the clutch and the primary drive. And for sealing the cover I'm using a thin layer of liquid gasket on each side of the paper gasket.

15. Installing the generator cover with the stator and the field coil. There is some surface rust on the parts. I have dried off the loose rust with a cloth and mineral spirit, but I don't want to use a wire brush or any other tool on the parts, so before installing the cover I have sprayed them with Quaker State QS14, a multi purpose oil that I have used for many years and that I know won't do any harm to the insulation on the stator windings. I also use a thin layer of liquid gasket on each side of this paper gasket.

16. Deglazing the cylinder bores. Normally I would have left this job to a workshop, but since I also had a set of new overbore pistons and rings that I could use just in case I had to re-bore the cylinders, I decided to give this a try and then have the bores measured afterwards. I used a flexi hone and a battery drill that was strong enough for the job, and it has the advantage of not spinning too fast. The ideal speed is 60~100 rpm and the hone should be moved fast up and down in the bore as it spins. This should give a cross pattern were the lines is crossing each other at an angle of close to 45 degrees. I let the hone spin for 20~25 seconds in each bore, and I used mineral spirit in the bores and on the stones (I could also have bought special honing oil). I didn't won’t to take away any of the metal, just rubbing it up. After the deglazing I washed the bores in hot soapy water several times, and between the washing I covered the bores with fresh engine oil and let is sit for a while. I then used a white paper cloth and cleaned out the oil. If there is no colour on the cloth, the bores are clean. If not, they must be washed again. And after rinsing the bores with water, the bores should be covered with oil immediately. They will start to rust incredibly fast. After I finished the bores, I took the cylinders with me and had the bores measured. And they measured well so I decided to use in new standard pistons and rings.

17. Installing the piston rings and the pistons. Before I installed the piston rings, I checked the ring gap on all rings by inserting them into the cylinder bores and using a piston for getting them square in the bore. I installed one of the piston pin circlips before I installed the pistons on the con rods. And before I installed the second, I covered the opening in the crankcase to avoid loosing a circlip into the crankcase.

18. I have also replaced the o-rings in the bottom of the cylinder liners, and the o-rings for the oil ways located between the crankcase and the cylinders. Then I installed a new rear cam chain guide into the cylinder block before I installed the base gasket and installed the cylinders. I used a small screwdriver for compressing the piston rings for entering them into the cylinder bores. A ring compressor would probably have been easier to use. At this stage I also installed the two dowel pins for the cylinder head.

19. Finally I can install the cylinder head gasket, the cylinder head, the camshaft and the cam chain sprocket. I had this cylinder head off recently and replaced the valve guide seals and lapped the valves so this time I have only cleaned out the soot. Then I timed the camshaft, bolted the cam sprocket to the camshaft and secured the bolts with thread lock. Finally I can install the cylinder head cover. This cover does not have a groove for a gasket, and the cam end plugs are the "new" rubber type. So again I have applied a thin layer of liquid gasket for sealing the cover. Then I torque the cylinder head bolts down according to the order in the workshop manual. This order is also marked with the numbers from 1 to 8 on the cylinder head cover. Then I installed the cam chain tensioner unit, adjusted the cam chain, and finally adjusted the valves.


And finally the engine has been installed in the bike, and here is a video and sound clip that was taken after the engine was installed:



Odd Ivar


KZ400D3 Crankshaft problem

This is the pictures I took of the crankshaft in my 400D3 engine. The sprocket for the balancer chain is worn out and the crankshaft has to be replaced. This wear is a result of a stretched balancer chain and worn balancer chain guides that has been left without attention for too long.