Bulletin#: 73 H-12
Date: July 29, 1972
Bike(s) affected: H1B
Subject: H1-B ignition timing

Action taken:
There has been some confusion concerning the proper ignition timing of the H1B.  It is the purpose of this bulletin to clear up this situation. Optimum ignition timing for the H1-B is 23 deg. (2.94mm) BTDC. However, as the graph below (not copied here) shows, if new points are initially set at 23 deg. they will soon retard 1 deg. because of rubbing block wearing-in, and then advance to more than 25 deg. (from contact erosion) where detonation causes piston holing and severe engine damage. Since engine performance varies little from 19 deg. to 25 deg., the factory recommends that new points be set at 20 deg. BTDC (2.23mm). From this setting the timing will advance to 23 deg. by itself in a matter of a few thousand miles. After 3000 miles, point wear levels off, so that when the points are adjusted after that time, they should be set at 23 deg. until they are replaced. If plug fouling and sluggish performance is a serious problem on a new H1-B, advancing the timing to 23 deg. right away may solve the problem, but it will be necessary to check and adjust the timing frequently during the first few thousand miles to prevent engine damage due to over advanced timing.

Bulletin#: 73 H-13
Date: August 30, 1972
Bike(s) affected: H2
Subject: H2 Rear brake modification

Action taken:

On early H2's there is a tendency for the brake pedal to bounce up and down when the brakes are applied on rough surfaced road. This is due to the length of the brake cam lever and associated geometry. The factory has redesigned the rear brake linkage parts to give a more positive brake feel. The torque link has been lengthened, the brake rod now has a 5 deg accommodation bend in it, and the brake cam lever and the brake pedal shaft lever have both been shortened. These changes greatly improve breaking smoothness without affecting overall brake leverage. The new parts had been incorporated on H2's after frame #H2F-05214. These parts are interchangeable as a set of four on any early H2. They are standard and must be used as replacement on all H2's frame #H2F-05215 and above.

 

Bulletin#: 73 H-14
Date: Sept. 20, 1972
Bike(s) affected: H2
Subject: High speed wobble

Action taken:

PROBLEM: There have been isolated complaints concerning the tendency of some H2's to wobble at high speeds on a straight course.  This is especially a problem to the rider who wishes to participate in road racing, drag racing, or other applications where speeds in excess of 80 mph are encountered.

CORRECTION: Based on the finding of an extensive testing program, it is suggested that the original 3.25-19 Yokohama Y-623 front tire be replaced with a new type Dunlop H3.25-19 F6 tire.  Thousands of test miles on a number of different H2's, under widely varying road and speed conditions, have shown that this new tire definitely improves the H2's high speed handling characteristics.

ADDITIONAL MEASURES:

A.  WHEEL TRUING: After mounting a new tire, making sure that all spokes are tight, adjust the lateral and radial runout.  Standard lateral runout is 1mm (.04") with a service limit of 3mm (.12").  Standard radial runout is also 1mm, but the service limit is 2mm (.08").

B. WHEEL BALANCING: Balance as carefully as possible to ensure maximum wheel stability at all speeds.

NOTE: Be sure that the wheel turns freely on its bearings before attempting to balance it.

C. AXLE TORQUE: Make sure the front axle is tightened to 55 lb ft (7.5 kg-m).  Several cases of speed wobble have been traced to loose axles.  NOTE: To ensure accurate torque measurement, use a torque wrench and an Oil Pump Pinion Socket, P/N 99990-064.  These sockets fit the flattened ends of the H2 axle perfectly.

D. REAR TIRE: In some cases, an excessively worn back tire will contribute to high speed wobble.  Any such tire should be replaced if instability is to be cured completely.

E. TIRE PRESSURE: Check to see that both tires are inflated to proper pressure: 26 PSI front, 31 PSI rear.

Bulletin#: 73 H-15
Date: Oct 1, 1972
Bike(s) affected: H1
Subject: H1 engine mount shims

Action taken:

H1 motors exhibiting high vibration should have engine mount shims installed.  These are the same shims used on the H2.  Installation has been done at the factory for H1's from frame number H1F-00001. The rear shim is 38mm long, the front is 20mm long. When installing, check the clearances between the engine bosses and frame lugs. (Picture shows the bottom 2 mounts the ones to be checked.)  Insert the correct sized shims, and tighten the 10mm bolts to 25 lb-ft of torque, and the 8mm bolts to 15 lb-ft.
 

Bulletin#: 73 H-16
Date: Oct. 20, 1972
Bike(s) affected: H1, H2
Subject: Oil pump modification

Action taken:

PROBLEM: There is a tendency for some three cylinder models to smoke excessively from one exhaust pipe.  On the H1 and H2, it is usually the right cylinder that is affected.

CAUSE: This problem has been traced to faulty O-ring seating in the oil pump end cover.  After installation, the two O-rings inside the cover shrink approximately .1 to .2mm in diameter.  This shrinkage allows oil to seep around the seals and into the end cover chamber.  From this point, the excess oil is pumped to the right cylinder which is serviced by the end cover orifice, resulting in smoking and premature sparkplug failure.

It should be noted that other symptoms may indicate oil pump malfunction, such as right hand piston seizure.  This may be caused by oil being forced back into the main pump body through defective O-rings.  As a result, the right cylinder is starved for oil, and this situation will eventually lead to seizing.

CURE: To remedy this problem, the oil pump end cover has been redesigned to prevent oil seepage.

A. The radius in the end of  the cover has been decreased in depth to give the O-rings less "squish" space.

B. The bottom radius has been eliminated.

C. The internal diameter of the chamber has been decreased from 14.0±.1mm to 13.7±.05mm to compensate for shrinkage.

D. A slight shoulder has been added to the chamber base to further compress O-ring.

A conversion kit is available to correct older model oil pumps.  The kit consists of two mounting screws, two O-rings, and a new oil pump end cover.  These parts will fit all three cylinder oil pumps.  Conversion kit P/N 99990-016.  IMPORTANT: Whenever an oil pump is disassembled for any reason, the O-rings must be replaced.  The end cover O-rings are P/N 16090-002.

NOTE per Dave Ray:

Bulletin#: 73 H-18
Date: Nov. 17, 1972
Bike(s) affected: H2
Subject: Modified oil pump

Action taken:
Graph to correspond with carburetor changes in service bulletin # 73 H-19, the oil pump has been modified for slightly reduced flow. Old pump,  part #16082-033, labeled "H2-1" or "H2-2" is not to be used.  New pump, part #16082-042, "H2-3" is to be used. This is a factory installation from H2E-16078.

Bulletin#: 73 H-19
Date: January 18, 1973
Bike(s) affected: H2
Subject: H2 carburetor modifications

Action taken:

By monitoring warranty records, it has been determined that carburetor jet needle breakage is a recurring problem on many H2's. This failure results from the combination of throttle valve bore wear and engine vibration. In some cases the broken jet needle becomes lodged in the engine, causing severe engine damage. To remedy the problem of jet needle breakage and reduce the possibility of engine damage, the three original carburetors must be replaced with new type carburetors designed specifically to eliminate this problem. The new carburetors incorporate a redesigned light weight throttle valve slide, a heavier return spring, a modified spring seat, and a steel throttle valve guide pin. All other component parts remained unchanged from the "H2-2" type carburetor. The carburetors must be replaced on all H2's below H2E-23846.

 

The new carburetors incorporate the following revised settings. This second change obsoletes previous changes and only the "H2-4" carburetors have been used in production since engine number H2E-23846. (Settings are same as for the H2-2 carburetors.)

Bulletin#: 73 H-20
Date: Jan. 10, 1973
Bike(s) affected: H1, H2
Subject: H1/H2 gearchange assembly

Action taken:

Early H1 models used a gear change lever with a toothed lever staked to a rod, which would work loose. The new assembly is welded, and used on H1's after KAE-43902 and all H2's.

Bulletin#: H-20
Date: Nov. 17, 1972
Bike(s) affected: H2
Subject: H2 Carburetor Settings

Action taken:

To improve gas mileage, new carburetor settings have been used.

Bulletin#: H-21
Date: Dec. 20, 1972
Bike(s) affected: H1, H2
Subject: H1/H2 gearchange assembly

Action taken:

Early H1 models used a gear change lever with a toothed lever staked to a rod, which would work loose. The new assembly is welded, and used on H1's after KAE-43902 and all H2's.

Bulletin#: 73 H-21
Date: Feb. 12 1973
Bike(s) affected: H1, H2
Subject: Transmission Adjustment

Action taken:

On early H1 and H2 models there have been problems of gear engagement from excessive play in the stationary gears on the drive and output shafts. Several shims have been added to the transmission to correct specific problems. These changes have been incorporated to all H1's from KAE-59017 and up, and all H2's from start of production. For H1's and H2's that jump out of gear or fail to engage correctly, corrective action may be taken in the following manner:

 

Bulletin#: 73 H-22
Date: Mar. 29, 1973
Bike(s) affected: H1
Subject: H1 top gear bushing

Action taken:

There is a possibility for unusually fast wear of the inside surface of the top gear on the drive shaft, which could eventually begin to wobble and cause problems in the transmission. A new gear has been designed that incorporates a pressed in bronze bushing for longer life. This has been incorporated from H1 frame number KAF-57161 and to all H2's from start of production. The old part# is 13136-022, the new part # is 13136-041.

Bulletin#: 73 H-23
Date: May 5, 1973
Bike(s) affected H1B:
Subject: H1B air cleaner and carb settings

Action taken:

There have been complaints on early H1-B motorcycles of sluggish performance in the low and middle RPM range. To improve the overall performance of the H1-B, a new air cleaner was designed and a new set of carburetor specifications was used from mid 1972 production. This change applied to all H1-B's from engine number KAE-61607 and up. The new air cleaner has two additional air intake ducts to increase the air intake capacity.

 

Bulletin#: 73 H-24
Date: August 20, 1973
Bike(s) affected: H1D, H2
Subject: Stator Inspection

Action taken:

PROBLEM: There are several different problems which can result from a stator assembly failure on the H1D or H2.  The purpose of this bulletin is to supply some of the possible effects of a defective stator and to offer a comprehensive guide for checking the stator assembly.

CAUSES:

1. The insulation of the coils can be too thin in areas causing an internal short or a short to ground.

2. Engine vibration can lead to an open or short circuit.

3. Engine heat contributes to stator assembly failure.

4. Water corrosion on the AC generator due partially to condensation but primarily resulting from leakage is a large contributor to stator assembly failure.

SOLUTION: The most important measures that a technician can take to prevent stator assembly failure are in preventing water from entering the LH engine cover.  Because the inspection cover gasket is stiff and quite narrow, it occasionally does not conform well to the sealing surfaces.  GE Silicone Seal or similar sealant should be used with this gasket and with the LH engine cover gasket.

STATOR INSPECTION: If the stator is suspected to be defective, remove the LH inspection cover and visually check for broken wires, loose coils, or other signs of damage.  If nothing is found, remove the LH side cover and disconnect stator wires. 

By using an ohm meter follow the circuit tests below.  NOTE: It is advisable to make these checks with the stator installed on the engine, because some problems such as the stator coils touching the crankcase may otherwise go undetected.

NOTES:

All of the connections to the stator wires must be checked.  A bad connection causes the same problem as a bad stator.
 

A stator defect may cause problems when the motorcycle is running but may not be detected during circuit tests.  In this case visual inspection is important.
 

Sometimes a problem only occurs after the motorcycle is driven some distance and then disappears when the motorcycle is parked for a while.  This can indicate a fault that is sensitive to stator temperature.  In such a case the engine should be warmed up before making the tests.
 

The H1D yoke and stator assembly can be used as substitute on the H2, however, the H2  leads are too short for that assembly to be used on the H1D.

Bulletin#: 73 H-25
Date: Sept. 20, 1973
Bike(s) affected: H2
Subject: Swing Arm Modification

Action taken:

At the beginning of 1973, H2A production, modifications to the swing arm, swinging arm pivot shaft, and bushings were initiated.

SWINGING ARM:

The rear cushion bracket on the H2A swinging arm is welded 5mm to the rear of the H2 bracket position.  The H2A has seven chain adjustment marks as opposed to six for the 1972 H2.  Otherwise the two are identical.

SWINGING ARM PIVOT SHAFT:

The H2A pivot shaft has a smooth polished surface as compared to the H2 pivot shaft which has a semi-rough machined surface.

BUSHINGS:

The H2 uses phenolic bushings made of cotton or asbestos filler bonded with a phenolic resin.  The H2A uses sintered iron bushings for better resistance to wear and fracture.  The sintering process produces a spongelike structure in the metal making it capable of absorbing 20 percent of the total volume with lubricant. 

These changes were effective with H2E-23848.

Bulletin#: 74 H-26
Date: Jan. 15 1974
Bike(s) affected: H1, H2
Subject: 3rd Gear Shift Fork Modification

Action taken:

H1/ H2 transmission problems have often included poor third gear engagement.  This may be caused by two possible problems including the play of the fixed gears on the shafts and the lack of positive action in the third gear shift fork.

SOLUTION: Adjustment of the play in the transmission has been improved in H1 production since KAE-59017, and H2's from beginning of production.

The second problem has been counter measured by widening the base of the shift fork from 21.0mm to 24.5mm to keep the fork more rigid on the shift drum.  This wider fork is supported on both sides of the groove on the shift drum.  This modification is effective on H1's with KAE-87023 and H2's with H2E-31941.

Bulletin#: 74 H-27
Date: Apr. 26, 1974N
Bike(s) affected: H1
Subject: H1E engine ground wire

Action taken:

Early H1-E motors may misfire when under heavy electrical load- headlight on and turn signals flashing, for example. The problem was the new rubber mounts for the motor, which isolate the motor from the frame. The small black/yellow ground wires are too small to support the amperage of the ignition and lighting system. The problem was fixed after H1F-023021 by installing a ground wire, part #26011-084 between the frame and the engine chain cover. This should be installed on all H1-E's prior to H1F-023021.

Bulletin#: Ser. 74 H-28
Date: May 23, 1974N
Bike(s) affected: H1E
Subject: Brake fluid leak

Action taken:

On Some H1E's between H1F-025000 and H1F-030300 there may be a brake fluid leak around the allen bolt on the bottom of the steering stem. The solution is to tighten this bolt on affected H1's to 3.0 kg-m (22 ft lb.)

Bulletin#: 2/500-1
Date: December 19, 1975
Bike(s) affected: KH500-A8
Subject: Neutral positioner

Action taken:

The 1976 KH500 has a neutral positioning bolt on the upper crankcase. On some early KH500's the positioning bolt boss (In the crankcase body) was machined too short. Installation of the positioning bolt and pin in a short boss may interfere with normal gear changing. (A diagram shows a transmission measured in neutral. From the top indent in the shift drum detent plate to the top of the boss should be 22mm, 20mm is bad.)

The factory action is to install an extra gasket and washer under the positioning bolt. Dealer action is to reinstall added parts when servicing units, and check for added parts any time the neutral positioner is removed or a customer complains of shifting problems on an affected unit.
 

Bulletin#: 73 S-1
Date: Nov. 15, 1971
Bike(s) affected: S2
Subject: S2 Cracked Cylinder Heads

Action taken:

On early S2's there may be a possibility of cylinder heads cracking.  Head thickness has been increased from 16mm to 19mm.  Part number is unchanged.  Newer design heads were installed from S2E-07595 on.

Bulletin#: 73 S-2
Date: Nov. 20, 1971
Bike(s) affected: S2
Subject: S2 clutch rattle

Action taken:

Early S2's may develop a rattling sound on the right hand side of the motor, most noticeable in neutral with the clutch released. In gear or with the clutch pulled in the noise is eliminated. The cause is excessive clearance between the clutch housing drive fingers and the driven tabs on the friction plates. Standard clearance is .002-.022 in., (.05-.555mm) but the rattle becomes more prominent as the clearance exceeds .0010 in. (.25mm) To correct this clutch finger shims have been prepared. Part #92037-079 (.014 in, .35mm thick) and part #92037-080 (.010 in. .25mm thick.) Three are needed to repair one clutch.

Bulletin#: 73 S-3
Date: February 29, 1972
Bike(s) affected: S2, H1B
Subject: Shop Manual Errors

Action taken:

The following corrections should be made to the SM-2 revised. (July 1, 1971.)

Note: The SM-2 Revised does not contain any service information for the H1-B. Use the new H series shop manual for the H1-B.

A. Page 10
Remove the headings from photographs Number 29 and 30.

B. Page 18, Table 6
Compression pressure for the H1 should be 142 lb/in²  at 200 RPM. Compression pressure for the S2 should be 156 lb/in² at 200 rpm.

C. Page 20, paragraph e.
The connecting rod small end play service limit should be 0.0039in. (0.10mm).

D. Page 27, Second Column. The eighth line from the bottom should read:
"with 6 friction plates (7 in H series) and 5 clutch"

E. Page 28, Second Column. Line 5 should read:
"the clutch hub. Thus the drive train is as"

F. Page 46, 47. These two pages are correct for the S2, but not for the H1. See correction for pages 44 and 45 of the new H series shop manual for the H1.

G. Page 97. Diagram #407 should be correct to match the diagram below:

(Shows wiring diagram of AC generator and voltage regulator.)

Bulletin#: 73 S-4
Date: July 20, 1972
Bike(s) affected: S2
Subject: New S2 Oil Pump

Action taken:

In some areas S2 owners have complained of excessive exhaust smoke, spark plug fouling, and oil wetting of the muffler tips.  A new oil pump, part #16082-041, has been developed for the S2 350cc. The oil flow has been changed for reduced output. The I.D. make is S2-2, and is used on all new S2's from S2E-16293. The old pump is part #16082-030.

Bulletin#: 73 S-5
Date: Sept. 30, 1972
Bike(s) affected: S2
Subject: S2 crankcase and crankshaft modification

Action taken:

To correct some instances of crank bearing failure, a new crankcase/crankshaft assembly has been designed. All S2's from S2E-18507 and above have been fit with a new six bearing crankshaft similar to that on the H1. The new crank can be installed on older S2's with a 4 bearing crank. The old crank assembly part # is 13031-037, the new is 13031-040. The crankcase has had additional oil passages drilled in the upper half, and is used on S2's from S2E-24749 up. The part number is unchanged, #14001-049.

Bulletin#: 73 S-6
Date: Oct 1, 1972
Bike(s) affected: S2
Subject: S2 engine mount shims

Action taken:

S2 motors exhibiting high vibration should have engine mount shims installed.  These are the same shims used on the H1 and H2.  Installation has been done at the factory for S2's from frame number S2F-26858. The rear shim is 38mm long, the front is 20mm long. When installing, check the clearances between the engine bosses and frame lugs. (Picture shows the bottom 2 mounts the ones to be checked.)  Insert the correct sized shims, and tighten the 10mm bolts to 25 lb-ft of torque, and the 8mm bolts to 15 lb-ft.
 

Bulletin#: 73 S-7
Date: Dec 5, 1973
Bike(s) affected: S2
Subject: S2 Oil Pump Modification

Action taken:

PROBLEM: There is a tendency for some three cylinder models to smoke excessively from one exhaust pipe.  On the S2, it is usually the right cylinder that is affected.

CAUSE: This problem has been traced to faulty O-ring seating in the oil pump end cover.  After installation, the two O-rings inside the cover shrink approximately .1 to .2mm in diameter.  This shrinkage allows oil to seep around the seals and into the end cover chamber.  From this point, the excess oil is pumped to the right cylinder which is serviced by the end cover orifice, resulting in smoking and premature sparkplug failure.

NOTE:  On some very early S2's the end cover chamber was connected to the center cylinder, rather than the right.  On all later models ('72, '73) the end chamber is connected to the right cylinder.

It should be noted that other symptoms may indicate oil pump malfunction, such as right hand piston seizure.  This may be caused by oil being forced back into the main pump body through defective O-rings.  As a result, the right cylinder is starved for oil, and this situation will eventually lead to seizing.

CURE: To remedy this problem, the oil pump end cover has been redesigned to prevent oil seepage.

A. The radius in the end of  the cover has been decreased in depth to give the O-rings less "squish" space.

B. The bottom radius has been eliminated.

C. The internal diameter of the chamber has been decreased from 14.0±.1mm to 13.7±.05mm to compensate for shrinkage.

D. A slight shoulder has been added to the chamber base to further compress O-ring.

A conversion kit is available to correct older model oil pumps.  The kit consists of two mounting screws, two O-rings, and a new oil pump end cover.  These parts will fit all three cylinder oil pumps.  Conversion kit P/N 99990-016.  IMPORTANT: Whenever an oil pump is disassembled for any reason, the O-rings must be replaced.  The end cover O-rings are P/N 16090-002.

Bulletin#: 73 S-8
Date: Sept. 30, 1972
Bike(s) affected: S1/S2
Subject: S1/S2 Clutch Cable

Action taken:

To correct instances of excessive clutch cable breakage the cable diameter has been increased from 2.0mm (54011-040) to 2.5mm (54011-053) and has a teflon coating on the inside of the cable.  The new cables have been used after engine numbers S1E-08257 and S2E-38301.

Bulletin#: 74 S-9
Date: Mar. 22, 1974
Bike(s) affected: S1/S2/S3
Subject: S1, S2, S3 Voltage Regulator

Action taken:

The voltage regulator has been changed to reduce the charging voltage from 16.0 +/-0.5 volts to 15.0 +/-0.5 volts in an effort to reduce excessive blown headlights. 

The new regulators were first manufactured in August, 1973 beginning with the first lot of the month.  This information is contained in lot number 3H1.  Any voltage regulator for the S1/S2/S3 manufactured before August, 1973 is the old 16 volt regulator.  The date of manufacture of any voltage regulator can be determined by referring to the following information:

First charactor: year, ie. 3=1973

Second character: month, A=Jan, B=Feb, etc,

Third character: Lot#, ie, 1=1st lot of the month

Old part#= 21066-012   New part#= 21066-020

Effective I.D.:

S1= S1F-13618

S3= S3F-02356

Bulletin#: 74 S-10

Date: Apr. 5, 1974
Bike(s) affected: S3
Subject: S3 engine ground wire

Action taken:

Early S3 motors may misfire when under heavy electrical load- headlight on and turn signals flashing, for example. The problem was the new rubber mounts for the motor, which isolate the motor from the frame. The small black/yellow ground wires are too small to support the amperage of the ignition and lighting system. The problem was fixed after S3F-0005187  by installing a ground wire, part #26011-084 between the frame and the engine chain cover. This should be installed on all S3's prior to S3F-0005187.

Bulletin#: 2/400-1

Date: Oct. 10, 1975
Bike(s) affected: KH400
Subject: Ignition Testing

Action taken:

The KH400 ignition system consists of three signal generating coils, two capacitor charging coils, a CDI unit, and three ignition coils.  Components can be tested using either of the two methods outlined.