Browse Category: Suzuki GT750 Engine overhaul

When I did the first restaurtion of the bike the engine was not opened. It was running fine exept from some loss in power from time to time. I thought it was an issue with the carburetors / fuel system. Later on I understood it was related to the sealings in the crankshaft. Had to start all over again, the engine out of the frame and get going with the overhaul of the engine.

SRIS system

According to the information in fig 1 the SRIS tube from the front side should go from the left cylinder inlet ( see the label C in fig.2) to the center cylinder SRIS outlet port. The SRIS type 2 system. Center to Right and Right to Left, all according to fig.6-13 from the manual






From left cylinder inlet




To the Center cylinder SRIS check valve outlet.



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Fig.4 shows the two remaining tubes. From Right to Left (red arrow) and Center to Right (yellow arrow ) .

Cover on the left hand side

Did the mounting of the cover on the left hand side today. The cover will also house the timing plate, points and capacitors.

I was advised to add some silicone gasket in addition to the new paper gasket, please see the pictures.




Add silicone.

Don’t add silicone where I have the yellow marker. I did it wrong and had to wipe it off after the mounting.



Mount the gasket. I had both alignment studs in the cover and therefore I put the gasket as shown.



Add silicone gasket.

left side cover

To be able to align the side cover in its correct position the pin must hit the hole in the disk rotating the timing camshaft. Be gentle and don’t use force. Rotate a bit to left and right until the cover snap on.



I still had the original screws. Did some polishing on the heads before the mounting.

Done !

Cylinder in place

The difficult job is done, got the cylinder block down onto the pistons without breaking any of the piston rings. Got a helping hand from a friend, was too scared to do it alone.




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Hmm, rusty bolts. A new kit has been ordered from UK. The attempt to refurbish the old ones was not a success. Let’s hope I soon get the parts and can mount the cylinder head the next weekend.

Verifying the thermostat

Step 1. Remove the thermostat housing

Not an easy task, all of three screws were stuck. Applied some anti rust solvent and went ahead with the job the next day.

The housing were heated up by using a butane torch and in addition I used an impact screwdriver to get the screws loose.



Finally I had the parts separated



Cleaning of the parts using the ultrasonic washer


Step 2, verify the function of the thermostat:

According to the service manual the vale opening temperature is 82 deg C and wide open (8mm)  at 95 deg C.


82 deg C and closed



85 deg C and half opened


90 deg C and almost fully opened

Good to go, the thermostat is functioning as specified.


Thermostat response time:

See how it’s closing only seconds after it is out of the boiling water.


Step 3, polishing the thermostat housing:


Nice and shiny 🙂


Installing pistons

New parts to be mounted


Part no


Step 1: Circlip


Mount one circlip in all three pistons. Move the end position away from the cutout. Be gentle and don’t bend the circlip too much. Use a screw driver as a tool to flip it into the position in the groove. Always new circlips, never reuse old one.


Step 2: Piston rings

Piston rings

Mount the piston ring as shown on the photo. Be aware of the pin locking the ring, see the arrows. You don’t need any special tools for mounting the piston rings. They are quite expensive an if you are afraid of braking any of them, drink a beer before you start 🙂

Step 3: Gasket and O-rings



Mount the gasket, don’t forget to mount three O-rings underneath the gasket.



Before you continue, cover all holes so you don’t drop any parts inside the engine. Can be difficult to retrieve.


Step 4: Pistons



Oil the bearing before and after it’s installed in the rod.

Piston mounting

Remeber the washers (31)




Push in the piston pin and mount the last circlip at the end.




Make sure the right piston (label R) is on the right hand side and the arrow is pointing forwards. The left and center piston are identical and are both labeled L

Generator and front sprocket

Mounted the rotor part of the generator yesterday + the o-ring and the cover behind the front sprocket


Use some pieces of wood to lock the crank.




Mount the rotor part of the generator and torque to about 20 Nm




Mounting a new oil seal in the cover behind the front procket.


Mounting a new O-ring, use some grease to keep it in place


Mounting the cover

Assembling the clutch and the kick starter

The photo below shows how I did the assembly of the clutch and the kick starter.


Step 1: Fit the oil guide plate. Drive all three screws well home. If you are to use thread locker or not depends on your religion. Do you believe in it or not. Someone says ” don’t use it, you will never get them loose”. Others say….And I’m not gonna tell you what I did .





Step 2:


Mount the shim ( no.16)


Step 3:


Mount the spacer, chamfer side goes in back.


Step 4:


Mount the clutch


Step 5: 


Mount the bearing assembly



Step 6:


Mount the spacer, chamfer side at the front.


Step 7:


Mount the clutch sleeve hub (5),  locking washer (7) and center nut (6)

Always use a new locking washer, not the old one like I did on the photo.Why did I use the old one ? I didn’t know I had a new one until I had completed the assembly process. Can save the washer for the next time.


Step 8:

Torque setting for the center nut is about 50 Nm.

Before torquing up the center nut you need to some how lock the sleeve hub (5) Never use a screwdriver on the edges. You can make a special tool using old steel plates from a clutch. I had no such tool but did it in this way:


Lock into one of the gears and do something clever to lock the front sprocket, like I did on the photo above.


Don’t forget to bend the “new” lock washer. One of the edges is enough.


Step 9:

Before mounting the clutch check the specifications of the cork plates and the springs


STD lenght: 40,4mm. Spring setting limit :1,4mm


STD thickness: 2,9-3,1mm. Wear limit: 0,2mm



Let the cork plates be quite oily before you mount them




Grind off any layers from the steel plates.





Start with the cork plate, then the steel plate. The last plate should be a cork plate. The steel plate has a little radius on one side and a flat side on the other side. The flat side at the bottom and the radius facing  against the front.

8 cork plates and 7 steel plates.

And as you can see, I found the new lock washer after I had completed the assembly.


Step 10:

Mounting the clutch pressure disk.



Remeber the mount the clutch release shaft (17)

Mount the bolts in a pattern for an even distribution of the force. When all bolts are driven home you just give it a tap . No torque settings


Step 11

Kick starter


Mount the spring holder (and the plate behind if not already mounted)



Mount the spring


Competed !



Step 12

Mounting oil seals, gasket and side cover


There are two oil seals in the cover, both should / can ( depends on age) be replaced. Add grease on the seal side.



I found both mounting studs quite stuck in the cover, not at the case side. Therefore I put the gasket at the cover side.




Done !