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.

Case closed

Phuu, the crankcase is finally sealed and closed.

Please see the summary of how I did it: ( And this is not the time to say I did it wrong, not in a mood to undo, please let me stay happy )

Step1:

Cleaning the surface and do a test assembly to verify it’s all good.

I had a tube of the genuine Suzuki seal but I was afraid to use it. The first impression was a thin soup, looking more like an old oil leakage from 1976 ūüôā Therefore I bought something more modern from Loctite.

Loctite 574Suzuki seal

After some evaluation and testing of the Suzuki seal I think it’s might be good after all. After few minutes in air it changes to a more sticky paste. Totally different from the Loctite 574. The Loctite is curing after it is pressed against the alu surfaces, not in air. Then, what to use ? Since I had bought the modern stuff from Loctite and it’s made for this purpose I took the Loctite and applied the glue according to the instructions in the data sheet. It’s recommended to apply in one string and on only one surface.¬†On the bottom case I only took some glue around the o-ring connecting the water pump. Remember to add ¬†some silicone seal around the black plastic cover at the end of the gear shaft.

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Step 2

Mount the top case and install all the bolts on the top side. Secure the bolts but don’t use the maximum torque at this stage. ¬†Check to see the crankshaft is still movable.

Turn around the engine to the bottom side and mount all the bolts according to the correct torque settings. And now is the pay off time for using a carton to keep track of the placements.

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Please see the placement order and torque settings below. I have labeled 6mm bolts blue, 8mm green and 10mm yellow.

Click on the images for detailed information

Since I live in Norway I use Nm as tourque settings.
10mm bolts 32Nm
8mm bolts 15 Nm
6mm bolts 8 Nm

Torque20160319_135520

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Bottom torque sequence

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Bolt no 13 need a copper or alu washer + some extra silicone sealing

 

Top torque sequence

 

Step 3

Installing the tachometer drive.

Mount a 6mm screw at the top to secure the inner part.

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Tap the drive down to the position where you can see the mounting hole for the screw.

Step 4

Enjoy the work, dry off remains from the seal and do something clever to avoid parts falling into the engine.

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Am I ready ?

Hmm, what is missing before I glue and mount on the upper part of the crankcase…. Am I good to go ? I will double check up against instructions on the DVD. If anyone see something missing, PLEASE let me know.

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Upper part of the crankcase

Started the day planning how to mask and paint the upper part of the crankcase. The lower part is left as naked raw aluminium as it came from the factory in 1976. I know it’s common to paint both parts as it will look better, at least in the beginning before the lower part of the crankcase is getting worn after some time on the road.¬†Then I got a second thought, why not polish the parts. All side covers will be polished and if I polish the visible parts of the crankcase it might look good. And I don’t have to worry about any damage on the paint during the assembly process.

Here is the result:

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I think the result came out quite okay using AutoSol.

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Kick Starter Sequence

Here is the sequence of the kickstarter. I had to assemble without paying attention to the alignment marks, because the one of them is not present. ( look at my privious post )

Both punch marks at the end of the axle and the kick starter are present and aligned.

Sequence 1B

See the punch marks at the yellow and green arrows.

 

Sequence 1                       Klick on the images for details

Sequence 1

The front shaft is connected to the clutch and will rotate like the red arrow shows.

The rear shaft is connected to the front sprocket and will rotate like the yellow arrow shows.

The little clutch on the kick starter shaft is in released position and is not in contact with the rotating gears.

Sequence 1A

The oil guide hole is also facing upwards. Everything should be okay.

 

Sequence 2

Sequence 2

The engine is stopped and we try to restart the engine by kicking down.

The little clutch will connect and the rotations on the shafts will be according to the yellow arrows. And of course, in the same direction as while the engine is running.

When the kick starter is released it all goes back to sequence 1

Kick Starter

This was a bit tricky, I need some FB help to verify my assumptions.

As far as I understand this is the correct assembly of the kick starter.

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The oil guide hole (3 in the drawing below) is facing upwards and the kick starter is in contact with the kick starter quide 4.

In this position the motor can run and the kick starter is in released position, free from any contackt with the gears. See the next picture.

 

released

No contact with the gears.

So far so good, but now it all fells apart ? Map and terrain does not fit anymore.

Punch mark

In all manuals and also on the DVD from the Kettle clinic it shows a punch mark on the starter shaft and the spline on the shaft. They have to be aligned. If I do so it all comes out wrong and the oil guide is not longer facing upward when the kick starter is in contackt with the kick starter guide.

It looks like it’s only a punch mark on the kick starter shaft on my bike. The second mark is difficult to find. There are som scratches and a groove but nothing like a punch mark. See the next picuture. (click on the image for details)

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If I align according to the orange arrow the facing of the oil guide hole comes out wrong.

 

Compare the assembly against the instructions at the DVD.

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If I don’t care about the punch mark and try to mount according to the DVD from the Kettle Clinic it looks alright. The oil guide will face upwards as it should when the kick starter is in released position ( disconnected from the gears )

Please give me some feedback about this issue. ¬†When I’m 100% sure it’s all correct I might post a video showing the entire sequence of the kick starter in action.

 

Gear shifting

The fun part of the engine overhaul: Playing with the gear shifting

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This weekend I have mounted the gear assembly. First I study the drawing in the service manual, spare parts manual, Haynes and Clymer workshop manuals, looked all over again.. ??? Perhaps I’m stupid or something, but I don’t get it. After the mounting process and playing with the gear shifting I think I have some answers.

Let’s go back and take one step at a time:

Step 1: 

Look at the picture below. While shifting gear the CAM will rotate, and as you can see, the shifting FORK is fixed in the groove and will be moved to left or right depending of the track pattern in the shifting CAM

The gears are mounted on top of the forks and will therefore be moved according to the tracks in the CAM.

drum and fork

For detailed information about mountig the CAM and FORK, please look at my privious post ” Mounting the cam for the gear shifting”

Step 2:

Mount the gear assembly according the the first picture on this post. Remember to mount the all C-rings for locking the gear shaft. Slide the front and rear gear assembly down into the forks.

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Rear assembly, notice the position of the forks. Rotaton of the CAM will slide the gears to left or right.

 

Step 3:

Mount the CAM stopper:

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The spring loaded CAM stopper (items 17-20 on the drawing)  will prevent the cam to rotate out of its correct position.

 

 

Step 4:

How do we rotate the CAM ? We all know we are kicking the gear shifter down into the lowest 1-gear and upwards for the higher 2-5 gears. But how does the CAM rotate all the way ?

Shifting down:

 

shift down

Shifting down, the movement follow the red arrow og the rotation of the cam the yellow arrow. The upper little metal part is spring loaded and will be pushed by a tiny little piston into a cut out in the CAM. In this position it’s locked and will move the entire CAM to a left side rotation in the picture.
When you release the pressure from the gear shifter the spring loaded mechanism will return to right and grab into a new cut out, ready for a new rotation.

 

 

Shifting up:

shift up

Same explanation as above but opposite direction.

 

The  spring loaded mechanism in details:

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A bit tricky to keep all parts in position before mounting.

 

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Mount the brackets and use thread lock on the screws.

 

Step 5:

Check the gear shifting:

Gear ratio

The table above shows the gear ratio. I put a piece of tape on the outgoing axle aligned to the mark on the incoming axle from the clutch.

1-gear

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By counting the revolution on the incoming axle for one turn on the outgoing axle I got the same ratio as in the specifications. Almost three turns (2,8) in the 1-gear position for one revolution at the outgoing.

 

Neutral position:

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2- gear. Ratio of 1,7:

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3-gear. Ratio of 1,3:

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4-gear. Ratio of 1,1:

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5-gear. Ratio of 0,9

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All gears are shifting according to the specifications. It would be stupid to proceed with the assembly without checking the gear shifting.

The gearbox is not without any worn parts. Based on the experience before dismounting it still shifts smooth and nice without any problems at all. I dont’ want to spend money and work on parts if it’s not needed.

I can sleep well tonight ūüôā

 

 

Mounting the water pump

Finally, after a lot of discussion regarding the facing of an oil seal, it’s time to mount the water pump.

Align the pump:
Use the mounting hole inside the case and turn the pump until it’s aligned to the groove in the pump, see the yellow arrow.

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Picture from the bottom side

 

 

Monteringshull

Align against the mounting hole for the screw

 

Monteringshull topp side

Mounting hole for the screw seen from the other side.

 

 

 

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Use a socket for a more easy mounting. Push the pump all the way down.

When you see the groove for the big circlip you know it’s at the bottom.

 

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Check the alignment of the groove and the mounting hole, put a small screw driver into the hole and use it to turn the pump if it’s not in correct placement. Make sure the groove is underneath the hole. See the red arrow on the picture.

 

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Secure the pump using the correct screw. 6-10 Nm.

 

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Mount the circlip

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Mount the impeller

 

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Mount the circlip

 

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In addition to the new paper gasket you can add a thin layer of silicone gasket to secure the sealing

 

 

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Fasten the bolts, 6-10 Nm according to the service manual.

Powder blasting of the cylinder

I got hold of a “new” cylinder for my bike. Seems to be in a good shape but is full of old burned oil. Not easy to clean. Can the powder blasting do the job ? Lets try !¬†The powder is¬†ordinary baking soda and will not do any harm to the cylinder.

Click on the images for a close-up view.

Before the powder blasting:

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 After the blasting:

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Drying up after a wash with water and soap. A layer of WD40 inside the cylinders.

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I’m very pleased with the job. Nice and clean, like a new one from the factory.

Water pump overhaul

I have got the water pump kit from GT Reiner in Germany and done the overhaul of the pump today. Here is a summary of the job:

First of all, some explanation :¬†There are two parts in the kit that is not part of any drawings in the service manual. It is not intended to repair the pump but exchange the old pump in a new one. Thanks to the kit it’s possible to repair the pump and the “hidden” parts are shown on the picture

Click on the image for details

mechanical seal

The parts not included in the drawing is the oil seal and the mechanical seal. Both labeled with a yellow arrow.
The upper part is the oil seal placed underneath the bearing.

When ¬†dismounting the old pump the mechanical seal consist of 3 parts as shown in the picture. Make sure to remove all parts, also the metal cup. The new mechanical seal in the kit is mounted in one assembly. Don’t try to separate any of them.

 

Tools to get the job done:

A simple shop press makes the process more easy. In addition I decided to make a special tool (adapter ) to fit the mechanical seal. It’s quite fragile and must be squeezed with care into its position.

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Using my lathe and making an adapter fitting for the mechanical seal

 

 

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Water pump housing, mechanical seal and the adapter

 

 

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Mounting the mechanical seal into the adapter

 

 

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Apply a thin layer of silicone

 

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Press the seal all the way down to the bottom of the water pump housing.

 

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Turn the water pump housing to the other side and mount the oil seal. Put the seal lips upwards facing aginst the bearing and the crankcase.

Suzuki mounted the seal with the flat side facing down, according to feedback I got on my post yesterday.

First I did this wrong, put the seal upside down. Warning !, wrong again ?  Continue to read.

Oobs, I did it again…¬†The first attempt where I mounted the seal with the flat side against the bearing might be correct after all. The high pressure side should always be against the seal side (the lips of the seal ) Based on the latest findings of “old” pumps from Suzuki, two of them have the flat side facing down and the seal side against the bearing. A brand new pump from Suzuki is the opposite. The flat side against the bearing, like I did the mounting the first time. Perhaps it doesn’t matter ? Quite odd if Suzuki has a random mounting procedure on this one. The basic question might be, is the high pressure side on the water side? If so, the first attempt was probably right and if a brand new pump is the blueprint I probably have to redo the mounting once more. But first I will wait and see if anyone else knows the correct answer.

11.02.2016, end of discussion:
I got an answer from the supplier of the water pump kit. All new pumps from Suzuki have the flat side facing the baring and the seal side down against the water pump, like I did the mounting the first time. The seal in the kit is compliant with seal in the latest water pumps from Suzuki and should therefore be mounted in the same way.
I have to wait one week for a new seal and mount it the proper way, again ūüôā

Lesson learned:
There are two ways to mount a seal, one is the right one, or … ?
There is a high and low pressure side, the seal side (lips) facing against the high pressure side.

Conspiracy theory:

Perhaps Suzuki after many years and many water pump breakdowns drew the conclusion: The oil seal ¬†has been mounted wrong, let’s turn the flat side against the bearing and don’t tell anyone about the blunder ..

 

A never ending story..
A new theory is coming up: The oil seal is spring loaded and if the spring is not made of stainless steel it will corrode in a short period of time if the seal side is facing the water pump. That can explain why all old pump have the lips with the spring facing against the bearing and the oil. I checked the oil seal from the kit, the spring react on a magnet and is therefore NOT made of stainless steel. Perhaps the new pump from Suzuki has stainless steel spring ? I don’t know. I have ordered a new oil seal from a local supplier and if it’s magnetic I will place the seal side against the baring like it’s done in all old pumps. If it can corrode it will for sure end up rusty if facing down to the pump. The mechanical seal (checked, non magnetic ) is between the water and the oil seal but the spring in the oil seal will steel corrode if not covered in oil.
Is this end of the story ? Time will show….

Lates update:

vannpumpe

The drawing from Haynes Service manual shows the orientation of the oil seal. As on all old pump the seal side is against the bearing and will be protected against corrosion.

I got the new seal.¬†Checked the seal with a magnet and the result tells it’s not made of stanless steel. Mounted the seal with the lips ( seal side) against the bearing like on the photo below.

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Mount the bearing

 

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Press the bearing all the way down to the edge.

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Mount the axle

 

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All the way down as shown in the picture

 

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Next part, sealing seat.

 

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New locking pin

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Done !
Remember to replace all o-rings, also the small one on the axle.