Browse Category: GT380 Engine assembly

Clutch and timing cover

Polishing the engine cover on the right side:

Phuu, a lot of work, dirty work as well. Dust all over my face.

I have three engine covers to choose from. Two of them have some very bad scratches, too bad to ever look good again. Got hold of an unused one, the new type with 1500cc oil level label.

The bad ones:

Parts for the timing will be removed and reused in the new cover. One of them has a very good nylon gear for the timing assembly.

Timing cover:

Before and after one hour of grinding and polishing. Had to grind off a lot of material to remove some deep dents and scratches. Still some scratches left but the cover will be replaced later on with a J cover with engraved Suzuki logo. This is a later model with a sticker in the middle.

Cylinders

Got a surprise when starting to assemble the cylinders. Some of the 8mm stud bolts where missing and had been replaced with 6mm bolts.

This is what happens when working on a 48 years old project. Previous owners must have been too careless while mounting the pipes, as usually, too much torque and the threads are gone. A bit odd fix. They have used 6mm insterts in three places. I can’t have a mix of 8mm stud bolts and 6mm bolts. Not on a bike as stunning as this 🙂 So, what to do ?

Having a lathe is a big advantage while doing overhaul on a bike, a worn out bike.

Made four new studs. One original with 8mm threads in both ends and three with 8 and 6mm. One of the 6mm came out a bit bent, will fix it.

Done ! 🙂

Threads :

I did a refresh of the threads on both the bolts and the nuts. Not to get a surprise during the mounting.

10mmx1,25mm fine pitch threads.

Piston rings:

Before mounting the cylinder, make sure the gap in the piston ring is above the pin located in the groove.

Mounting of the cylinders:

Mount the gaskets and start with the cylinder in the middle. Apply some 2-stroke oil and slide the cylinder down. Don’t forget about the position of the piston ring to close above the little pin. Should slide easy down, not needed to use any force.

The last one and it’s done.

I was not able to find any torque settings for the cylindres, only for the cylinder head. Since there is no space to use torque wrench on the nuts I used the tools I had and fasten using sensible amount of torque 🙂

SRIS:

All of the cylinders have plugged SRIS outlets. I will therefore mount the case without the SRIS valve no.17. Dont’ see any issues of burning a bit more smoke at startup.

Pistons

Time to assemble the pistons. Bought a kit with piston, circlip, bearing and the pin.

The procedure is wery much the same as shown in my GT750 post some years ago:

GT750 post:

Please we aware of some differences: For the GT 380 all three pistons are identical. There are no washer in the piston as on the latest GT750 models, only the circlip to keep the pin in position.

Pictures from the GT380:

Remember to move the circlip gap at the opposite position to the groove, picture 3-4.

Insert the last circlip and you are done (picture 6 )

Done 🙂

First parts to be mounted after closing the crankcase

Rear drive shaft

The parts above are for the rear drive shaft. Remember to add thread lock on the screws holding the no 33 retainer

Oil pump and tacho drive

Mount the gear for the axle driving the oil pump and the tacho drive.

Crankshaft gears

Have to buy a new lock washer before I torque the nut.

Crankshaft set plate

Apply thread lock on the screws.

Clutch

A new lock washer must be bought here as well. Don’t mix the thrust washers, they are different.

Case closed

The upper part of the crankcase was glued using Loctite 574 as sealing. In the same way as I did on my GT750.

The Loctite 574 does not harden in air, only under pressure. A very common type of sealing for all type of crankcase.

Closing the crankcase:

All bolts are labeled with numbers. If you look close at the image you will see the number 25 is written into the case, just below the yellow arrow. That’s the order of the torque settings. If the crankcase is clean it’s easy to see the numbers. Mount all the bolt on the top side but don’t thight too much at this point. Make sure the crank is moving freely before turning the case onto the other side.

Since I have stored the bolts on a picture glued to a carton It’s easy to pick the right bolts with the correct length. All of them have been cleaned and polished. The S mark indicate bolts with more strenghts than bolts without the lable. The S bolts are for GT models but not for GS models. The GS bikes have labels with 7 on, not S. I found only GS bolts mounted on a spare crankase from a late GT model, 76-77. Not sure if that was original from the Suzuki factory or if someone had swapped them all. On my GT380 engine I mounted all the S-bolts I had except from a couple of 7-bolts.

Torque order:

Bottom case:

In addition to my picture above you will find the torque order in the manual and it’s written onto the case.

Top case:

From the manual:


In Nm:

8 mm bolts: 20 Nm

6 mm bolts: 13Nm

DONE:

Crankshaft

Before mounting the crankshaft, make sure the C-ring is in place in the groove, see the yellow arrow. There is only one to be fitted.

The grooves shown from the red arrows are meant to grab the oil seals. When I got my crankshaft back from overhaul the seals had no marks to fit into the grooves. The old ones had. Don’t know why but they should be original Suzuki seals according to the workshop. Probably a design change on later models.

Align the studds into the grooves as shown on the pic.

The seals should be moved into the bearings, see the red arrows.

A bit of 2 stroke oil will not harm.

Kickstarter

Hmm, was not able to align the punch marks as described in the workshop manual.

If I follow the procedure, the spring on image 3 is way too loose. If I turn it all the way around it will be too tight. Got advice from guys on FB and will ignore the punch marks. Mounted as on pic 1 and after the case is closed I will rewind the ratchet wheel 3/4 of a turn to give the correct tension. The rachet wheel is outside the crank case and can easely be adjusted. By the way, the punch marks were also wrong on my GT750 engine.

Don’t forget to mount the gears for the oil pump and tachometer:

Gear assembly

After repairing the crankcase :

I mounted all the gears before I spotted the damages caused by the lock pins. See my previous post explaining the issue.

http://mc.grenasberg.no/2019/12/30/lock-pin-repair/

I therefore had to remove it all and assemble the gears once more after repairing the crankcase.

Step 1, see the previous post, GT380 Gear shifting.

http://mc.grenasberg.no/2019/08/05/gt380-gear-shifting/

For a detailed view on how to mount the gear shifting mechanism, see how it’s done for the GT750. It’s very much the same:

http://mc.grenasberg.no/2016/02/21/gear-shifting/

One difference is of course the number of gears. Five on GT750 and six on GT380.  In addition, the CAM stopper is not mounted from the bottom side of the crankcase as it’s done on the GT750.

Step 2:

Mount the pin and spring:

Step 3:

Mounting the forks:

As always on my blog, click on the images for a more detailed view.

Step 4:

Don’t use thread lock on the screws at this point. Wait until you have checked all the functions of the gears.

 

Step 5, gears.

Front axle 

Running smooth and nice.

Rear axle:

 

Checking the shifting of all six gears:

Added labels on both axles to easy count the ratio of the gear shifting. It all looks good 🙂

No issues as I can see while shifting the gears up and down. The no 1 gear runs a bit tight compare to the rest. Don’t think i will cause any problems. I will open up the spare engine and check to verify its condition and compare the gear shifting against this one, but not today.

The outer C-ring is missing on the rear gear axle. Will borrow one from the spare engine later on.

Lock pin repair

After months of doing nothing on the GT380 I’m now back on track. This fall has been very busy and I had to focus all on work and not much spare time to invest on my GT380. Hopefully it will be better the following winter and spring.

Two weeks of Christmas vacation has been good and I was able to get some steps further on the project, but then…..I spotted a disaster.

 

Two of the lock pins holding the bearings at the gear shaft in place were squeezed all the way down into the crankcase. I should have spotted this at a previous stage, but what now. Is it game over. Do I have to get a new case ? Cracks on the other sides as well due to the brutal force into the aluminum.

Previous owner must have done this without thinking properly before assembling the engine. And on both gear axles…This is what happens when you rush into unknown stuff without taking the time needed to think twice and think it through.

I have a spare engine I can use,  but consider all the work I had put into this it’s worth giving it a try to fix this one. And if it works I will still have two GT380 engines.  This is how i did it :

Step 1:

Drilled and milled holes at the rear side and was able to push the pins out.

Step 2:

Drilled 2,5mm hole from the top side. Threaded 3mm and inserted a set screw and adjusted to the correct depth.

Step 3:

Gluing using Speedy-Fix

If something is too good to be true, .. it’s not true. That was also what I thought about Speedy-Fix, cost nothing from E-bay. Can it work ? Yes, I have tested it extensively on plastic, wood and metal. It really works. A totally damage plastic side cover was saved using this powder and hardener.

I could have TIG welded a tap onto the pin and pulled it out, but I don’t have any welding tools. Since the aluminium already had cracks I don’t think it added much structural damages to do the drilling and milling. A lot of materials left and if the gluing fails the set screw will still be in place.

 

 

 

GT380 Gear shifting

Step 1:

The needle bearing for gear shifting cam must be installed again. Use a socket to drive the bearing in place.

The needle bearing seen from the inner and outer side of the crankcase.

 

Step 2:

Cam and forks mounted:

 

A greate help to look at the pictures taken while stripping down the engine :

 

 

 

 

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