1975 GT380 - Repair and restoration log

     I bought this bike in good shape off eBay from a guy in 2007. This GT380 is the same year model and color as the bike I owned in 1976. I also bought a non-running 380 (74 model, I think) from a local guy, to use as a parts bike. I swapped a few parts onto the running 380 to help it cosmetically, including a '76 model front fender (I like the fender with one stay as opposed to the original with two stays).  Some of the parts were sold on eBay to cover the cost of buying the bike.

     I rode the 380 off and on for about a year, when gas started appearing out of the overflow drains on one of the carbs. I pulled the carbs, cleaned them, and put in a Keyster kit, and adjusted the float levels (badly).

    After a few tries, I got the carbs to stop leaking, but the bike would not start. After checking, the points cam was not turning, and it seemed the nylon gear had fractured. I replaced the gear, and put the clutch cover back on with the timing marks aligned, but did not get around to test running the bike or seeing if it would fire up. It went on my "List of things to do".... and stayed there for two years.

    Finally, the guilt and shame overcame my laziness and I started back on the bike. My first move was to determine if the two cables laying across the seat were off the 380, or I had simply laid them there and they belonged to another bike. I posted a query (the first of many) on the Yahoo Suzuki GT Triples forum, and my education, and the bike's restoration began.



July 2, 2010  --  POST ONE: A Tale of Two Cables, or how I plan to resurrect my '75 GT380

My 380 has the throttle cable splitter with TWO cables coming out of the splitter

(my '73 or 74 380 parts bike has FOUR, see below)

Two cables

Another angle
I see the one cable goes to the oil pump, and further back is the tach cable.

This is my 1974 (or '73) GT380 parts bike, it has four cables coming out of the splitter....

Oil Injector pump -
bleeding and checking for bubbles.
Removing the oil pump - be careful not to lose the small drive pin.

To take it out you take out the three Phillips screws in the LOWER flange and lift straight up. The pin I referred to is in the shaft below the pump body. It is just slid into a hole in the shaft, and easily falls out when you turn the pump on it's side. If you don't watch for it, it's easy to lose, and then the pump doesn't get driven, and so no oil to the bearings and cylinders = bad things happen.

Someone else mentioned that the o rings that seal the pump bottom flange discharge holes to the top of the distribution manifold (the plastic tube thing) have a tendency to stick to the bottom of the pump. You don't want to lose those either.

I put a pistol oiler to the input holes in the distribution manifold and force 2 stroke oil out through the tubing. Use a different color oil than you have in the lines and you can see the tubes change color. Then, when you put the pump back and start the engine, you can watch the oil tubing change color back to whatever is in the tank, and confirm the pump is working.

Don't get carried away and pump a lot of oil through into the engine. It'll smoke quite a bit with just part of a squirt through each of the tubes.


Purging air from the injector lines.

I used a dab of grease on the pin to help it stay in place as I moved the oil pump back in place.

Part bike



July 2010

Setting the timing and points




Running again video
July 18, 2010

But the tachometer was not turning, and the experts tell me this is a sign that the small shaft that turns the
tach drive is not working properly, and this shaft also turns... the oil pump!



July 20, 2010 - Pulled the tach drive, looks ok. Something is definitely wrong with the oil pump shaft.

Pulled the clutch cover (again).

This is what I found... see the small gear at the bottom... well, that's the end of the shifter it's on. I may as well have hung it on the turn signal. Not sure how I missed this, guess I was in a hurry.

This is the proper place for the gear. Now it will turn the oil pump shaft and tach. There is a small pin that goes crossways in the shaft and connects the gear and shaft. Same part number and part as the pin in the oil pump mentioned above.

The proper fitment.



After putting it together, it ran and the oil pump and tach are working. But I FUBARed the kickstarter spring mechanism and the kickstarter
drooped down by the footpeg like a Harley rider in need of Viagra.

So, off comes the clutch cover (again).

The manual says to align the punch marks on the shaft and the ratchet.

It's hard to see but there is a small punch mark on the shaft...

And the backside (naturally) of the ratchet.


The trick is to get the ratchet on properly and turn it and the shaft counter-clockwise until it slips into place behind the holder, with some tension.

Video of how the spring and ratchet like to pop off when the kickstarter is turned with the clutch cover off. Be sure to hold the big gear in place when turning the engine over to align the timing marks.      

Aligned the timing marks on the crank, aligned the L mark on the timing plate, put it back together and added oil. She runs, kickstarter works, and it's getting oil. But it's clear
that the carbs are out of adjustment.



Next: clean the carbs and the petcock, to ensure good fuel flow.  Carb Inspection post.

July 31, 2010

1. The floats are all different, so each needed to be measured and adjusted to ~26 or 27mm. Why are these main jets all different heights? They are fully seated...
turns out two of them had a pair of washers, instead of just one.

2   3
This is the position I have the carbs to check the floats.
Setting my t-square for 27mm

Checking. The T-square is set at 1 3/16". It should be  1  1/16, that is closer to 27mm (not pictured). I readjusted the T-square and set the floats to 27mm. Note the end of the rule is set inside the bowel where the gasket touches.


After putting the carbs back on, the bike would run, but not idle well--it wanted to rev up to 5000rpm when the clutch was pulled in or it was in neutral. I decided that the starter circuit (choke)
 must be leaking, so off come the carbs again.


August 2, 2010

I managed to ride the bike to a state inspection center to get the sticker and get a Vehicle ID Certification, in order to transfer the out of
state title and get a license plate.

At Jiffy Lube for the VIN certification
and inspection sticker.

Success! Street legal after 3 years.

Cleaning the starter plunger seat and adjusting the slides.

The starter plunger seat.

Starter plungers, hard to get now.

Per Mike, I suplerglued a bit of 400 sandpaper on a dowel and then polished the plunger seats, followed by some cleaning spray and compressed air.

Both of these fittings are vents and should be left open to atmosphere.


August 3, 2010
After putting the carbs back on, the bike began to run much better. It idles smoothly at 1300rpm and accelerates well. It does not respond crisply below 3000rpm, so I will put the stock
airbox back on and see if that helps. I put the oil pump cover, Ram Air Induction cowling, and side panels back on and gave the bike a 70 mile road test. She came through with flying colors.

Video: Test ride with my friend Jesse.


August 5, 2010 - New petcock

New petcock

Inspecting the SRIS system... there doesn't appear to be one.


August 6, 2010 - replacing the clutch cable

Well, well, pulled off the left trans cover and looked what surprises awaited me-- spring was laying on the bottom...

Looks like this area saw some welding repairs...

And I don't like the way this looks.

New clutch cable on, spring replaced. I'm leaving the shaft alone for now, it works.


August 13, 2010: Time to polish all the aluminum.

I polished the sprocket cover, compare
with the mag cover.

Mag cover before

Many years of exposure to the elements
makes aluminum oxidize (rust).

After some time with the multi-tool
using 220 paper.

After 400 paper.

After 600 and 1200, then buffing with Mother's polish

Solid improvement


May 2012: Replacing the gauge glass

The glass on my 380's gauges was from a Yamaha, the previous owner informed me.

You can get a good sense of how scratched, dusty, and cracked the old glass was.

I had some glass cut but I was unhappy with the flat glass--then I discovered a great source for curved glass that fit perfectly.

Flat glass - Yamaha glass - new curved glass

Flat glass - Yamaha glass - new curved glass

PO glued the glass to the back of the black instrument housing. I know some purists will machine a tiny bevel into the gauge housing (the white plastic cylinder that gauge sits in, see next pic) and fit the glass to that, but I think this is a simpler and effective solution.

Replacing with new curved glass.

Of course, the tripmeter boot crumbled, so I had to buy all manner of vacuum caps, rubber fittings and stuff to rig up a new one.






July 2012 - Inspection time



Nov 2012: Replacing fork seals

With riding weather quickly going away, I thought to do some maintenance. The fork seals have been leaking a while now, and I have done fork seals before on a couple of bikes.

My 1975 380 has a clip on top of the seal, that came out pretty easily, but getting the seals out is TOUGH! I read somewhere about immersing the seal in boiling softened the rubber but still couldn't get the seal out.

I tried prying gently with a screwdriver and chewed up the seal, but it stayed in place.

Success! A combination of a chisel, screwdriver and gently applied dremel cuts. It was really stuck in there.

The top does not have the customary large fork cap that comes off with a wrench; a circlip holds a bung in place. Some penetrating lube and persistent taps with a socket and hammer and it came out. It is under a little pressure, so keep a glove over it to prevent it flying into space.

All apart.

The seal is in the fork leg correctly--the opposite is being held for display.

Not wanting to dare the dremel again, I searched the toolbox and found this--a seal remover! Actually, it's a tire iron but it worked perfectly. Just take it easy on the pressure, pry a little at a time, don't fracture the fork tube.

Yes, it eases the seal up. Of course, once the seal gets flush with the foruk tube, the tire iron pushes it back down on the near side, so to get the seal fully out,...

...I used vice-grips and the edge of the workbench for leverage, and worked it on out.



Last revved up: 11/15/2012