Welcome to my blog where I describe my journey in Suzuki GT restoration.
Hopefully at help for myself an others with the same interest. Scroll down for for new posts.
The main idea with this blog is to use it as a reference guide for Suzuki GT 750A and GT 380J model.
Don’t hesitate to give me feedback and guidance if you see me doing it wrong.
I made the best out of the old exhaust pipes, and the bike looks pretty good with all four pipes mounted. Really happy with how it turned out.
Rear view
Right side
The chain was cut and mounted on the front and rear sprockets.
The wiring is from the GT750 diagram, but will be valid for most of the Suzuki models.
I had some issues with the ignition switch on my GT750. It started as an intermittent fault, but by the next day, it completely died. I had to hot-wire it just to get the bike running. I did it like this:
By adding two wires to the switch connector located inside the headlamp, I was able to bridge the red and orange wires, leaving it open when the bike wasn’t running. Note: Be sure to insulate the wires with tape. Any contact with the frame will cause a short and blow the fuse. Doing so, it all worked except from the tail light, but the brake light was OK.
The next day I came home from my ride and could start to repair the ignition switch. This is how it was done:
Both the orange and red wire had bad connection to the terminals. In addition the red terminal was loos and i took the switch all apart:
The loose terminal was glued with epoxy and all the wires were replaced with new ones.
One of the insulation spacers was broken. The brown was OK, and I made the gray one from a PCB sheet. The material for the sheet / spacer has to withstand some temperature since all the current to the bike goes through the switch. I also added som grease for electrical connectors before the assembling.
All done and it worked perfect 🙂
The exhaust clamps were ugly and rusty. I don’t have any new ones and did some cleanup.
Sandblasted and nickel plated. Not prefect and shiny, but look better and give some protection against corrosion.
Rear footrest:
I bought new rubber for the footrest. The metal parts were sand blasted, sanded and nickel platet.
The lock pins were missing but I made new ones from brass using my lathe and they were nickel plated.
Front, right side footrest: (this parts for the J-K modes are hard to find)
Left and right side have different part numbers. The right one has a the groove at the front side, see the picture above.
Front, left side:
The groove is on the bottom side.
The early models have three outputs from the fuel tap to each carburetor. The later models have one output to a rack mounted manifoil distributing the fuel to the carbs.
There are three fuel filters. One for the main tank and one for the reserve tank. The last one is in the bottom and can easily be maintained and cleaned.
How to test the function:
The valve in the tap is vacuum driven. Here is a simple test setup to verify its function:
I’m using a syringe to make the vacuum for opening the valve. I let the denatured alcohol stay in the upper syringe over night to be sure there were no leakage at the ON postion. When moving the lower syringe the vacuume open the valve and it all works fine. Please watch the video:
If the fuel tap is not working you can strip it down, clean and replace parts (if you can find a new part).
I swapped some parts from the later model, but most parts are different. I was only able to swap the bottom filter + the gasket.
The bottom filter:
Looks like the filters are the same on all models.
Petrol tap switch:
The gasket behind the cover is different on J-K models compared to later models. Don’t waste money and buy the wrong one.
This is the correct type of gasket for the J-K model. The hole at the center is smaller on the early models + layout of the channels are a bit different too. You can’t swap the gaskets from later to old models.
If you have a leakage, the tension of this spring located under the cover can be the issue. If the movement of the arm feels to loose, bend the spring a bit to make a better tension to the gasket.
How it all works:
ON postion:
Main tank will flow to the vacuum valve (as the arrow on the picture in the middle show)
RES postion:
The RES will flow to the vacuum valve.
PRI postion:
The RES will flow to the PRI (direct to the carbs bypassing the vacuum valve)
Vacuum valve:
If you open the vacuum valve, be sure to assemble correct. The hole in the diaphragm have to fit to the gasket and hole shown in the picture above.
Replace the o-ring in the valve if needed.
Was lucky to get hold of the real thing. Genuine Suzuki mirror with the S-mark.
The threads were wrong, 10mm, but should be 8mm. I made adapters in brass using my lathe, and thereafter they were nickel plated and mounted on the bike.
8mm outside and 10mm ( fine pitch) internally.
8mm
Nickel plated, still using my 13 years old nickel bath.
Time to start the overhaul of the carbs. The first time I’m doing this, so it has to be learning by doing + take a lot of photos and watch YouTube.
Sorting out the cables and carbs:
L, M and R :
This carburetor is the 33011 type. The last letter will be L, M og R for Left, Middle and Right.
Remember to organize all parts in boxes and don’t mix between L,M and R.
Removing the throttle valve:
Uncrew the top and slide off.
Removing the throttle cable and return spring:
Remove the throttle cable from the valve.
Return spring:
Remove the return spring.
Removing the choke ( starter piston):
Remove and inspect the starter valve (choke)
Remove the Drain plug and the inspection bolt for the throttle valve.
Removing the float, float valve and seat:
Inspect the valve for any worn.
Removing jets:
Needle jet:
Insert a screw and give it a tap with a hammer to get loose. Remove from the other side.
Note: The needle jet is also named Needle nozzle in the manual.
Ultrasonic cleaning:
Wather blasting:
After the ultrasonic cleaning I got all the alu parts wather blasted, looks very nice 🙂
Next step will be the assembling process, but not today.
Assembling:
All channels were well air blasted, cleaned with solvent, and air blasted again.
Mounting the needle jet (Needle nozzle):
I made a tool in brass for a more easy way to insert the needle jet. Please be aware of the lock pin and the orientation of the needle jet. Insert the jet from the other side and give tap the tool gently if needed.
Mounting the Main Jet:
Use correct size (with) of the washer. If it’s too narrow, the Needle nozzle can slide out. As shown in the picture above the Main jet will also lock the Needle nozzle in place.
Hard to see how it can slide through on the other side, working against gravity, but can happen during the assembling process it the carburetor is turned upside down. But as mentioned above, the main jet will lock it all in place if the spacer has the correct diameter.
The standard Main jet size is 0,8mm, marked as 80.
Mounting the pilot jet:
#22,5 size according to the manual.
Mounting the Air Jet:
Turn the Air jet all the way in, than 1,5 turn backwards.
Note: The picture is from the left carburetor. For the M and R, the jet is fitted from the other side.
Mounting the Idle Jet:
Did some cleaning and polishing before mounting.
Gasket:
I used the old gasket as a template, drew the outline and cut a new one in 1mm gasket material. Seems to fit quite well.
Float:
Warm the water almost to the boiling point and dip the float into the hot water.
To check the float for leakages ( it’s 50 years old and fragile) put in hot water and look for bubbles. Locate the hole and clean well before soldering.
This is not easy to fix. Clamp the part gently so it doesn’t fell apart due to the pressure inside when heating up.
Mounting the Float Seat and valve:
You can use the old one if it’s not worn.
Mounting the Float and Float Pin:
The float height will be adjusted later on when I have all three carbs ready.
Almost done:
A simple test to see how it all fit together. I think I have learned a bit so far. Hopefully the images can be at help for other as well. At least for me, when I’m doing the M and R carburetors. But not tonight.
Drain plug and inspection screw:
Float height :
Adjusting the fuel level according to the service manual.
Needle jet height:
The circlip at the needle jet for the center carburetor should be in the middle position. For the right and left carb, mount the circlip in the second groove from the top. This will give a bit more fuel to the center cylinder.
Rubber hose:
Replace the rubber hose if it’s old and hardened. I got them all new and the yellow arrow shows the directions for mounting the rubber hose.
Mounted on the bike:
Before routing the throttle and choke cables I mounted them all on the bike. Will buy new clamps for the rubber hoses so it all looks nice shiny.
Ground (GND) to the lamps:
For the rear lamps the GND is not any issue. The indicators are mounted direct into the frame.
For the front indicators it’s more difficult. On my GT750A model the head light house is all metal and clamp GND direct to the headlamp bracket. On my GT380J it’s different. To make a proper grounding I solder wires to copper spacers and they were both connected to the GND wires inside the head light.
Wires from the spacers connected to GND.
Green wire (right indicator lamp) Black wire ( left indicator lamp)
All indicators worked fine, + the instrument lamp as well 🙂
Looks like all of the electronics are working fine without any smoke 🙂
