1983 suzuki gs450t won't start

[Ditch dog]

Bike has been sitting for 15 years! I've replaced the Cdi, reg/rect, plugs as well as tested all circuits. I have a new carb kit installed because I dropped the stock air box and went to pods. She's got good compression but all she does is backfire but won't start. Any ideas would greatly be appreciated. This model has no adjustment at ATU. The tank and carbs were cleaned at time of carb kit install. The only thing I noticed was when I slackened the throttle cable at the carbs, she decided to backfire more consistently!!!

[tom203]

Has it been sitting with you for 15 years? i.e. have you ever seen it run??? You likely have an ignitor (not CDI)- did you get new one or used ebay/salvage one?
If you got compression and some fuel in cylinders, all you need is spark at right time and it should start although a bunch of other issues might make it run poorly (valve adjustments, stuck piston rings, etc). Have you checked camshaft to crankshaft timing in case camchain jumped?

[Ditch dog]

1983 gs450t

The ignitor was a used one from ebay, it said it was for a gs400e and was good for the gs450t. The manual I have shows the igniter wiring for the 400e to be the same as the 450t, so the $70 for the used one seemed to be a good bet compared to the $500 for a new one. I had no spark at all until I swapped out the ignitor. Then as I was testing the regulator I found no continuity between 2 wires where there should have been. so I replaced it with a new one. Before I even purchased a battery I turned the engine over with a wrench on the atu bolt. Could this have moved it out of time any? I compression tested it and it was good on both cylinders and only 2 lbs difference between cylinders. If I hold my hand over the carb mouths, I can feel the suction and the the exhausts are puffing out which would lead me to believe that the valves are functioning.

[tom203]

What's an "atu bolt" ? which direction did you turn engine and from which side?
The regulator ain't needed for starting (bike will run just on good battery for an hour)- best to disconnect stator wires from it for now to be safe- bad ones can fry ignitors, but you can't test yours until the bike is running , so disconnect for now.

[Ditch dog]

atu bolt

The models prior to 1983 had an atu at the signal generator on the right side of the block. This model-1983, has a fixed unit with a large bolt head on it. I wrenched it over in a clock-wise direction which is the same direction the starter is turning it.

[Ditch dog]

atu bolt pic

I don't know if this picture will help on the atu subject.

[BassCliff]

Greetings and Salutations!!

Hi Mr.

These old GS bikes love maintenance. In your "mega-welcome" you will find a list of maintenance tasks. All of these tasks must be properly addressed in order to have a happy GS. Skipping steps or taking shortcuts will be frustrating at best, dangerous and deadly at worst. Note: "carb kits" are mostly junk. It's always better to use the OEM parts, properly clean them, and replace all of the internal O-rings in the carbs. You'll find lots more information on my little website.

If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. In the links below you'll find maintenance lists, documentation, wiring diagrams, "how to" guides, vendor links, tips, tricks, and a whole lot of GS goodness. This is your "mega-welcome". Let's get started.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

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Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

More links to helpful threads in the forum:
Help! Your Bike Won't Start
DON'T DO THESE THINGS
Help! Your Bike Won't Run Well
Oh God! Pods!


Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[tkent02]

ATU, what's that, a sneeze?

[Ditch dog]

Atu

Automatic Timing Unit. used on models previous to mine. The 1983 that I have has a fixed rotor or reluctor used in its place. The manual that I have refers to the new modification as an Ignition Pickup Assembly.

[tkent02]

Huh, learn something new every day. I always thought it was a spark advance.

[Ditch dog]

spark advance

Well, whatever it's called, my question was..."could turning the engine over with a wrench on its bolt cause any change to the timing?" The reason that I ask is because I don't know!!

[tom203]

...."could turning the engine over with a wrench on its bolt cause any change to the timing?"

No that's the correct direction to turn. However, maybe someone else has been at that bolt/other stuff before you, so best to check cam to crank timing.Unknown history offers plenty of surprises.
You replaced the ignitor, are you sure its properly connected to ignition coils so the the plugs are firing correctly? Older models had mechanical advance on timing, your bike has advance built in to ignitor box- doublecheck part numbers to make sure.

[Ditch dog]

Simple fix

Switched coil wires......bike fired up! Stays running for 3-5 seconds. thanks, now I'll get her running and dialled in.