Author Topic: 1982 Suzuki GS450 Ignition timing system  (Read 266 times)

Offline Phelicks

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1982 Suzuki GS450 Ignition timing system
« on: May 31, 2021, 07:29:14 PM »
Hey guys, this is my first post on here and I got a question for my project bike!

Recently bought a cheap GS450 and i'm currently in the process of getting it to run. I made some progress and was able to make it idle pretty good, but I was having some issue with revs sometimes and decided to take a look at the ignition timing system. I was ready to see some rusty points but saw something else.

It's a breakerless ignition system, on a 1982 bike... First time i've seen that! Cleaned some light rust on the center magnet and turned the motor by hand a bit to see if everything was smooth. Cleaned everthing else and changed the gasket, done deal.

But sadly, when I tried to start the bike again, it seemed to start, but died quickly. Gave it some choke, started even better but died really quick again. Despair starts to kick in, try to give some gas, nothing.

Mhmmm what is going on... Decided to stop trying and do some research to find pretty much nothing on those systems, found a PDF showing you how to find TDC but that is pretty much it.

So now i'm wondering what could i've done to timing by rubbing of so surface rust and turning the motor by hand (with a 19 mm socket). Do you guys know if you need to put the crank on a specific position before trying to start the bike again or there is no such settings for a breakerless system?

Thanks!  :angel:

Offline The Buddha

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #1 on: May 31, 2021, 08:15:55 PM »
You got the classic GS500 ignition advancer and TCI ? You may have made a bad conenction somewhere in the ignition circuit, or just have clogged carbs or got some crap in the fuel.
Cool.
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Offline Phelicks

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #2 on: June 01, 2021, 05:20:33 AM »
I guess i'll take the cover back off and test for spark, will try to post a picture for people to see what it looks like.

Thanks!

Offline Phelicks

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #3 on: June 01, 2021, 11:22:53 AM »
Rookie mistake, was out of gas  :icon_razz:

Offline Phelicks

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #4 on: July 17, 2021, 02:38:19 PM »
Might restart this post because it seem's I still got an issue with the ignition.

I took the bike out since my last post for a couple of test ride and the bike is bogging bad at higher RPM. It feels like the bike just stops and it won't rev over 7k un first gear. Took the bike back ans rev it on the centre stand and I was able to rev it all the way to 10k no problem.

Then I took it out for another ride to test the other gears and see how the bike would act. Seem's like every gear I go up, it bogs sooner in the RPM range, so in 2nd gear it bogs at 6k, 3rd 5k and on 6th, I can't go faster than 60km/h because it bogs around 4k.

I don't think it's clutch related because it should free rev after it starts slipping. For the carbs I think it's pretty good, cleaned it, check the float height it's good, bench synced them and changed the jets because I have pods. The only part i'm not too sure about is the diaphragm, I tried the put your tumb over the air intake and I can feel a good resistance when moving the slide, but it bas some split on the edge of the rubber.

Nevers tested the coils but i'm thinking they should be fine because the bike can free rev. I don't know what to check next to make some progress on the bike.

Offline mr72

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #5 on: July 18, 2021, 05:46:05 AM »
If there's a rip in the diaphragm, you have to fix that FIRST. Even a tiny pinhole will make the entire carb not work correctly.

Pod filters may make this harder to tune. It slows the air velocity, which is why you need bigger jets... slower, higher pressure air means we have to add more fuel per unit over time to achieve the same mixture as with the faster, lower pressure air.

To me, this sounds like it's running too rich on the main jet. I should say, this is precisely how my GS500 ran when it was too rich on the main jet. At first I thought my problem was ignition, and I was wrong.

Offline Phelicks

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #6 on: July 18, 2021, 06:39:59 AM »
For the diaphragm, I couldn't see any holes in the wall of it, just the ridge portion that goes in the carb groove and some rips. I do have a replacement pair, but I want to be sure I need to replace them because it looks like a pain to change.

For the jet issue, I tried everything, stock jets on the main and pilot, +1 pilot with stock main jet, +1 pilot with +2 main jet and yesterday I tried +1 pilot with +4 main jet. The plugs on the 2nd setup looked a little lean so I decided to put a bigger main.

The story was the same for the last two setup, bogs down like the engine just want to stop completly and it won't rev past the different "walls" in each gears.

Offline Phelicks

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #7 on: July 18, 2021, 10:18:20 AM »
Well well well, thank you mr72 for giving me doubts and thinking about my choice of main jet all night long  :icon_confused:. This morning I got to work and put the original main jet (117.5) and leaving the +1 pilot jet (45) and the bike ran alort better reving out in first gear, but not quite in 2nd, 3rd and the other gears.

So now i'm confused, because in my mind my "pod" setup would let more air in, looks like im wrong about that  :dunno_black:. I'm saying "pod" because I made my own setup with some plumbing rubber and a foam filter that is oiled. So now it looks like i'm restricting the air flow making the stock jet too rich. Should I order new jets to take more fuel out at wot or could I play around with the needle height?

Offline mr72

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Re: 1982 Suzuki GS450 Ignition timing system
« Reply #8 on: July 18, 2021, 03:54:30 PM »
Yeah it's a common misconception that a "less restrictive" air filter "lets in more air". The bike was getting plenty of air with the stock filter. The amount of air is a function of the displacement, and the rate at which it consumes that air is a function of the rpm, within reason anyway.

So the air filter doesn't "let in" air. It just filters it. By filtering it, it may be adding some resistance which will decrease the air PRESSURE for an instant, and that lower pressure air as it comes through the carburetor doesn't require as much fuel as higher pressure air that would come through if there was less restriction. But this isn't like creating lower density or higher density air, it just changes the time over which the air comes in.

You have to put in bigger jets with the pod filters because the air is moving slower at any given instant, so it pulls less fuel from the jet. So the jet has to be bigger to supply the same amount of fuel to the lower velocity air.

Once you switch the intake, you have to go through a lot of trial and error with needles, shims, jets, and even stuff like the slide return spring to get it to run right. Or someone else has done that work for you and you can put together a tried and true setup.

FWIW I think 45 sounds like a real big pilot jet. But I'n no pro on GS450 carbs by any means.

 

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