ATU shows 135Ω needs replacement?

[Guest]

Hello. I tried getting answers in a thread in general but don't seem to get anything about the ATU, which I suspect is faulting. It shows a resistance (between green/white and brown cable) of 135Ω. In the Haynes it says it should be 60-80, a suzuki mechanic to be contacted if LOWER than that.

Has anyone had any problems similar to mine? The way it acts is that one cylinder is weak, one is functioning as normal. It's a GS450 1981

The weak one gives less pressure in the exhaust, weaker appearance, no idle at all when working alone.

carb - single carb (acted the same with the old double)
exhaust - acts the same with or without pipes
compression - OK
valve clearance - OK
coils - acts the same when switching places

Best regards
/Gofika, Sweden

[pete]

Depending which manual you're reading, it can be a bit misleading.

You need to measure from the green/white to black/white for one signal generator coil, then measure from brown to black/white for the other signal generator coil.

Each of those measurements should be 60 - 80 ohms.

The way you're measuring at the moment is across both coils, so 135 ohms is actually measuring ok.

The ignitor module in these is notorious for failing unfortunately, and there are tests in the Clymer manual to see if it is functioning ok.

It could also be your spark plug cap on the end of the spark plug lead. You can take them off, trim the lead back 1/4" or so, then screw the cap back on again.

You can also measure resistance from the coil to the spark plug cap to see if that's ok as well.

And you can measure resistance across the + and - leads of the coil input to check the primary resistance.

I can't remember what the measurements should be off the top of my head but they will be in the manual from memory.

[cletus@live.se]

Depending which manual you're reading, it can be a bit misleading.

You need to measure from the green/white to black/white for one signal generator coil, then measure from brown to black/white for the other signal generator coil.

Each of those measurements should be 60 - 80 ohms.

The way you're measuring at the moment is across both coils, so 135 ohms is actually measuring ok.

The ignitor module in these is notorious for failing unfortunately, and there are tests in the Clymer manual to see if it is functioning ok.

- So the Haynes manual is faulty, in other words?

- I would be very happy if you could retell the tests from the Clymer manual, when you have spare time!

It could also be your spark plug cap on the end of the spark plug lead. You can take them off, trim the lead back 1/4" or so, then screw the cap back on again.

You can also measure resistance from the coil to the spark plug cap to see if that's ok as well.

And you can measure resistance across the + and - leads of the coil input to check the primary resistance.

I can't remember what the measurements should be off the top of my head but they will be in the manual from memory.

Since I swapped places of the coils with no difference it has to
a) be before the coils
b) be something completely different

Thanks a lot for your help!

[pete]

- So the Haynes manual is faulty, in other words?

- I would be very happy if you could retell the tests from the Clymer manual, when you have spare time!

Yes, they Haynes manual has a few mistakes in it. It also has incorrect torque listed for some bolts.

It would be easier to download the manual and read the test instructions... they can be a little confusing

The manual is available on BassCliff's site here:

https://skydrive.live.com/redir?resi...PM7hx6Q2ynLu-A

Since I swapped places of the coils with no difference it has to
a) be before the coils
b) be something completely different

Thanks a lot for your help!

Yes I forgot you swapped the coils, so I think you're right there.

Edit: I forgot to say... is that your 450 in your avatar? I need to see bigger pic's of it

[cletus@live.se]

all right I'll see if it works. Thanks a bunch!

Yes it is. My first motorcycle and my first customization of a motor vehicle. Small album in my profile.

Cheers
/V

[pete]

No worries, good luck!

I found your album and the bike looks good. I like the pipes too

[cletus@live.se]

No worries, good luck!

I found your album and the bike looks good. I like the pipes too

Book seems great! Could one make a generalisation that Clymer keep higher quality than Haynes? Here Haynes are available everywhere, but I've barely heard of Clymer...

Thanks for the nice words!

[pete]

I find the Clymer more accurate than the Haynes, but the Haynes has better descriptions of some processes.

Keep them both, use the Clymer for the facts though.

You can get a reproduction factory manual from eBay seller "eClassic Bike" for a good price as well.

I have all three and use them all.

[cletus@live.se]

I find the Clymer more accurate than the Haynes, but the Haynes has better descriptions of some processes.

Keep them both, use the Clymer for the facts though.

You can get a reproduction factory manual from eBay seller "eClassic Bike" for a good price as well.

I have all three and use them all.

I just started studying, hardly know how to pay rent let alone keep all of my vehicles on the road or buying books about them . Guess I'll have to sneak into my old work and borrow their printer

Anyways: My bike gives visible sparks when pushing the start button with the spark plugs laying on the engine - do you/Clymer mean that there is a chance/risk that this will not occur when doing it with ohm meter/1.5V battery? Sorry about my electrical dyslexia (My 1/4th of a car space in a workshop is 15km away otherwise I'd be in my non existant garage trying it already)

[pete]

If you get sparks like that then there's a good chance that the ignitor is ok.

A couple of things I just realised I haven't mentioned.

Have you checked the voltage at both coils with a multi meter? And have you checked your charging system according to the stator papers here? http://thegsresources.com/garage/gs_statorfault.htm

It could simply be something like dirty connectors and voltage loss causing this issue for you.

Also, the ignitors on these are failure prone, so it's important to ensure your charging system is healthy.

[cletus@live.se]

If you get sparks like that then there's a good chance that the ignitor is ok.

A couple of things I just realised I haven't mentioned.

Have you checked the voltage at both coils with a multi meter? And have you checked your charging system according to the stator papers here? http://thegsresources.com/garage/gs_statorfault.htm

It could simply be something like dirty connectors and voltage loss causing this issue for you.

Also, the ignitors on these are failure prone, so it's important to ensure your charging system is healthy.

I did check the Voltage to the coils at an early stage of this problem. It was somewhere around 12-13 and only differed by 0.1 or so.

Will continue trouble shooting when there's time, which is even more scarce than cash...

But there's got to be some quality difference between the test with 1.5V battery/multimeter and just plain starter engine/look at the sparks, otherwise they would of course not tell you to do the more complicated 1.5V test... God I wish I had a brain to understand electrics.

I'll look into it when there's time. The weekend might have some in storage

cheers!

[pete]

The 1.5V test of the ignitor is more of an isolation test.

Basically it's to test it independently of the signal generator.

[cletus@live.se]

Found some time and did the following:

Unplugged the ATU and the Ignition control Unit from each other. Started trying to get a spark by connecting the brown/greenwhite connections to the blackwhite, closest to the Ignition Control Unit. Nothing. Realised nothing was connected since it's a box with six cables, so the Unit wasn't connected to anything else but ground .
Took out the three (blackwhite brown greenwhite) from the connection box, connected the box and tried again. Nothing, the spark plugs won't fire. at all. Still the bike runs as soon as you plug it back in again, but as described before - weak on the right cylinder strong on the left one.

The Clymer does say replace the Ignition Control Unit when not firing when doing this test, so I guess I should - but isn't it strange that not even the left side (good) will fire a spark? Yes ignition was on while doing the test I have this feeling that if I change the ICU it will still be there, the problem... At the same time I've got to do something.

Also measured the ATU the right way and it was 63Ω on one side and 64Ω on the other.

When measuring the voltage over the battery it said almost 13.4V on 2500 rpm and at 5000 rpm 13.85. It's said it should be 13.5V but can it make such a difference with 0.1V?

Have a nice weekend!

[pete]

If the ignitor doens't fire sparks on either side with the test, then I wouldn't assume it's faulty.

If I recall correctly, the way to do the test is leave the ignitor (6 pin) plugged into the harness, but unplug the signal generator (4 pin). You shouldn't need to remove pins from the connector for the test.

Your battery voltage sounds fine too.

[cletus@live.se]

Finally had some time. During customization I guess I had to lengthen the cables because I had no 4 pin. So I cut the cables and did the test. Nothing. Soldered it back together. BUT! A guy I know has a gsx400 and lets me try his cdi box instead of risking to buy one (not that cheap...) and it's something else...

I will keep you posted when I've tried his cdi box. If it's not that then I'll throw it in the river

Thanks for your help Pete!