GSX 250 spluttering over 45 - 50 Carbs ? elecs ?

[ukjules]

Update: It is very hard to get this down to a firm sequence of events causing the issue
of hesitation / misfiring.

I got some more coils - they tested the same (meaning ok) on the multimeter, primary and secondary the same as the other ones.
they generate spark
I think we can discount the coils. although it is possible that the ones i bought are faulty too but unlikely now.

Status:
the bike runs bad. Hard to start even with choke and a long time to warm up. It simply did not do this a few weeks ago !
I noticed however that it runs on 1 cylinder sometimes at start up - the left hand one
while has spark is not sometimes firing.

I have the carbs off again and am cleaning them.
Points:
Right hand carb has minute pinhole in it
LH one is fine. (the cylinder that sometimes does not fire at startup.

On both carbs the needle valve bucket seals (o rings) are suspect !
Going to order some more as the kit i got simply does not fit correctly ! trash from an ebay supplier.

The needle in needle jet is set to 3 on both. I kept it standard.

Intention:
Put carbs back on.
Run with fuel cap off / on
Check elec connections - i.e. wiggle them then test again. spark plugs leads / primary coil leads / pickup cable

 

[ukjules]

It gets worse:

It now by doing i think nothing , does not spark.

so i now have clean carbs and it wont spark.
old coils on
plugs ok
plug caps ok.

Would you agree the next thing is the pickups ? perhaps
they died today and they were on the way out anyway causing this issue ?

 

[Guest]

I have a rule: never, ever turn a motor over on the starter with the plug leads hanging. They must have a plug on them which is grounded. Otherwise, the spark has nowhere to go and can back up through the coils and who knows how far back.

You could disregard this with a points system and, while it wasn't so good for the coil, the systems usually tolerated it. Suzuki off road bikes of the late '70s were famous for blowing immediately if there was no easy route to ground. They just had a hernia trying to get rid of 30k+ volts.

It isn't just bikes. I was buying a late '80s Dodge truck and wanted the compression checked before I bought it. I pointed out to the boss that the way the yard monkey was doing it would stress the ignition system, but was told that 'it don't matter none'. Well, after the compression check it wouldn't run. The nose of the coil was leaking oil and cracked and the ignition module was cooked. I wanted them to replace the trigger unit as well, but it still worked?..for another six months. I don't know if they learned anything or not; probably not, as the messenger has to be shot and a bad idea doubled down on. It's cultural.

The ignitor box can be scarce and expensive. Keep everything downstream of it in spec and grounded and it will last a long time. Shorted coils, bad plug leads and non grounded plugs all add stress to the system.

 

[ukjules]

I am positive i did, what you described not too, a few times not thinking ....
The bottom line is out of no where there is now, no spark ?

No spark i almost role my eyes at diagnosing but this one is a bit more difficult.
Coils on multi meter pass ok so i have to change the pickups next ? and the cdi unit if that fails.
Can you test the pickups ?

Hellish expense for a old bike i used to love and was meant to be a run around.

and remember this started with me pulling the carbs to bits..

 

[Gorminrider]

Maybe it's just the stop switch. Bypass it... or at least check voltage drop across it in ON position and/or between each side and ground to ensure it HAS voltage from the key switch. Likewise at the coil connections...

 

[Guest]

I am positive i did, what you described not too, a few times not thinking ....
The bottom line is out of no where there is now, no spark ?

No spark i almost role my eyes at diagnosing but this one is a bit more difficult.
Coils on multi meter pass ok so i have to change the pickups next ? and the cdi unit if that fails.
Can you test the pickups ?

Hellish expense for a old bike i used to love and was meant to be a run around.

and remember this started with me pulling the carbs to bits..

Before you panic, it could be something simple and cheap. I've never bothered to test a pickup, but in theory it's just a generating coil - about as complex as an electric guitar pickup. BUT, there may be some sort of threshold gizmo inside or diode, so you need to find out the correct way to test these specific units. I'd suspect that having your multimeter on AC and cranking the engine would give some sort of output, but I've never done that.

Most of the Suzuki ignitor [CDI] boxes are pretty much identical inside but with different wiring attachments. The four cylinder engines just use coils with double HT leads; the twins have enough sparks to run four cylinders but just throw the other ones away on the off stroke. So you should be able to adapt most early ignitors if you can't find the right one. Most later models use a digital advance system so you don't want those. OTOH, you could probably use the system from a GS500 as long as you took the whole thing from the advanceless rotor on. I've only looked into it enough to be aware of my options if disaster strikes; haven't done it yet as I've been lucky so far.

 

[Guest]

Maybe it's just the stop switch. Bypass it... or at least check voltage drop across it in ON position and/or between each side and ground to ensure it HAS voltage from the key switch. Likewise at the coil connections...

As I said, it could be something simple and cheap - or free. And if the bars vibrate enough above 5K to rattle the switch??..maybe just bypass it and see.

 

[ukjules]

Ok voltage drop test on switch and coils .
It was so sudden , one moment looking at fuel starvation
then out of no where no spark on either ?

So it is cdi box next if today's testing fails.

 

[Gorminrider]

and you can bypass the keyswitch too. unplug connector then jumper wire to connect red->orange

Outside chance but imagination boggles: also, you mentioned awhile back you had an electrical issue....

3) i do have a loose connection that i thought / think i have fixed.
It is on the starter solenoid and "occasionally " when i switch on i have to jiggle the wire !

this solenoid trouble might relate to the starter button which is inside the same handlebar cluster as Kill switch...possible that coil supply at kill switch is going wrong here?

 

[ukjules]

Could not look at today but will tomorrow.
also looked for cdi ecu igniter box off ebay just in case.

Will try and look at tomorrow and thanks

 

[ukjules]

Voltage drop results

Voltage drop results

I attach a pic of the voltage drop results.

Can i explain i am hopeless at electrics and have issues with colour vision.
you can see why i have always steered away from it !

I can just about understand voltage drop testing and here are the results.

does this show anything at issue ?
(Remeber i am now not getting a spark on the bike - a sudden event when
before it was suffering from terrible spluttering / hesitation at mid range
and more recently at all ranges.

Be great if someone could explain what they mean ......

I am trying to look at the kill switch.
To some it is simply to "isolate" this - to me ................. not

 

[ukjules]

I have been unable to disable the kill switch.
I simply don't know how to do it.

Cleaned all connections , changed coils , no spark.

Do you think all these issues could be caused
by a cdi unit going wrong and finally
becoming useless ?

I am going to order a second hand one and see
by swapping it out does. No other option really
with a no spark issue.

I dont suppose anyone has a spare one on their coffee table they
would send me to swap out and check to see if it is that ?

 

[Gorminrider]

<click me
Yes, your connector is more complicated than mine but if you can do without the lights, you can unplug the connector and place jumpers (the blue line is for your starter but you could do without and use a jumper at the solenoid itself....
Of course if you are colour blind it's a matter of counting off the positions of the wires given you can tell which is the diagram's left or right to match yours.

The above is maybe not required anyways but it does seem you are running into more difficulty with "Help" than without it. Maybe don't run off ahead ...
I think you You should stay with "ohms" for the coils (disconnected) AND you might just look up some basic electric troubleshooting because I can't see what you are exactly doing with the probes- I wouldn't bother with VD at the coils- it can be complicated when the bike is turning over ...a digital multi is not great for quick variations...Oscilliscopes and such will be wanted the way you are going!
But Voltage drop at switches and fuses and along wire lengths is very simple and has the benefit of involving the "real case" of current flow (which testing for ohms is not so great at)

 

[ukjules]

the coils check out fine !
both the original and the seconds !
both primary and secondary !

I am going to bite the bullet and get a cdi !

 

[Gorminrider]

fingers crossed! good luck! Since yours was replaced already once, it could have been a bad one in the first place. It wouldn't be the first time old broken stuff was re-sold!

 

[ukjules]

CDI ordered will arrive by Friday. Also got a rectifier and other bits on the panel checked in.

I think it is a good bet that this is the issue all along.

 

[ukjules]

Update:

I got a CDI box and a lot of other bits on the side elec board.
CDI fitted and still no spark !
BUT

I went through the wiring briefly and while turning it over wiggled all the wiring. No effect
When i wiggle the pickup connection box to the central wiring it intermittently sparks !
Only wiggling that wire does it spark !!
(I will put the old cdi box back on and report as this might not have anything to do with the cdi.)

this would and could explain everything ?

would you consider the next thing is to try and fix the pickup cable ..... by cleaning .....
that is all clean and secure to be honest ? but to get a pickup ?

 

[ukjules]

Update on update.

It was the block connector from pickups to main
loom.
As someone said ! It might simple.

Test run and it runs like a dream , zero bogging !
I will update in days on whether cdi was faulty too
but it was def block connector.

Now I really need to learn once and for all how to 're do
one of these as I have not fixed it but just sprayed
and prodded it about.

How do I strip one of these boxes and
renovate ? What and where the crimping tools ?
I would so like to know how to do this !

But the bike works !!!

 

[Gorminrider]

AHA! Good one; the ol' "loose connection needs a wiggle" ! and as often happens on these troublesome threads...it's something "simple"..
It's why I never buy anything until I am absolutely sure the old one is broken.

Don't say that. It's just something wrong on a list that grows shorter. Often on these threads, it's something simple that you discover all by yourself. Consider us to be blind men in a dark room with only your verbal clues coming in via speakers.

but hopefully someone will remember your thread and conclusion and add it to the lifelines tossed into the murk for the next poor sod floundering in.... the Twilight Zone.

 

[Guest]

I agree it's so often something simple, discovered by just wiggling stuff around. I bought a four year old Kawasaki ZZR600 with 2800 miles on it because "it doesn't run right". Turned out to be the side stand safety switch connection came adrift. $0 to repair.
Just recently bought a GS450GA with 14,000 miles. "No key, no title, doesn't run" New key was $35, new title was $40, the stator wires had dropped down onto the cross over pipe and burned thru. Total repairs? Less than $100 and now it runs!
I have an official head scratchers chair in the work area that I use to just look at the bikes, consider how they've been used and think of problems/solutions related to that.
A Very Useful restoration tool!