GSX 250 spluttering over 45 - 50 Carbs ? elecs ?

[ukjules]

All inlet and air box rubbers fine ! I have a way of sorting old rubbers.
Carbs are fine.
Remember the engine runs like a dream to 5k revs.

O rings: (What o rings ?) O rings on the carbs were replaced. Hard to get all of them with the kits available
but i got one from japan with most of the carb bits.
HOWEVER having taken them to bits so many times i am not 100% on the state of them now.
thing is there is absolutely no change to the issue whatsoever !

Todays test:
I re did many many connections around the battery. Earths all cleaned up.
Warmed up the bike not going over 5k. Went like a dream as i remember it many years ago when
I had a new one.
Over 5 k immediately the hesitation.
(I now cant be sure if over 7k it is fine. mid to high range throttle is where the issue lies.
If i stopped and simply revved the bike 1,2,3,4,5,6,7k all no hesitation on the engine i could hear at all ??
The second i move off and go over 5k immediately the hesitation again.

I think i am going to discount fuel totally now.
(I WILL CHECK THE NEEDLE HEIGHT HOWEVER WHEN I GET THE RIGHT CIRCLIP PLIERS)
I think this is the Coil, a faulty coil.
The reason why i think this is this is the only thing i can think of what i did something too
since "i think" it was working better. I yanked the ht lead thinking it would come out ?
Of course the useless design has it fixed into the coil , all i wanted to do was check the ht leads.

That is my intention to backtrack from a coil (the left hand one), pickups from coil to atu, atu.

if anyone has any of these bits please let me know !
I simply must know what is causing this issue.
I have never ever had anything like it and been totally stumped for so long.

I do appreciate your help chaps too ! We must know why this is happening ?

[steveb922]

Bit of a long shot, but could you use the coils from your RD250 to test?

[Gorminrider]

^good idea,Steve-or from the closest match on another bike that has 12v system...... or even gently wiggling (wearing your rubber gloves! and or a wooden clothespeg ) on the coil lead might do it . Inspect the HT lead closely. You might see cracks in rubber from a sharp bend.

The goal posts keep moving per high rpm (was ok above 7k rpm) but Intermittent stuff ican be very difficult.

[ukjules]

As for goal posts moving when testing a bike on a country road it is hard to provide the exact rpm.
4.5 / 5 ...
Lets call it 5k. What has changed is that i cant detect if it is ok over 7k - the bike is screaming at that point !!
its a 250 ! I think after listening intently it is not ok and still hesitating.

Re rd250 coils - Damned good idea ! I will do this tomorrow !
I have the rubber gloves ready for tomorrow to test and wiggle.

I really do think the "yank" i gave the ht lead on the coil is the reason .... a long shot i know
but i am done with the fuel system.
Remeber the ht lead is "fixed" into the coil and if it was damaged it cannot be changed.
(I have inspected it to ignore this but i will look again)

thanks again guys - i cant fix this alone and these ideas may be nothing to
you but each one helps.

[Gorminrider]

suzuki troubleshoot.jpg
found this...click it if it's too small.

[Gorminrider]

suzuki troubleshoot.jpg


found this...click it if it's too small.

[ukjules]

I cant get to the rd 250 coils the bike is in a place i simply cant be
bothered to get too. Stuck at the back of a shed.
Ill have to risk and buy others.
this bike was meant to be an easy fix up and run around and i am getting quickly sick of it.

I like the check list you posted !
I am now convinced it is the coil, atu, .... and will go down that route purely as i reckon when i tugged on one of them
i caused some damage.

SO if anyone has any coils, pickups , atu ? let us know.
Cant do much else until i get those now but wil inform when i do.

JUST THOUGHT OF SOMETHING ELSE:
I have had issue getting the timing right. It is right on the camshaft visibly
but with the strobe i cant get it right ? (not that there is much adjustment at all on this bike) (I did a post few weeks back)
Odd issues such as poor flashing on the strobe when on the ht leads and at one point no flashing
on one of them. This after i yanked the ht lead !!

I am clutching straws here and "think" the above to be correct although it was a while ago...

(Remeber it is "perfect" and I mean perfect at revs below 5k)

LH coil (the one i yanked) ordered.
ll then get a RH one if tha fails then a atu.

[fastbysuzuki]

I cant get to the rd 250 coils the bike is in a place i simply cant be
bothered to get too. Stuck at the back of a shed.
This after i yanked the ht lead !!.

Why don't you pick out the old leads from the coil being carefull not to damage the metal post at the bottom and epoxy new ht leads that's if you want to be bothered of course.

[ukjules]

they are sealed units - poor design ! no metal post .
to consider this i could destroy them. they test good with a multimeter.
I would have to do a wiring extravaganza and that is not to be done on coils.

I have ordered a LH coil and will go that route.
i will order the RH one if that fails .

so no i cant be bothered !

[Gorminrider]

...the HT leads themselves are pretty stout wire so excepting a spark jumping through cracked wire insulation, if there's an issue, it's more likely in:

the epoxied coil connection to them?

or the plug cap which has an assembly inside it? Inside it are:

the brass plug-end snapon,
a ceramic resistor with silver coated ends,
a teeny-weeny little disc!!!
and a spring that sits on the brass connector to the stout wire HT lead

lots of room for error in that cap like missing parts....

Much less chance imo at the epoxied-in end of the HT lead... I know ways the insulation can be ripped and cracked by pulling on it but getting the wire disconnected is a much much stronger pull.

[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 ?

[John Park]

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...