GSX 250 spluttering over 45 - 50 Carbs ? elecs ?

[ukjules]

Took the bike out for a test run this morning full of hope.
- again anything over 4500 revs it spluttered and hesitated

Pulled the petcock off - put plumbers tape on the prime screw thread.
For the first time the tank did not leak when off in the standard position.
I was hopeful at this point.

-Took the bike out and again exactly the same issue
-unscrewed the prime and exactly the same issue - hesitation

It is beyond me this one - how can a bike be in perfect tune below 4500 revs
and when on the road anything above it it starts to hesitate / splutter ?

I have ordered another petcock off eBay (second hand so a risk)

I did leave the spring out to see what would happen but it simply poured out
of the fuel pipe. This is what was wanted but i could not get it connected quick
enough without getting soaked in petrol.

I am beginning to return to the cdi unit ?
I wonder if it is the wrong one ?

anyway ill try the other petcock when it arrives.
consider the cdi unit ?
if this fails ill buy a new petcock

if that fails i am totaly stumpedIMAG0627.jpg

[Gorminrider]

CDI looks to be very similar to mine on GSX 400's. Looks like it has been replaced from a wreckers given the painted label....Does it indicate the Previous owner had the same problem and has followed the "faulty CDI" path already?

Another easy way to be too lean is leaking rubber carb boots at the intake manifold...but I think the "symptoms" would be the case at lower rpm too, when you are starting off.... it's not an issue I have had so someone might chime in..
Also, Confirm for us you don't have "pods"? and that the bike has stock airbox .

if that fails i am totaly stumped

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.

so, some eclectic problems it might turn out to be:
-the resistors inside the spark-plug cap, (but I readon another thread you have replaced these caps? hate to say it, but sometimes the last thing you did is the first place to revisit )
-stuck advance weights,
-faulty spark plugs (You should change these now if you don't know how old they are because I bet you will when the bike runs perfectly anyways, so why not do it now?)
-a loose or leaky power connection with a symptom that you might not bother to tell us or haven't noticed yet ie: headlamp dims/flickers because key switch poor

[ukjules]

Notes:

-My bike has the standard airbox on it , a foam filter.
-carb - cylinder head inlet rubber i am sure are ok and give good seals - will double check
-looking at the cdi unit it is the right one but as you say someone has changed it - unknown why and if it sorted the issue.
-the plugs i renewed but used ngk instead of what was in there (one was faulty)
-Valve clearance all within limits
-Good compression stats
-No electrical issue i can think of

Remember it runs as sweet as you can imagine ticking over and up to 4000 -4500 revs.
It then jutters and stutters and if i am annoyed i thrash it and it clears and runs ok from 6500 - 9000 revs.
(I dont like doing this though and this too might be intermittent.

I can now take the carbs off , strip them down totally and replace in 1 hour as
I have done it so much.

Next:
1)I will get new plugs an check again ht leads and coil as it is simple.
I wil get the other type - x277esr-u if i can

2) Another petcock has been posted and will try that one

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 !
"I hear you all gasp now .....!"
I sorted this last night but again my electrical connections skills are crap.
It is the live from the battery through the fuse and on.
Thinking about it if i tugged on this going along it might give that very fault ?
But why every time at 4-4500 revs ?

4) AtU i am sure is ok and moves freely.

[John Park]

It's possible that the needle is in the wrong position. Once you get the slides up and it's on the main jet it runs but the middle rpm, partial slide up, may be lean. Or way rich. Do you have a spec for the stock needle position, or are you just assuming that where it was when you got the bike is the original setting?

Suzuki also was very proud of their 'twin swirl's' ability to run on lean mixtures; remember, this was the 'lean burn' era. So probably the same guy set up the stock carb settings as did the GSX400 and they are on the edge of lean surge. Raising the needles a notch from stock - whatever that was - is usually a good move, especially in view of modern gasoline which tends to be rather 'lean' - read adulterated - to begin with. I find that if you're on the edge of mixture, even a change of brands of gas can put you over. Modern feedback loop FI eliminated the reason for the oil companies to get too fussy. Even my Honda lawnmower will surge on anything but ethanol free 94. A difference in gasoline density or viscosity will throw your carbonation off.

If it's like the GSX400 carb, there will be some spacers in there and you need to get it all in the right order, but the results can be measured by comparing the needle projection from the base of the slide. IOW, take notes. It looks like you're moving the needle a lot, but as a percentage of how far the slide moves it's not that much.

The nice part is that you only have to take the top off the carb to access the slides and needles; easy stuff. Glad to hear that it does 6500 to 9000.

I'm kind of a 250cc light bike fan, but in Canada we never got the GSX250E because the insurance cutoff was at 400cc. I've always wanted to thrash the daylights out of one…..just because. I'd buy one in a heartbeat and see how low and light I could get it….

[Gorminrider]

Ok, well, I went back and listed things

-a few weeks ago run ok all the way up the power band so this is a new issue

-When it was running fine i noticed petrol leaking out of the carbs air inlet

- soon as i try and open it up it hesitates as described...it happens probably over a 1/4 turn on throttle

-Carbs removed, dismantled "totally", new needle jet, main jet , pilot jet, float valve and float valve holder put in ...Initial run it went fine. Took it for a 20 mile run and it started (not as bad as before though) to hesitate again....Petrol put in and it went better.

-(applied) the choke when it is "hesitating" - It went worse
-unscrewed the prime and exactly the same issue - hesitation

There were also petcock troubles in the mix but that can now be worked around....The first is the very important- Something has changed since you got the bike. Otherwise given new info of bike running ok above 6500, perhaps the slides are sticking or there is trouble with the cv diapragm. DID you take care to replace it correctly? You can test for proper operation of CV slides by lifting slides with your finger and plugging the lozenge-shaped hole on the air-box end with your thumb. Slides should fall very slowly. At least that's how mine work on two well-running bikes and the spare carbs I have. It is a pretty ez test if you can get at them. On my bike airbox can be wobbled back aways especially if I unbolt the section of rear fender there and shift it off the knobs...hard to explain but the bodywork on my GSX400E is identical to yours, I think.

and John Park mentioned needle settings a good possibility especially if people have been in and out of there a lot. I have a set of spares so I can check out what is stock setting if my 400's carbs are identical, but given they are identical , is there a possibility 250's would be set a step leaner or richer? to allow the same carbs to be used? (Beyond my paygrade,this... )

[ukjules]

I am making notes of all the suggestion and will do them in sequence.
All much appreciated - Be assured i will never stop until this bike is going sweet !

NOTE: i didnt say before but it has a 2 into 1 motad thing on it. I hate it but
i need to find someone who has or can make the 2 into 2 like the original ....
(The issue still is it has gone ok in this setup)

I have stripped the carbs countless times. Top and bottom and have put them back carefully.
I am 100% positive the cv diaphragms are back ok.
However
- the needle i have not recorded its setting.
This i will do next.
Haynes says 3rd groove for my gsx 250 et 1980

ordered:
new plugs
ebay'd petcock

I was possibly incorrectly thinking coils ? would / could they produce this type of fault you think ?

[John Park]

Ok, well, I went back and listed things



There were also petcock troubles in the mix but that can now be worked around....The first is the very important- Something has changed since you got the bike. Otherwise given new info of bike running ok above 6500, perhaps the slides are sticking or there is trouble with the cv diapragm. DID you take care to replace it correctly? You can test for proper operation of CV slides by lifting slides with your finger and plugging the lozenge-shaped hole on the air-box end with your thumb. Slides should fall very slowly. At least that's how mine work on two well-running bikes and the spare carbs I have. It is a pretty ez test if you can get at them. On my bike airbox can be wobbled back aways especially if I unbolt the section of rear fender there and shift it off the knobs...hard to explain but the bodywork on my GSX400E is identical to yours, I think.

and John Park mentioned needle settings a good possibility especially if people have been in and out of there a lot. I have a set of spares so I can check out what is stock setting if my 400's carbs are identical, but given they are identical , is there a possibility 250's would be set a step leaner or richer? to allow the same carbs to be used? (Beyond my paygrade,this... )

The carbs are 30mm rather than 34 and look a bit different - not that I've ever had a set in hand.

Sometimes you can have leaky float needles and such and the bike will run okay because the float levels are higher than stock; when you get that sorted, the settings that worked end up a bit leaner. Just did that one last week. Finally got rid of some leaky and worn needles and seats and set the float levels and ended up having to raise the needles a notch.

I just replaced the stock clamps - so called - on the intake boots with hose clamps and I swear it runs butter. Even new, those things were a bit of wishful thinking, not to mention flimsy and asking to be stripped.

[Gorminrider]

I am 100% positive the cv diaphragms are back ok.

Ok. I had one that was not staying up after reassembly so It's a pet of mine I always lead out when I can

I was possibly incorrectly thinking coils ? would / could they produce this type of fault you think ?

I wouldn't think so Wierd spooky gremlin stuff like a leaky plug lead getting a resonant wobble at 5000rpm and shorting intermittently to the frame is possible but electric faults I've experienced are not so particular in rpm. Even a "stiction" problem at the advance weights is much rarer than not re-assembling them correctly. I think I've reassembled everything wrong at one time or another!

I just replaced the stock clamps - so called - on the intake boots with hose clamps and I swear it runs butter

Smooth as butter you mean? the threads get loose alright...taking mine off when rusty half-wrecked em...I think too the rubber must be shrinking as it gets older and harder -my stock clamps almost marry ends right together I suppose it's another sign I should fork $ out and buy new boots some day.

[hugo151]

You need new O rings in carb & double check diaphrams

[ukjules]

Still awaiting parts. Will post when fitted sequentially and tested.
I got my carb rebuild kits off eBay.
I could do with new needle valve bucket seals having taken them to bits
so many times.

I am in UK , where bar eBay can I get carb kits ?

[fastbysuzuki]

I am in UK , where bar eBay can I get carb kits ?

You could try Technical support: tech@allensperformance.co.uk.
Your bike is not listed however it's worth a email.

[ukjules]

Right I will do a recap as i am forgetting how this issue started and what has been done:

Overview:
I am convinced although can barely remember now that the bike has worked on a long run
prior to these issues with the same setup - carbs, tank, petcock, plugs and exhaust.

so i am starting from scratch:
All i have done is clean the tank out ! (I have done this many many times with zero issues)

Added new plugs today and took it for a test ride:
ISSUE: Perfectly tuned up to 5000 revs and then started hesitating almost as if
it wasn't even sparking or it was on reserve ?
Basically the exact same issue as before.

Tested the coil:
I am going to continue another thread on this as even though this coil tests
fine the only bike i have that it tests right on (this one) it doesnt work is this one and all the other
bikes test fail but work perfectly ? (they fail on the secondary giving "1" on 20k setting.
On both coils Primary - 4.2 ohms Sec 16000 ohms

Put on a new (second hand) fuel tap:
Took it for a test ride and exactly the same issue - hesitating ....

took carbs off for the 20th time:
Cleaned and think the needle jet a few holes were blocked or was it just petrol residue ....
anyway all cleaned up.
I could not check the height of the needle as my circlip pliers are not good enough to get the circlip out !
(If anyone in the uk knows where i can get a "good" set tomorrow let me know !)

Vacuum piston - the big thing i n the mddle:
These moved freely but one did stall coming down.
Cleaned and they are now fine.
Took it for a test run and exactly the same issue.

Diaphragms:
No tears or pinholes and seat perfectly.
Testing with pushing up the piston and blocking the oval inlet they both come down slowly.

So thi is where i am - the bike runs perfectly at idle and all the way
up to 5k revs.
Over that is splutters and i cant be sure now about it being fine over 7k revs.

so that is the status, something that i simply cannot understand or fix.

[Gorminrider]

Well, I've shot my bolt too, as to things that are simple and at a distance from my own spatulates but there's always things to try....to find the cause.

Here's one that hasn't been tried. Warm up the bike first so you are sure it's running as described, then before it goes entirely cold but after it's so hot as to vapourise gas fumes ,
Disconnect your fuel line to duplicate "running out of gas". Now, can you then rev beyond 5k as the fuel level drops? It's the opposite test of applying choke/enricher.


Your coil testing process sounds a little indefinite...I don't understand it. The numbers you get seem alright. The rest I didn't get.

I do not know how good this is for you or anybody but from a pdf per Ignitors =TCI (transistor controlled ignition) I have downloaded from http://ridersofvision.net/
Really, the first thing is "bad connections" and "voltages". It calls to mind that a voltmeter across the suspects when this stuttering is happening can be a clue.
Both cylinders misfire,
Engine runs real erratic,
May run fine high RPM but not low, (or visa-versa)
May not start or spark at all,
Worse when hot=
Most likely TCI problem or bad connection to TCI
Check connections and voltages
TCI -> power on tests
TCI -> Inspection
Ignition good till under load Bad Battery=
Connections - Voltage drop somewhere
Ignition good some days not others=
Bad Connections
TCI -> Open Inspect for obvious flaws / moisture

Also go here and look for help

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html

there's an intersting pdf per ignitors and more

[ukjules]

Coils tested to be fine.
What I am saying us the only bike that tests fine is the one that doesn't work.
All my bikes that work perfectly fail the coil test.
I am at a total loss to explain this.
This is not the forum for this though.

Anyway next is :
- clean second petcock
- check for fuel starvation
- find some aftermarket coils in same range.
- drain out all petrol and use new
- check needle height , poss lean out.
- another atu
- atu pickups

It really is depressing , a bike in perfect tune but only until it
gets to 5 k revs.
I really need someone with another gsx to swap parts out
to test.

[hugo151]

I had similar problems when i 1st got mine. O rings were rock hard as were carb to airbox rubbers. Diaphrams holed choke cable not shutting off properly. Then it didnt help when i got the cam timing one tooth out which is easily done. Have you change all o rings ? They will probably be 35yrs old now &rock hard