GS550 Leccy help!

[Dougie]

Okay,here's the symptoms:-
Ticks over fine,no probs up to about 4-5000 rpm,over that there's a misfire,like it's going onto 3 or even 2 pots.Plug chop shows 1 & 4 are fine,2 & 3 look sooty or damp.

What's been checked,adjusted or replaced:-
Points gap and timing checked and spot on
Swap coils,no joy
New points,same
New condensers,same
Swap plugs,same
Swap plug caps,same
Live feed from ignition switch is fine
All connectors clean & tight
All that hasn't been changed is the lead from 2-3 points to the coil.As it's damn near 30 years old could an internal problem mean that it's fine at low revs but breaking down causing a weak spark at higher revs?
Gonna replace it tomorrow (weather permitting),but need a bit reassurance that I'm looking in the right area....... :confused:

[Grav]

Are the carbs balanced?
Vapour lock has similar symptoms too........

[John Hopkins]

After you have checked all the other things, you might check the compression, my thinking is that if the timing chain has stretched... although I agree that for 2&3 to both go down it does look like a coil problem breaking down at high revs...good luck anyway you obviously know what you are doing...John

[Dougie]

Are the carbs balanced?
Vapour lock has similar symptoms too........
Carbs are fine Grav,compression is good John,and the camchain ain't that old.And remember,the GS camchain tensioner is the only automatic one that really works!

[Dougie]

Looks like I'll be doin' hee-haw to the bike today,it's pissin' down big style out there.Tomorrow's out as well,going to Dublin for the day. :D

[Hillbilly Deluxe]

sounds like carb balance/set up to me or weak coil,my gsx 750 had same symptoms,turned out to be mixture settings,it was running too weak.
has it got airbox on ?if so....cover inlet with your hand while reving up engine,if flat spot gone then its your mixture/balance if not its prob weak spark to those 2 plugs.theres loads of info on old skool suzuki site,but you prob already know that.

[Dougie]

Not the carbs,they're balanced and the mixture's fine.S&B filters,they've been cleaned and swapped between carbs.It's looking more and more like the points to coil wire breaking down and giving a weak spark.It's the only bloody thing I haven't checked or swapped....... :rolleyes:

[pyro]

Swap the coils over and see if the misfire moves to the other cylinders, I would suspect the coil for 2&3

[Dougie]

Swap coils,no joy

Pyro,please see above. :rolleyes: :p

[contail]

had similar prob with mates new gs 550 chop. checked everything you have. it was a dodgy wire coming from points. right in the gap where wires come out of points cover. his carbs are nice and clean/balanced and all his wiring is now neat and hidden. always the last bludy thing en it

[Dougie]

Good,I ain't alone! :D :D :D

[pyro]

Pyro,please see above. :rolleyes: :p

Doh!! Read the whole thread first....

[Dougie]

Charging system is fine HB,I did the Superdream reg/rec mod! :D The battery is nicely charged.Gonna change the points-coils lead today and keep you posted.

[Dougie]

Well HB I owe you a couple pints!Wasn't the alternator,but you put me in the right direction.I changed EVERYTHING on the 2-3 ignition circuit,points,condensers,coil,l/t leads,plugs,plugcaps to no effect.Thought what the hell and had a look at the charging circuit.Several of the connectors were corroded and one off the reg/rec dissolved as I disconnected it.Replsced and cleaned where neccessary and it's running much better.I think there may be a small carburation issue as well which didn't help,but I can worry about that later........

[Hillbilly Deluxe]

glad its sorted bud.

[Dougie]

Not 100% but at least I can sit at m/way speeds now......

[Hillbilly Deluxe]

suzuki leccys are brill,a new challenge every time.

[pyro]

Not 100% but at least I can sit at m/way speeds now......

Are you allowed on the m/way with 'L' plates?




Sorry

[Dougie]

And you can FUCK RIGHT OFF! :rolleyes: :p

[Dougie]

How do I say this?
Well,it's as bad as ever,I changed the reg/rec for a spare one (which I now know is dead).Put the old one back,the lights brighten when I rev so that works.Checked and reset the points gap and timing,set the gap at .04.Ruff as fuck so it's going back to .03.Bought new plug caps (£20!!!),no change but now I've got spares (Whoopee fuck!).Checked the plugs and 1 & 2 are looking a bit rich,but now 3 & 4 are looking damp and ain't sparking too well.I have now changed the entire circuit on 2 & 3,it's driving me round the bend.
Tomorrow,Friday or Sat'day I'm gonna do the following:-
Reset the points gap to 0.3,reset the timing,give the plugs a good clean and see what happens.

[Dougie]

Can't do sod all today,too wet and windy (the weather,not me.....).
However I've been thinking,dangerous I know but bear with me.This whole tale of woe really started a couple months ago when I went for the first long run since a head gasket replacement a couple of years before.The weather was VERY wet,got a misfire and naturally suspected water in the petrol.Added some of thon stuff that absorbs it (wouldn't do any harm at all) and went for a thrash up the bypass,high revs all the way,9000 or so.Did a plug check and although there was a misfire all 4 plugs looked the right colour.Found that the points gaps had closed right up which was probably causing the misfire in the first place.Now here's where my thoughts get stranger than usual.I discovered that the head nuts were a bit loose,got a torque wrench and torqued them down to the settings in both Haynes & Clymer manuals.Since then I've had this serious pig of a problem.Could it be that torquing the head to its proper setting has altered the compression just enough to upset the carburation on 2&3 enough to cause a rich mix misfire?No matter what I do to the ignition circuit nos 2&3 plugs seem sooty and damp.I know this might be total bollox,but is it possible?

[Grav]

Could be........

I did ask if the carbs were right......

and mentioned vapour lock......

[Dougie]

Aye well,the carburation was fine before I retorqued the head so I had no reason to suspect that. :rolleyes:
Now all I need's dry weather........ :(

[Dougie]

When I get a chance I'm going to drop the needles on 2&3 one notch and see if it makes any differerence.Thing is tho',if the gasket IS burnt why were the plugs fine before I retorqued?

[Dougie]

No probs,I'm just trying to get as many ideas to possible causes as I can.The exhaust is generally clear,only some black smoke if I grab a handful.The plugs don't look oily,just black and a bit damp and smelling of petrol,like having the choke on too long.I've already checked the choke BTW....... :p
Anyhow,I'll have a go at it when the weather lets me and of course I'll post the results. :D

[Mikesmad]

That could well be the answer........

.........especially if not all the head bolts were torqued down.....

....................or in the right order.

[Dougie]

Found the problem!It's a coil!Yes yes,I know,but I'd swapped them before with no joy.This time I swapped the points wires and the HT leads and went out.5500 rpm,there's the misfire,so cut ignition and check the plugs.1&4 sooty,2&3 the right colour.Cool.Now this begs a question-I have two coils with EXACTLY the same symptoms,fine at low revs,crap at middle to high.I can read a wiring diagram but the theory?The question is-does the coil body earth through the steel bar through the centre to the frame,and would a crappy earth cause this problem? :confused:
BTW thanks to everybody who has given advice.

[John Hopkins]

Found the problem!It's a coil!Yes yes,I know,but I'd swapped them before with no joy.This time I swapped the points wires and the HT leads and went out.5500 rpm,there's the misfire,so cut ignition and check the plugs.1&4 sooty,2&3 the right colour.Cool.Now this begs a question-I have two coils with EXACTLY the same symptoms,fine at low revs,crap at middle to high.I can read a wiring diagram but the theory?The question is-does the coil body earth through the steel bar through the centre to the frame,and would a crappy earth cause this problem? :confused:
BTW thanks to everybody who has given advice.

Most probably shorted turns...the coil is usually made of copper wire that has been coated in a thick varnish..once it is dry it acts as a pretty good insulator to keep the turns of the coil apart...poor manufacturing can wind the coil too tight and crush the insulation or too loose and allow vibration which can weaken the coating...the coil is then coated in a resin seal to protect it from water..a pinhole crack in this can cause problems...finally if the coil overheats the same problems occur....a crappy earth could cause the coil to overheat..John

[Dougie]

Don't really answer this tho'..... :confused:
"The question is-does the coil body earth through the steel bar through the centre to the frame,and would a crappy earth cause this problem?"

[noizy git]

It's a very long time since I've played with GS's but I managed to find an old manual and going by the wiring diagram the low tension side earths through the points earths through the spark plugs so I'm guessing the steel bar is just to mount the coils on.
I do remember having a misfire problem on my old GS750 that turned out to be a couple of valve guide oil seals that had gone, that was similar in that the problem was worse at higher engine loads. It's a bugger to fix though so best exhaust all other possibilities before you take the head off.
One thing it might be is the engine earth. I once worked on a Z650 that was running rough and bizarrely the owner was getting shocks from the clutch lever and it was down to a bad engine earth. This one's an easy check-remove the engine earth from the engine and see if it has a good contact, over time the ally seems to corrode and stick to the copper connector but a quick rub over with a file or emery cloth sorts it. while you're about it don't forget to check the connection at the battery end too.

Best of luck with it mate
Dave

[Dougie]

It gets better.....
The coil that was playing silly buggers finally went tits up this morning,totally broon breid!So I put on the coil I'd taken off in the first place as it was suspect,guess what,it works fine!But I'm still getting the misfire,this time on the coil that was fine before.Here's the thing tho',I swapped the coils over on the mounts,and it appears that the coil mounted over 3 & 4 pots plays up,no matter what leads are attached,which set of points it's being fed by,or whichever coil is mounted there.I really don't get it.
If I put coil A on the bracket over 1 & 2 pots and wire it to 1 & 4 those plugs fire and run happily.If I wire it to 2 & 3 they fire and run happily.BUT if I put it on the other bracket it plays up.The same with coil B. :confused: :confused:

[John Hopkins]

you could run a jumper lead cable from a bare nut on one bracket to a bare nut on the other bracket and see if that cures your problem..John

[Dougie]

I was thinking that,guess it's off to Maplins in the morning for ring connectors.
I bloody hate electrics,but at least I know I've got 2 working coils.

[John Hopkins]

I was thinking that,guess it's off to Maplins in the morning for ring connectors.
I bloody hate electrics,but at least I know I've got 2 working coils.

I meant just use one car jumper lead with crock leads just to test it...and it does look as if the earth is important..one way or another...either the bracket is supposed to be isolated from the frame in which case bothe sides will be duff...or it's supposed to be at earth potential which means a crack or rust or paint on the earth nut...John

[Dougie]

I used to bolt the condensers to the coil brackets so they DO earth,but I get the feeling one doesn't earth as good as it should.I dare say running earth wires from one coil to the other won't hurt.Gotta try anything now.......

[Dougie]

Success (of sorts),ran a pair of wires from one coil bracket to the other,now the leccy misfire seems to have gone.BUT (there's always a but..... :rolleyes: ) I'm still getting a misfire.However this feels like crap in the fuel as it happens at wide throttle openings,no matter what revs.I'm getting popping from the carbs,but it sounds and feels like all four pots now.Considering that I've had the tank on and off like a hoor's drawers and the fuel level was getting low I wouldn't be surprised if that's the case.I had to replace the inline fuel filter yesterday as the old one had clogged completely,no flow at all,and what was in it looked like mud!Anyway she runs a lot better now than a week ago,I know that I should clean the float bowls,but I've just managed to repair a carb rubber and I don't want that fuckin' up again.I could just drain the bowls in situ but I don't fancy petrol sloshing all over the crankcases.Spose I couls rinse it off with a couple gallons of water........