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Old 07-01-23, 06:56 PM   #1
redtrummy
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Default running on one

Went a run the other day. Bike running on one cylinder (rear) most of the time. But it ticks over without stalling. Thought I would swap ignition coils over to prove but I cannot locate them. Took airbox off and tried to follow Ht lead without success. Anyone know their location? Looks like the coils come with the Ht lead attached are they interchangeable anyway. Any words of wisdom greatly appreciated I do not consider myself a spanner man!

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Old 07-01-23, 06:58 PM   #2
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Default Re: running on one

ts amazing what a bit of sun through the window can do. located the coils but swapping them over does not look easy. Still welcome an words of wisdom on my way forward
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Old 07-01-23, 06:59 PM   #3
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Default Re: running on one


Its amazing what a bit of sun through the window can do. located the coils but swapping them over does not look easy. Still welcome an words of wisdom on my way forward
by SEEKER



You ought to have started a new thread.

Are you saying that it is running on one cylinder occasionally but will idle normally? My AL7 is reluctant to idle on one but occasionally at a petrol stop will have a hiccough and try (badly).

How old are your plugs (mileage and age)? Has the bike been in heavy rain/wet roads? The SV's front cylinder has always been prone to suffer especially if the plug drain holes are blocked. Is the petrol "fresh"?
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Old 07-01-23, 07:18 PM   #4
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Default Re: running on one

Thanks Seeker for the reply - Please delete your post in suspension and brakes. I have corrected my error!!


It is running mainly on one cylinder. Pretty certain it starts on one only . It did clear for a very short distance on the run for about a couple of hundred yards. It does not backfire at all. Its not water related I only ride it in the dry and its in need of a wash!. I did fit new plugs not so long ago but have ordered a new set in case one is duff. Bike has only done 8.5k in 23 years . Petrol fresh and has been Redex and fuel stabilizer treated.

My thinking is that if its on one cylinder at tickover and also at 4k revs + it is more likely to be electrical than a

carburetion problem. Any suggestions greatly appreciated
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Old 07-01-23, 09:59 PM   #5
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Default Re: running on one

Quote:
Originally Posted by redtrummy View Post
Bike has only done 8.5k in 23 years
So, it's not an SV650X which you put in your first post? It's a curvy - a carb model?
One problem that can afflict curvy's is sticking choke plungers.

I haven't owned a curvy in a while but one problem I encountered was a failing fwd cylinder plug - the bike started ok and would run for bit then start misfiring. It's the only bike I've owned that has a plug malfunction (other than a 2 stroke oil fouling - but that went with the territory).

Make sure you buy your NGK plugs from a reputable source - there are a lot of counterfeits.
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Old 09-01-23, 10:09 AM   #6
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Default Re: running on one

first thing you need to do is check/swap the plugs. take the plugs out and check the spark by putting it in the plug cap and holding the plug cap against the outside of the cylinder (try to hold it against an unpainted part like a nut or bare part of the frame) with a plastic/wooden spoon or insulated pliers. it should be a nice crisp blue/white colour, if not then either the plug is duff or the plug cap/HT lead/coil or igniter (curvy) is duff. do this with both plugs. or just swap the front and rear plugs if the rear stops firing then its the plugs.

with all models the RR connectors get furred up causing bad running problems due to not letting the battery charge properly. the pointy connector is a nightmare.

with curvy as seeker said its sometimes the choke plunger getting stuck.

bad card/TB balance wont cause running on one cylinder but its always a good idea to have them balanced once every 3 or so years. later twin spark bikes need an electronic tool to balance the TB's.

with pointys its sometimes the TPS out of tune but this does not let the bike only run on one cylinder.
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Old 09-01-23, 08:19 PM   #7
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Default Re: running on one

Quote:
Originally Posted by Seeker View Post
So, it's not an SV650X which you put in your first post? It's a curvy - a carb model?
I believe SV650X is the correct official designation for the first year of curvy models (It never helps when manufacturers re-use designations does it?!)

Anyway, back to trying to help OP, a few thoughts:
  • Swapping coils is a bit fiddly if you have larger hands, but not impossible. Getting the small wiring connections re-attached was what I found most awkward due to the limited length out of the loom.
  • From memory, I think the front coil low-tension wiring is what pulses the tacho, so if the rev-counter works but the front cylinder not then that narrows electrical gremlins to coil, HT lead or plug. Bibio's suggestion of plug swap first will help narrow further.
  • I seem to recall the HT leads are different length front and rear so that may impede a check by swapping. I can't remember if HT leads can be changed out from stock coils.
  • Is it possible the front carb float or plunger has stuck, causing fuel supply randomness? Does the exhaust have a stronger smell of petrol than usual? If not, the fuel is possibly not getting through, and this may also be why it's not backfiring at all? A few gentle taps of the float bowl may free it (though impossible to know for sure, or how permanent a fix it will be), otherwise I fear it's a carb off and stripdown required to check.
redtrummy, I know I'm not very far away from you but unfortunately I have a car in pieces that I need to dedicate most of my spare daylight time to, so sadly I can't offer much right now to come and get hands' on. I could probably plan in something for Feb/Mar if you want a second pair of eyes and can wait a bit?
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Old 09-01-23, 10:30 PM   #8
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Default Re: running on one

If it turns out to be the ignitor (CDI?) then drop me a message as I have a spare one gathering dust.
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Old 12-01-23, 11:24 AM   #9
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Default Re: running on one

Thank you all for the replies, and a special thanks to Ruffy and Dak for their respective offers.
I have had a bit of a domestic re the Brother in Law which needed resolving so have been somewhat preoccupied of late, plus I am waiting for the plugs to arrive and due to the poor light in the garage I need a mildish day, when its dry and can get the doors open to move things forward. I have a poor sense of smell but I did think there was a petrol smell when pulling up to a stop, will get the wife to verify.
Will keep you informed and thanks once again.


Does any one know do the Ht leads disconnect at the coil end?



And one final point, I have dug out the service record and it is designated a 650X in there.
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Old 14-01-23, 01:49 PM   #10
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Default Re: running on one

The coils leads are fixed at the coil IIRC.

Check the plug caps and drain holes as well.

Click here,

https://halnico.com/SV650/PlugCaps/S...PlugsCaps.html

Or,

http://straticus.epizy.com/SV650SparkPlugsCaps.html
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