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Only Running on 2 cylinders ? FIXED.

Posted: Mon May 06, 2019 4:07 pm
by mick 63
Hi Fellas My GT750 A model , is giving me some trouble , i went to the ponderosa cafe with Richard yesterday and my kettle performed great till on the way home , it went on to 2 cylinders , i could hear it popping and backfiring like it wanted to chime back in on 3 but never did, i stopped at charnock richard and had a quick check but couldn't find anything obvious and the bike was ticking over ok , i set off up the slip road and it started misfiring and went back on to 2 again, i made it home like this ,

i had a quick look last night and the offending cylinder is the right hand side one when your sat on the bike , i had a spark at the plug but didn't really take a lot of notice how good it was ? , i took of the points cover and noticed that the set of points for that cylinder were sparking so i presumed it was a condensor failing ?

today i changed the condenser and there was no change still on 2 cylinders but no sparks at the points , and no spark at the plug ?
i have taken the left hand cylinder plug cap and plug that are working ok and tried them on the right hand side cylinder no change ? , i have tried the right hand plug cap and plug and they work great on the left hand cylinder ? , i also took the tank off and checked all the wiring connections they are all ok ,

i checked for power to the points plate with a small test light and i connected the crocodile clip to one of the mounting screws and with the ignition on i had power to all 3 sets of points,

am i right in thinking after all these tests its probably a coil that was and has failed ? looking forward to any suggestions ? cheers Mick ;)

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 4:15 pm
by BAZ
your falt finding method is sound best try coils by substitution remember that you could fit another faulty set so get them off a running bike.. another possibility is a fouled plug due to not burning properly when you had the fault. mizzy ain't using his coils at the moment..

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 4:18 pm
by julian
Hi are the points opening ok I had a problem on the centre cylinder that turned out to be spring on points had gone soft could straighten spring by hand,fitted new points no trouble after.

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 4:53 pm
by mick 63
BAZ wrote:your falt finding method is sound best try coils by substitution remember that you could fit another faulty set so get them off a running bike.. another possibility is a fouled plug due to not burning properly when you had the fault. mizzy ain't using his coils at the moment..
Hi Baz i tried the plug in the left hand cylinder and it works fine so i guess that rules out fouled plug ? cheers ;)

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 4:55 pm
by mick 63
julian wrote:Hi are the points opening ok I had a problem on the centre cylinder that turned out to be spring on points had gone soft could straighten spring by hand,fitted new points no trouble after.
Hi julian yeah the points are ok i took them off the back plate and cleaned them with some electrical contact spray refitted them and gapped them and they are opening and closing
ok , cheers ;)

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 4:56 pm
by PaulD738
After all you have tried and given the fact it runs on three ticking over I would suspect the carb?

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 6:11 pm
by raysunners
Hi Mick, are you saying that after changing the condenser it is worse? As in no spark at the plug

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 9:33 pm
by mick 63
PaulD738 wrote:After all you have tried and given the fact it runs on three ticking over I would suspect the carb?
Hi Paul it seemed to be ticking over ok when i was at charnock richard ?, but it definitely is only running on 2 now now spark at all on the right hand side plug ?

but if i swap the right hand plug and cap to the left they work ok , thats why i think it might be a coil ? cheers

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 9:40 pm
by teazer
Throw away the points and condensors and fit a decent modern ignition - Accent.de do a very good ignition at very reasonable prices and that will eliminate one possible cause of failure.

Could also be a coil that is failing under load when it gets hot. or the plug leads and caps. If that lot isn't new, I'd replace them for peace of mind.

Re: Only Running on 2 cylinders ?

Posted: Mon May 06, 2019 9:41 pm
by Roger Ackery
Hi, my A model has dropped the left cylinder before,spark at the plug, but not running !!
Sprayed the inside of the spark plug cap with contact spray, let dry, & that fixed the problem.
Give it a try....maybe an easy fix,I did notice a lot of muck came out of cap ;)