left plug not sparking

mrjones
Posts: 63
Joined: Mon Mar 21, 2016 3:38 pm
Location: wakefield

left plug not sparking

Postby mrjones » Mon Jun 04, 2018 11:47 am

hello everyone, after a winter lay up I got my bike ,gt750m, out on 20th may (mot free day!) it had fresh petrol in and a fully charged battery, it was ok but seemed a bit sluggish and maybe down on power, as the points where the ones it came with and unsure of how old they were, I changed them for new,

however it then wouldn't spark on the left side I changed the points back and it still wouldn't spark, ive double checked the gap and swapped condensers around still nothing, I left the timing as it was, any ideas? Marcus

teazer
Posts: 472
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: left plug not sparking

Postby teazer » Tue Jun 05, 2018 2:14 am

Given that it ran until the points were changed, I would suspect that the points wires may either have an internal break or they are in the wrong sequence with the insulating washers.

Having said that, you mention it was down on power, so it's possible that one cylinder was dead all along. If that's the case, after you double check the insulating washers, check for power to the points and coils. It may be a coil died, crappy connection with corrosion over the layup period or even just a condensor that gave up the ghost. Condensors are cheap, so maybe start with that - almost any old car one will work.

mrjones
Posts: 63
Joined: Mon Mar 21, 2016 3:38 pm
Location: wakefield

Re: left plug not sparking

Postby mrjones » Tue Jun 26, 2018 9:52 am

Since my last post ive reset the points and checked all the insulators and wiring are correct,checked the timing ,there is power to the points the left cylinder sparks (although its slightly yellow) but the bike wont start!

ive checked the float heights put new float valves and pilot jets in, the petrol was fresh on the 20th of may,ive also found the fuel tap isnt stopping the flow of petrol (brand new 18 months ago and not had much use since!) so ive been disconecting it when im not trying to start the bike, it nearly starts on the first kick having been left overnight but its downhill after that. the battery is fully charged and although the electric start does work i havnt been using it.

on may 20th it started first kick after 8 months unused and i was pleased about that but it was very smokey for about 5 minutes after, it ran ok and i did twelve miles on it and then came home and changed the points , the crank was rebuilt with new seals 300 miles ago, so thats where im up to ,any ideas?

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BATTS
Posts: 394
Joined: Sun Jul 15, 2012 6:47 pm
Location: Lancashire

Re: left plug not sparking

Postby BATTS » Tue Jun 26, 2018 4:35 pm

Sounds like a blocked pilot jet circuit, simply changing the jets wont solve it as the muck sits in the internal capillaries in the carb body itself. Best solution is to strip the carbs and get into an ultrasonic cleaner if you have one. My centre cylinder wouldn't run after the winter lay up when It ran perfectly well at the end of last summer, it was surprising how much rubbish came out in the "bath" despite the float bowls looking relatively clean.
Chris
76 GT750, 78 GT550, BMW K1600gtl

Kettletimes3
Posts: 1431
Joined: Thu May 03, 2012 12:58 am
Location: Sunny Wales

Re: left plug not sparking

Postby Kettletimes3 » Tue Jun 26, 2018 11:10 pm

I'm with teazer on this sounds like the coil has gone down,
I wouldn't think it's pilot related as it should still start on choke,
Although you may still find a pilot issue when you eventually get it to run.

teazer
Posts: 472
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: left plug not sparking

Postby teazer » Thu Jun 28, 2018 3:10 pm

BAtts made a good point that it could just be in teh carbs. The pilot circuits contain some very small passages and it's quite common for one or more to clog over a layup. If it runs more or less OK at higher revs and not so much at idle or low revs, I'd pull the carbs again and spray through every drilling.

mrjones
Posts: 63
Joined: Mon Mar 21, 2016 3:38 pm
Location: wakefield

Re: left plug not sparking

Postby mrjones » Sat Jul 14, 2018 5:50 pm

I took the carbs off again stripped and checked them they were spotless anyway, then i thought to remove the check valves and quite a bit of unburnt fuel came out i left it for a day with the plugs out as well reassembled everything and it started! ive been for a 20 mile ride today and everything seems ok , tomorow im doing a full 50 miles to clay cross so i might see some of you there!


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