Lost a cylinder

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solly
Posts: 1
Joined: Sun Sep 13, 2020 7:34 am

Lost a cylinder

Post by solly »

Hi
Wondered if anyone could shed any light.... bought the GT as a restored bike had a few issues with aftermarket coils so went back to OEM second hand bike ran fine then due to illness and a badly lined fuel tanlk issue went off the road for a year or so.
Got the tank back refurbished refitted and road tested all seemed fine. I was concerned about overoiling so took it to someone who defintiely knows his kettles, and we put it on a dyno to simulate road use. The verdict was the bike was underused so go out an use it. On that basis took it for a 70 mile trip to a mates house. Ran beautifully aboslutely crisp an lovely. On the way back and about 30 miles in it started farting on the offside (rh) cylinder pulled up to check the usual, nothing obvious so went to start it and the battery (new) was flat as a nuns t*t. Thought I would nurse it back home but not to be it lost that cylinder completely so I recovered it home.
On inspection this morning after the battery was put on charge last night got 12.8v accross the battery terminals. I haven't popped the tank off yet to check the electrics to the coils. Plugs 1& 2 from the left are beautiful and as I would expect. Plug 3 wet and oily as I did expect
Any thoughts would be greatly appreciated
Thanks
Martin
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mizzytheman
Posts: 2227
Joined: Tue Dec 28, 2010 1:17 pm
Location: Knowsley, Liverpool

Re: Lost a cylinder

Post by mizzytheman »

Welcome to the forum martin.

Anything between 12.4v and 12.8v is an indication that the battery is in good condition. I would check what voltages you are getting with the bike running. You should be getting around 14.4v at 3000 rpm. Low battery voltages and undercharging can cause cylinders to drop out and misfire.

Let us know whereabouts you live as there may be someone who lives nearby who can offer some help.

Further information about charging here viewtopic.php?f=11&t=12653
Roger Ackery
Posts: 3693
Joined: Wed Jul 20, 2011 3:40 am
Location: Sydney NSW Australia

Re: Lost a cylinder

Post by Roger Ackery »

Absolutely need good electrics on these old girls, if the battery is new then I suspect an alternator / electrical problem some where, your readings are a little low, something over 13 volts would be better. My bike did the same as yours after standing for awhile, took spark plug leads off, sprayed caps internally with electric contact spray, & she started on 3, do you have a good spark at the plug while holding the Spark plug against the cylinder, what plugs are you using .

The Coils on these bikes very rarely give problems, so you can probably rule them out, are the carbs set up correctly & clean .Can you post a little more info about the bike & it’s overall condition, model & history, if known
Cheers.
Roger
GT750A.
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canaletto5
Posts: 5228
Joined: Tue Jul 23, 2013 8:43 pm
Location: Derbyshire

Re: Lost a cylinder

Post by canaletto5 »

If the battery has gone flat while you are running then it is just not charging. Check all connections involving the alternator, regulator and rectifier first, they can be manky, even on restored bikes. If they are good, then you need to work back through the units to see who isn't doing their job. Kev
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Alan H
Posts: 12104
Joined: Fri Aug 05, 2011 6:38 am
Location: Wombwell, Republic of South Yorkshire

Re: Lost a cylinder

Post by Alan H »

solly wrote: Sun Sep 13, 2020 7:46 am Any thoughts would be greatly appreciated
Thanks
Martin
Yup. You haven't introduced yourself before asking questions.
Proof that four strokes are over complicated
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