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Author Topic: Front cylinder colder than rear ????  (Read 1219 times)

Rjbez

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Front cylinder colder than rear ????
« on: January 08, 2018, 10:44:49 AM »

Ive recently taken the engine apart on my 2013 efi gt650, split casing to repair a broken second gear from previous owner. Engines back together and back in the bike but I have been having some difficulties with backfire from front cylinder and not being no where near the same (touch) temperature as the rear. It is slightly warming up but Im at a loos as to why the cylinder is not firing correctly. Bike was working as per before taking engine apart. Timing in correct on cylinders and spark occurs on both. Any ideas ?
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spit051261

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Re: Front cylinder colder than rear ????
« Reply #1 on: January 08, 2018, 11:36:12 AM »

If it wasn't an EFI , I would say timing issue .
How about an intake leak , exhaust leak or even U/S valve on that cylinder ?
You sound like a mechanic who has taken the engine apart for a customer and is now scratching his head  ;)
« Last Edit: January 08, 2018, 11:53:29 AM by spit051261 »
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Sid

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Re: Front cylinder colder than rear ????
« Reply #2 on: January 08, 2018, 12:04:32 PM »

Have you checked the coil / plug? The coils can be troublesome.
They don't always spark when under compression, even though they may do when you have the plug out for a physical check. You could try swapping the coils at first.
« Last Edit: January 08, 2018, 12:08:41 PM by Sid »
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spit051261

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Re: Front cylinder colder than rear ????
« Reply #3 on: January 08, 2018, 12:27:40 PM »

Not sure a bad plug would cause the issues listed .
If the cylinder is getting hot , I doubt it would be a rich burn . Sounds more like a lean burn .
Would also see smoke pissing out of the exhaust if it was a rich burn.
He could also see the plug tips "wet" .
That is why I think air is getting in .
« Last Edit: January 08, 2018, 12:31:17 PM by spit051261 »
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Sid

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Re: Front cylinder colder than rear ????
« Reply #4 on: January 08, 2018, 12:48:47 PM »

You could be right Spit, but it's not always that easy.
Unburnt fuel can get burnt up by the cat, so you don't always see anything from the exhaust.
I agree it could be a vacuum leak though. Also may be worth doing a compression test on the front cylinder and compare to the rear. That would eliminate a valve issue.

Initial thoughts though - if it was running ok before the repairs, it may well point to something that's not been put back correctly after.
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2011 GV650

spit051261

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Re: Front cylinder colder than rear ????
« Reply #5 on: January 08, 2018, 12:53:55 PM »

You could be right Spit, but it's not always that easy.
Unburnt fuel can get burnt up by the cat, so you don't always see anything from the exhaust.
I agree it could be a vacuum leak though. Also may be worth doing a compression test on the front cylinder and compare to the rear. That would eliminate a valve issue.

Initial thoughts though - if it was running ok before the repairs, it may well point to something that's not been put back correctly after.
Spot on there  ;)
It sounds painful but I think he has to pull everything apart again and find that "missing" washer  ;D
Cylinders should be fine unless something has been dropped in them (like the missing washer  :o) .
It will be something loose and no biggie , I bet you  8)
« Last Edit: January 08, 2018, 01:00:35 PM by spit051261 »
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Sid

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Re: Front cylinder colder than rear ????
« Reply #6 on: January 08, 2018, 12:58:11 PM »

Those missing washers are always a pain!...... ;)
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2011 GV650

spit051261

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Re: Front cylinder colder than rear ????
« Reply #7 on: January 08, 2018, 01:03:43 PM »

Those missing washers are always a pain!...... ;)
that's why you should always have a crisp packet to put them in . Saves loosing them and wondering , where the fook did that go  :o
Any good mechanic should always have "left overs" , hence the 'crisp packet"  ;D
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2010  GT650R in the best colour RED

Sid

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Re: Front cylinder colder than rear ????
« Reply #8 on: January 08, 2018, 01:05:14 PM »

Hopefully the OP will get back to us.
It seems annoyingly common on forums that people don't update threads where there has been an issue. So, nobody becomes any the wiser as to what the issue / fix was.
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2011 GV650

Sid

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Re: Front cylinder colder than rear ????
« Reply #9 on: January 08, 2018, 01:07:25 PM »

Those missing washers are always a pain!...... ;)
that's why you should always have a crisp packet to put them in . Saves loosing them and wondering , where the fook did that go  :o
Any good mechanic should always have "left overs" , hence the 'crisp packet"  ;D

As long as all you have left over is the crisp packet with no washers in it!
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