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Black smoke, glowing exhaust ?

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chickenchaser
Squiddy
Squiddy

Posts : 10

Black smoke, glowing exhaust ?

Post by chickenchaser on Sat 21 Nov 2015, 10:03 am

Hi, my dad has a cb500 which has suddenly gone wrong.
It was previously running fine and was recently given a basic service. He tried to start it the other day but it would not fire on the R/H cylinder.
He left it overnight and then tried again, this time it fired up but was spewing out black smoke and the exhaust header was red hot ( i don't know if this was just on the r/h).
He stopped it and tried again and now it wont start at all.
I don't know how long it had sat since he last used it but it will only be a couple of weeks and it was running fine when he last used it, any ideas what it could be ?
I am thinking either exhaust valve or timing but he wants to get stuck in before i can get there to have a look. 
The first thing i will do is a compression check, if it were the timing surely it would effect both cylinders.
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chickenchaser
Squiddy
Squiddy

Posts : 10

Re: Black smoke, glowing exhaust ?

Post by chickenchaser on Sat 21 Nov 2015, 10:10 am

My other thought was a plug breaking down, this would explain it not firing on one cylinder and also why that cylinder is running rich if it is firing a bit but not the glowing exhaust.
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teamster1975
Admin
Admin

Posts : 2480
Location : Woking, Surrey

Re: Black smoke, glowing exhaust ?

Post by teamster1975 on Sat 21 Nov 2015, 10:18 am

I think the first thing to do is check the state of the spark plugs, keep us posted!
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eternally_troubled
Admin
Admin

Awesome!
Posts : 3698
Location : 'ere be fens. (near Cambridge)

Re: Black smoke, glowing exhaust ?

Post by eternally_troubled on Sat 21 Nov 2015, 11:59 am

I wouldn't worry too much about he glowing exhaust - that can happen if you leave the bike running for too long without going anywhere.  It's most obvious on a dark evening.

I would agree that it is best not to just dive in and start taking things apart - always best to change the plugs, check the spark,  do the compression check etc before getting stuck in too deep.

Good luck sorting it out, keep us posted and we'll try and offer some sensible suggestions Smile
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rob75
Rossi
Rossi

Posts : 50
Location : Holland

Re: Black smoke, glowing exhaust ?

Post by rob75 on Wed 25 Nov 2015, 10:52 pm

Checking ignition would be my first step. Sudden timing problems or valve failure is unlikely.
The glowing exhaust is a sign of bad combustion or lean mixture. So after ruling out the ignition it may be blocked jets (dirt after period of inactivity). This may be checked with some carburettor cleaner (or starting aid) sprayed in the airbox. If you can start the bike fuel starvation is the problem.

Succes,
Rob
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chickenchaser
Squiddy
Squiddy

Posts : 10

Re: Black smoke, glowing exhaust ?

Post by chickenchaser on Sat 05 Mar 2016, 8:10 pm

Hi all, its been a while since my last post, both me and dad are busy so finding time when were both free is rare.
Anyway i finally got to have a bit of a look at his bike today.
First off one of the plugs was not firing, not the side that caused the initial problem and possibly just a coincidence. Changed it and both have a nice fat spark.
Would'nt fire so gave it a burst of easystart and it fired up, running on one cylinder (left one if you look down whilst sitting on it)
Unscrewed the drain bolt in both floats and got fuel out of left (running) one and nothing out of the right.
Problem solved !
Carbs off, both float valves working, cleaned crap out of right drain hole, carbs back on, open both drains and fuel from both. Problem not solved. Bugger.
Put some fresh fuel in and it now fires easily but only on left cylinder. 
No black smoke and the downpipe did'nt glow. Did'nt even get warm on that side so no way its working.
Did'nt have my compression tester with me so could'nt test that.
Going back in a couple of weeks but going tooled up this time so will get stuck in and have a proper go at it. 
Will update again once i have been back.
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chickenchaser
Squiddy
Squiddy

Posts : 10

Re: Black smoke, glowing exhaust ?

Post by chickenchaser on Fri 18 Mar 2016, 9:10 pm

Had another look at it.
Checked everything i could think of and still not working.
Compression is low (140) on the side thats not firing, obviously an issue but not enough for it to not run.
As a last resort checked plugs again.
Ones not sparking so it now has the old plugs in and it is working fine again.
All that and it was the new plugs that were fitted a couple of hundred (if that) miles ago.
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skyrider
the 900
the 900

Posts : 1749
Location : preston lancs

Re: Black smoke, glowing exhaust ?

Post by skyrider on Fri 18 Mar 2016, 9:36 pm

one of the new plugs could have been dodgy to start with Neutral

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