running on 3 cylinders

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saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

running on 3 cylinders

Postby saber » Sun Jul 07, 2013 7:04 pm

found out thr #1 cylinder is not working. The exhaust pipe is cold when the others get hot. Any thoughs on how to approach fixing it? Otherwise the 79 CB650 runs ok.

usbear
Posts: 361
Joined: Sun Mar 10, 2013 9:55 pm

Re: running on 3 cylinders

Postby usbear » Sun Jul 07, 2013 7:11 pm

1) Check spark!
Pull plug and wire. Plug in and hold to cylder head and check for hot spark.
Hot spark is Bright blue and wide arc. (not thin weak spark)
Change plugs and check again.
No spark then switch wire with the same coil and check wire condition
Both sides of the coil working? One coil fires two wires at same time.
If one works and one does not then narrow search.
2) good spark? than check fuel.

saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

Re: running on 3 cylinders

Postby saber » Sun Jul 07, 2013 7:23 pm

thanks usbear. I am new to this. Can I keep #1 cylinder open when I check for spark?

Nevernoluck2
Posts: 22
Joined: Thu Jun 20, 2013 8:24 am

Re: running on 3 cylinders

Postby Nevernoluck2 » Sun Jul 07, 2013 7:35 pm

Yes keep it open is fine

saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

Re: running on 3 cylinders

Postby saber » Sun Jul 07, 2013 7:38 pm

thanks Nevernoluck2

saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

Re: running on 3 cylinders - 79 CB650

Postby saber » Tue Jul 09, 2013 1:14 pm

#1 cyliner is not firing so I pulled the plug on #1 today and checked the spark. Spark looks good. Also pulled #4 plug to see how that one fired and they are the same. #4 cylinder is working.

Next I opened the float drain on #1 to make sure that gas was flowing to the #1 carb and that looked good.
It seems the gas is not making it into the cylinder.

Question, will it damage the bike to ride it with one cylinder not firing? I would like to continue using it until I can firgure out the problem.

User avatar
Volker_P
Posts: 5508
Joined: Mon Mar 06, 2006 1:53 am
Location: southern Germany

Re: running on 3 cylinders

Postby Volker_P » Wed Jul 10, 2013 12:23 am

Start with swapping plugs 1 and 4.

Running on three for longer is a problem due to unburned fuel in that cylinder washing oil from the cylinder walls.
If it does not fire due to no fuel (dry plug) this is of course not a real problem.

Neverheless avoid high loads and it may also have some thermal consequences.
Cosky's great (free) online manual: http://cosky0.tripod.com

forum links to common technical issues

If you really like this site and you would not like to see it vanish soon, have a look there: Urgent: Future of HondaCB650.com Forum

saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

Re: running on 3 cylinders

Postby saber » Wed Jul 10, 2013 5:22 pm

I exchanged the plugs and #1 fired. Bought new plugs and installed them. I thought the spark looked ok but I guess it wasn't. Been riding 3 months on three cylinders and all it took to fix was $10 in plugs. Wow it feels like a different bike. Thanks for the advice.

cmouta
Posts: 74
Joined: Tue Aug 14, 2012 8:23 am
Location: West Haven, CT

Re: running on 3 cylinders

Postby cmouta » Thu Jul 11, 2013 8:10 am

Like Volker_P said, the unburnt fuel could be mixing in with the oil. Now that you have it running, I would do an oil change to be safe!
Chris

1982 Candy Flair Blue Honda CB650SC Nighthawk
2006 Bajaj Chetak 4T with scooterworks usa sidecar
2013 Fiat 500C Abarth
1988 Mono Rosso Red Merkur XR4Ti T5 MT

saber
Posts: 40
Joined: Thu Jan 31, 2013 6:46 pm

Re: running on 3 cylinders

Postby saber » Thu Jul 11, 2013 9:05 am

Good advice, I didn't think of that. Will change the oil. Ran about 300 miles on three cylinders. Thanks


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