Author Topic: 79 cb650; cold exhaust headers on both cylinders 1 and 2  (Read 785 times)

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Offline my79650

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79 cb650; cold exhaust headers on both cylinders 1 and 2
« on: May 19, 2016, 08:36:57 AM »
Was going to run my motorcycle to work yesterday; no choke; so i have to twist the throttle 5 or 6 times to pump gas to start it. Flooded it; gave it a boost; ran a few minutes holding a rough idle at 1500rpm, anyhow i went to go around to the left to get on it after i noticed the exhaust didn't sound right. Placed my hand behind left muffler, blowing cold; right...hot; grabbed the muffler bare handed was still cold on the left; right could and would burn me if i held on(not that stupid); exhaust headers for 1 and 2 were cold to the touch.
I know to check the plugs; wires; plug caps; and carb drain screws to see if i am not getting any gas in the 1 and 2 carbs; no time to research it but has anyone else ever had this happen to 2 out of 4 cylinders on their sohc honda or other inline engine?
One i a million chance of the two coils frying out at the same time? Or just age catching up to nearly 40 yr old parts? Will repost results of basic checks in a few hours; if anyone has something that i may have missed in diagnosis; post it up please and thanks.

 

Offline Johnny340

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Re: 79 cb650; cold exhaust headers on both cylinders 1 and 2
« Reply #1 on: May 19, 2016, 09:19:03 AM »
When this exact same thing happened to me, it was plugged pilot jets/circuits.
Was it running properly recently?  If not, I'd go with carbs that need cleaning.  That combination doesn't make sense for a bad coil..
1975 CB750F0 Super Sport
1972 CB750K2
1981 CB650
1974 T-500
2003 GSXR750
2006 YZ250

Offline my79650

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  • old school 750 carbs on a cb650
Re: 79 cb650; cold exhaust headers on both cylinders 1 and 2
« Reply #2 on: May 19, 2016, 10:01:56 AM »
Got gas; check; no problems there. Other than the silicone spray on the wires and plug caps; they are good. Waterproofing  in a can; great for those caught in the rain times.
Pulled #1 plug; soaked with gas; too much of a good thing. #2 plug; wet but not as bad. Checked 3 and 4; both dry and no soot; great shape; real good compression; old school finger in hole check;  bring on the comments about that one lol.
Had  2 spare new plugs on hand; replaced them in #1 and #2; she fired up and purred like a kitten.
Sometimes  the simplest thing is the most terrible problem; can run to work and stop at bike shop and grab 4  new plugs; glad i had spares on me.