Author Topic: Smoking head question  (Read 514 times)

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Offline Big Cobra

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Smoking head question
« on: August 20, 2016, 07:56:44 AM »
Hi,
still kinda newbie at this---Just got my 74 cb750 running/idling nice..or much better than it had been before.  Drove it a couple miles in order to get a read on my plugs.  After driving around town I parked it and let it idle for a few while picking up my garage.  After a few minutes I noticed a moderate amt of white smoke rising from the head on the right side, above the #4 cylinder (or 3, and 4 not sure).  The right side does have visibly more oil and gunk buildup around the spark plug port vs the left side--also looks pretty fresh or moist close to plug.  I am attaching picks of right and left head for comparison as well as pics of my plugs (sorry there sort of crappy).  Just wanted to ask some smarter folks what this may symbolize. 

Little background: compression test was good way back when I started working on this bike.  I've clean and rejetted the carbs a lot of times-- it's generally run very lean, up until now.  Running 4 into one exhaust, 130 mains, 40 idles, just bench synced carbs, was running some older fuel, but recently filled tank.  A while back I added a shot glass of Seafoam to full tank of gas.

Thanks very much,

 

Offline flybox1

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Re: Smoking head question
« Reply #1 on: August 20, 2016, 08:03:39 AM »
Leakiy exhaust seal.  Has the exhaust been off recently, and did the exhaust gaskets get replaced?
'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

"This is my CB. There are many like it, but this one is mineā€¦"

Offline Big Cobra

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Re: Smoking head question
« Reply #2 on: August 20, 2016, 08:06:28 AM »
I replaced the exhaust a while back, and yes I replaced the crush gaskets.  I suppose I could try tightening it up, or pull it off and try another set.  I've heard of some folks using this particular exhaust having to double up on the gaskets.

Offline Big Cobra

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Re: Smoking head question
« Reply #3 on: August 20, 2016, 08:13:40 AM »
here are those pics

Offline Big Cobra

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Re: Smoking head question
« Reply #4 on: August 20, 2016, 08:15:32 AM »
here are those pics