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Author Topic: Certain smell coming from brike  (Read 2763 times)

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Offline Dos

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Certain smell coming from brike
« on: October 12, 2016, 12:06:23 PM »
I have noticed on my Cb350f there's a particular smell coming from my engine. My bike runs rich to keep the engine cooler so normally it smells alittle gassy but there's this smell that sort of smells like burning mixed with plastic. I can't really put my finger on it. The smell comes from the upper end of my engine.

Is this just the smell of heat or a gasket maybe?

My bike does have slight weeping coming from the upper cylinder head
« Last Edit: October 12, 2016, 12:08:16 PM by Dos »
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Offline flybox1

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Re: Certain smell coming from brike
« Reply #1 on: October 12, 2016, 12:51:22 PM »
Quote from: Dos on October 12, 2016, 12:06:23 PM
My bike runs rich to keep the engine cooler
Did you set it this way on purpose?  ???

Tune it the way Honda meant it to be and then see if the smell goes away.
If it doesnt, it could just be crank vapor, or that oil burning off....
Maybe your vreg is working overtime  :o
« Last Edit: October 12, 2016, 12:53:25 PM by flybox1 »
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Offline Gene

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Re: Certain smell coming from brike
« Reply #2 on: October 12, 2016, 02:29:00 PM »
Reset to regular, as Fly says.  I'm chiming in because I have noticed that some bikes smell different than others and you have to get used to them to be able to tell if something's off.  A gasket shouldn't be melting - that would be bad.  If you're smelling plastic my first thought would be electrical - or . . . make sure your plug wires aren't leaning on the head.
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Offline Don R

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Re: Certain smell coming from brike
« Reply #3 on: October 12, 2016, 04:06:59 PM »
 Aftermarket coils? I've melted a couple of those,
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Offline Gene

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Re: Certain smell coming from brike
« Reply #4 on: October 12, 2016, 04:49:53 PM »
BTW Dos - I've tried that myself - the rich setting to "keep it cooler" in Summer - or so I thought.  It seems like a reasonable idea, especially for a smaller bike (I did it on my ex-360), scientific reasoning blah blah blah - but it's not.:)
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Offline Dos

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Re: Certain smell coming from brike
« Reply #5 on: October 12, 2016, 06:07:05 PM »
I thought it would be better to run it rich to keep it cool. So I shouldn't? Won't the bike get hotter with the air screw out more?


Also what is a vreg? My regulator? The smell is coming from the top ensnared of the engine
« Last Edit: October 12, 2016, 06:09:21 PM by Dos »
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Offline DaveBarbier

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Re: Certain smell coming from brike
« Reply #6 on: October 12, 2016, 07:35:13 PM »
The Honda engineers were quite capable. You're aware that the hundreds of thousands of motorcycles sold in the 70's throughout the world didn't overheat, right?
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Offline Gene

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Re: Certain smell coming from brike
« Reply #7 on: October 12, 2016, 08:04:55 PM »
Quote from: Dos on October 12, 2016, 06:07:05 PM
I thought it would be better to run it rich to keep it cool. So I shouldn't? Won't the bike get hotter with the air screw out more?

No - but I get your logic. "If running lean makes it overheat, wouldn't running rich keep it cooler?"

Again, I get it, thought the same thing.  But the science doesn't support it. 1.5 turns out on the screw to start - adjust as necessary to have all 4 running properly.

P.S. - to all reading this, that's part of the trouble-shooting section in the manual re: overheating.
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Offline Gene

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Re: Certain smell coming from brike
« Reply #8 on: October 12, 2016, 08:08:03 PM »
Quote from: Dos on October 12, 2016, 06:07:05 PM

Also what is a vreg? My regulator? The smell is coming from the top ensnared of the engine

Voltage Regulator.  If it's not regulating properly - keeping the charging to a reasonable level - it can be doing nasty things. 
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Offline 754

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Re: Certain smell coming from brike
« Reply #9 on: October 12, 2016, 08:45:19 PM »
Maybe your breather hose off the valvecover came off or split right behind where it mounts..
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Offline seanbarney41

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Re: Certain smell coming from brike
« Reply #10 on: October 13, 2016, 03:25:20 AM »
Is this a new build?  All that new paint and stuff is gonna smell funny for a while until all the chemicals burn off and paint fully cures.
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Offline madmtnmotors

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Re: Certain smell coming from brike
« Reply #11 on: October 13, 2016, 04:18:09 AM »
Do you need a shower?  :o

(sorry, I couldn't resist)  ;)


An overly rich condition can eventually lead to carbon fouling of the plugs, pistons, and valves. In extreme cases this can ultimately lead to pre-detonation if IIRC.
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Offline flybox1

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Re: Certain smell coming from brike
« Reply #12 on: October 13, 2016, 06:46:50 AM »
Quote from: Gene on October 12, 2016, 08:04:55 PM
Quote from: Dos on October 12, 2016, 06:07:05 PM
I thought it would be better to run it rich to keep it cool. So I shouldn't? Won't the bike get hotter with the air screw out more?

No - but I get your logic. "If running lean makes it overheat, wouldn't running rich keep it cooler?"

Again, I get it, thought the same thing.  But the science doesn't support it. 1.5 turns out on the screw to start - adjust as necessary to have all 4 running properly.

P.S. - to all reading this, that's part of the trouble-shooting section in the manual re: overheating.
7/8ths turn out on the air screws is stock.   Start from there.
Honda had their best engineers designing these bikes....they set these values in the manual for a reason. 
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'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

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Offline Stev-o

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Re: Certain smell coming from brike
« Reply #13 on: October 13, 2016, 06:50:30 AM »
New Jersey gets hot?  Or, did you take a trip to Death Valley?!
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Offline Dos

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Re: Certain smell coming from brike
« Reply #14 on: October 13, 2016, 06:59:19 AM »
Alright alright I get it haha.

I'm going to adjust the air screws

Thank you
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Offline Dos

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Re: Certain smell coming from brike
« Reply #15 on: October 13, 2016, 10:10:26 AM »
I have been running the bike rich for quite a while maybe it's time to set it back to normal I'm a little confused though I've heard different things with the CB350F and the air screw being at 1.5 turns out or 7/8

I have a 4 into pipe so which one is appropriate? Should I listen and see what sounds "good" but then I run the risk of it being lean and melting into alittle piece of tin foil
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Offline flybox1

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Re: Certain smell coming from brike
« Reply #16 on: October 13, 2016, 10:15:51 AM »
7/8 is for a stock bike.  Start there.
You make further adjustments to each individual carb based on A/F mixture readings, or idle plug (chop) color.
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'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 mine…"

Offline flybox1

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Re: Certain smell coming from brike
« Reply #17 on: October 13, 2016, 10:20:37 AM »
Ride your bike to get it hot.
swap in a set of new D8EA plugs, and let it idle, with a fan on the engine, for 4-5 minutes.
Pull the plugs, and check their insulator color.   Compare to the chart below.
Turn your air screws IN for richer, OUT for leaner based on that carbs need.


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'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

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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 mine…"

Offline Sigop

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Re: Certain smell coming from brike
« Reply #18 on: October 13, 2016, 10:45:33 AM »
Great plug chart.
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Offline Dos

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Re: Certain smell coming from brike
« Reply #19 on: October 13, 2016, 11:30:39 AM »
Thank you for that chart my plugs are definitely foiled I'm going to sync the carbs and adjust the air screw soon.

I'll start at 7/8
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Offline TomsK8resto

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Re: Certain smell coming from brike
« Reply #20 on: October 13, 2016, 05:11:30 PM »
Quote from: 754 on October 12, 2016, 08:45:19 PM
Maybe your breather hose off the valvecover came off or split right behind where it mounts..

I had this happen on my '78 750K bike, the garage always smelled like oil, but no leaks.  I cut the hose and put it back on the fitting and put a decent hose clamp on it.  Problem solved.

Tom
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