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Cause for concern? Seriously odd pipe discoloration...

11K views 47 replies 19 participants last post by  Stinky Pete 
#1 ·
Ok - so I've been screwing around with the shovelhead timing and finally got a good startup.

Here's the setup - '76 stock displacement motor, Andrews B grind, Super E carb (jets unknown), Morris magneto timed with a buzz box at the advanced timing mark with Autolite 4265 plugs.

My best start method to-date has been no primer kicks, no throttle squirts, no enricher. Trying to gas it just seems to wet the plugs.

Yesterday when starting the pipes got a crazy discoloration. I figured it was too advanced. I retarded it different amounts and but couldn't get it to fire.

Today I polished the heat marks of the pipe and reset timing to recommended and started it right up. Two kicks, no help with the gas. Let it run for about two min, no enricher and would idle on it's own.

Take a look at the pics and tell me what you can discern. The discoloration is exactly the same as yesterday. To me it's spooky how pronounced the cutoff in color is.

Front pipe:


Rear pipe:


Pipe design:


Plugs look good (for two min idle):


Thoughts?
 
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#3 ·
Yes - I should check the jets, and will, but it was such a hassle to get this thing running and idling that I didn't want to muck with the carb until I had everything else sound.

Pipes are new and bare metal.

Side note - the stop on the discoloration on the front pipe is a seam. The pipes are butt welded, not sleeved so it still seems a little odd.

I'm gonna go for a quick spin.
 
#6 · (Edited)
.....Wow.....

Make sure no intake leak is there....
Need to look at the jetting .....
Make sure of the timing...

The plugs are only showing the color for the idle circuit...At cruising speed, the rpm will be higher and on a diff. circuit of the carb.
Depending on gearing, he may or may not be off of the idle/intermediate circuit at cruising speed. On most carbs, main circuitry doesn't really come on until 2500-ish rpm. Or under acceleration.

Low rpm, steady state coughs at cruising speed, are almost always a lean condition on the idle/intermediate circuitry. Vacuum leaks as a cause of being too lean, included.

I agree that tests done so far, do not afford an accurate plug read, but by the looks of those pipes, he is either waaaaay lean on the idle circuit, or timing is off considerably.

Here is a pretty good link on tuning the E.

OP might try swapping out that tiny air cleaner for a real one and see if it makes any difference first.

Also, I just noticed, is that 1/4 wall pipe for the rest of the exhaust? You may be having more of a problem getting the exhaust out, than you are having getting air/fuel in. Help me understand what I am seeing at the exhaust tips
 
#7 · (Edited)
whats up with the pipe ends ? maybe too restricting opening looks tight in photo.maybe you just got some weird pipes and thats just how it looks,it is a nice even discoloration front and rear.if the things not getting too hot on you then I would consider that it is how the bare metal colors.you might look into ceramic coating them.there is an outfit in fla.performance coatings {I Think} google them its high performance stuff dissipating heat,and the never blue on you they have one that looks like chrome,I think its called showchrome and the prices are cheaper than chrome,love those rocker covers
 
#8 ·
Ok - regarding the pipes. They're 1 3/4" throughout. The tips are a little tricky to describe, but they're basically straight pipe with a flared trumpet tip that I boxed in.

Here's the two parts for a tip:


How they fit together:


With the face boxed in (this is what makes the pipe wall look thick):


Hogster - Definitely going to get coated with something once I get to go for a few rides. I'll check out the performance coatings guys - thanks for the heads up. Those rocker covers are beautiful - Josh at Throwback is the man!

Thanks for the link on tuning. I was the carb instructions and was going to reset to stock settings, but didn't want to add another variable to the mix until it was running. Seems like I may have no choice?

I didn't end up going for that ride. Seems like whenever the bike warms up it won't fire or when it does, won't run. I'm guessing the pushrods may be too tight?

Given my keeping it running issues, should I add carb changes to the mix? It ran with current carb setup on drag pipes before. Of course that was before new pipes and magneto.

Dragstews - you need an emoticon with the ...wow..., I'm guessing you mean wow that's terrible. I should do an intake leak. I'll put that on the to-dos for tomorrow as well as check the jets.

FearNoEvo - switch air cleaner covers or just start and idle without the cover?
 
#9 ·
Thanks for the link on tuning. I was the carb instructions and was going to reset to stock settings, but didn't want to add another variable to the mix until it was running. Seems like I may have no choice?

FearNoEvo - switch air cleaner covers or just start and idle without the cover?
It is best to tune it with what you plan on running, but as a quick check you can go with out it. All that is going to do is make it leaner though. I would suggest throwing whatever the previous owner of the carb had on it, if you know? Maybe you don't?

You may be be on to something with the valves too. It wouldn't hurt to check them.

Re: the factory settings, it isn't very often that a bike without other problems, won't start with a baseline tune from the factory.

Nice job on the tips, they look good.
 
#11 ·
Pete,
straight pipes with out baffels of any kind are a bitch to tune to! A "fix" (I've found out it is putting a bandaid on the problem) is putting a 1/4", 3/4" long bolt in the pipe. I always put it in at about 7 or 8 o'clock so ya couldent see it.

On your jetting, try Idle at 1 and 1/2 turns out from bottoming out (be carefull bottoming out the needle, you can screw it up.) Intermedate, a 28 and a 68 on the main. this should get ya close but you should adjust each circuit. While ya got the carb off, check your intake for leaks. Bike's lookin good to btw.
 
#12 ·
My first thought is too rich. If it idles within 2 min you are definitly on the rich side. But those pipes!! Look cool but hard to tune for. If the air mix screw is less than 1 turn out and you don't have to choke or throttle squirt it your intermediate jet is too big. If it was too lean it probably wouldn't idle anyway. Run it out and read the plugs. Good luck. Cool ride! peace
 
#19 ·
Not trying to hijack, but I see this Autolite 4265 discussion on alot of boards and it's never been explained, it's just said they are resistor and "wrong" for a mag. But it's true, Morris recomends them for mags.

I used to run RN12YC and RJ12YC (dual plugged heads) But I was fouling them like crazy. I went to an AC Dleco (can't remember the number) and they lasted forever. But then I ran across the Morris recomended 4265 and have had zero problems with them, other than people saying they are a resistor plug and "wrong" for a magneto.

I run solid core wires btw...

But the funny thing is, I ran suppresion core wires for years on my first ever mag bike and never had any issues.

I'd just like to know from those that say the 4265 is wrong for a mag because it's a resistor plug, then why does Morris recomend them?

Sixball
 
#20 ·
Not trying to hijack, but I see this Autolite 4265 discussion on alot of boards and it's never been explained, it's just said they are resistor and "wrong" for a mag. But it's true, Morris recomends them for mags.

I used to run RN12YC and RJ12YC (dual plugged heads) But I was fouling them like crazy. I went to an AC Dleco (can't remember the number) and they lasted forever. But then I ran across the Morris recomended 4265 and have had zero problems with them, other than people saying they are a resistor plug and "wrong" for a magneto.

I run solid core wires btw...

But the funny thing is, I ran suppresion core wires for years on my first ever mag bike and never had any issues.

I'd just like to know from those that say the 4265 is wrong for a mag because it's a resistor plug, then why does Morris recomend them?

Sixball
Good question because early on Morris recommended Motorcraft A-42 or AG-32A plugs for 1975 and later.
 
#24 ·
Yeah, I know the pipe problem isn't the cause of the brand or type of plug, we were just discussing the recomendation of a resistor type plug with a mag when others say they are wrong.

Heat is the issue, yes. Take a look at the timming, advanced or retarded, or as said, a possible lean condition or intake leak.

Sixball
 
#25 ·
Thanks guys - just got home and realized I don't have an air valve to run the pressure test. Gonna go get one and test for leaks.

Since the carb will be off I'll drop the bowl and check the jets as well.

I'm still holding that the timing is good (or good per timing instructions). Regarding the plugs...I can worry more about those later down the road.

I'll take some pics of the bike before I pull the carb. Thanks for the compliments. The pipes, as well as all the other raw stuff will be coated or chromed at some point. I need to braze in some low spots beforehand.
 
#28 ·
76 is a HUGE main jet for your application, which leads me to believe that Cotten may be onto something. .295 is also a pretty big intermediate for bone stock.

I'll put it into perspective...I have the same setup, Super E, B grind, M5, Autolite 4265s gapped at .20 on a 9.78:1 100ci Shovelhead and I run a 72 main and .295 intermediate.
 
#29 ·
the blue flares up 1/2 inch from gasket surface then travels to the weld .
the welds high temp and maybe its heat sinking at the butt joint.
looks pretty cool...(hot)
theres HPC coatings for the inside of pipes for that reason.

the air filter looks small surely thats gotta play a part in fuel mix.

The resistor saga is an interesting 1, aluminium is used as conductor in cables as well as copper , the motor is ali = low resistance , the solid wires are low resistance then up springs resistor plugs!!

the circuit of coil,lead,plug,gap,head-head,gap,plug,lead back to coil has a series of resistances, the gap is supposed to be the higher resistance of 3000 ohms per mm at 1 atm , in the motor ,compression is raised
8 :1
maybe the resistor plug allows the gap resistance to be seen as a low resistance point .....just thinking and now......back to the blue pipes...
 
#32 ·
Carburetion and jetting are on the long list of things I've never learned much about. Larger jets would make for richer fuel?

To be fair - I guess I can't say definitively that it's stock displacement. I never looked, but it never felt really beefy.
The jet size is indicative of the diameter of the hole in the jet itself, so the larger the number, the more fuel.

Download the user manual for a Super E and read it before you go to bed at night for a couple of days. You'll learn a lot and knowing how tune a carb is necessary when owning an old bike.
 
#35 ·
Pete,
Those are some BIG jets.
I've seen that same condition (seriously blued pipes or pipe) on a bike with a bad air leak at the manifold. I don't think we know enough about the history of your motor to really nail this down, but I'll throw my 2 cents in. Could the jet size have been bumped way up in an attempt to compensate for an intake leak? I've also seen that same condition with retarded timing, the pipes will get hot and blue right before your very eyes in about the same time its taken me to type this (I'm a slow typer, but the bluing will happen real quick with the timing retarded too much). As far as your plugs, in our part of the world (Cleveland area) 4265's are the plug of choice for shovels.
 
#41 ·
THE PIPES ARE BARE METAL PEOPLE!!!!!!!!! raw steel will color like that with a little heat.............................
Lets look at the facts . . . for raw steel to aquire those particular heat oxidation colors it has to be heated to well over 600 degrees. If you look at Pete's pipes you will see a brownish-purple color (approx. 540 degrees) close to the exhaust manifold connection. As you move down the pipe you'll notice a change to a deeper blue (approx. 590 degrees), then transitioning to a lighter blue indicative of a minimum temperature of 640 degrees. You can continue to raise the heat without too much noticeable color change from this point on until it darkens and then starts to turn a dark red. Thats red, as in red-hot. Depending on your frame of reference, some folks may say thats "a little heat" but from what Pete has related to us it sounds like that heat developed pretty rapidly. I remember riding with a few guys one night and I noticed a very wierd reddish glow coming off of my buddies rear pipe. Yep, his rear pipe was starting to glow red up towards the connection to the head. In the dark, you will notice a red glow start to come off the steel at approximately 1000 degrees. That bike was NOT running right. For your reference, all temps are given in degrees farenheit.

Regards,
Geo.
 
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